Planet KDE

Qt for MCUs 2.5.4 LTS (Long-Term Support) has been released and is available for download. This patch release provides bug fixes and other improvements while maintaining source compatibility with Qt for MCUs 2.5. It does not add any new functionality.

A while ago a colleague of mine asked about our crash infrastructure in Plasma and whether I could give some overview on it. This seems very useful to others as well, I thought. Here I am, telling you all about it!

Our crash infrastructure is comprised of a number of different components.

• KCrash: a KDE Framework performing crash interception and prepartion for handover to…
• coredumpd: a systemd component performing process core collection and handover to…
• DrKonqi: a GUI for crashes sending data to…
• Sentry: a web service and UI for tracing and presenting crashes for developers

We’ve looked at KCrash previously. This time we look at coredumpd.

Coredumpd

coredumpd collects all crashes happening on the system, through the core_pattern system. It is shipped as part of systemd and as such mostly available out of the box.

It is fairly sophisticated and can manage the backlog of crashes, so old crashes get cleaned out from time to time. It also tightly integrates with journald giving us a well-defined interface to access crash metadata.

But before we dive into the inner workings of coredumpd, let’s talk about cores.

What are cores?

A core, or more precisely: a core dump file, is a copy of the memory image of a process and its process status (registers, mappings, etc.) in a file. Simply put, it’s like we took a copy of the running process from RAM and stored it in a file. The purpose of such a core is that it allows us to look at a snapshot of the process at that point in time without having the process still running. Using this data, we can perform analysis of the process to figure out what exactly went wrong and how we ended up in that situation.

The advantage is that since the process doesn’t need to be running anymore, we can investigate crashes even hours or days after they happened. That is of particular use when things crash while we are not able to deal with them immediately. For example if Plasma were to crash on logout there’d be no way to deal with it besides stopping the logout, which may not even be possible anymore. Instead we let the crash drop into coredumpd, let it collect a core file, and on next login we can tell the user about the crash.

With that out of the way, it’s time to dump a core!

Core Dumps

We already talked about KCrash and how it intercepts crashes to write some metadata to disk. Once it is done it calls raise() to generate one of those core dumps we just discussed. This actually very briefly turns over control to the kernel which will more or less simply invoke the defined core_pattern process. In our case, coredumpd.

coredumpd will immediately systemd-socket-activate itself and forward the data received from the kernel. In other words: it will start an instance of systemd-coredump@.service and the actual processing will happen in there. The advantage of this is that regular systemd security configuration can be applied as well as cgroup resource control and all that jazz — the core dumping happens in a regular systemd service.

The primary task here is to actually write the dump to a file. In addition, coredumpd will also collect lots of additional metadata besides what is in the core already. Most notably various bits and pieces of /proc information such as cgroup information, mount information, the auxillary vector (auxv), etc.

Once all the data is collected a journald entry is written and the systemd-coredump@.service instance quits again.

The journal entry will contain the metadata as entry fields as well as the path of the core dump on disk, so we can later access it. It essentially serves as a key-value store for the crash data. A severely shortened version looks like this:

Tue 2024-08-27 17:52:27.593233 CEST […] COREDUMP_UID=60106 COREDUMP_GID=60106 COREDUMP_SIGNAL_NAME=SIGSYS COREDUMP_SIGNAL=31 COREDUMP_TIMESTAMP=1724773947000000 COREDUMP_COMM=wine64 COREDUMP_FILENAME=/var/lib/systemd/coredump/core.wine64.….zst … Example

Since this is all rather abstract, we can look at a trivial example to illustrate things a bit better.

Let’s open two terminals. In the first we can watch the journal for the crash to appear.

journalctl -xef SYSLOG_IDENTIFIER=systemd-coredump

In the second terminal we run an instance of sleep in the background, and then trigger a segmentation fault crash.

sleep 99999999999& kill -SEGV $!

In the first terminal you’ll see the crash happening:

Aug 27 15:01:49 ajax systemd-coredump[35535]: Process 35533 (sleep) of user 60106 terminated abnormally with signal 11/SEGV, processing... Aug 27 15:01:49 ajax systemd-coredump[35549]: [🡕] Process 35533 (sleep) of user 60106 dumped core. Stack trace of thread 35533: #0 0x0000729f1b961dc0 n/a (/lib/ld-linux-x86-64.so.2 + 0x1cdc0) ELF object binary architecture: AMD x86-64

So far so interesting. “But where is the additional data from /proc hiding?” you might wonder. We need to look at the verbose entry to see all data.

journalctl -o verbose SYSLOG_IDENTIFIER=systemd-coredump

This actually already concludes coredumpd’s work. In the next post DrKonqi will step onto the stage.

Here at KDE neon tower we have been busy rebasing our KDE software builds from Ubuntu 22.04 (jammy) to Ubuntu 24.04 (noble). This always takes longer than you’d think, mostly because it’s a moving target so we also have to keep updating the incoming releases from Plasma, Frameworks, Gear and even Calligra. We had a couple of delays when Jonathan caught Covid (4 years after it was worth sympathy to do so) and then the build server had issues and needed itself rebuilding. But the package archives are there and the Docker images are there and today the first ISO got built which boots successfully. Next steps are making sure all the software is up to date and getting the upgrade solid. Be with you soon!

First KDE neon ISO based on Noble

The Breeze icons used in message boxes always felt a little odd with a status icon placed inside some kind of speech bubble, effectively an icon within an icon. Three months ago they got replaced by more simplistic ones that I felt didn’t fit very well either. Therefore I put my Inkscape skills to the test and created a new set of Breeze-style dialog icons.

As you may know I have a secret passion for vector graphics. I am not very good at it but I love that you have proper shapes and objects to work with as opposed to a mush of pixels. Sure, more sophisticated graphics programs have layers and masks and what not but my proficiency there doesn’t go much beyond Kolourpaint. More importantly, though, I can easily copy paste together various bits and pieces of other icons to implement the icon I had in mind.

A few of the file icons I have worked on but didn’t finish (feel free to take as an inspiration)

Over the years I have created a couple of Breeze icons, mostly for (exotic) file types since I am on a quest to have a thumbnailer or at least a proper icon for every file type imaginable. Take for example the Apple Wallet icon we use for KDE Itinerary, our fantastic travel companion app: it’s just a ZIP file with a JSON description and graphical assets for a boarding pass or event ticket. I used a generic blue file icon combined with the wallet-open icon. My original idea was actually a plane alongside a QR code but I couldn’t help but view it as a plane that crashed into a building.

The other day I received concert tickets in the form of an Apple Wallet bundle which contains multiple passes, something I didn’t know existed and probably didn’t back when I created the original icon. For this purpose I used the generic package icon in the same light blue, zipper shifted to the right to match the Android APK icon, and wallet emblem added.

How the Apple Wallet passes icon came to be

Friday night I sat down to finally create some new dialog icons for error, warning, question, and information. Breeze come with has shield-shaped security icons similar to the message box icons we used to have. I just wanted a triangle with a Breeze-style gradient and angled drop shadow, how hard can it be? I ended up twisting the security-medium icon (an orange shield with exclamation mark), removing nodes, stretching objects, and straightening Bezier curves until I got what I wanted.

For the error icon I initially wanted a simple circle with an X. This time security-low (a red shield with a cross) served as a base. I drew a simple circle and used the shield’s gradient as fill. I couldn’t figure out how to bend the shield-like outline at the bottom to match the circle so I went looking for a similar circular icon I could steal it from. Luckily, there was exactly one circular 64 px icon I could copy. For question and information I also used purple and blue circles, respectively.

