Platform Wranglers Meeting Notes

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2023

Next

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

16. November 2023

Roundtable
- Windows
  - Trying to get ARM VMs for our CI
  - Windows 12 on the horizon, no details yet, but no likely major changes
  - Finishing up Windows 11 style
  - Improvements to high-DPI
- X11
  - Gnome and KDE moving to Wayland
- WASM
  - Updating to WebGL 2 (GLES 3)
- Android
  - Android 14 in CI, now supported for 6.7
  - Some issues with emulator in CI
  - QPA refactoring making good progress
  - Child window support in review
  - JNI improvements by Volker merged
- macOS
  - macOS 14 significant in CI now
- iOS
  - iOS 17 issues due to libmobiledevice no longer being supported
- Wayland
  - Discussion around behavior when window minimum size is larger than available size (tiling window manager e.g.)
    - Killing app in response is not a good behavior
Topics
- Window states for child windows
  - Always use NoWindowState
- Internal platform window handle changes
  - Only on XCB, exposed as winId
  - on macOS and Wayland, changes, but not exposed as winId
- Synchronous mouse/touch
  - Many platforms already do this

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

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