Re: [PATCH 1/5] winex11: Use GLX_OML_sync_control to synchronise buffer swaps with X11DRV_FLUSH_GL_DRAWABLE requests.

[Ken Thomases]

On Mar 23, 2017, at 4:49 PM, Henri Verbeet  wrote:
> @@ -3330,17 +3343,26 @@ static BOOL glxdrv_wglSwapBuffers( HDC hdc )
>                                    gl->rect.right - gl->rect.left, gl->rect.bottom - gl->rect.top );
>             break;
>         }
> -
>    pglXSwapBuffers(gdi_display, gl->drawable);
> -
>    if (pglXSwapBuffersMscOML)
> -
>        target_sbc = pglXSwapBuffersMscOML( gdi_display, gl->drawable, 0, 0, 0 );
> -
>    else
> -
>        pglXSwapBuffers( gdi_display, gl->drawable );
>   break;
> case DC_GL_CHILD_WIN:
>       if (ctx) sync_context( ctx );
>       escape.gl_drawable = gl->window;
>       /* fall through */
>   default:
> -
>    pglXSwapBuffers(gdi_display, gl->drawable);
> -
>    if (pglXSwapBuffersMscOML)
> -
>        target_sbc = pglXSwapBuffersMscOML( gdi_display, gl->drawable, 0, 0, 0 );
> -
>    else
> -
>        pglXSwapBuffers( gdi_display, gl->drawable );
>   break;
>
> }
> -
>
> if (escape.gl_drawable && pglXWaitForSbcOML)
> -
>    pglXWaitForSbcOML( gdi_display, gl->drawable, target_sbc, &ust, &msc, &sbc );
> -
>
> release_gl_drawable( gl );
>
> if (escape.gl_drawable) ExtEscape( ctx->hdc, X11DRV_ESCAPE, sizeof(escape), (LPSTR)&escape, 0, NULL );

According to the spec https://www.khronos.org/registry/OpenGL/extensions/OML/GLX_OML_sync_control.txt, glXSwapBuffersMscOML() does not perform an implicit glFlush() as glXSwapBuffers() does.  Also, there's no indication that 
glXWaitForSbcOML() performs one either, although it sort of seems like it should.  Is that a problem?

-Ken

[PATCH 1/5] winex11: Use GLX_OML_sync_control to synchronise buffer swaps with X11DRV_FLUSH_GL_DRAWABLE requests.

[Henri Verbeet]

On 23 March 2017 at 23:26, Ken Thomases  wrote:
> According to the spec https://www.khronos.org/registry/OpenGL/extensions/OML/GLX_OML_sync_control.txt, glXSwapBuffersMscOML() does not perform an implicit glFlush() as glXSwapBuffers() does.  Also, there's no indication that
> glXWaitForSbcOML() performs one either, although it sort of seems like it should.  Is that a problem?

Possibly, although it isn't clear that wglSwapBuffers() is necessarily
guaranteed to flush either. It's probably safer to explicitly flush
anyway though.