First iteration of the new dialog-error icon

Afterwards I figured I probably want a different shape for the error icon so it’s not all circles and to keep it from looking like a close button. That’s actually the main reason our message widget lost its icon, people confused the error symbol on the left with a close button to dismiss the message. I checked what other icon themes did and found squares were quite popular (also used by the KDE 4 Oxygen theme) as well as octagons. I tried a square by modifying the utilities-terminal (Konsole) icon but that just looked way too massive. After consulting the KDE Visual Design Group we settled on an octagon like a stop sign (reminds me of the glorious Windows 3.1 days which used an actual stop sign). Finally, Janet Blackquill and Andy Betts gave the icons some finishing touches and needed polish, taking into account our Colorful Icon HIG.

This post illustrates (in more than one sense of the word) nicely that contributing to KDE is more than writing actual source code. Creating artwork, writing translations, doing promo work, managing IT infrastructure, and of course hosting community events like Akademy is just as important for a community to thrive!

Calligra is the office and graphics suite developed by KDE and is the successor to KOffice. With some traditional parts like Kexi and Plan having an independent release schedule, this release only contains the four following components:

• Calligra Words: Word Processor
• Calligra Sheets: Spreadsheet Application
• Calligra Stage: Presentation Application
• Karbon: Vector Graphics Editor

The most significant updates are that Calligra has been fully transitioned to Qt6 and KF6, along with a major overhaul of its user interface.

General

Words, Sheets, and Stage now feature a new sidebar design. Currently, this is implemented using a proxy style, which will no longer be necessary once the related merge request in Breeze is merged.

Sidebar with the new immutable tab design

I revamped the content of each sidebar tab, addressing various visual glitches and making the spacing much more consistent.

The “Custom Shape” docker has been removed, and custom shapes are now accessible through a popup menu in the toolbar across all Calligra applications.

Custom shapes popup

Regarding the toolbar, I streamlined the default layout by removing basic actions like copy, cut, and paste.

The settings dialogs were also cleaned up and are now using the new FlatList style also used by System Settings and most Kirigami applications.

Settings Dialog

Words

Word now features the new sidebar design, and the main view uses a shadow to define the document borders.

Calligra Words

The Style Manager and Page Layout dialog were also updated.

Style Manager

Page Layout

Stage

Stage didn’t really change aside of the sidebar redesign. But I am using it to work on my slides for Akademy and it is a pretty solid choice.

Calligra Stage

The tooltip for the slides are now compatible with Wayland.

Tooltip showing a slide

Calligra Sheets

As part of the Qt6 port, Sheets lost its scripting system based on the unmaintained Kross framework. In the future, it would be possible to add Python scriping, thanks to the work of Manuel Alcaraz Zambrano on getting Python bindings for the KDE Frameworks.

Visually a noticable change is that the cell editor moved from a docker positioned on the left of the spreadsheet view by default to a normal widget on the top. This takes a lot less space which can be used by the spreadsheet.

Calligra Sheets

Karbon

Karbon didn’t received much change outside of the one affecting the whole platform.

Karbon

Launcher

The intial window when opening one of the Calligra application was redesign and adopted the new “frameless style”.

Custom Document tab of the launcher page

Template tab of the launcher page

Other

• Braindump is now able to compile again, but since it lacks an active maintainer, the component is disabled in release builds.

• The webshape plugin has been ported from the outdated QtWebkit module to QtWebEngine and is no longer exclusive to Braindump. This means you can now embed websites directly into your word documents, slides, and spreadsheets.

Webshape

• The AppStream id of every components is prefixed by org.kde.calligra. This allow Flatpak to expose every Calligra applications to your application launcher.

Get Involved

Calligra needs your support! You can contribute by getting involved in development, providing new or updated templates, or making a donation to KDE e.V.. Join the discussion in our Matrix channel.

Credits

This release would not have been possible without the high quality mockups provided by Manuel Jesús de la Fuente. Also big thanks to everyone who contributed to this Calligra release: Evgeniy Harchenko, Dmitrii Fomchenkov and bob sayshilol.

Packager Section

You can find the package on download.kde.org and it has been signed with my GPG key.

Project Recap

As my Google Summer of Code 2024 journey concludes, I'm excited to share the updates on my project: Porting Arianna to Foliate-js. The main goal was to replace the outdated epub.js with actively maintained Foliate-js. In my previous blog post, I discussed the initial progress on integrating Foliate-js into Arianna, including the implementation of Table of Contents (TOC) and metadata handling.

My work done so far Overcoming Rendering Challenges

• Rendering Issues: One of the major hurdles was fixing the rendering issues that were causing the book to not be visible on the screen. This was a complex problem, but with the guidance of my mentor,we were able to resolve it successfully, and the book was able to visible on the screen.

• Text Color in Light Theme: I also addressed the text color issues in the light theme mode, ensuring other color can be visible and maintaining visual consistency across different themes.

• Navigation Buttons: Enabled the navigation buttons by setting backend.locationsReady to true when the book is ready. This was a key fix to enhance user navigation within the ebook, to move from one page to another expect through the arrow keys.

• Theme Color Handling: Lastly, I worked on the handling of theme colors to provide a consistent visual experience across different themes.

light: { fg: Config.invert ? Kirigami.Theme.backgroundColor.toString() : Kirigami.Theme.textColor.toString(), bg: Config.invert ? Kirigami.Theme.textColor.toString() : Kirigami.Theme.backgroundColor.toString() } User Experience and Functionality Refinements

• Slider and Progress Percentage: I fixed the slider functionality, making sure it accurately reflects the reading progress. This update ensures that users can track their progress through the ebook with precision.

QC2.Slider { anchors.fill: parent value: backend.progress * value onMoved: { backend.progress = value } onPressedChanged: { if (pressed) { backend.progress = value } } live: true Layout.fillWidth: true }

• Reading Position Accuracy: I also ensured that the slider accurately reflects the reading position when users interact with it, improving the overall usability.

• Book Progress Display: I resolved issues with the book progress display, update time left calculation, and popup behavior, refining the user interface for a smoother reading experience.

> Reflections and Takeaways

Project has been a significant learning experience. The most challenging part for me was making things work and realizing that not everything is as straightforward as I initially thought. It was daunting to dive into a large codebase and try to understand how everything fits together, but this experience taught me the importance of patience and how to reduce problems so they can be simply solved.

Looking Ahead

While significant progress has been made, many things are left to do:

• Fixing right-click copy and search functionality
• Implementing Ctrl+ shortcut for increasing font size
• Addressing link color and redirect issues
• Features like bookmarking and annotations

What’s next?

While my GSoC journey is coming to an end, my contributions to Arianna and the open-source community will continue.

I'd like to thank my mentor, Carl Schwan, for the guidance and support throughout the project, the KDE community, and the Google Summer of Code program for this opportunity. This experience has not only improved Arianna but has also been a transformative journey for me as a developer.

Thank you for following along with my progress, see you in my next blog with more progress.

With the Qt 6.7 release, Qt introduced a wide range of improvement for the text rendering and font shaping.

One element of this is that you can now configure OpenType font features.

Many of the 'new cool' programming fonts have such features integrated. That includes both free fonts like Cascadia Code or paid fonts like MonoLisa.

Let's use the features of Cascadia Code as an example, that is the stuff they promote on their GitHub page:

For example if you set the ss01 feature, you get some alternative italics. The same holds for MonoLisa, there that is the feature ss02. Already that shows: these feature are often not very usefully named and very font specific.

Thanks to Waqar and me, with the upcoming KF 6.6 release, one will be able to configure that in Kate and other KTextEditor based applications.

The generic KDE Frameworks font chooser allows now to configure that stuff and KTextEditor will keep these settings around.

See here enabled alternative italics in Kate with the enhanced font chooser still open (look at the SPDX markers in the code):

A remaining issue is how to best handle the configuration saving in a more generic way. Ideas how to add that to KConfig without breaking compatibility of the configuration files we write with older applications would be welcome. For KTextEditor we just add some extra key for just the features that will be ignored by old versions.

This year, I attended FrOScon for the first time . FrOScon is the biggest conference about free and open-source software in Germany. It takes place every year in Bonn/Siegburg (Germany) at the weekend and is free to attend.

