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Add a new hint SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT that allows SDL_CreateWindowFrom() to set the pixel format of another SDL_Window (and also will set the SDL_WINDOW_OPENGL flag on the window created with SDL_CreateWindowFrom()).

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The reasoning behind this change is that source2 in -tools mode has a single OpenGL context that is used with multiple different windows.  Some of those windows are created outside the engine (i.e. with Qt) and therefore we need to use SDL_CreateWindowFrom() to get an SDL_Window for those.  The requirement for sharing an OpenGL context across multiple different windows is that each window has the same pixel format.  To facilitate this, I now set SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT for the main window before calling SDL_CreateWindowFrom().  When I do this, SDL_CreateWindowFrom() will:

1. Set the pixel format of the returned window to the same pixel format as this SDL_Window passed in with the hint
2. The flag SDL_WINDOW_OPENGL will be set on the new window so it can be used for OpenGL rendering.

I only currently implemented this for Win32/WGL so implementing it for other platforms (i.e. X11) remains a TODO.

CR: SamL

Some pseudocode that shows how this is used in Source2:

HWND hExternalHwnd; // HWND that was established outside of SDL

// Create main window (happens inside platwindow.cpp)
SDL_Window *mainWindow = SDL_CreateWindow( , SDL_WINDOW_OPENGL .. );
// Create GL context, happens inside rendersystemgl
SDL_GLContext onlyContext = SDL_GL_CreateContext( mainWindow );

// Now I need to create another window from hEternalHwnd for my swap chain that will have the same pixel format as mainWindow, so set the hint
SDL_SetHint( SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT, CFmtStr( %p, mainWindow) );

// Create the secondary window.  This returned window will have SDL_WINDOW_OPENGL set and share a pixel format with mainWindow from the hint
SDL_Window *secondaryWindow = SDL_CreateWindowFrom( hExternalHwnd );

// To render to the main window:
SDL_GL_MakeCurrent( mainWindow, onlyContext );
// Do some rendering to main window

// To render to the secondary window:
SDL_GLMakeCurrent( secondaryWindow, onlyContext );
// Do some rendering to secondary window
This commit is contained in:
Sam Lantinga 2014-01-30 12:30:40 -08:00
parent d9f1c7b666
commit a09aac7720
4 changed files with 66 additions and 0 deletions
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20
src/video/windows/SDL_windowsopengl.c
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@ -759,6 +759,26 @@ WIN_GL_DeleteContext(_THIS, SDL_GLContext context)
_this->gl_data->wglDeleteContext((HGLRC) context);
}
SDL_bool
WIN_GL_SetPixelFormatFrom(_THIS, SDL_Window * fromWindow, SDL_Window * toWindow)
{
HDC hfromdc = ((SDL_WindowData *) fromWindow->driverdata)->hdc;
HDC htodc = ((SDL_WindowData *) toWindow->driverdata)->hdc;
BOOL result;
/* get the pixel format of the fromWindow */
int pixel_format = GetPixelFormat(hfromdc);
PIXELFORMATDESCRIPTOR pfd;
SDL_memset(&pfd, 0, sizeof(pfd));
DescribePixelFormat(hfromdc, pixel_format, sizeof(pfd), &pfd);
/* set the pixel format of the toWindow */
result = SetPixelFormat(htodc, pixel_format, &pfd);
return result ? SDL_TRUE : SDL_FALSE;
}
#endif /* SDL_VIDEO_OPENGL_WGL */
#endif /* SDL_VIDEO_DRIVER_WINDOWS */