The past two months were hectic, and many changes and new features landed just in time for the 3.37.90 release. As the release freezes approached (user interface freeze, API freeze, etc), part of the queue of merge requests needed a final decision on whether or not they were ready for the upcoming GNOME 3.38 release.

These two months were also punctuated by not one, but two conference talks related to Mutter and GNOME Shell.

As this is the final development summary before the 3.38 release, we decided to change the format a bit and cover the biggest changes that happened throughout this cycle.

Split Frame Clock

Back when Clutter was an application toolkit, it only had to deal with a single frame clock. However, now being a compositor toolkit, having a single frame clock became a limiting aspect of Clutter, since each monitor is ticking at potentially different rates and times. In practice, that meant that on multi-monitor scenarios, the monitor with the slowest refresh rate would limit other monitors.

A large surgery on Mutter’s fork of Clutter implemented a new frame clock, and made each ClutterStageView create its own frame clock, and that allowed monitors not to interfere with each other.

You can read more about it in our previous article “Splitting Up The Frame Clock.”

Compositor Bypass

Applications such as games, media players, etc, allow running in fullscreen mode. Ideally, when an application is fullscreen should be able to avoid needlessly compositing the desktop when the only visible thing is the client’s fullscreen window. This is usually called “compositor bypass”, or “fullscreen unredirect”.

During this cycle, Mutter on Wayland supports bypassing the compositor when possible. When bypassing the compositor, the window’s content is put directly on screen, without any unnecessary compositing. The results vary from hardware to hardware, but in principle this should reduce CPU and GPU usage and, consequently, improve performance.

Screencast Improvements

Another bunch of screencast improvements made its way to Mutter. Noticeably, screencasting now works correctly even when an application is bypassing the compositor, in which case Mutter directly copies the contents of the application directly to the screencast stream. Have a look:

In addition to that, window screencasting received a round of bug fixes and improvements.

At last, GNOME Shell’s built-in screen recorder was split into a separate system service, which should make recording your screen using it smoother.

Customizable App Grid

A big change in GNOME Shell will be part of GNOME 3.38, and that’s the ability to customize the app grid. This feature was a long wish, and required a substantial number of under-the-hood improvements, and other changes to support it.

It currently supports creating folders by dragging application icons over each other, moving applications from and to folders, and repositioning applications inside the grid.

Folder dialogs also received small visual improvements to match these new changes.

Despite being a feature in itself, the customizable app grid is a necessary step to unlock future design changes that we’ve been researching and investigating for some time now. Stay tuned as we release more information about it!

Calendar Menu Updates

The calendar menu received a handful of visual improvements as well. Calendar events are now displayed below the actual calendar, and sections as more visually prominent.

There are more improvements for this menu queued up for the next release. Google Summer of Code student Mariana is continuing to work on grouping notifications, and we expect it to be ready for the release after next.

Parental Controls

Various components of the desktop, including GNOME Shell, Settings, and others, now optionally integrate with the parental controls service that is part of GNOME 3.38.

This allows parents, guardians, supervisors, schools, among others, to limit which applications can be accessed by a particular user.

Other Changes

The shutdown menu was split, and “Restart” is now an entry, together “Shutdown”:

The layout algorithm of the app grid was rewritten, and should improve the icon arrangement on various scenarios. The number of rows and columns is now defined based on the aspect ratio of the monitor, and the available space, and the icons themselves grow and shrink accordingly.

The number of icons per page is fixed at 24 icons per page. That’s because changing the number of icons per page would potentially incur losing the customizations made to the app grid.

In addition to that, both Mutter and GNOME Shell received an influx of under-the-hood optimizations and improvements throughout the cycle, ranging from Cogl, the underlying OpenGL layer that Mutter uses internally, to Clutter and it’s layout machinery, to Mutter itself and GNOME Shell. Together, these changes bring polish and robustness, and add up for small but noticeable improvements to the experience of using GNOME on a daily basis.