For the first time, I was not at a conference to staff a KDE stand. My employer had a stand there, and it was a great occasion for me to meet some colleagues, fellow KDE, and Matrix contributors.

GnuPG Stand

So I spent the majority of my time at the GnuPG stand and discussing many things with Volker, including KDE PIM and the future of KWallet.

I also meet many Matrix community members and am excited to attend the Matrix Conference next month.

Matrix Stand

All in one, it was a great conference and I hope to see more KDE people there next year and maybe even having out own KDE stand.

Haruna version 1.2.0 is out with a new footer style.

Availability of other package formats depends on your distro and the people who package Haruna.

Windows version:

• haruna-1.2.0-windows-gcc-x86_64.exe
• haruna-1.2.0-windows-gcc-x86_64.7z
• haruna-1.2.0-windows-gcc-x86_64-dbg.7z

If you like Haruna then support its development: GitHub Sponsors | Liberapay | PayPal

Feature requests and bugs should be posted on bugs.kde.org, but for bugs make sure to fill in the template and provide as much information as possible.

Changelog: 1.2.0

• Added floating footer/bottom toolbar style with 2 ways to trigger it:
  • on every mouse movement of the video area
  • only when the mouse is in the lower part of the video area
• Removed the docbook and moved its content to tooltips
• Middle clicking the playlist scrolls to the playing item

Every two years, the KDE community selects three goals that serve as focal points for the entire community's efforts in the coming years. This cyclical process of goal-setting and community-wide focus is a great example of KDE's Cumulative Culture in action.

This concept, typically observed in human societies, refers to the ability to build upon previous knowledge and innovations to create increasingly complex and effective solutions. In KDE's case, each cycle of goals represents a new layer of accumulated wisdom, i.e. new features and more stability.

The First Cycle (2018-2020)

The first cycle of goals laid the groundwork with its focus on community growth, privacy, and usability.

• Streamlined Onboarding: Focused on attracting and retaining new contributors by making the onboarding process smoother and more engaging.
• Privacy Software: Prioritized user privacy and security, ensuring KDE software respects user data and complies with security standards.
• Usability & Productivity: Aimed to enhance the usability and productivity of KDE software, making it powerful yet easy to use.

The Second Cycle (2020-2022)

The second cycle tackled more complex challenges. Goals like Wayland implementation improvements (which layed the foundation for the Plasma 6 release), improving the app ecosystem, and ensuring consistency in design and functionality.

• Wayland: This task aimed at stabilizing Wayland support accross KDE apps.
• All About the Apps: Improved KDE's app infrastructure, enabling more efficient app delivery and better support services.
• Improve Consistency across the Board: Ensured uniformity in design and functionality across KDE software, improving usability and reducing redundancy.

The Third Cycle (2022-2024)

The third cycle, which is currently coming to an end, was about progress and adaptation. A focus to include environmental responsibility, operational efficiency, and inclusive design.

• Sustainable Software: Focused on making KDE software more energy-efficient and environmentally friendly by implementing practices that reduce resource consumption and ensure long-term sustainability.
• Automate and Systematize Internal Processes: Aimed to streamline KDE’s internal workflows by automating repetitive tasks, adding code tests across projects and creating a Quality Assurance team to name a few.
• KDE For All: Seeked to make KDE software accessible and inclusive for all users.

A New Cycle A Comin' (2024-2026)

Now, as we enter the fourth cycle of the KDE Goals, we see the full power of this cumulative process. Each goal, whether fully achieved or not, contributes to the collective knowledge and capability of the KDE community. Ideas and partial solutions from past cycles become a solid foundation of knowledge and experience that support future efforts.

The commmunity is currently voting on the following proposals for the next KDE Goals cycle that will guide our efforts and shape our focus for the coming years:

• Enhancing control and automation: integrate KDE Plasma (and apps) with Smart Home Ecosystems
• Freedom through Better Data and Workflow Organization and Management
• KDE Needs You! 🫵 - Formalise and boost KDE's processes for recruiting active contributors
• KDE-based Text Snippet Expansion
• Sandbox all the things!
• Plasma - A Beacon for Open Design
• Refining and Enriching KDE: Empowering Users with Convenient and Intuitive Features
• Streamlined Application Development Experience
• Unify the Plasma experience
• We care about your Input

KDE Goals at Akademy

The three most voted goals will be announced at Akademy, where there will also be a wrap-up talk about the achievements of the current goals. Also, there will be Birds-of-a-feather (BoF) sessions with the new goal champions.

Join the Matrix room and keep an eye on the website for the latest KDE Goals updates.

KDE's Okular is the first software which got awarded with the Blue Angel label for resource and energy-efficient software products. The certification was based on the first version of the criteria for this product criteria which were introduced in 2020. Now the criteria have been updated. What has changed and what does that mean for KDE?

The revised criteria are available as version 4 on the Blue Angel web site. Only the German version is currently available; the English version will follow shortly.

New software categories

The biggest change is the scope of the label. In the past it was limited to desktop software. With the updated version, the criteria also include software on mobile devices and server software or a combination of these categories, such as a web service with mobile and desktop clients.

The biggest challenge is the measurement of the energy and resource efficiency for these new categories, which requires a more flexible approach and must accommodate scenarios where the measurement cannot be done by inserting a meter in front of the power supply of a single device. The new criteria address this by defining applicable methods for the measurement of mobile and server applications.

The extended scope covers a much broader range of software. For KDE the desktop category is most relevant, but of course a lot of software also interacts with a server component, for example an email client like KMail, which could now be treated and assessed as a combined client-server system to give more realistic and relevant results.

More flexible measurement procedure

The expansion in scope requires an expanded view on the measurement of energy and resource efficiency as well. The first version of the criteria was quite strict and prescribed a very specific measurement procedure on specified reference systems. It was based on a comparison of measurements in a representative usage scenario and in idle mode. This gave a realistic impression of what the usage of a computer program meant in terms of energy consumption.

The new criteria allow for more variation in how the measurements are carried out. The original method is still there, but variations which lead to comparable results are possible as well. This change means that a new criterion was introduced to document the way measurements are done.

In addition to the measurement of the usage scenario, a new type of measurement was introduced. This measures total energy consumption of a production system over a longer period of time. This is particular useful for server applications, where this method can lead to more realistic numbers by averaging resource consumption over real-world usage of multiple users.

For mobile applications, the measurement also has to include the data volume transmitted during a standard usage scenario and the list of URLs it has accessed. This is based on the assumption that large volumes of data transfer imply a higher energy usage. It can also be used to assess if the application is using advertisements or is collecting tracking information. Both are forbidden under the revised Blue Angel criteria.

Ongoing assessment of energy and resource efficiency

The original criteria demanded that updates of the software still run on old reference systems and that the energy consumption does not increase more than 10%. They were not very clear in how exactly this should be proven and documented. Especially for software which is released very often, testing every individual update is impractical. For mobile and even more for server software, update cycles can be very short, up to multiple updates a day.

In the updated criteria there is a more precise way of handling updates. The general idea is still there that updated software run on old hardware and energy consumption not increase too much. But it's not tied to individual updates anymore. The required procedure is to do a measurement at least once a year and publish the results as part of the documentation of the software product. This includes documentation of the measurement setups and any changes to it as well as preserving the history of measurements, so that users can judge for themselves how much energy and resource usage is increasing over time.

This procedure clarifies the requirments and opens a pragmatic way of measuring updates. It implies a certain burden on updating documentation.

Consequences for KDE and Okular

KDE holds the Blue Angel label for its PDF viewer Okular. This is desktop software and the standard usage scenario doesn't include any network access. That means that the expanded scope does not change anything for the existing certification. The revised criteria open up the opportunity to apply for the Blue Angel label for mobile software, such as KDE Connect, and mixed scenarios which also include server components, but the eco-certification for Okular is covered as it was before.

