From 2ab858c6c38ee152299445f2810dbd4c3a0ac7ee Mon Sep 17 00:00:00 2001 From: Anatoly Trosinenko Date: Mon, 5 Feb 2018 16:32:28 +0300 Subject: [PATCH] sdl: restore optimized redraw The documentation on SDL_RenderPresent function states that "the backbuffer should be considered invalidated after each present", so copy the entire texture on each redraw. On the other hand, SDL_UpdateTexture function is described as "fairly slow function", so restrict it to just the changed pixels. Also added SDL_RenderClear call, as suggested in the documentation page on SDL_RenderPresent. Signed-off-by: Anatoly Trosinenko Message-id: 20180205133228.25082-1-anatoly.trosinenko@gmail.com Signed-off-by: Gerd Hoffmann --- ui/sdl2-2d.c | 23 +++++++---------------- 1 file changed, 7 insertions(+), 16 deletions(-) diff --git a/ui/sdl2-2d.c b/ui/sdl2-2d.c index 8ab68d67b9..1f34817bae 100644 --- a/ui/sdl2-2d.c +++ b/ui/sdl2-2d.c @@ -36,6 +36,8 @@ void sdl2_2d_update(DisplayChangeListener *dcl, struct sdl2_console *scon = container_of(dcl, struct sdl2_console, dcl); DisplaySurface *surf = qemu_console_surface(dcl->con); SDL_Rect rect; + size_t surface_data_offset = surface_bytes_per_pixel(surf) * x + + surface_stride(surf) * y; assert(!scon->opengl); @@ -46,27 +48,16 @@ void sdl2_2d_update(DisplayChangeListener *dcl, return; } - /* - * SDL2 seems to do some double-buffering, and trying to only - * update the changed areas results in only one of the two buffers - * being updated. Which flickers alot. So lets not try to be - * clever do a full update every time ... - */ -#if 0 rect.x = x; rect.y = y; rect.w = w; rect.h = h; -#else - rect.x = 0; - rect.y = 0; - rect.w = surface_width(surf); - rect.h = surface_height(surf); -#endif - - SDL_UpdateTexture(scon->texture, NULL, surface_data(surf), + + SDL_UpdateTexture(scon->texture, &rect, + surface_data(surf) + surface_data_offset, surface_stride(surf)); - SDL_RenderCopy(scon->real_renderer, scon->texture, &rect, &rect); + SDL_RenderClear(scon->real_renderer); + SDL_RenderCopy(scon->real_renderer, scon->texture, NULL, NULL); SDL_RenderPresent(scon->real_renderer); } -- 2.11.4.GIT