Conferences

GUADEC

GUADEC is the traditional, yearly GNOME conference. During the 2020 edition of this conference, Mutter & GNOME Shell contributors and maintainers had the chance to present the also traditional “State of the Shell”, where a recap of the past 2 cycles was made:

We appreciate the efforts of the GUADEC volunteers that made this year’s edition possible online.

Linux Plumbers Conference

In the 2020 edition of the Linux Plumbers Conference (LPC), we had the opportunity to be part of the debut of the Applications Ecossystem Micro-Conference, together with the Flatpak and Plasma Mobile projects:

We highly recommend everyone to watch and appreciate all three LPC talks in this video, for they contain lots of valuable and interesting information.

Congratulations for the LPC team for providing such a great online conference.

Epilogue

This release cycle was stuffed with new features, improvements, cleanups, code refactorings, and bug fixes, and we had a great time working on it. It is exciting to see such a large number of changes be part of a release, and we are proud of the advancements that we maintainers, contributors, and independent volunteers managed to achieve.

The results of our focus on GNOME Shell and Mutter have been really pleasing, but not just to us! Here are some folks who have great thoughts about it:

“The GNOME Shell team continues its steady path of technical and user experience improvements – not an easy thing to do in a codebase with diverse uses and a long history, such as GNOME Shell / Mutter. The team also sets an example for very successful cooperation between multiple companies and the community. Well done!”

— Matthias Clasen, GTK maintainer, Red Hat

“It’s incredible how polished and mature GNOME has become. I’ve used it to convert many new users away from Mac and Windows and I’m still looking forward to the future! Thanks GNOME team!”

— James (purpleidea)

As we celebrate the imminent GNOME 3.38 release, we also look forward the release after that, and contemplate the many challenges lie ahead.

Readers be advised, this is somewhat of a deep dive into the guts of Mutter. With that out in the open, lets start!

Not too long ago mutter saw a merge request land, that has one major aim: split up the frame clock so that when using the Wayland session, each monitor is driven by its own frame clock. In effect the goal here is that e.g. a 144 Hz monitor and a 60 Hz monitor being active in the same session will not have to wait for each other to update, and that the space they occupy on the screen will draw at their own pace. A window on the 144 Hz monitor will paint at 144 Hz, and mutter will composite to the monitor at 144 Hz, while a window on the 60 Hz monitor will paint at 60 Hz and Mutter will composite to the monitor at 60 Hz.

All of this is roughly achieved by the changes summarized below.

Preface

In the beginning of times, Clutter was an application toolkit. As such, it assumed (1) the existence of a window compositor, and (2) the compositor is a different process. Back then, Wayland was still in its early infancy, and those assumptions wouldn’t conflict with writing a X11 window manager. After all, a X11 window manager is pretty much just another client application.

Over time, however, Clutter started to grow Wayland integration in itself. Deeper and deeper surgeries were made to it to accomodate it being used by a Wayland compositor.

In 2016, the Cogl and Clutter codebases were merged with Mutter codebase, and they all live in the same repository now. However, to this day, relics from the time when Clutter was an application toolkit are still present in Mutter’s Clutter. One such relic is ClutterMasterClock .

ClutterMasterClock

ClutterMasterClock was the main frame clock that drove Clutter painting. As an application toolkit, only a single, global frame clock was necessary; but as a compositor toolkit, this design doesn’t fit the requirements for multi-monitor setups.

Over the last cycles, there has been some attempts to make it handle multiple monitors slightly better by juggling multiple monitors with their own refresh rates and clocks using various tricks, but the fundamental design was standing in the way for making substantial progress, so it has been completely decommissioned.

Enters ClutterFrameClock.

ClutterFrameClock is the new frame clock object that aims to drive a single “output”. Right now, it has a fixed refresh rate, and a single “frame listener” and “presenter” notifying about frames being presented. It is also possible to have multiple frame clocks running in parallel.