The more flexible measurement criteria give us more leeway in how we are doing the measurements. We have set up KEcoLab for being able to regularly do measurements. This setup follows the procedure prescribed in the original criteria. As this is still valid, it also means no change for us, and our measurements still fulfill the criteria. However, it gives us more opportunities to improve the lab and doesn't strictly tie us to the original list of reference systems anymore. We might want to take advantage of that.

The documentation of the measurement system is something we have always done in a transparent way, so this also doesn't require any big changes on our side. We have to consider how to best convey this in the documentation of Okular, but this is mostly a question on how we communicate the existing content.

The ongoing assessment of energy and resource efficiency ties very well into how we handle software updates. We have a continuous release stream with frequent updates and incremental changes. This fits the model of the new criteria. We have to review how we include regular updates of the documentation and measurement data in releases, but this again is mostly a question of how we communicate the existing content.

Conclusion

The revised criteria provide a welcome expansion of the Blue Angel to more categories of software and a more flexible way to do energy and resource efficiency measurements. They continue to align well with how KDE develops software in general and Okular in particular, so we do not see any issues with continuing the Blue Angel certification for Okular.

We would be happy if the new version of the criteria would increase adoption of the Blue Angel ecolabel for resource and energy efficient software. Sustainable software is an important topic and the Blue Angel can be one way of making progress in this area more visible to a broad audience.

I finally took an evening to get NextCloudPi installed on a Raspberry Pi 5 with a large-ish NVMe drive. This was not a smooth ride. For your pleasure, this is how I got it working.

First, use Jeff Geerling’s guide to get the Pi booting from the NVMe drive.

Second, use this guide to move from Debian networking to systemd-networkd, but do not hold the avahi-daemon package.

Third, run the NextCloudPi curl install script.

Next up – the migration from my old instance. I have 1.5TB of files on a spin disk connected via USB that I need to move to the new NVMe storage – but that is for another night.

For the record – I do love NextCloud and NextCloudPi, so no finger pointing here, just sharing some frustration and how I got around the issue.

This week was all about the quality of life features! As we close in on Plasma 6.2 (the soft feature freeze is in four days, eek!), some great work that’s been in progress for a long time got merged.

Notable New Features

Okular now has a “speak text from current page” feature (Athul Raj Kollareth, Okular 24.12.0. Link)

Plasma’s Brightness widget now shows individual brightness sliders for every connected monitor that supports this, so you can control them separately! If you want to adjust all of them together, you can still do that via global shortcut/keyboard key or by scrolling over the widget (Jakob Petsovits, Plasma 6.2.0. Link):

When there’s a pending offline system update, you’ve already got the option to update and then reboot, or just reboot and skip the update. Now, there’s also an option to complete the update and then shut down the computer! This option is exposed both on the logout screen, and also in Discover (Thomas Duckworth, Plasma 6.2.0. Link 1, link 2, and link 3):

Long-pressing an empty area of a Plasma panel using a touchscreen now enters edit mode for that panel (Niccolò Venerandi, Plasma 6.2.0. Link)

Notable UI Improvements

The “Add Widgets” sidebar has received a UX overhaul with numerous usability focused changes, including:

• Appearing on the right side of the screen when opened from a right-screen-edge panel
• Using wider grid cells to permit longer text without elision or unnatural word-wrap behaviors
• Improved appearance of the filter button, so now it looks like it opens a drop-down menu — because it does
• Sorting is now locale-aware, taking into account, for example, accented characters
• You access it from buttons and menu items labeled “Add or Manage Widgets,” since it also acts as the place where you get new widgets or delete unwanted ones
• Spacer widgets can also be found there, no longer only from the panel settings dialog
• When installing manually-downloaded widgets, the open dialog now accept all valid file types

And believe it or not, that’s not all that’s planned! But the rest will have to wait until next week… (Niccolò Venerandi, Plasma 6.2.0. Link 1, link 2 3, link 4, link 5, link 6, link 7)

When your system is using a non-default power profile, it’s now shown as a badge on the battery icon, so you can see both the power profile and also the battery status at the same time (Louis Moureaux and me: Nate Graham, Plasma 6.2.0. Link 1 and link 2):

At the moment this only works with the Breeze icon theme, and 3rd-party icon themes will have to add some more icons to opt into it. Until then, users of those icon themes will get the old appearance when using a non-default power profile

A panel popup opened from a widget on the end of a limited-width panel now tries its best to align its edge with that of the panel (Niccolò Venerandi, Plasma 6.2.0. Link):

Maybe I just really like clocks, ok?

You can now give a custom display name to your custom command shortcuts (Yifan Zhu and Thenujan Sandramohan, Plasma 6.2.0. Link):

Discover is now more accurate about how it presents licenses, and communicates the subtle distinctions between “proprietary” and “non-free”, rather than branding everything that isn’t free software as proprietary (me: Nate Graham, Plasma 6.2.0. Link):

When you change keyboard layouts, the labels of the language codes that appear in the system tray no longer subtly change in size based on the shape of their letters (Sauf Lvc, Plasma 6.2.0. Link)

Added a Breeze icon for Applet Wallet bundle files (Kai Uwe Broulik, Frameworks 6.6. Link):

Notable Bug Fixes

When Spectacle is configured to save in a format other than PNG by default, pasting a just-copied screenshot now always works in every target app, with the caveat that some apps that don’t advertise support for non-PNG image pasting (like Firefox and Chromium, annoyingly) will get a PNG version anyway, rather than your preferred file format. This is better than it not working at all, at least! (Noah Davis, Spectacle 24.08.1. Link)

You can once again use the arrow keys to move focus out of Kickoff’s favorites grid view (Arjen Hiemstra, Plasma 6.1.5. Link)

Fixed a complex bug that could cause KWin to crash when X11 or XWayland-using apps monkeyed with the window stacking order in specific ways (Vlad Zahorodnii, Plasma 6.1.5. Link. And thanks to the reporter Peter Strick for being incredibly helpful in making the issue reproducible! All bug reports should be so good.)

Fixed an annoying bug that caused text copied from cells in LibreOffice Calc to never make it onto the clipboard unless you changed the clipboard’s settings to always store images (Fushan Wen, Plasma 6.1.5. Link)

Fixed a bug that caused tooltips to appear at the last location the mouse pointer was located at when interacting with the system using a stylus (David Redondo, Plasma 6.1.5. Link)

Fixed a funny bug that could make Plasma crash when you have a Media Player widget on your panel (not the System Tray, directly on a panel) and play certain specific songs whose titles are exactly the right length to trigger an obscure layout bug (Fushan Wen, Plasma 6.2.0. Link)

Fixed a weird issue that made modifier-only global shortcuts in the X11 session fail to switch keyboard layouts as expected while on the lock screen and other places (Yifan Zhu, Plasma 6.2.0. Link)

Exporting your shortcuts on System Settings’ Shortcuts page now includes any custom script shortcuts you’ve created, so that when you import them elsewhere, they work (Akseli Lahtinen and David Redondo, Plasma 6.2.0. Link)

Other bug information of note:

• 2 Very high priority Plasma bugs (down from 3 as last week). Current list of bugs
• 36 15-minute Plasma bugs (up from 30 last week; bug triage activities discovered some more old issues that seemed important to fix soon, which were added to the list). Current list of bugs
• 156 KDE bugs of all kinds fixed over the last week. Full list of bugs

Notable in Performance & Technical

Improved KWin’s HDR tone mapping, allowing it to do a better job of displaying colors in cases where HDR content specifies a brightness level higher than what the screen is capable of outputting. There’s even more that can be done, but it’s already a big improvement. (Xaver Hugl, Plasma 6.2.0. Link)

Even further optimized the system performance impact in KWin of using an ICC profile to change your screen’s color calibration (Xaver Hugl, Plasma 6.2.0. Link)

Improved KWin’s performance for some multi-GPU systems (Xaver Hugl, Plasma 6.2.0. Link)

Added a bunch of autotests for X11-specific behavior in KWin, since fewer people are exercising that code now that 80+% of Plasma 6 users are using Wayland (Vlad Zahorodnii, Plasma 6.2.0. Link)

…And Everything Else

This blog only covers the tip of the iceberg! If you’re hungry for more, check out https://planet.kde.org, where you can find more news from other KDE contributors.

