98 lines
3.9 KiB
Markdown
98 lines
3.9 KiB
Markdown
## Window creation for Retina displays
|
||
|
||
The file info.plist sets NSHighResolutionCapable to true. This is fine for High-DPI
|
||
and retina displays.
|
||
|
||
The `SDL_CreateWindow` is called with the flag `SDL_WINDOW_ALLOW_HIGHDPI`.
|
||
On Mac OS it means that, in source file `video/cocoa/SDL_cocoawindow.m`, from
|
||
function `Cocoa_CreateWindow`, SDL calls:
|
||
|
||
```objc
|
||
/* highdpi will be TRUE below */
|
||
BOOL highdpi = (window->flags & SDL_WINDOW_ALLOW_HIGHDPI) != 0;
|
||
[contentView setWantsBestResolutionOpenGLSurface:highdpi]
|
||
```
|
||
|
||
Documentation for `setWantsBestResolutionOpenGLSurface`:
|
||
|
||
https://developer.apple.com/documentation/appkit/nsview/1414938-wantsbestresolutionopenglsurface
|
||
|
||
with more details in "OpenGL Programming Guide for Mac", chapter
|
||
"Optimizing OpenGL for High Resolution":
|
||
|
||
https://developer.apple.com/library/archive/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/EnablingOpenGLforHighResolution/EnablingOpenGLforHighResolution.html#//apple_ref/doc/uid/TP40001987-CH1001-SW4
|
||
|
||
Citation from the official documentation:
|
||
|
||
You can opt in to high resolution by calling the method
|
||
`setWantsBestResolutionOpenGLSurface:` when you initialize the view, and
|
||
supplying YES as an argument:
|
||
|
||
```objc
|
||
[self setWantsBestResolutionOpenGLSurface:YES];
|
||
```
|
||
|
||
If you don’t opt in, the system magnifies the rendered results.
|
||
|
||
The wantsBestResolutionOpenGLSurface property is relevant only for views to
|
||
which an NSOpenGLContext object is bound. Its value does not affect the behavior
|
||
of other views. For compatibility, wantsBestResolutionOpenGLSurface defaults to
|
||
NO, providing a 1-pixel-per-point framebuffer regardless of the backing scale
|
||
factor for the display the view occupies. Setting this property to YES for a
|
||
given view causes AppKit to allocate a higher-resolution framebuffer when
|
||
appropriate for the backing scale factor and target display.
|
||
|
||
To function correctly with wantsBestResolutionOpenGLSurface set to YES, a view
|
||
must perform correct conversions between view units (points) and pixel units as
|
||
needed. For example, the common practice of passing the width and height of
|
||
[self bounds] to glViewport() will yield incorrect results at high resolution,
|
||
because the parameters passed to the glViewport() function must be in pixels. As
|
||
a result, you’ll get only partial instead of complete coverage of the render
|
||
surface. Instead, use the backing store bounds:
|
||
|
||
```objc
|
||
[self convertRectToBacking:[self bounds]];
|
||
```
|
||
|
||
## Coordinates
|
||
|
||
The SDL function `SDL_GL_GetDrawableSize` will provide the size of the underlying drawable
|
||
in pixels. From the `SDL_video.h` header.
|
||
|
||
```c
|
||
/**
|
||
* \brief Get the size of a window's underlying drawable in pixels (for use
|
||
* with glViewport).
|
||
*
|
||
* \param window Window from which the drawable size should be queried
|
||
* \param w Pointer to variable for storing the width in pixels, may be NULL
|
||
* \param h Pointer to variable for storing the height in pixels, may be NULL
|
||
*
|
||
* This may differ from SDL_GetWindowSize() if we're rendering to a high-DPI
|
||
* drawable, i.e. the window was created with SDL_WINDOW_ALLOW_HIGHDPI on a
|
||
* platform with high-DPI support (Apple calls this "Retina"), and not disabled
|
||
* by the SDL_HINT_VIDEO_HIGHDPI_DISABLED hint.
|
||
*
|
||
* \sa SDL_GetWindowSize()
|
||
* \sa SDL_CreateWindow()
|
||
*/
|
||
extern DECLSPEC void SDLCALL SDL_GL_GetDrawableSize(SDL_Window * window, int *w,
|
||
int *h);
|
||
```
|
||
|
||
In turns it calls `Cocoa_GL_GetDrawableSize` from source file
|
||
`video/cocoa/SDL_cocoaopengl.m`. The function use the method
|
||
`[contentView convertRectToBacking:viewport]`:
|
||
|
||
```objc
|
||
if (window->flags & SDL_WINDOW_ALLOW_HIGHDPI) {
|
||
/* This gives us the correct viewport for a Retina-enabled view, only
|
||
* supported on 10.7+. */
|
||
if ([contentView respondsToSelector:@selector(convertRectToBacking:)]) {
|
||
viewport = [contentView convertRectToBacking:viewport];
|
||
}
|
||
}
|
||
```
|
||
|
||
to give back the sizes in pixels.
|