However, ClutterFrameClock alone isn’t enough to achieve independence of monitor redraws.

Stage Views

Mutter has a single stage that covers the union of all monitor rectangles. But how does it render different contents to each one of them?

That’s one of the main responsibilities of ClutterStageView.

ClutterStageView was the answer to the need of drawing the stage at different framebuffers. ClutterStageView corresponds roughly to one monitor. Each ClutterStageView holds the on-screen framebuffer that the monitor displays; if using shadow framebuffers, ClutterStageView also handles them; and finally, it also handles the monitor rotation.

Now, ClutterStageView also handles the monitor’s frame clock. By handling the frame clock, each view is also responsible of notifying about frames being presented, and handling the frame clock dispatching

The frame scheduling related logic (including flip counting, schedule time calculation, etc) was spread out in ClutterMasterClockDefault, ClutterStage, ClutterStageCogl, MetaRendererNative, MetaStageNative, and MetaStageX11, but has now now been concentrated to ClutterFrameClock and ClutterStageView alone.

Actors, Actors Everywhere

When animating interface elements, the core object that does that is ClutterTimeline and its subclass, ClutterTransition .

Timelines and transitions saw frames whenever the master clock ticked. With the master now clock gone, they need to find an appropriate frame clock to drive them. In most (and after this change effectively all) cases a timeline was used to directly drive an animation related to an actor. This indirect relationship is now made explicit, and the timeline uses the actor to find what stage view it is being displayed on, and with that information, picks an appropriate frame clock to attach to.

For transitions, used extensively by GNOME Shell to implement animations, this is handled by making a ClutterAnimatable provide the actor, and for stand-alone timelines, it’s a property set directly on the timeline before it’s started.

This means that when an actor moves across the stage and enters a different stage view, the timeline will be notified about this and will decide whether to migrate to a different frame clock.

What About X11?

In the X11 session, we composite the whole X11 screen at once, without any separation between monitors. This remains unchanged, with the difference being where scheduling takes place (as mentioned in an earlier point). The improvements described here are thus limited to using the Wayland session.

Be aware of API changes

This is quite a substantial change in how painting works in mutter, API changes could not be avoided. With that in mind, the changes needed are small, and mostly handled transparently by GNOME Shell itself. In fact, in all of GNOME Shell’s Javascript code, only two places needed change.

To be specific, for extension developers, there are two things to keep in mind:

• If you use a St.Adjustment. You must now pass an actor when constructing it. This actor will determine what frame clock will drive the adjustment.
• Some signals saw their type signatures change, namely ClutterStage::presented, ClutterStage::after-paint.

Final Thoughts

This is a big achievement to Mutter, GNOME Shell, its users, and especially to the contributors that were part of this. The road to reach this point was long and tortuous, and required coordinated efforts of dozens of contributors over the course of at least 5 years. We’d like to take a moment to appreciate this milestone and congratulate each and every single contributor that was part of this. Thank you so much!

The volunteers and contributors working on Mutter and GNOME Shell have been busy in the past couple of months — so much so that we didn’t have bandwidth to write the May development report!

As a consequence, this development summary will have an above average number of changes to highlight.

GNOME Shell

Preparations for Customizable App Grid

As part of the preparations for a customizable application grid, a new layout manager was written and replaced the current icon grid code. This new layout manager is in many ways more suitable for current and future changes:

• It follows the delegation pattern that is common to Clutter. As such, it is a layout manager, and not an UI element itself.
• It allows more precise control over the how the grid is displayed.
• It uses modern JavaScript practices and is, in general, a more maintainable and comprehensive code.

The most visible impact is that it now selects a row x column configuration that is closest to the aspect ratio of the display:

There are still improvements to make, especially with ultra-wide displays, but the foundation work is already there, and it will be vastly easier to fine-tune the behavior of the app grid on different scenarios.

Also as part of the preparations for a customizable application grid, the Frequent tab was removed. You can read more about the reasons for this removal in the corresponding issue.

