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Updated SDL high DPI support

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We have gotten feedback that abstracting the coordinate system based on the display scale is unexpected and it is difficult to adapt existing applications to the proposed API.

The new approach is to provide the coordinate systems that people expect, but provide additional information that will help applications properly handle high DPI situations.

The concepts needed for high DPI support are documented in README-highdpi.md. An example of automatically adapting the content to display scale changes can be found in SDL_test_common.c, where auto_scale_content is checked.

Also, the SDL_WINDOW_ALLOW_HIGHDPI window flag has been replaced by the SDL_HINT_VIDEO_ENABLE_HIGH_PIXEL_DENSITY hint.

Fixes https://github.com/libsdl-org/SDL/issues/7709
This commit is contained in:
Sam Lantinga
2023-05-16 16:29:52 -07:00
parent 0fbb9c779c
commit c699f3d1d8
51 changed files with 506 additions and 882 deletions
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18
docs/README-highdpi.md Normal file
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@@ -0,0 +1,18 @@
SDL 3.0 has new support for high DPI displays
Displays now have a content display scale.
The display scale is the expected scale for content based on the DPI settings of the display. For example, a 4K display might have a 2.0 (200%) display scale, which means that the user expects UI elements to be twice as big on this display, to aid in readability.
The window size is now distinct from the window pixel size.
The window also has a display scale, which is the content display scale relative to the window pixel size.
For example, a 3840x2160 window displayed at 200% on Windows, and a 1920x1080 window on a 2x display on macOS will both have a pixel size of 3840x2160 and a display scale of 2.0.
You can query the window size using SDL_GetWindowSize(), and when this changes you get an SDL_EVENT_WINDOW_RESIZED event.
You can query the window pixel size using SDL_GetWindowSizeInPixels(), and when this changes you get an SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED event. You are guaranteed to get a SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED event when a window is created and resized, and you can use this event to create and resize your graphics context for the window.
You can query the window display scale using SDL_GetWindowDisplayScale(), and when this changes you get an SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED event.

8
docs/README-migration.md
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@@ -1085,9 +1085,9 @@ The SDL_WINDOWPOS_UNDEFINED_DISPLAY() and SDL_WINDOWPOS_CENTERED_DISPLAY() macro
The SDL_WINDOW_SHOWN flag has been removed. Windows are shown by default and can be created hidden by using the SDL_WINDOW_HIDDEN flag.
The SDL_WINDOW_ALLOW_HIGHDPI flag has been removed. Windows are automatically high DPI aware and their coordinates are in screen space, which may differ from physical pixels on displays using display scaling.
The SDL_WINDOW_ALLOW_HIGHDPI flag has been replaced by the SDL_HINT_VIDEO_ENABLE_HIGH_PIXEL_DENSITY hint, which is enabled by default.
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_DisplayMode now includes the pixel density which can be greater than 1.0 for display modes that have a higher pixel size than the mode size. You should use SDL_GetWindowSizeInPixels() to get the actual pixel size of the window back buffer.
The refresh rate in SDL_DisplayMode is now a float.
@@ -1100,8 +1100,8 @@ Rather than iterating over display modes using an index, there is a new function
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_Log("Display %" SDL_PRIu32 " mode %d: %dx%d@%gx %gHz\n",
display, i, mode->w, mode->h, mode->pixel_density, mode->refresh_rate);
}
SDL_free(modes);
}