video: Added a hint to override the display's usable bounds.

include/SDL_hints.h

@@ -1229,6 +1229,20 @@ extern "C" {
  */
 #define SDL_HINT_WAVE_FACT_CHUNK   "SDL_WAVE_FACT_CHUNK"
 
+/*
+ *  \brief Override for SDL_GetDisplayUsableBounds()
+ *
+ *  If set, this hint will override the expected results for
+ *  SDL_GetDisplayUsableBounds() for display index 0. Generally you don't want
+ *  to do this, but this allows an embedded system to request that some of the
+ *  screen be reserved for other uses when paired with a well-behaved
+ *  application.
+ *
+ *  The contents of this hint must be 4 comma-separated integers, the first
+ *  is the bounds x, then y, width and height, in that order.
+ */
+#define SDL_HINT_DISPLAY_USABLE_BOUNDS "SDL_DISPLAY_USABLE_BOUNDS"
+
 /**
  *  \brief  An enumeration of hint priorities
  */

src/video/SDL_video.c

@@ -706,13 +706,25 @@ SDL_GetDisplayBounds(int displayIndex, SDL_Rect * rect)
     return 0;  /* !!! FIXME: should this be an error if (rect==NULL) ? */
 }
 
-int SDL_GetDisplayUsableBounds(int displayIndex, SDL_Rect * rect)
+static int
+ParseDisplayUsableBoundsHint(SDL_Rect *rect)
+{
+    const char *hint = SDL_GetHint(SDL_HINT_DISPLAY_USABLE_BOUNDS);
+    return hint && (SDL_sscanf(hint, "%d,%d,%d,%d", &rect->x, &rect->y, &rect->w, &rect->h) == 4);
+}
+
+int
+SDL_GetDisplayUsableBounds(int displayIndex, SDL_Rect * rect)
 {
     CHECK_DISPLAY_INDEX(displayIndex, -1);
 
     if (rect) {
         SDL_VideoDisplay *display = &_this->displays[displayIndex];
 
+        if ((displayIndex == 0) && ParseDisplayUsableBoundsHint(rect)) {
+            return 0;
+        }
+
         if (_this->GetDisplayUsableBounds) {
             if (_this->GetDisplayUsableBounds(_this, display, rect) == 0) {
                 return 0;