How You Can Help

Otherwise, visit https://community.kde.org/Get_Involved to discover other ways to be part of a project that really matters. Each contributor makes a huge difference in KDE; you are not a number or a cog in a machine! You don’t have to already be a programmer, either. I wasn’t when I got started. Try it, you’ll like it! We don’t bite! Or consider donating instead! That helps too.

Let’s go for my web review for the week 2024-34.

Unbundling Profile: MIT Libraries - SPARC

Tags: research, copyright, open-access

It’s good to see major institutions like this get out of contracts with scientific publishing companies. Those unfortunately became mostly parasitic. Open access should be the norm for research.

https://sparcopen.org/our-work/big-deal-knowledge-base/unbundling-profiles/mit-libraries/

Make Firefox Private Again

Tags: tech, mozilla, privacy

Since they unfortunately turned on private attribution by default (why? Mozilla, why?). Here is an easy automated way to turn it off.

https://make-firefox-private-again.com/

Being on The Semantic Web is easy, and, frankly, well worth the bother

Tags: tech, web, semantic

With all those bots and scripts crawling the Web, some of the semantic web vision got silently implemented.

https://csvbase.com/blog/13

Markov chains are funnier than LLMs

Tags: tech, ai, machine-learning, gpt, markov-chains, funny

Interesting musing. The predictability in tone doesn’t make for very funny content indeed. Also as a side-effect this might help people remember that Markov chain are a thing and much less expensive.

https://emnudge.dev/blog/markov-chains-are-funny/

ugh. I picked up a shitty NUC from ewaste…

Tags: tech, security

Scary thread… developers should know better than do this and ship it on devices around the world. Their data is now anyone for the taking and users’ privacy can’t be ensured.

https://digipres.club/@foone/112990331505043510

NetAlert X

Tags: tech, networking, security, tools

Looks like a nice tool to monitor your network.

https://netalertx.com/

Free, OpenSource IPv6 Textbook

Tags: tech, book, ip, networking

Looks like an interesting resource to learn about IPv6.

https://ipv6textbook.com/

Andries Brouwer on the OOM killer

Tags: tech, linux, kernel, memory

Funny musing about the OOM killer. With nice pointers if you want to dive further into the topic.

https://quuxplusone.github.io/blog/2024/08/22/overcommit/

The Closed-Loop Benchmark Trap

Tags: tech, benchmarking

Be sure to pick the right behavior model when you make a benchmark. Otherwise you might just measure the wrong thing.

https://buttondown.com/jaffray/archive/the-closed-loop-benchmark-trap/

What is std::ref?

Tags: tech, c++

A little refresher about std::ref and std::cref. They come in handy sometimes, but also if you don’t realize you need them you’ll generate more copies than necessary.

https://www.sandordargo.com/blog/2024/08/21/std-ref

SIMD Matters :: Box2D

Tags: tech, cpu, simd, performance, physics, simulation

SIMD is hard to use, not all problems can apply to it. But when they can, the performance gain can be great.

https://box2d.org/posts/2024/08/simd-matters/

uv: Unified Python packaging

Tags: tech, python, tools

Looks like there’s another contender for package management for Python. This is sooo fragmented now… this one is compelling though.

https://astral.sh/blog/uv-unified-python-packaging

Common Causes of Memory Leaks in JavaScript

Tags: tech, javascript, memory, leak

There are many ways to create a memory leak in Javascript. Here is a good list of the things to pay attention to.

https://www.trevorlasn.com/blog/common-causes-of-memory-leaks-in-javascript

Toasts are Bad UX – Max Schmitt

Tags: tech, web, frontend, ux

It’s better than no feedback. It’s a bit lazy and far from perfect though.

https://maxschmitt.me/posts/toasts-bad-ux

Reckoning

Tags: tech, web, frontend, ux, criticism

Interesting series about the rise of the javascript frontend framework, the bad practices which came with them and the very real impacts on the users. There are indeed better ways.

https://infrequently.org/series/reckoning/

Don’t Repeat Yourself and the Strong Law of Small Numbers - iRi

Tags: tech, design, programming

This is a good point. The DRY principle has value but the trick is finding the right time to apply it.

https://jerf.org/iri/post/2024/dry_strong/

Code review antipatterns

Tags: tech, codereview

Starts like a satire, but there’s a serious conclusion in the end. Indeed, mind the power dynamics in code reviews. Be nice, steer away from those antipatterns, especially since you might be on the receiving end the next time.

https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/code-review-antipatterns/

Interview with Ron Jeffries

Tags: tech, agile, history, criticism

Very nice interview. This is an interesting reflection on the past 20+ years of Agile Software Development.

https://ronjeffries.com/articles/-x024/-v04/8/

Decision Logs

Tags: tech, product-management

Nice way to keep in check how and why behavior changes as the requests from various stakeholders come in.

https://buttondown.com/j2kun/archive/decision-logs/

Bug squash: An underrated interview question

Tags: tech, hr, interviews, debugging

This is indeed a nice way to approach technical interviews. Unfortunately it requires quite some effort to setup and maintain. You also have to find the right bugs to put in the interview and this is a rarity.

https://blog.jez.io/bugsquash/

Bye for now!

Since Plasma 5.18, nearly five years ago, Plasma has shipped with a "telemetry" system. It’s opt-in, allowing users to send a small amount of data back to us.

Was it useful or worth it? It's a question that comes up occasionally, and the answer is mixed. I believe it showed real potential, though the reality of our implementation was somewhat underwhelming and didn't really deliver. There are many lessons learned that are worth sharing with other projects that might face similar endeavours.

The good bits

Where we had data available for topics being discussed it worked. To give two concrete examples from memory:

• A developer claimed, "No one is using a screen smaller than 1024x768," while bumping the minimum size of a window. This was proved wrong; the number of users at 800x600 or even 640x480 is surprisingly high. Still low as an overall percentage, but higher than you would ever intuitively think. Presumably, it's the default for a lot of virtual machines.

• Four years ago, a developer claimed, "No one still uses only OpenGL2; we can change the code to do XYZ." A check of our user base showed it would have affected nearly 5% of our users, so the change was abandoned.

Interestingly, this last topic came up again very recently, as it held back colour management improvements, but in a narrower Wayland-only path and with a fallback. After checking metrics again, the usage was below 1%, so we went ahead with that merge request.

So, are metrics worth it just to stop developers and designers from making nonsense claims out of thin air? Absolutely! 90% of stats are just made up on the spot. Metrics are just as much about preventing changes as it is about sparking changes.

Indirect impact

The other important part is having a more general sense of the landscape. Currently, we have a lot of hard conversations about how quickly we push the move to Wayland. We have voices wanting to maintain support, and we have voices wanting to push quicker. These decisions shouldn't be made just by who can be the loudest. For every individual topic that came up in those discussions, I would always have in mind our current adoption value at the time.

Should we care about Nvidia? Knowing they make up about 25% of our user base makes the decision for us. I ran with an Nvidia card in one machine because of this, implementing Nvidia context loss handling and doing what we could during the Wayland transition
We don't test BSD while developing Plasma, but we also let it hold us back. Should we care about it more or less? My opinion matches exactly what the metrics say.

Some stats and graphs:

Another role of metrics is being a conversation starter—people will fawn over a graph. More topics on Reddit will be about our Wayland usage rather than the topic I'm trying to discuss. I'll focus on Wayland examples beacuse that's a topic close to me.

