This function wasn't consistently correct across platforms and devices.
If you want the UI scale factor, you can use display_scale in the structure returned by SDL_GetDesktopDisplayMode(). If you need an approximate DPI, you can multiply this value times 160 on iPhone and Android, and 96 on other platforms.
This fixes rounding errors with coordinate scaling and gives more flexibility in the presentation, as well as making it easy to maintain device independent resolution as windows move between different pixel density displays.
By default when a renderer is created, it will match the window size so window coordinates and render coordinates are 1-1.
Mouse and touch events are no longer filtered to change their coordinates, instead you can call SDL_ConvertEventToRenderCoordinates() to explicitly map event coordinates into the rendering viewport.
SDL_RenderWindowToLogical() and SDL_RenderLogicalToWindow() have been renamed SDL_RenderCoordinatesFromWindow() and SDL_RenderCoordinatesToWindow() and take floating point coordinates in both directions.
The viewport, clipping state, and scale for render targets are now persistent and will remain set whenever they are active.
Rather than iterating over display modes using an index, there is a new function SDL_GetFullscreenDisplayModes() to get the list of available fullscreen modes on a display.
{
SDL_DisplayID display = SDL_GetPrimaryDisplay();
int num_modes = 0;
SDL_DisplayMode **modes = SDL_GetFullscreenDisplayModes(display, &num_modes);
if (modes) {
for (i = 0; i < num_modes; ++i) {
SDL_DisplayMode *mode = modes[i];
SDL_Log("Display %" SDL_PRIu32 " mode %d: %dx%d@%gHz, %d%% scale\n",
display, i, mode->pixel_w, mode->pixel_h, mode->refresh_rate, (int)(mode->display_scale * 100.0f));
}
SDL_free(modes);
}
}
SDL_GetDesktopDisplayMode() and SDL_GetCurrentDisplayMode() return pointers to display modes rather than filling in application memory.
Windows now have an explicit fullscreen mode that is set, using SDL_SetWindowFullscreenMode(). The fullscreen mode for a window can be queried with SDL_GetWindowFullscreenMode(), which returns a pointer to the mode, or NULL if the window will be fullscreen desktop. SDL_SetWindowFullscreen() just takes a boolean value, setting the correct fullscreen state based on the selected mode.
SDL_DisplayMode now includes the pixel size, the screen size and the relationship between the two. For example, a 4K display at 200% scale could have a pixel size of 3840x2160, a screen size of 1920x1080, and a display scale of 2.0.
* SDL 3.0 is going to be high DPI aware and officially separates screen coordinates from client pixel area
The public APIs to disable high DPI support have been removed
Work in progress on https://github.com/libsdl-org/SDL/issues/7134
