區別如下：
| SDL_Flip() | 假如有設定SDL_DOUBLEBUF時，會直接呼叫Framebuffer Driver的fb_pan_display()，藉此快速刷屏，假如沒有設定，則執行SDL_UpdateRect() |
|---|---|
| SDL_UpdateRect() | 一個區塊慢慢複製(透過blitFunc()) |
(SDL 1.2.15)src/video/SDL_video.c
1105 int SDL_Flip(SDL_Surface *screen)
...
1147 if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) {
1148 SDL_VideoDevice *this = current_video;
1149 return(video->FlipHWSurface(this, SDL_VideoSurface));
1150 } else {
1151 SDL_UpdateRect(screen, 0, 0, 0, 0);
1152 }
1153 return(0);
1154 }
(SDL 1.2.15)src/video/fbcon/SDL_fbvideo.c
1423 static int FB_FlipHWSurface(_THIS, SDL_Surface *surface)
1424 {
1425 if ( switched_away ) {
1426 return -2; /* no hardware access */
1427 }
1428
1429 /* Wait for vertical retrace and then flip display */
1430 cache_vinfo.yoffset = flip_page*surface->h;
1431 if ( FB_IsSurfaceBusy(this->screen) ) {
1432 FB_WaitBusySurfaces(this);
1433 }
1434 wait_vbl(this);
1435 if ( ioctl(console_fd, FBIOPAN_DISPLAY, &cache_vinfo) < 0 ) {
1436 SDL_SetError("ioctl(FBIOPAN_DISPLAY) failed");
1437 return(-1);
1438 }
1439 flip_page = !flip_page;
1440
1441 surface->pixels = flip_address[flip_page];
1442 return(0);
1443 }
1014 void SDL_UpdateRect(SDL_Surface *screen, Sint32 x, Sint32 y, Uint32 w, Uint32 h)
1015 {
1016 if ( screen ) {
1017 SDL_Rect rect;
1018
1019 /* Perform some checking */
1020 if ( w == 0 )
1021 w = screen->w;
1022 if ( h == 0 )
1023 h = screen->h;
1024 if ( (int)(x+w) > screen->w )
1025 return;
1026 if ( (int)(y+h) > screen->h )
1027 return;
1028
1029 /* Fill the rectangle */
1030 rect.x = (Sint16)x;
1031 rect.y = (Sint16)y;
1032 rect.w = (Uint16)w;
1033 rect.h = (Uint16)h;
1034 SDL_UpdateRects(screen, 1, &rect);
1035 }
1036 }
1037 void SDL_UpdateRects (SDL_Surface *screen, int numrects, SDL_Rect *rects)
...
1097 video->UpdateRects(this, numrects, rects);
1098 }
1099 }
1100 }
1183 this->UpdateRects = FB_DirectUpdate;
1496 static void FB_DirectUpdate(_THIS, int numrects, SDL_Rect *rects)
...
1600 blitFunc((Uint8 *) src_start,
1601 shadow_right_delta,
1602 shadow_down_delta,
1603 (Uint8 *) dst_start,
1604 physlinebytes,
1605 scr_x2 - scr_x1,
1606 scr_y2 - scr_y1);
1607 }
1608 }