Wayland adoption over time

I keep tabs on what our metrics show here. We can see the slow increase from under 20% to around 45% over time, showing the progress as both we and the Wayland ecosystem evolved. At Plasma 6, we switched the defaults a small bump in the graph can be seen. but 45% still seemed rather disappointing.

Filtering on just Plasma 6 reveals the true story:

There's still 20% of users switching away, or using a distro with a different default, or having carried over presets, but it's more promising. Interestingly, we can see that the GPU vendor distribution differs between X11 and Wayland.

Problems and lessons learned

Ultimately, despite the positive parts it would be hard to call our telemetry a staggering success. For the handful of examples above, there are a hundreds of cases where we had no data to back anything up. The range of data points was pitiful and it wasn't often used

The viewing tool is really, really important!

Data collection without viewing it is meaningless. As shown above, we often need to drill down and cross-reference filters to extract conclusions.

The original plan was to use the existing UI provided by kuserfeedback, which did not scale at all and quickly fell over. It was designed for high-fidelity data for a small number of users, not what we had.

In a rush, we pivoted to using Grafana because there was already a setup hosted.

It worked—ish, but it’s not designed for this, especially combined with our data structure, which was a manual NoSQL in normal SQL. Every graph needed to be written by hand, and it felt very much like fighting the system rather than working with it. Combined with the limited access permissions granted, it wasn't used by many people.

It being used is the number one indicator of its usefulness!

We need to find a tool specifically designed for visualization and querying datasets (maybe Apache Superset?).

Time-based data just makes noise

Our system sent updates every N days with basically the same data every time. This made writing queries way messier than it should have been. It never added any value; I would always be interested in what the current stats are. As described in the Wayland usage graphs above, if I'm making a Wayland decision, it doesn't matter what most people are using; it matters what people on the latest release are using. We always ended up having to add filters to focus on just the latest version.

The upgrade story needs planning in advance

The amount of data we collected was tiny—some GPU information, screen information, language, and a few other fragments. The plan was to slowly add more and more stats over time, but we hit a wall. Our UX involved the user selecting to enable metrics and it being a fire-and-forget operation.

What do we do when we want to add more data? For example, whether you use an analog or digital clock. We would need to prompt the user and reset their settings in the meantime, which is at odds with it being a setting. The whole thing became such an ordeal that made it not worthwhile.

Wrap up

The project didn't fail, when we had data and it was used it worked, but overall our implementation falls short. I would like to open a discussion at Akademy on how we move forward with our current system potentially starting from scratch treating it more like a survey that we prompt to auto populate and submit each year.

The End Product

Throughout this summer, I’ve developed a C++ library called MankalaEngine, implementing three opponents for the games of Bohnenspiel and Oware.

The current library is highly extensible. After implementing all the base classes and Bohnenspiel, adding Oware to the library was fairly fast and straightforward. This focus on extensibility has been a priority since the beginning of the project. Given that the Mancala family of games comprises numerous variants, designing the API with this in mind has proven valuable.

The three provided opponents use a random selection algorithm, Minimax, and MTD-f. The Minimax and MTD-f opponents were implemented with optimizations like alpha-beta pruning and transposition tables, making them both very capable, consistently outperforming the random opponent.

For a more detailed overview of what was accomplished, I wrote a work report on KDE’s wiki.

What I’ve learned

The last few months have been a very enriching experience from a technical standpoint.

Contributing to a “real-world” project allowed me to learn about technologies I hadn’t used before. For example, I learned how to use CMake and how to set up a CI pipeline.

I also faced concerns that don’t typically arise when developing a school or personal project, such as adhering to an organization’s software standards. To this end, I learned about open-source licenses and new programming idioms.

Interacting With The Community

Since MankalaEngine is a completely new library, my interaction with the community was limited, as there isn’t an existing group of contributors for this particular project.

I mainly interacted with my mentors, who were very helpful. Although less frequently, I also had the opportunity to communicate with other KDE contributors through mailing lists, from whom I also learned a great deal.

Hello everyone! Time flies and now we’re already in the final week of GSoC. In this blog post I’ll be sharing the progress I’ve made since my last update, focusing primarily on subtitle styling.

Subtitle Editor

The first thing I did was to enhance the existing subtitle editor. The updated editor now serves as an interface for editing ASS events, which include various components. With the new subtitle editor, we can easily modify elements such as the event’s layer, style, margins, and more. I’ve also simplified the effects section, allowing us to control subtitle scrolling by simply adjusting checkboxes and combo boxes for speed, direction, and range.

However, the most significant change is the text field and the buttons above it. To better understand these changes, it’s important to first introduce the relationship between ASS styles and events. In ASS files, each event must be assigned a valid style that applies to the entire event text. Additionally, ASS override tags are special text blocks within events that allow precise control over the styles of different parts of the text, rather than the entire text. (There are some exceptions, like “Set Position.”)

The text field has been enhanced to assist users in inputting ASS override tags using the provided buttons. For instance, when a user clicks the “Toggle Bold” button, tags are automatically inserted or adjusted to toggle the bold style for either the selected text or the text following the cursor if nothing is selected. Additionally, the text field features a highlighter that renders different parts of the tags in distinct styles, making them more distinguishable, and an auto-completer that lists all valid presets as we start typing a tag name.

For those who prefer the previous subtitle editor, which only displays the rendered text, a “Simple Editor” is also available. This editor syncs with the normal editor but displays only the text without tags while rendering some basic tag effects. However, due to the complexities of ASS tag rules, style editing in the Simple Editor can sometimes behave unpredictably. So it’s best suited for simpler use cases before or after editing styles.

Subtitle Manager

Continuing from the previous improvements, the Subtitle Manager is now integrated with style management and has been divided into four sections: File, Event, Style, and Info, which correspond to the four main components of ASS subtitles. Each section, except for the File section, includes a sidebar for switching between different subtitle files. Additionally, when in the Style section, we can drag and drop a style item onto a subtitle file name in the sidebar to efficiently move or copy styles between files. The same functionality is available in the Event section, where we can move or copy an entire layer to another file.

Misc Style Editor

A new widget, the Style Editor, was created to edit styles and provide a preview.

Convert Old Global Style

Old styles will now be automatically converted to the “Default” style in the new project. Font size, outline, and shadow will be scaled to maintain the original effects.

Different Default Styles for Layers

Now, we can assign different default styles to each layer, which will automatically be applied to a subtitle event when it’s created on the corresponding layer. This feature is especially useful for quickly building a subtitle file with multiple speakers, allowing each speaker to have a distinct style.

Summary

It has been a wonderful summer getting involved in the KDE community and contributing to Kdenlive! I may not be the best at coding, but I’ve learned a lot throughout this journey. Thanks for everyone who has gave me guidence — Eugen Mohr, Farid Abdelnour, and especially my mentor, Jean-Baptiste Mardelle. While GSoC is coming to an end, my journey with KDE is just beginning. After these updates, I plan to continue improving subtitle functions, including making it easier for users to input more ASS override tags and refining the UI and user experience. See you in my next blog :)

Motivation

When using Qt Multimedia to play audio files, it’s common to use QMediaPlayer, as it supports a larger variety of formats than QSound and QSoundEffect. Consider a Qt application with several audio sources; for example, different notification sounds that may play simultaneously. We want to avoid cutting notification sounds off when a new one is triggered, and we don’t want to construct a queue for notification sounds, as sounds will play at the incorrect time. We instead want these sounds to overlap and play simultaneously.

Ideally, an application with audio has one output stream to the system mixer. This way in the mixer control, different applications can be set to different volume levels. However, a QMediaPlayer instance can only play one audio source at a time, so each notification would have to construct a new QMediaPlayer. Each player in turn opens its own stream to the system.

The result is a huge number of streams to the system mixer being opened and closed all the time, as well as QMediaPlayers constantly being constructed and destructed.

