ffplay: fill the unused part of the window with black

Should fix ticket #1667.
Signed-off-by: Marton Balint <cus@passwd.hu>

ffplay.c

@@ -234,6 +234,7 @@ typedef struct VideoState {
 #if !CONFIG_AVFILTER
     struct SwsContext *img_convert_ctx;
 #endif
+    SDL_Rect last_display_rect;
 
     char filename[1024];
     int width, height, xleft, ytop;
@@ -461,6 +462,42 @@ static inline void fill_rectangle(SDL_Surface *screen,
         SDL_UpdateRect(screen, x, y, w, h);
 }
 
+/* draw only the border of a rectangle */
+static void fill_border(int xleft, int ytop, int width, int height, int x, int y, int w, int h, int color, int update)
+{
+    int w1, w2, h1, h2;
+
+    /* fill the background */
+    w1 = x;
+    if (w1 < 0)
+        w1 = 0;
+    w2 = width - (x + w);
+    if (w2 < 0)
+        w2 = 0;
+    h1 = y;
+    if (h1 < 0)
+        h1 = 0;
+    h2 = height - (y + h);
+    if (h2 < 0)
+        h2 = 0;
+    fill_rectangle(screen,
+                   xleft, ytop,
+                   w1, height,
+                   color, update);
+    fill_rectangle(screen,
+                   xleft + width - w2, ytop,
+                   w2, height,
+                   color, update);
+    fill_rectangle(screen,
+                   xleft + w1, ytop,
+                   width - w1 - w2, h1,
+                   color, update);
+    fill_rectangle(screen,
+                   xleft + w1, ytop + height - h2,
+                   width - w1 - w2, h2,
+                   color, update);
+}
+
 #define ALPHA_BLEND(a, oldp, newp, s)\
 ((((oldp << s) * (255 - (a))) + (newp * (a))) / (255 << s))
 
@@ -761,6 +798,12 @@ static void video_image_display(VideoState *is)
         calculate_display_rect(&rect, is->xleft, is->ytop, is->width, is->height, vp);
 
         SDL_DisplayYUVOverlay(vp->bmp, &rect);
+
+        if (rect.x != is->last_display_rect.x || rect.y != is->last_display_rect.y || rect.w != is->last_display_rect.w || rect.h != is->last_display_rect.h || is->force_refresh) {
+            int bgcolor = SDL_MapRGB(screen->format, 0x00, 0x00, 0x00);
+            fill_border(is->xleft, is->ytop, is->width, is->height, rect.x, rect.y, rect.w, rect.h, bgcolor, 1);
+            is->last_display_rect = rect;
+        }
     }
 }