kc3-lang/SDL

2022-04-18T17:03:05

Wayland: Emulate mouse warp using relative mouse mode Several games (including Source and GoldSrc games, and Bioshock Infinite) attempt to "fake" relative mouse mode by repeatedly warping the cursor to the centre of the screen. Since mouse warping is not supported under Wayland, the viewport ends up "stuck" in a rectangular area. Detect this case (mouse warp while the cursor is not visible), and enable relative mouse mode, which tracks the cursor position independently, and so can Warp successfully. This is behind the SDL_HINT_VIDEO_WAYLAND_EMULATE_MOUSE_WARP hint, which is enabled by default, unless the application enables relative mouse mode itself using SDL_SetRelativeMouseMode(SDL_TRUE). Note that there is a behavoural difference, in that relative mouse mode typically doesn't take mouse accelleration into account, but the repeated-warping technique does, so mouse movement can seem very slow with this (unless the game has its own mouse accelleration option, such as in Portal 2).