Actor Tree Inspector

GNOME Shell’s development tool, the Looking Glass, received a handy new tab to inspect the actor tree:

This new inspector has been useful for developing GNOME Shell, and hopefully it’ll help extension developers too.

App Folder Dialog Updates

App folder dialogs received a bunch of visual and behavioral improvements, such as covering the entire monitor, and not changing the size of the app grid itself. Take a look:

These dialogs are now paginated, and fixed to 9 app icons per page:

Like the app grid, folder dialogs now also have better support for touchpad gestures and Drag n’ Drop.

Updates to the Message List Popup

This year, GNOME Shell has a Google Summer of Code intern working on the messages dialog. As a preparation for this project, some cleanups and reorganizations of the message list popup landed. More work in this front is happening, and an influx of improvements is expected to come soon, stay tuned!

Other Changes

GNOME Shell now supports the PrefersNonDefaultGPU key of the Desktop File specification, and will set the appropriate environment variables to launch applications using a dedicated GPU when available.

An unfortunate oversight was causing the Do Not Disturb setting to be reset on startup. This bug was fixed. A potential D-Bus race condition when creating MPRIS media players was corrected. App icons do not vertically stretch in the top bar anymore. These bugfixes were backported to GNOME 3.36.

The rendered contents of labels are now cached in the GPU.

The code that deals with workspaces in GNOME Shell is old, but a large number of cleanups to it has landed (!1119, !1251, !1294, !1297, !1298, !1307, !1310, !1313, !1320, !1333), and even more is under review. These cleanups were much needed in order to improve the overall quality and maintainability of the codebase.

The Extensions app saw some improvements too. The Logout button now works correctly.

When the host system changes timezones, GNOME Shell now properly updates the timezone offsets of the “World Clocks” section of the messages popover.

Finally, the Wacom buttom mapping on-screen display received various quality-of-life improvements.

Mutter

Layout Machinery Optimizations

A few exciting optimizations and improvements to Clutter’s layout machinery landed, and they bring groundwork for future improvements as well.

The removal of allocation flags allowed skipping the allocation phase of actors whose absolute position (that is, the on-screen position after performing the linear transformation of the actor vertices) didn’t change.

While routinely profiling Mutter, it was noticed that an abnormally high number of safety type checks were happening in a rendering hot path, during the redraw cycle. Those checks were removed.

Combined, these changes are of notable significance due to how expensive it is to recalculate the layout of actors. Some of them are also required for per-CRTC frame clocks.

Rendering Pipeline Improvements

Cogl now supports setting a maximum mipmap level, in addition to the minimum one, and background set a maximum mipmap level. This avoids creating mipmaps  that won’t be used.

Last year, MetaShapedTexture was made into a ClutterContent implementation. This change was important for a multitude of reasons, and will play a special role in the future with upcoming cleanups. However, it also introduced an unforeseen regression: Clutter paints ClutterContents before running the main painting routines, and this broke the existing culling mechanism of Mutter. After some investigation, culling was fixed again.

At last, MetaShapedTexture now uses a lighter, more appropriate function to combine opaque areas of windows.

Other Changes

Mutter saw a very, very, very, very large number of code cleanups. In fact, these cleanups combined got rid of almost the entirety of deprecated code!

Mutter also received a series of improvements to its test suit. These improvements range from fixing broken tests, make CI more reliable, add more tests, reorganize the entire test suit, among other changes.

Damage tracking, especially when combined with shadow framebuffers, is now working reliably and correctly. Importing DMA buffers is more careful about failures when importing scanout buffers. Finally, a couple of small memory leaks were plugged.

A bit later than usual, but nonetheless here the changes that happened during April on GNOME Shell and Mutter.

