SDL/docs/README-wayland.md

Wayland

Wayland is a replacement for the X11 window system protocol and architecture and is favored over X11 by default in SDL3 for communicating with desktop compositors. It works well for the majority of applications, however, applications may encounter limitations or behavior that is different from other windowing systems.

Common issues:

Window decorations are missing, or the decorations look strange

• On some desktops (i.e. GNOME), Wayland applications use a library called libdecor to provide window decorations. If this library is not installed, the decorations will be missing. This library uses plugins to generate different decoration styles, and if a plugin to generate native-looking decorations is not installed (i.e. the GTK plugin), the decorations will not appear to be 'native'.

Windows do not appear immediately after creation

• Wayland requires that the application initially present a buffer before the window becomes visible. Additionally, applications must have an event loop and processes messages on a regular basis, or the application can appear unresponsive to both the user and desktop compositor.

SDL_SetWindowPosition() doesn't work on non-popup windows

• Wayland does not allow toplevel windows to position themselves programmatically.

Retrieving the global mouse cursor position when the cursor is outside a window doesn't work

• Wayland only provides applications with the cursor position within the borders of the application windows. Querying the global position when an application window does not have mouse focus returns 0,0 as the actual cursor position is unknown. In most cases, applications don't actually need the global cursor position and should use the window-relative coordinates as provided by the mouse movement event or from SDL_GetMouseState() instead.

Warping the global mouse cursor position via SDL_WarpMouseGlobal() doesn't work

• For security reasons, Wayland does not allow warping the global mouse cursor position.

The application icon can't be set via SDL_SetWindowIcon()

• Wayland doesn't support programmatically setting the application icon. To provide a custom icon for your application, you must create an associated desktop entry file, aka a .desktop file, that points to the icon image. Please see the Desktop Entry Specification for more information on the format of this file. Note that if your application manually sets the application ID via the SDL_APP_ID hint string, the desktop entry file name should match the application ID. For example, if your application ID is set to org.my_org.sdl_app, the desktop entry file should be named org.my_org.sdl_app.desktop.

Using custom Wayland windowing protocols with SDL windows

Under normal operation, an SDL_Window corresponds to an XDG toplevel window, which provides a standard desktop window. If an application wishes to use a different windowing protocol with an SDL window (e.g. wlr_layer_shell) while still having SDL handle input and rendering, it needs to create a custom, roleless surface and attach that surface to its own toplevel window.

This is done by using SDL_CreateWindowWithProperties() and setting the SDL_PROPERTY_WINDOW_CREATE_WAYLAND_SURFACE_ROLE_CUSTOM_BOOLEAN property to SDL_TRUE. Once the window has been successfully created, the wl_display and wl_surface objects can then be retrieved from the SDL_PROPERTY_WINDOW_WAYLAND_DISPLAY_POINTER and SDL_PROPERTY_WINDOW_WAYLAND_SURFACE_POINTER properties respectively.

Surfaces don't receive any size change notifications, so if an application changes the window size, it must inform SDL that the surface size has changed by calling SDL_SetWindowSize() with the new dimensions.

Custom surfaces will automatically handle scaling internally if the window was created with the high-pixel-density property set to SDL_TRUE. In this case, applications should not manually attach viewports or change the surface scale value, as SDL will handle this internally. Calls to SDL_SetWindowSize() should use the logical size of the window, and SDL_GetWindowSizeInPixels() should be used to query the size of the backbuffer surface in pixels. If this property is not set or is SDL_FALSE, applications can attach their own viewports or change the surface scale manually, and the SDL backend will not interfere or change any values internally. In this case, calls to SDL_SetWindowSize() should pass the requested surface size in pixels, not the logical window size, as no scaling calculations will be done internally.

All window functions that control window state aside from SDL_SetWindowSize() are no-ops with custom surfaces.

Please see the minimal example in tests/testwaylandcustom.c for an example of how to use a custom, roleless surface and attach it to an application-managed toplevel window.