#302 Bad input lag in GNOME Wayland when run in fullscreen

[Chong Kai Xiong]

Hi,

Tux Paint exhibits unusable input lag on GNOME (Wayland) when painting with the brush or any tool with a dynamically updated cursor. The problem happens only in fullscreen.

Every mouse motion event during painting triggers brush_draw() and finishes with SDL_RendererPresent() to update the screen. Unfortunately, each call to SDL_RendererPresent() waits for VSync and this produces the horrible lag.

I've tried to use the following without success:

• Disabling VSync in SDL using SDL_SetHint(SDL_HINT_RENDER_VSYNC, "0")and SDL_RenderSetVSync(renderer, 0);
• Switching the SDL video driver between X11 and Wayland

Moving forward, I think Tux Paint's responsiveness could be improved by completing moving away from the rendering assumptions made in SDL 1.2 and decoupling frame rate from input rate.

[Pere Pujal i Carabantes]

Hi, thanks for reporting this,
this issue reminds me a report that came on a private mail, sumaryzing:
lag in fullscreen, work in windowed mode, run in Arch Linux (which uses SDL3 via sdl2-compat) with Plasma and a very high resolution mouse.

The user fixed it for himself by lowering the mouse resolution, and we added a filter in tuxpaint.c to discard very small mouse events.
https://sourceforge.net/p/tuxpaint/tuxpaint/ci/8c6f8a9dc3aa7f778efc263ed1a73c1401c1060c/

If you can compile Tux Paint from source, you could try if latest source solves also the lag on your computer.

HTH
Pere