TODO:

• handle --allow-highdpi on an exe that has "Windows Explorer -> Properties -> Compatibility -> High DPI -> Scaled by Application" set.
• touch events probably need DPI scaling applied
• report/send patch for D3D_ActivateRenderer(renderer); after data->updateSize = SDL_TRUE; in SDL_render_3d.c issue
• prototype "always DPI aware" approach (grab code from first squashed commit on the branch)
• use SDL's logging categories rather than ifdef's?
• (2021-11-22): can't go exclusive fullscreen with testwm2 with --allow-highdpi --info all --renderer direct3d11
  • can't repro?
• (2021-11-21): testgl2 with --allow-highdpi --resizable, 150% monitor. Ctrl+Enter for fullscreen, then Ctrl+Enter to exit fullscreen. Window is too small
  • fixed by putting a break; at the start of the WM_DPICHANGED handler
  • edit: this didn't actually fix it
  • --renderer direct3d11 seems to resolve this though? DX9 only?
  • actual fix: call D3D_ActivateRenderer(renderer); after data->updateSize = SDL_TRUE; in SDL_render_3d.c
• Fullscreen (Ctrl+Enter in testwm2) on 2 monitor setup, 125% and 100%, goes fullscreen on wrong window. Also happens on main
  • also both monitors seem to change modes, when only 1 should
  • 2021-11-06: can't seem to reproduce going fullscreen on the wrong window in this case, but it goes into the wrong fullscreen mode as displayed by the monitor's OSD (1280x740), window before going fullscren is 640x480 points (800x600 pixels) on 3840x2160 px 125% monitor.
• testwm2 with --allow-highdpi --info all on 3840x2160 px @ 125% monitor. Alt+Enter gives the following - shouldn't Window size be 3072x1728 points, and the mouse position is also in pixels not points. (global mouse pos is in points though!)
  
• (2021-11-21): testgl2 with --allow-highdpi, 150% monitor, renders like:
  • calling data->SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
  • data->AreDpiAwarenessContextsEqual(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2, data->GetThreadDpiAwarenessContext()) was returning true
  • fixed by changing SetThreadDpiAwarenessContext call to SetProcessDpiAwarenessContext. Apparently the OpenGL driver (nvidia) needs the process DPI awareness set?

Notes:

• beware of Windows flagging processes as DPI aware after they change the display mode, see: Document DPI awareness quirks on Windows libsdl-org/SDL#4908 (comment)

Testing matrix:

• render / video backends:
  • testwm2 --renderer direct3d11
  • testwm2 --renderer direct3d
  • testwm2 --renderer opengl
  • testgl2
  • testvulkan
  • testgles2
• DPI awareness levels
  • unaware
  • system
  • per-monitor
  • per-monitor V2