GNOME Shell

The command-line extensions tool received a round of improvements, and now reports extension errors better. Switching the scale of a monitor now should update all interface elements properly on GNOME Shell. Another quality of life improvement that landed was the inclusion of ASCII alternatives in the search index, which for example allows “eteindre” match “éteindre” (French for “power off”).

GNOME Shell now integrates with the parental controls technology being developed across the GNOME stack. If there are user restrictions in place, GNOME Shell now filters the applications that are not supposed to be used by the particular user.

One important improvement that landed during April is the rewrite of GNOME Shell’s calendar daemon. This updated version should prevent a lot of heavy background processing of events. Given the extents of the improvements, this is being considered for backporting to GNOME 3.36, but the size of the changes are also considerable. Testing and validation would be appreciated.

April then ended with the release of both GNOME Shell 3.36.2 as well as 3.37.1.

Mutter

On Mutter side, we say improvements to various parts of Clutter, such as ClutterOffscreenEffect, paint nodes, ClutterActorMeta, and various gestures. All these improvements are tiny steps to a cleaner, more maintanable codebase, and thus are much welcomed.

The most prominent addition to Mutter during April was the introduction of Wayland fullscreen unredirect. This code has been under review for many months, and required coordination between different parts of the stack, to work properly. Unfortunately, because it requires a very recent version of Xwayland (1.20.8) containing the fixes necessary for it to work properly, it is not suitable for backporting.

Improvements to the screencasting code landed in preparation for further improvements to GNOME Shell’s built-in screen recorder. We hope to be able to have a single code path for capturing the screen contents, regardless of whether the consumer is the Desktop portal, or the built-in recorder.

Also an issue many users had ran into where the Super key did not work as it should when using multiple keyboard layouts in the X11 session was fixed!. A handful of other bug fixes and improvements was made for the GNOME 3.36 stable branch was also included in the 3.36.2 release in the end of the month.

Like GNOME Shell, April ended with Mutter’s 3.37.1 release as well.

During March, GNOME Shell and Mutter saw their 3.36.0 and 3.36.1 releases, and the beginning of the 3.38 development cycle. We’ve focused most of the development efforts  on fixing bugs before starting the new development cycle.

From the development perspective, the 3.36.0 release was fantastic, and the number of regressions relative to the massive amount of changes that happened during the last cycle was remarkably small.

GNOME Shell

GNOME Shell saw continued improvements in its new Extensions app. New APIs were added to the Shell, which allows moving the Extensions app away into its own codebase. It also allows Shell to expose fewer interfaces through D-Bus.  The Extensions app is now available on Flathub.

A number of other small bugs and crashes were fixed for 3.36.1. Notably, the blur effect now works properly with fractional scaling.

Initial 3.38 work includes an improved Bluetooth state reporting, and the usage of JavaScript promises to simplify various asynchronous operations.

Mutter

Following the 3.36.0 release, Mutter received various fixes to window streaming support. In contrast to streaming entire monitors, which was working properly, window streaming had a few quirks and misbehaviors. For 3.36.1, we’ve tracked down many issues around it and fixed them. Streaming windows is also done using DMA buffer sharing mechanisms.

On Wayland, sometimes new windows would use the wrong position to animate, leading to the zoom in animation look broken. This issue was fixed as well. Pasting images from Firefox does not freeze apps, specially Xwayland apps, anymore. We also fixed a series of bugs where Xwayland windows would show a black border when resizing.

Mutter now properly handles hardware cursors when hotplugging GPUs, and cursor hotspots now work correctly again on virtual machines. Sometimes cursors would rotate wrongly when on already rotated displays, and this was also fixed.

On the X11 front, Mutter now respects manually configured RandR panning on X11, and a bug preventing the correct monitor scale from being applied on X11 was also fixed.

Mutter now also finally respects the “middle mouse button” emulation setting exposed via GSettings.

As we enter the different feature freezes that come before the 3.36, development starts to wind down, and focus shifts to testing and fixing bugs. Nonetheless, this was an exciting month for Mutter & GNOME Shell! The changes that landed, just in time for the 3.36 release, range from code cleanups, new features, quality-of-life improvements, and preparations for future important features.

