This looks good to me:<div> </div><div>Reviewed-by: Robert Bragg <<a href="mailto:robert@linux.intel.com">robert@linux.intel.com</a>></div><div> </div><div>thanks,</div><div>- Robert</div><div class="gmail_extra"> <div class="gmail_quote">On Tue, Nov 13, 2012 at 12:10 PM, Neil Roberts <<a href="mailto:neil@linux.intel.com" target="_blank">neil@linux.intel.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> The ‘length’ for the swap chain is initially -1 which is supposed to mean ‘no preference’. However, both of the SDL winsys's were explicitly setting the SDL_GL_DOUBLEBUFFER attribute to zero in that case which would try to disable double buffering. On OS X, the equivalent to eglSwapBuffers (ie, [NSOpenGLContext flushBuffer]) does nothing for a single buffer context. The cogl-sdl-hello example does not specify the swap chain length so presumably it would end up with a single buffer config. When cogl_onscreen_swap_buffers is called it therefore does nothing and nothing is painted. I guess to make single-buffered contexts actually useful we should expose some public equivalent to glFlush so that you can ensure the rendering commands will actually hit the buffer. Alteneratively we could document that cogl_onscreen_swap_buffers performs this task on single-buffered configs and then we could make the SDL winsys explicitly call glFlush in that case. --- cogl/winsys/cogl-winsys-sdl.c | 5 +++-- cogl/winsys/cogl-winsys-sdl2.c | 5 +++-- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/cogl/winsys/cogl-winsys-sdl.c b/cogl/winsys/cogl-winsys-sdl.c index ccb0764..63abbd0 100644 --- a/cogl/winsys/cogl-winsys-sdl.c +++ b/cogl/winsys/cogl-winsys-sdl.c @@ -135,8 +135,9 @@ set_gl_attribs_from_framebuffer_config (CoglFramebufferConfig *config) SDL_GL_SetAttribute (SDL_GL_STENCIL_SIZE, config->need_stencil ? 1 : 0); - SDL_GL_SetAttribute (SDL_GL_DOUBLEBUFFER, - config->swap_chain->length > 1 ? 1 : 0); + if (config->swap_chain->length >= 0) + SDL_GL_SetAttribute (SDL_GL_DOUBLEBUFFER, + config->swap_chain->length > 1 ? 1 : 0); SDL_GL_SetAttribute (SDL_GL_ALPHA_SIZE, config->swap_chain->has_alpha ? 1 : 0); diff --git a/cogl/winsys/cogl-winsys-sdl2.c b/cogl/winsys/cogl-winsys-sdl2.c index 4c0583b..0df2607 100644 --- a/cogl/winsys/cogl-winsys-sdl2.c +++ b/cogl/winsys/cogl-winsys-sdl2.c @@ -131,8 +131,9 @@ set_gl_attribs_from_framebuffer_config (CoglFramebufferConfig *config) SDL_GL_SetAttribute (SDL_GL_STENCIL_SIZE, config->need_stencil ? 1 : 0); - SDL_GL_SetAttribute (SDL_GL_DOUBLEBUFFER, - config->swap_chain->length > 1 ? 1 : 0); + if (config->swap_chain->length >= 0) + SDL_GL_SetAttribute (SDL_GL_DOUBLEBUFFER, + config->swap_chain->length > 1 ? 1 : 0); SDL_GL_SetAttribute (SDL_GL_ALPHA_SIZE, config->swap_chain->has_alpha ? 1 : 0); -- 1.7.11.3.g3c3efa5 _______________________________________________ Cogl mailing list <a href="mailto:Cogl@lists.freedesktop.org">Cogl@lists.freedesktop.org</a> <a href="http://lists.freedesktop.org/mailman/listinfo/cogl" target="_blank">http://lists.freedesktop.org/mailman/listinfo/cogl</a> </blockquote></div> </div>