Added SDL_GetCurrentVideoDisplay()

include/SDL_video.h

@@ -403,14 +403,25 @@ extern DECLSPEC int SDLCALL SDL_GetNumVideoDisplays(void);
  *
  * \brief Set the index of the currently selected display.
  *
- * \return The index of the currently selected display.
- *
- * \note You can query the currently selected display by passing an index of -1.
+ * \return 0 on success, or -1 if the index is out of range.
  *
  * \sa SDL_GetNumVideoDisplays()
+ * \sa SDL_GetCurrentVideoDisplay()
  */
 extern DECLSPEC int SDLCALL SDL_SelectVideoDisplay(int index);
 
+/**
+ * \fn int SDL_GetCurrentVideoDisplay(void)
+ *
+ * \brief Get the index of the currently selected display.
+ *
+ * \return The index of the currently selected display.
+ *
+ * \sa SDL_GetNumVideoDisplays()
+ * \sa SDL_SelectVideoDisplay()
+ */
+extern DECLSPEC int SDLCALL SDL_GetCurrentVideoDisplay(void);
+
 /**
  * \fn int SDL_GetNumDisplayModes(void)
  *

src/video/SDL_video.c

@@ -355,13 +355,21 @@ SDL_SelectVideoDisplay(int index)
         SDL_UninitializedVideo();
         return (-1);
     }
-    if (index >= 0) {
-        if (index >= _this->num_displays) {
-            SDL_SetError("index must be in the range 0 - %d",
-                         _this->num_displays - 1);
-            return -1;
-        }
-        _this->current_display = index;
+    if (index < 0 || index >= _this->num_displays) {
+        SDL_SetError("index must be in the range 0 - %d",
+                     _this->num_displays - 1);
+        return -1;
+    }
+    _this->current_display = index;
+    return 0;
+}
+
+int
+SDL_GetCurrentVideoDisplay(void)
+{
+    if (!_this) {
+        SDL_UninitializedVideo();
+        return (-1);
     }
     return _this->current_display;
 }