GNOME Shell

GNOME Shell’s CSS engine now supports auto.  The icon grid spring animation was optimized to reduce the number of relayouts, which reduces CPU usage. Another batch of cleanups, refactorings, and fixes to GNOME Shell’s SCSS files landed.

Thanks to the ongoing efforts of extending and improving Sysprof, various bottlenecks and misbehaviors were identified in GNOME Shell and Mutter, and subsequently fixed. In particular, GNOME Shell now avoids doing I/O operations in the main thread when saving notification data on disk, and the local timezone is now cached, which avoids reading the contents of /etc/localtime more than necessary. As a consequence, GNOME Shell should behave better under heavy I/O loads on the host system.

The blur effect that is used by the new lock screen received further optimizations, and should be quick enough to not have any noticeable performance impact.

Animations are now disabled on various circumstances, such as when using a software renderer, when sharing screen with VNC streams, and when asked to by remote desktop sessions.

Extensions App

GNOME Shell now ships a new app to manage extensions:

This is now the primary way for users to manage extensions. It supports globally disabling extensions, uninstalling and updating user extensions, and toggling individual extensions on or off.

Mutter

Improved Screencasting Support

For a few years, Mutter implements a D-Bus API that allows screencasting. The screencast engine is implemented on top of PipeWire, and exports a PipeWire node that can be read and consumed by other applications.

Until now, this API would download the contents of the monitor framebuffers from the GPU to the system memory, and pass it to PipeWire. However, this was highly inneficient.

PipeWire 0.3 has support to another kind of buffer: DMA buffers. This allows Mutter not to download any framebuffer contents, and instead simply pass a file descriptor (an integer) to the clients. This results in far less CPU usage when screencasting.

A deep dive into how this was implemented will be published in the future.

Stage View Changes

Mutter is based on Clutter, which was originally developed as an application toolkit. Evidently, applications have very different constraints compared to compositors. One such constraint is about how refresh rates should be handled: applications only need to target a single refresh rate, whereas compositors need to draw on different monitors that may be running with different refresh rates.

These differences translate directly on how the code is architectured. Clutter has a single frame clock driving animations, and that does not play well with the problem domain that compositors live in.

During February, a major change on how Mutter handles drawing monitors landed. This is the first step towards achieving the goal of one frame clock per monitor.

Other Improvements

A stream of fixes to culling out rendering is being landed, and it potentially cuts down unnecessary rendering on various scenarios. For example, Mutter detects more cases when windows are completely obscured by other windows, and doesn’t ask them to render themselves.

A nice improvement to how the wallpaper is rendered allows Mutter to save resources when a scale is applied to any monitor.

Various fixes to Wayland subsurfaces support landed, and some small memory leaks were plugged. Lastly, Mutter now avoids flickering when X11 windows either ask to be unredirected or not.

The upcoming GNOME 3.36 release includes a major update to the system login and unlock experience. The new design has been anticipated for a long time, and we’re excited that it has finally arrived!

Some history

GNOME’s existing login and unlock design has been largely unaltered since it was first introduced in GNOME 3.6, back in September 2012. That’s seven and a half years ago! It’s therefore no surprise that we’ve wanted to update the design for some time.

The initial round of design work for the new lock screen took place in 2017, at the GNOME UX hackfest in London. There, the GNOME design team, along with GNOME Shell developers, reviewed the goals and requirements, as well as the issues with the existing design, including the main areas of feedback that we’ve had.

The design concept that we came up with during that event has undergone significant refinement since 2017, but the basic principles and goals remain the same. These can be summarised in three words: smooth, beautiful and personal.

Reducing friction

Unlocking the system is something that people do over and over, so it’s important that it doesn’t feel frustrating, and it needs to get you from A to B as quickly as possible. One of the goals of the design update was therefore to reduce the amount of friction involved in unlocking (or logging in for that matter).