To resolve this, the application needs a mixer of its own. It will open a single stream to the system and combine all the audio into the one stream.

Before we can implement this, we first need to understand how PCM audio works.

PCM

As defined by Wikipedia:

Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps.

Here you can see how points are sampled in uniform intervals and quantized to the closest number that can be represented.

Image Source: Wikipedia

Description from Wikipedia: Sampling and quantization of a signal (red) for 4-bit LPCM over a time domain at specific frequency.

Think of a PCM stream as a humongous array of bytes. More specifically, it’s an array of samples, which are either integer or float values and a certain number of bytes in size. The samples are these discrete amplitude values from a waveform, organized contiguously. Think of the each element as being a y-value of a point along the wave, with the index representing an offset from x=0 at a uniform time interval.

Here is a graph of discretely sampled points along a sinusoidal waveform similar to the one above:

Image Source: Wikimedia Commons

Description from Wikimedia Commons: Image of a discrete time sinusoid

Let’s say we have an audio waveform that is a simple sine wave, like the above examples. Each point taken at discrete intervals along the curve here is a sample, and together they approximate a continuous waveform. The distance between the samples along the x-axis is a time delta; this is the sample period. The sample rate is the inverse of this, the number of samples that are played in one second. The typical standard sample rate for audio on CDs is 44100 Hz – we can’t really hear that this data is discrete (plus, the resultant sound wave from air movement is in fact a continuous waveform).

We also have to consider the y-axis here, which represents the amplitude of the waveform at each sampled point. In the image above, amplitude A is normalized such that A\in[−1,1]. In digital audio, there are a few different ways to represent amplitude. We can’t represent all real numbers on a computer, so the representation of the range of values varies in precision.

For example, let’s say we have two different representations of the wave above: 8-bit signed integer and 16-bit signed integer. The normalized value 1 from the image above maps to (2^{8}\div{2})−1=127 with 8-bit representation and (2^{16}\div2)−1=32767 with 16-bit. Therefore, with 16-bit representation, we have 128 times as many possible values to represent the same range; it is more precise, but the required size to store each 16-bit sample is double that of 8-bit samples.

We call the chosen representation, and thus the size of each sample, the bitdepth. Some common bitdepths are 16-bit int, 24-bit int, and 32-bit float, but there are many others in existence.

Let’s consider a huge stream of 16-bit samples and a sample rate of 44100 Hz. We write samples to the audio device periodically with a fixed-size buffer; let’s say it is 4096 bytes. The device will play each sample in the buffer at the aforementioned rate. Since each sample is a contiguous 2-byte short, we can fit 2048 samples into the buffer at once. We need to write 44100 samples in one second, so the whole buffer will be written around 21.5 times per second.

What if we have two different waveforms though, and what if one starts halfway through the other one? How do we mix them so that this buffer contains the data from both sources?

Waveform Superimposition

In the study of waves, you can superimpose two waves by adding them together. Let’s say we have two different discrete wave approximations, each represented by 20 signed 8-bit integer values. To superimpose them, for each index, add the values at that index. Some of these sums will exceed the limits of 8-bit representation, so we clamp them at the end to avoid signed integer overflow. This is known as hard clipping and is the phenomenon responsible for digital overdrive distortion.

x Wave 1 (y_1) Wave 2 (y_2) Sum (y_1+y_2) Clamped Sum 0 +60 −100 −40 −40 1 −120 +80 −40 −40 2 +40 +70 +110 +110 3 −110 −100 −210 −128 4 +50 −110 −60 −60 5 −100 +60 −40 −40 6 +70 +50 +120 +120 7 −120 −120 −240 −128 8 +80 −100 −20 −20 9 −80 +40 −40 −40 10 +90 +80 +170 +127 11 −100 −90 −190 −128 12 +60 −120 −60 −60 13 −120 +70 −50 −50 14 +80 −120 −40 −40 15 −110 +80 −30 −30 16 +90 −100 −10 −10 17 −110 +90 −20 −20 18 +100 −110 −10 −10 19 −120 −120 −240 −128

Now let’s implement this in C++. We’ll start small, and just combine two samples.

Note: we will use qint types here, but qint16 will be the same as int16_t and short on most systems, and similarly qint32 will correspond to int32_t and int.

qint16 combineSamples(qint32 samp1, qint32 samp2) { const auto sum = samp1 + samp2; if (std::numeric_limits<qint16>::max() < sum) return std::numeric_limits<qint16>::max(); if (std::numeric_limits<qint16>::min() > sum) return std::numeric_limits<qint16>::min(); return sum; }

This is quite a simple implementation. We use a function combineSamples and pass in two 16-bit values, but they will be converted to 32-bit as arguments and summed. This sum is clamped to the limits of 16-bit integer representation using std::numeric_limits in the <limits> header of the standard library. We then return the sum, at which point it is re-converted to a 16-bit value.

Combining Samples for an Arbitrary Number of Audio Streams

Now consider an arbitrary number of audio streams n. For each sample position, we must sum the samples of all n streams.

Let’s assume we have some sort of audio stream type (we’ll implement it later), and a list called mStreams containing pointers to instances of this stream type. We need to implement a function that loops through mStreams and makes calls to our combineSamples function, accumulating a sum into a new buffer.

Assume each stream in mStreams has a member function read(char *, qint64). We can copy one sample into a char * by passing it to read, along with a qint64 representing the size of a sample (bitdepth). Remember that our bitdepth is 16-bit integer, so this size is just sizeof(qint16).

Using read on all the streams in mStreams and calling combineSamples to accumulate a sum might look something like this:

qint16 accumulatedSum = 0; for (auto *stream : mStreams) { // call stream->read(char *, qint64) // to read a sample from the stream into streamSample qint16 streamSample; stream->read(reinterpret_cast<char *>(&streamSample), sizeof(qint16))); // accumulate accumulatedSum = combineSamples(sample, accumulatedSum); }

The first pass will add samples from the first stream to zero, effectively copying it to accumulatedSum. When we move to another stream, the samples from the second stream will be added to those copied values from the first stream. This continues, so the call to combineSamples for a third stream would combine the third stream’s sample with the sum of the first two. We continue to add directly into the buffer until we have combined all the streams.

Combining All Samples for a Buffer

Now let’s use this concept to add all the samples for a buffer. We’ll make a function that takes a buffer char *data and its size qint64 maxSize. We’ll write our accumulated samples into this buffer, reading all samples from the streams and adding them using the method above.

The function signature looks like this:

void readData(char *data, qint64 maxSize);

Let’s achieve more efficiency by using a constexpr variable for the bitdepth:

constexpr qint16 bitDepth = sizeof(qint16);

There’s no reason to call sizeof multiple times, especially considering sizeof(qint16) can be evaluated as a literal at compile-time.

With the size of each sample and the size of the buffer, we can get the total number of samples to write:

const qint16 numSamples = maxSize / bitDepth;

For each stream in mStreams we need to read each sample up to numSamples. As the sample index increments, a pointer to the buffer data needs to also be incremented, so we can write our results at the correct location in the buffer.

That looks like this:

void readData(char *data, qint64 maxSize) { // start with 0 in the buffer memset(data, 0, maxSize); constexpr qint16 bitDepth = sizeof(qint16); const qint16 numSamples = maxSize / bitDepth; for (auto *stream : mStreams) { // this pointer will be incremented across the buffer auto *cursor = reinterpret_cast<qint16 *>(data); qint16 sample; for (int i = 0; i < numSamples; ++i, ++cursor) if (stream->read(reinterpret_cast<char *>(&sample), bitDepth)) *cursor = combineSamples(sample, *cursor); } }

The idea here is that we can start playing new audio sources by adding new streams to mStreams. If we add a second stream halfway through a first stream playing, the next buffer for the first stream will be combined with the first buffer of this new stream. When we’re done playing a stream, we just drop it from the list.

