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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 dbd4a917e0
commit d76c2cc1da
4 changed files with 66 additions and 0 deletions
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19
include/SDL_hints.h
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@ -328,6 +328,25 @@ extern "C" {
*/
#define SDL_HINT_VIDEO_WIN_D3DCOMPILER "SDL_VIDEO_WIN_D3DCOMPILER"
/**
* \brief A variable that is the address of another SDL_Window* (as a hex string formatted with "%p").
*
* If this hint is set before SDL_CreateWindowFrom() and the SDL_Window* it is set to has
* SDL_WINDOW_OPENGL set (and running on WGL only, currently), then two things will occur on the newly
* created SDL_Window:
* 1. Its pixel format will be set to the same pixel format as this SDL_Window. This is
* needed for example when sharing an OpenGL context across multiple windows.
*
* 2. The flag SDL_WINDOW_OPENGL will be set on the new window so it can be used for
* OpenGL rendering.
*
* This variable can be set to the following values:
* The address (as a string "%p") of the SDL_Window* that new windows created with SDL_CreateWindowFrom() should
* share a pixel format with.
*/
#define SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT "SDL_VIDEO_WINDOW_SHARE_PIXEL_FORMAT"
/**
* \brief An enumeration of hint priorities
*/