From this perspective, the most obvious change in the lock screen is that the grey login screen is now gone. Rather than removing the “shield” to show the password field, the password field is shown right on the lock screen itself. This doesn’t necessarily change how many keystrokes or clicks are required to unlock, but it does reduce how many distinct visual steps are involved, and makes the whole experience feel faster and more direct.

We’ve also incorporated other changes which are intended to make it quicker and easier to unlock. There are more methods to show the password field than before: you can click with a mouse or touchpad button. You can also scroll with a mouse, or swipe with a touchpad or touchscreen. Small changes like this add an extra degree of convenience in many situations.

Other changes in this area are planned for the future. One of the biggest is to jump straight to the last-logged in user after boot, rather than requiring a user account to be selected every time. In most situations, this will take an extra step out of logging in: all you’ll have to do is boot, then enter your password, and off you’ll go.

More happy times

If getting to your work more easily is one of the big themes for the updated design, then the other is having a more joyful experience along the way. Unlocking is a chore, but it shouldn’t have to feel like one. It can and should be pleasurable.

With the new design, we wanted unlocking to be beautiful, and we’ve put a lot of work into visuals. The most obvious change is the use of the blurred background, which we love. Not only does it look great, but it also serves as an effective background for legible, light-weight typography, so it’s possible to have elegant text, without the need for heavy type or drop-shadows.

There’s also been lots attention to detail throughout design and development process, which we hope will make the login and unlock experience feel delightful to use. This includes things like the updated layout of the authentication elements, the subtle use of animation to communicate incorrect authentication attempts, and the transition from the clock to the password field.

Making it personal

A final, and perhaps more subtle, aspect of the updated design is the effort to make it feel personal. We want to connect the login and unlock with the user’s desktop experience, so the user gets a hint of their session even when they are logged out or the system is locked. The main way we’re doing this is the use of the blurred wallpaper, which is intended to communicate what lies on the other side of login/unlock.

The use of strong personal elements, like the user avatar and blurred background image, is also something that we intend to build on in future versions, by bringing them into the user selection screen itself. The goal here is to bring user selection alive: to make it more expressive and indicative of the person to which each account belongs.

Getting to this point

On the development side, the login/unlock redesign has primarily been carried forward by Georges Stavracas, with significant assistance from Umang Jain and Florian Müllner. It has been a significant amount of work and we owe them a lot of gratitude for the time and effort they have invested in this project.

Next steps

The login/unlock redesign was merged slightly late in the GNOME development cycle. To compensate for this, it is undergoing an intensive testing and bug fixing effort. Help is needed with this, and there is a test plan available for those who would like to try the new design and report any issues they find.

As mentioned above, looking beyond GNOME 3.36, there are a number of aspects of the design which are yet to be implemented and which we hope to have for the next release, version 3.38, so there is hopefully plenty more to look forward to in this area.

GNOME Shell

Unified Layout for Dialogs

One area of focus during this cycle was unifying the layout, content structure, and feel of dialogs in GNOME Shell. Many dialogs were redesigned, polished, and updated as a result of this effort:

Improved Gesture Support

The gestures to switch workspaces, and navigate through the application grid pages, were dramatically improved, and now follow the touchpad movement.

Password Peek

The password entries in GNOME Shell now support peeking passwords! Take a look:

Folders as Dialogs

A major change on how GNOME Shell handles application folders has landed this month. Instead of being displayed as popups within the application grid, folders are now displayed above it in the form of a dialog.

Miscellaneous

A new blur effect was added to GNOME Shell. It will be used by future work, such as a redesigned lock screen, among others.

Due to the VP9 encoder being too CPU-intensive, the built-in screen recorder changed back to the VP8 encoder.

As part of a code refactoring effort, the bits of StBoxLayout that deal with hiding overflowing content were moved to a new class, StViewport. This simplifies in various ways the implementation of overflowed content in GNOME Shell.