 

Next Steps

In Part 2, we’ll use Qt Multimedia to fully implement our mixer, connect to our audio device, and test it on some audio files.

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A script element has been removed to ensure Planet works properly. Please find it in the original post. Manage

Many of the new features in Dolphin are designed to make it easier to access and manage files and folders that require administrative privileges. Visual cues, wizards to help install needed software, and menu options to elevate your privileges make it easier than ever to use Dolphin as a superuser.

New usability features include:

• A new "Move to New Folder…" option that pops up when right-clicking a file, allowing you to create a folder and copy the file into it all in one go.
• Double-clicking the view background that triggers the "Select All" action by default.

Filelight is a complementary application to Dolphin, and can be installed directly from Dolphin by clicking the down arrow in the lower right corner of the main window.

Filelight helps visualize how much space your files and folders are taking up. Version 24.08 comes with a friendlier home page, and the Windows version (available from the Microsoft Store) has been redesigned to improve its overall appearance.

Konsole 24.08 also comes with a brand new usability enhancement: if you need to bookmark something important in a long output, double-click the scroll bar to set a position marker. You can then quickly scroll back and locate it later.

Create

Kdenlive is KDE's professional video editor, and this new release is all about the curves.

You can now use the brand new keyframe curve editor to customize effects, and easing methods (Cubic in/out and Exponential in/out) for fades.

To make things easier, we've redesigned the effects stack widget and improved the Transform effect, which now lets you select clips directly from the monitor. It also comes with a new grid, and improved design and behavior for the handle.

Travel

Coming to Akademy 2024? Don't forget to install the updates for Itinerary and Kongress and make your journey easy.

Itinerary is KDE's travel assistant. It lets you plan and manage your trips, providing an overview of where you need to be and when. It keeps boarding passes, tickets, and health certificates all in one place, and the latest version adds more details, including seat information displayed directly in the timeline.

Once you arrive at your destination, it's time to fire up Kongress so you don't miss any of the sessions or activities. Kongress now makes things easier by providing indoor maps of the venue, so you not only know when and what's going on, but also where.

Both Itinerary and Kongress work on desktop and laptop computers and most mobile devices.

Communicate

NeoChat is KDE's client for the Matrix chat system — and KDE's official way of chatting. Version 24.08 increases your safety by allowing you to preemptively block invites from unknown users not in any rooms with you.

Tokodon not only helps you read and post on Mastodon, but also manage your own server. Speaking of which, the version being released today can notify you of sign-ups on your server for better user management.

For posting, you can easily attach images from the internet, quote other posts and pop out the text editor to comfortably compose your toot.

When reading, Tokodon 24.08 supports scrolling up whole screenfuls of posts using the PageUp and PageDown keys.

Develop

Whether you want to help KDE implement features and fix bugs, or develop the next killer app, KDE's advanced text editor Kate has you covered.

Kate 24.08 improves its document formatting plugin with better support for bash, d, fish, Nix config, opsi-script, QML and YAML files. In related news, the Language Server Protocol (LSP) feature adds support for the Gleam, PureScript, and Typst languages.

If you're working on a CMake-based project, the Project and Build plugin now allows you to open the build directory and get both files and targets.

Surf

Falkon is KDE's full-featured web browser. The new release implements many bug fixes and optimizations that make surfing the web with Falkon smoother, easier and safer.

A new feature in 24.08 allows you to customize things that affect privacy and functionality on a site-by-site basis. Say you don't mind JavaScript on one site because the authors are trustworthy and it actually provides useful functionality, but you want to block it elsewhere for security reasons. You can now configure this in Falkon's Settings.

And all this too…

• Okular — KDE's eco-certified document reader — improves compatibility for fillable forms in PDF documents, gets a makeover for Windows, and adds a more usable zoom feature.
• PlasmaTube — a player for watching online videos from popular sites on your desktop — adds an option to block sponsored sections in videos.
• Elisa — our elegant music player — gets a "Play this next" feature, and allows resizing of the sidebar and playlist panes.

Full changelog here Where to get KDE Apps

Although we fully support distributions that ship our software, KDE Gear 24.08 apps will also be available on these Linux app stores shortly:

Flathub Snapcraft

If you'd like to help us get more KDE applications into the app stores, support more app stores and get the apps better integrated into our development process, come say hi in our All About the Apps chat room.

A while ago a colleague of mine asked about our crash infrastructure in Plasma and whether I could give some overview on it. This seems very useful to others as well, I thought. Here I am, telling you all about it!

Our crash infrastructure is comprised of a number of different components.

• KCrash: a KDE Framework performing crash interception and prepartion for handover to…
• coredumpd: a systemd component performing process core collection and handover to…
• DrKonqi: a GUI for crashes sending data to…
• Sentry: a web service and UI for tracing and presenting crashes for developers

We will look at them in turn. This post introduces KCrash.

KCrash

KCrash, as the name suggests, is our KDE framework for crash handling. While it is a mid-tier framework and could be used by outside projects, it mostly doesn’t make sense to, because some behavior is very KDE-specific.

It installs POSIX signal handlers to intercept crash signals and then prepares the crashed process for handover to coredumpd and DrKonqi. More on these two in another post. Once prepared it sends the crash signal into the next higher level crash handler until the signal eventually reaches the default handler and cause the kernel to invoke the core pattern.

Before that can happen, a bunch of work needs doing inside KCrash. Most of it quite boring, but also somewhat challenging.

You see, when handling a signal you need to only use signal-safe functions. The manpage explains very well why. This proves quite challenging at the level we usually are at (i.e. Qt) because it is entirely unclear what is and isn’t ultimately signal-safe under the hood. Additionally, since we are dealing with crash scenarios, we must not trigger new memory allocation, because the heap management may have had an accident.

To that end, KCrash has to use fairy low-level API. To make that easier to work with, there are actually two parts to KCrash:

• The Initialization Stage
• The Crash Stage

The Initialization Stage

Initialization is generally triggered by calling KCrash::initialize. You may already wonder what kind of initialization KCrash could possibly need. Well, the obvious one is setting up the signal handling. But beyond that the init stage is also used to prepare us for the crash stage. I’ve already mentioned the serious constraints we will encounter once the signal hits, so we had best be prepared for that. In particular we’ll do as much of the work as possible during initialization. This most important includes copying QString content into pre-allocated char * instances such that we later only need to read existing memory. The second most important aspect is the metadata file preparation for use in…

The Crash Stage

Once initialization has happened, we are ready for crashes. Ideally the application doesn’t crash, of course. 😉

But if it does the biggest task is rescuing our data!

Metadata

Inside KCrash we have the concept of Metadata: everything we know about the crashed application: the signal, process ID, executable, used graphics device… and so on and so forth. All this data is collected into a metadata file on-disk in ~/.cache/kcrash-metadata at the time of crash.

Here’s an example file:

[KCrash] exe=/usr/bin/kwin_wayland glrenderer= platform=wayland appname=kwin_wayland apppath=/usr/bin signal=11 pid=1353 appversion=6.1.80 programname=KWin bugaddress=submit@bugs.kde.org

The actual fields vary depending on what is available for any given application, but it’s generally more or less what is shown in the example.

This metadata file will later be consumed by DrKonqi in an effort to obtain information that only existed at runtime inside the application - such as the version that was running, or whether it was running in legacy X11 mode.

Handoff

Once the metadata is safely saved to disk, KCrash simply calls raise(). This re-raises the signal into the default handler, and through that causes a core dump.

What happens next is up to the system configuration as per the core manpage.

The recommended setup for distributions is that a crash handler be configured as core_pattern and that this handler consumes the crash. We recommend an implementation of the coredumpd and journald interfaces as that will then allow our crash handler to come in and log the crash with KDE.

So that was KCrash, the first in our four-step crash-handling pipeline. In the next blog post I’ll tell you all about the next one: coredumpd.