GetMouseState dont calculate for scaling SDL3

[CptFisk]

Problem

When using SDL3_Renderer with SDL_SetREnderScale the mouse cordinates that is recived throught event->motion.x and event->motion.y dont account for scaling offset.

Solution

Before io.AddMousePosEvent the scalefactor is applied to the mouse cordinates

Changes

ImGui_ImplSDL3_ProcessEvent now fetches the scaling and apply it to the mouse cordinates.

[ocornut]

I am rather puzzled by this. You are highlighting a real problem if using SDL_SetRenderScale() but it seems like absolutely nothing in this PR was tested?

• Variables scaleX/scaleY are not declared.
• The correct formula here seems to a divide rather than a multiply.
• There is also call to AddMousePosEvent() in ImGui_ImplSDL3_UpdateMouseData() which hasn't been scaled.
• bd->Renderer may be NULL on other backends.
• The io.WantSetMousePos path has not been handled.

I can't comprehend how this would have possibly worked on our end. Could you clarify?

[ocornut]

Also see https://wiki.libsdl.org/SDL3/SDL_ConvertEventToRenderCoordinates