forked from Green-Sky/tomato
224 lines
11 KiB
Markdown
224 lines
11 KiB
Markdown
Wayland
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=======
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Wayland is a replacement for the X11 window system protocol and architecture and is favored over X11 by default in SDL3
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for communicating with desktop compositors. It works well for the majority of applications, however, applications may
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encounter limitations or behavior that is different from other windowing systems.
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## Common issues:
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### Window decorations are missing, or the decorations look strange
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- On some desktops (i.e. GNOME), Wayland applications use a library
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called [libdecor](https://gitlab.freedesktop.org/libdecor/libdecor) to provide window decorations. If this library is
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not installed, the decorations will be missing. This library uses plugins to generate different decoration styles, and
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if a plugin to generate native-looking decorations is not installed (i.e. the GTK plugin), the decorations will not
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appear to be 'native'.
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### Windows do not appear immediately after creation
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- Wayland requires that the application initially present a buffer before the window becomes visible. Additionally,
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applications _must_ have an event loop and processes messages on a regular basis, or the application can appear
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unresponsive to both the user and desktop compositor.
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### ```SDL_SetWindowPosition()``` doesn't work on non-popup windows
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- Wayland does not allow toplevel windows to position themselves programmatically.
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### Retrieving the global mouse cursor position when the cursor is outside a window doesn't work
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- Wayland only provides applications with the cursor position within the borders of the application windows. Querying
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the global position when an application window does not have mouse focus returns 0,0 as the actual cursor position is
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unknown. In most cases, applications don't actually need the global cursor position and should use the window-relative
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coordinates as provided by the mouse movement event or from ```SDL_GetMouseState()``` instead.
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### Warping the global mouse cursor position via ```SDL_WarpMouseGlobal()``` doesn't work
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- For security reasons, Wayland does not allow warping the global mouse cursor position.
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### The application icon can't be set via ```SDL_SetWindowIcon()```
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- Wayland doesn't support programmatically setting the application icon. To provide a custom icon for your application,
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you must create an associated desktop entry file, aka a `.desktop` file, that points to the icon image. Please see the
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[Desktop Entry Specification](https://specifications.freedesktop.org/desktop-entry-spec/latest/) for more information
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on the format of this file. Note that if your application manually sets the application ID via the `SDL_APP_ID` hint
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string, the desktop entry file name should match the application ID. For example, if your application ID is set
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to `org.my_org.sdl_app`, the desktop entry file should be named `org.my_org.sdl_app.desktop`.
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## Using custom Wayland windowing protocols with SDL windows
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Under normal operation, an `SDL_Window` corresponds to an XDG toplevel window, which provides a standard desktop window.
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If an application wishes to use a different windowing protocol with an SDL window (e.g. wlr_layer_shell) while still
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having SDL handle input and rendering, it needs to create a custom, roleless surface and attach that surface to its own
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toplevel window.
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This is done by using `SDL_CreateWindowWithProperties()` and setting the
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`SDL_PROPERTY_WINDOW_CREATE_WAYLAND_SURFACE_ROLE_CUSTOM_BOOLEAN` property to `SDL_TRUE`. Once the window has been
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successfully created, the `wl_display` and `wl_surface` objects can then be retrieved from the
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`SDL_PROPERTY_WINDOW_WAYLAND_DISPLAY_POINTER` and `SDL_PROPERTY_WINDOW_WAYLAND_SURFACE_POINTER` properties respectively.
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Surfaces don't receive any size change notifications, so if an application changes the window size, it must inform SDL
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that the surface size has changed by calling SDL_SetWindowSize() with the new dimensions.
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Custom surfaces will automatically handle scaling internally if the window was created with the
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`SDL_PROPERTY_WINDOW_CREATE_HIGH_PIXEL_DENSITY_BOOLEAN` property set to `SDL_TRUE`. In this case, applications should
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not manually attach viewports or change the surface scale value, as SDL will handle this internally. Calls
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to `SDL_SetWindowSize()` should use the logical size of the window, and `SDL_GetWindowSizeInPixels()` should be used to
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query the size of the backbuffer surface in pixels. If this property is not set or is `SDL_FALSE`, applications can
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attach their own viewports or change the surface scale manually, and the SDL backend will not interfere or change any
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values internally. In this case, calls to `SDL_SetWindowSize()` should pass the requested surface size in pixels, not
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the logical window size, as no scaling calculations will be done internally.
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All window functions that control window state aside from `SDL_SetWindowSize()` are no-ops with custom surfaces.
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Please see the minimal example in `tests/testwaylandcustom.c` for an example of how to use a custom, roleless surface
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and attach it to an application-managed toplevel window.
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## Importing external surfaces into SDL windows
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Wayland windows and surfaces are more intrinsically tied to the client library than other windowing systems, therefore,
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when importing surfaces, it is necessary for both SDL and the application or toolkit to use the same `wl_display`
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object. This can be set/queried via the global `SDL_PROPERTY_GLOBAL_VIDEO_WAYLAND_WL_DISPLAY_POINTER` property. To
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import an external `wl_display`, set this property before initializing the SDL video subsystem, and read the value to
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export the internal `wl_display` after the video subsystem has been initialized. Setting this property after the video
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subsystem has been initialized has no effect, and reading it when the video subsystem is uninitialized will either
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return the user provided value, if one was set while in the uninitialized state, or NULL.
