Platform Wranglers Meeting Notes

2023

Next

• Roundtable
  • New versions/changes in the underlying platform?
  • Current focus areas
  • Known problem areas
  • Features on the horizon
• Topics
  • Relative window stacking

12. October 2023

• Roundtable
  • X11
    • Looking into a11y improvements
      • Object creation and destruction not supported in Qt
        • Needed for testing tools. Unclear if Squish needs it
  • Android
    • Android 14 released
      • Problems getting into CI
    • QPA refactoring getting into shape
    • Improvements to JNI APIs
  • macOS
    • Sonoma (macOS 14) released
    • Problems with Xcode 15's new linker not providing default linker paths
      • Breaks qmake in all Qt versions. Patch submitted.
  • iOS
    • iOS 17 released
    • New protocol for device management (deploying, running)
      • Breaks Qt Creator integration.
  • Wayland
    • New discussions about windows being able to absolutely position
      • Clients want positioning, compositors don’t
    • XDG session, tying window to tag/id for restoring
      • Not clear if useful as cross platform API, but can be QWaylandWindow API
    • Synchronizing window flushes during resizing
      • Similar issues on other platforms
      • Need to figure out which parts are Wayland quirks and which parts are Qt
    • Window capturing is actually possible on Wayland via pipewire
  • WASM
    • 64 bit mode getting traction and fixes
    • Improvements to locale integration
• Topics
  • Version support
    • Android range of versions, testing min and max
    • macOS, support 3-4 latest version, test full range in CI
    • WASM, latest browser needed.
      • Runtime check features between browsers
      • EM SDK locked per Qt release
    • Wayland
      • Every protocol individually versioned
      • Supporting both desktop compositors and embedded compositors
        • Mutter, Plasma, Qt Compositor
    • X11
      • Rely on XCB
        • Must verify that distros have any new XCB libraries we depend on
  • Application startup / lifecycle
    • Event loop might already be running
      • WASM
      • iOS
      • Plugins
    • Need some kind of callback based API
      • One for startup
      • One for shutdown
    • Should QApp be created automatically for the user?
    • Can no longer create windows and other things on the stack
    • If we move to a new paradigm it should replace the main one
      • Ie the user shouldn’t need to provide both
    • Requires updating of QtC templates, examples, etc
    • Effort should be compared against fixing the main case for the platforms where this is an issue
      • E.g. running main on secondary thread on WASM

13. September 2023

• Introductions
  • Tor Arne - macOS,iOS,QPA
  • Morten - WASM
  • Oliver - Windows
  • Liang - X11
  • Assam - Android
  • David - Wayand
• Ways of working
  • Monthly meeting
  • Desktop/mobile platforms
• Roundtable
  • iOS
    • iOS 17 end of September
      • Things mostly work as before
    • Moving to FFMpeg for Qt Multimedia
    • Technical debt in window management, modern iOS has more advanced window/screen management
    • Exposing safe area margins properly as public Qt Quick API (anchors, etc)
  • macOS
    • macOS Sonoma end of September
      • No major changes, doing nightly builds, weeding out issues
      • One regression in Xcode 15, causing build failures with qmake
        • https://codereview.qt-project.org/c/qt/qtbase/+/503172
    • Key/text input, complex text, shortcut handling
    • Modern window look, blurred/effect windows, etc
  • WASM
    • Emscripten is the SDK
      • Follows Chrome release model (4-6 weeks)
      • No versions are “more stable” than others
      • Upgrade close to feature freeze to get latest fixes
    • 32-bit platform (one of our few)
    • Has a no-thread build option
    • Uses static linking
    • WASM64 is coming, looking at that
    • Dynamic linking is in the works
    • Major challenge is web platform is async, but Qt expects synchronous APIs
    • Complex text difficult
    • Accessibility difficult
  • X11
    • Not much underlying changes on X11
      • Ubuntu 22.04 in CI
      • Updating RedHat and OpenSuse
    • Increased requests for more XDG support
      • Use XDG services more, file dialogs, drag and drop, etc
      • Harald Sitter (?) knows about KDE drag and drop
  • Windows
    • New OS updates every 6 months
      • But usually no new major features
      • CI updates, doesn’t change much
    • Focus areas
      • Finalising Windows 11 style for widgets
      • Modern look of apps
        • Window decorations
      • Windows on ARM
    • Problem areas
      • Windows on ARM, hard to virtualise in CI
  • Android
    • Android 14 coming up
      • Been tested in CI
      • Some new permissions we need to deal with
        • Storage permissions deprecated
    • Bumped minimum from Android 6 to Android 8
    • Focus areas
      • Safe area margins for short edges
      • Refactoring QPA plugin
        • Modernize
        • Remove layers
        • Make more maintainable
      • Generator for JNI APIs
        • Making it easier to invoke Android APIs
  • Wayland
    • A set of generated wire protocols
      • Some core protocols, fairly stable, can be expected everywhere (all compositors/servers)
      • Standard body maintains additional extension protocols
        • Some more essential, eg XDG shell
        • Some more esoteric, for car manufacturers etc
    • Some DEs use Wayland nowadays, but also with XWayland for X11 support
      • Gnome
      • Plasma (KDE), switching soon
    • Deadline for Qt adopting a protocol is in practice when a big bistro adopts a DE version that has support for the protocol
    • Focus areas
      • Fractional scaling
      • Support for clients outliving crashing compositors
      • Support for minimised windows
    • Problem areas
      • Popups
        • Windows don’t know their own screen positions
        • Can not control screen positions
        • Popups need to declare intent about where to be placed
        • Possible solutions
          • Turn window geometry into hints to Wayland
          • Expose placement-intent-based API as public Qt API
            • https://codereview.qt-project.org/c/qt/qtbase/+/491545
      • Qt Quick threaded render out of sync with window resize
        • Needs graphics team attention
      • QWindow setGeometry not emitting geometryChanged
        • We wait until GeometryChangeEvent
      • QWidget updates not going through QWindow::requestUpdate
• Topics
  • Keyboard input and shortcut handling
    • Investigated at https://bugreports.qt.io/browse/QTBUG-116873
  • Custom window decorations
    • Frameless windows on Windows not usable for the use-cases people have
      • Need to figure out if it's a Windows bug fix, or a missing feature in QWindow
      • Olli to write up summary in JIRA task