When managing the icons in the application grid, such as creating, renaming, or deleting folders, or moving app icons in and out of these folders, the icons will animate to their positions smoothly now.

GNOME Shell’s performance profiling framework was fixed and updated to also work on Wayland.

The SCSS code that is used to generate the default GNOME Shell theme was completely revamped and reorganized, making it easier to find specific theme classes. It also received a small visual update.

At last, GNOME Shell now supports NVidia GPU offloading by showing the “Launch on Discrete GPU” entry on systems with a NVidia discrete GPU available.

Mutter

More Cogl Cleanups

Cogl is the GPU rendering abstraction used by Clutter to render its contents on screen. Clutter itself is the base of Mutter and GNOME Shell, which add window management and compositing on top of Clutter.

During the past few months, there were continued efforts to cleanup and modernize Cogl by removing dead and unused code, using more modern OpenGL features, etc.

This work continued during December and January too, with more dead code saying goodbye, and more modern code being welcomed to the codebase.

Implicit Cogl API Removal

Due to historical reasons, Cogl has two major APIs: an explicit one, with properly defined types, and functions that receive the objects they should act on; and an implicit one, that is closer to the OpenGL model, and acts on an implicit state machine with the objects to be worked on.

Many parts of the Clutter, Mutter, and GNOME Shell codebases were using the implicit Cogl API. Those usages were updated, and allowed us to remove most of the implicit API from Cogl.

ClutterOffscreenEffect Improvements

ClutterOffscreenEffect is an effect applied on UI elements that allow them to be rendered in offscreen framebuffers. This allows interesting, shader-based effects to be applied to these elements, such as contrast and brightness, blur, among others.

A few bugs were found in this effect, and were ironed out. It also received some optimizations that allow the effect to release GPU memory more often.

Introduction of ClutterSeat

Clutter’s representation of input devices was designed in the X11/XI2 times, and the API was modeled after it. This change brings the internal input model closer to Wayland.

While it may sound an unimpressive change, it’s the cornerstone for an unification of the multiple input grabbing mechanisms in use by GNOME Shell.

Between other internal refactors that are now possible, it will also facilitate the introduction of an input thread in the native backend, so the pointer cursor is no longer frozen on stalls.

This will be covered in detail in a separate article.

Improve layout phase of no-layout actors

The Clutter toolkit follows the traditional rendering pipeline, composed of the layout, paint, and pick phases. The layout phase is where the elements (in Clutter terminology, “actors”) get to know their position and size; the paint phase is where these actors paint their contents on the framebuffer; and the pick phase is where Clutter figures out which actor is hovered by the pointer.

When we know beforehand that an actor is not going to move around the screen, we can tell Clutter about it, and the layout phase can be optimized to avoid some calculations. This mode is called “no-layout”.

During January, Clutter received another set of optimizations when dealing with no-layout actors. This can reduce CPU use on some specific scenarios, such as when dragging windows.

Miscellaneous

The ClutterContent interface now is better integrated in the size negotiation phase of ClutterActors, by making actors that follow their content’s sizes report their content’s geometry.

Many improvements to how Mutter tracks Wayland windows landed. Specifically, a crasher related to wl_subsurface was ironed out, a unit test framework was introduced, and a harmless runtime warning was fixed.

When dealing with multi-GPU setups, Mutter needs to share framebuffers across GPUs. There are currently three ways to do that:

1. The secondary GPU does an accelerated copy of the primary GPU framebuffer;
2. The primary GPU does an accelerated copy of its own contents to the secondary GPU framebuffer;
3. A slow, non-accelerated framebuffer is created on the secondary GPU, mapped to CPU memory, and the primary GPU contents are copied to this memory;

Mutter now features an additional way to share framebuffers: the primary GPU exports a framebuffer that is imported and read directly by the secondary GPU. This method is useful with virtual secondary GPUs, such as DisplayLink docks.