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Once this is done, and the application has created or obtained the `wl_surface` to be wrapped in an `SDL_Window`, the
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window is created with `SDL_CreateWindowWithProperties()` with the
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`SDL_PROPERTY_WINDOW_CREATE_WAYLAND_WL_SURFACE_POINTER` property to set to the `wl_surface` object that is to be
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imported by SDL.
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SDL receives no notification regarding size changes on external surfaces or toplevel windows, so if the external surface
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needs to be resized, SDL must be informed by calling SDL_SetWindowSize() with the new dimensions.
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If desired, SDL can automatically handle the scaling for the surface by setting the
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`SDL_PROPERTY_WINDOW_CREATE_HIGH_PIXEL_DENSITY_BOOLEAN` property to `SDL_TRUE`, however, if the surface being imported
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already has, or will have, a viewport/fractional scale manager attached to it by the application or an external toolkit,
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a protocol violation will result. Avoid setting this property if importing surfaces from toolkits such as Qt or GTK.
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If the window is flagged as high pixel density, calls to `SDL_SetWindowSize()` should pass the logical size of the
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window and `SDL_GetWindowSizeInPixels()` should be used to retrieve the backbuffer size in pixels. Otherwise, calls to
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`SDL_SetWindowSize()` should pass the requested surface size in pixels, not the logical window size, as no scaling
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calculations will be done internally.
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All window functions that control window state aside from `SDL_SetWindowSize()` are no-ops with external surfaces.
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An example of how to use external surfaces with a `wl_display` owned by SDL can be seen in `tests/testnativewayland.c`,
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and the following is a minimal example of interoperation with Qt 6, with Qt owning the `wl_display`:
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```c++
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#include <QApplication>
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#include <QWindow>
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#include <qpa/qplatformnativeinterface.h>
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#include <SDL3/SDL.h>
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int main(int argc, char *argv[])
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{
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int ret = -1;
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int done = 0;
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SDL_PropertiesID props;
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SDL_Event e;
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SDL_Window *sdlWindow = NULL;
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SDL_Renderer *sdlRenderer = NULL;
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struct wl_display *display = NULL;
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struct wl_surface *surface = NULL;
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/* Initialize Qt */
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QApplication qtApp(argc, argv);
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QWindow qtWindow;
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/* The windowing system must be Wayland. */
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if (QApplication::platformName() != "wayland") {
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goto exit;
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}
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{
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/* Get the wl_display object from Qt */
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QNativeInterface::QWaylandApplication *qtWlApp = qtApp.nativeInterface<QNativeInterface::QWaylandApplication>();
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display = qtWlApp->display();
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if (!display) {
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goto exit;
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}
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}
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/* Set SDL to use the existing wl_display object from Qt and initialize. */
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SDL_SetProperty(SDL_GetGlobalProperties(), SDL_PROPERTY_GLOBAL_VIDEO_WAYLAND_WL_DISPLAY_POINTER, display);
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SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS);
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/* Create a basic, frameless QWindow */
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qtWindow.setFlags(Qt::FramelessWindowHint);
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qtWindow.setGeometry(0, 0, 640, 480);
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qtWindow.show();
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{
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/* Get the native wl_surface backing resource for the window */
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QPlatformNativeInterface *qtNative = qtApp.platformNativeInterface();
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surface = (struct wl_surface *)qtNative->nativeResourceForWindow("surface", &qtWindow);
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if (!surface) {
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goto exit;
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}
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}
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/* Create a window that wraps the wl_surface from the QWindow.
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* Qt objects should not be flagged as DPI-aware or protocol violations will result.
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*/
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props = SDL_CreateProperties();
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SDL_SetProperty(props, SDL_PROPERTY_WINDOW_CREATE_WAYLAND_WL_SURFACE_POINTER, surface);
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SDL_SetBooleanProperty(props, SDL_PROPERTY_WINDOW_CREATE_OPENGL_BOOLEAN, SDL_TRUE);
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SDL_SetNumberProperty(props, SDL_PROPERTY_WINDOW_CREATE_WIDTH_NUMBER, 640);
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SDL_SetNumberProperty(props, SDL_PROPERTY_WINDOW_CREATE_HEIGHT_NUMBER, 480);
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sdlWindow = SDL_CreateWindowWithProperties(props);
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SDL_DestroyProperties(props);
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if (!sdlWindow) {
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goto exit;
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}
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/* Create a renderer */
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sdlRenderer = SDL_CreateRenderer(sdlWindow, NULL, 0);
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if (!sdlRenderer) {
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goto exit;
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}
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/* Draw a blue screen for the window until ESC is pressed or the window is no longer visible. */
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while (!done) {
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while (SDL_PollEvent(&e)) {
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if (e.type == SDL_EVENT_KEY_DOWN && e.key.keysym.sym == SDLK_ESCAPE) {
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done = 1;
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}
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}
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qtApp.processEvents();
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/* Update the backbuffer size if the window scale changed. */
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qreal scale = qtWindow.devicePixelRatio();
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SDL_SetWindowSize(sdlWindow, SDL_lround(640. * scale), SDL_lround(480. * scale));
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if (qtWindow.isVisible()) {
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SDL_SetRenderDrawColor(sdlRenderer, 0, 0, 255, 255);
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SDL_RenderClear(sdlRenderer);
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SDL_RenderPresent(sdlRenderer);
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} else {
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done = 1;
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}
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}
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ret = 0;
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exit:
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/* Cleanup */
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if (sdlRenderer) {
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SDL_DestroyRenderer(sdlRenderer);
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}
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if (sdlWindow) {
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SDL_DestroyWindow(sdlWindow);
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}
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SDL_Quit();
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return ret;
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}
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```
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