rcore.c : mouse offset and scaling consistency - part 1

I did not want to touch `rcore.c`, but it was required for cross-paltform consistency, so that `SetMouseScale()` and `SetMouseOffset()` have same effect on every platform, and don't interfere with mouse offset and scaling required and preset by a platform which should, instead, use the new `CORE.Input.Mouse.platformOffset` and `CORE.Input.Mouse.platformScale`.

src/rcore.c

@@ -310,11 +310,14 @@ typedef struct CoreData {
 
         } Keyboard;
         struct {
-            Vector2 offset;                 // Mouse offset
-            Vector2 scale;                  // Mouse scaling
+            Vector2 offset;                 // Mouse offset in CORE.Window.screen coordinate (set by the user)
+            Vector2 scale;                  // Mouse scaling in CORE.Window.screen coordinate (set by the user)
             Vector2 currentPosition;        // Mouse position on screen
             Vector2 previousPosition;       // Previous mouse position
 
+            Vector2 platformOffset;         // Extra mouse offset set by the platform (for cross-platform consistency)
+            Vector2 platformScale;          // Extra mouse scaling set by the platform (for cross-platform consistency)
+
             int cursor;                     // Tracks current mouse cursor
             bool cursorHidden;              // Track if cursor is hidden
             bool cursorOnScreen;            // Tracks if cursor is inside client area
@@ -628,12 +631,20 @@ void InitWindow(int width, int height, const char *title)
     memset(&CORE.Input, 0, sizeof(CORE.Input));     // Reset CORE.Input structure to 0
     CORE.Input.Keyboard.exitKey = KEY_ESCAPE;
     CORE.Input.Mouse.scale = (Vector2){ 1.0f, 1.0f };
+    CORE.Input.Mouse.offset = (Vector2){ 0.0f, 0.0f };
+    CORE.Input.Mouse.platformScale = (Vector2){ 1.0f, 1.0f };
+    CORE.Input.Mouse.platformOffset = (Vector2){ 0.0f, 0.0f };
     CORE.Input.Mouse.cursor = MOUSE_CURSOR_ARROW;
     CORE.Input.Gamepad.lastButtonPressed = GAMEPAD_BUTTON_UNKNOWN;
 
     // Initialize platform
     //--------------------------------------------------------------
-    InitPlatform();
+    if ( InitPlatform() != 0 )
+    {
+        TRACELOG(LOG_ERROR, "Platform backend: Window initialization failed.");
+        CORE.Window.ready = false;
+        return;
+    }
     //--------------------------------------------------------------
 
     // Initialize rlgl default data (buffers and shaders)
@@ -3028,27 +3039,43 @@ bool IsMouseButtonUp(int button)
     return up;
 }
 
-// Get mouse position X
+// Get mouse position X in screen coordinate
 int GetMouseX(void)
 {
-    int mouseX = (int)((CORE.Input.Mouse.currentPosition.x + CORE.Input.Mouse.offset.x)*CORE.Input.Mouse.scale.x);
+    // First : apply the platform's offset and scaling :
+    int mouseX = (int)((CORE.Input.Mouse.currentPosition.x + CORE.Input.Mouse.platformOffset.x)*CORE.Input.Mouse.platformScale.x);
+
+    // Second : apply user's offset and scaling :
+    mouseX = (int)(((float)mouseX + CORE.Input.Mouse.offset.x)*CORE.Input.Mouse.scale.x);
+
     return mouseX;
 }
 
-// Get mouse position Y
+// Get mouse position Y in screen coordinate
 int GetMouseY(void)
 {
-    int mouseY = (int)((CORE.Input.Mouse.currentPosition.y + CORE.Input.Mouse.offset.y)*CORE.Input.Mouse.scale.y);
+    // First : apply the platform's offset and scaling :
+    int mouseY = (int)((CORE.Input.Mouse.currentPosition.y + CORE.Input.Mouse.platformOffset.y)*CORE.Input.Mouse.platformScale.y);
+
+    // Second : apply user's offset and scaling :
+    mouseY = (int)(((float)mouseY + CORE.Input.Mouse.offset.y)*CORE.Input.Mouse.scale.y);
+
     return mouseY;
 }
 
-// Get mouse position XY
+// Get mouse position XY in screen coordinate
 Vector2 GetMousePosition(void)
 {
     Vector2 position = { 0 };
 
-    position.x = (CORE.Input.Mouse.currentPosition.x + CORE.Input.Mouse.offset.x)*CORE.Input.Mouse.scale.x;
-    position.y = (CORE.Input.Mouse.currentPosition.y + CORE.Input.Mouse.offset.y)*CORE.Input.Mouse.scale.y;
+    // First : apply the platform's offset and scaling :
+    position.x = (CORE.Input.Mouse.currentPosition.x + CORE.Input.Mouse.platformOffset.x)*CORE.Input.Mouse.platformScale.x;
+    position.y = (CORE.Input.Mouse.currentPosition.y + CORE.Input.Mouse.platformOffset.y)*CORE.Input.Mouse.platformScale.y;
+
+    // Second : apply the user's offset and scaling :
+
+    position.x = (position.x + CORE.Input.Mouse.offset.x)*CORE.Input.Mouse.scale.x;
+    position.y = (position.y + CORE.Input.Mouse.offset.y)*CORE.Input.Mouse.scale.y;
 
     return position;
 }
@@ -3064,14 +3091,14 @@ Vector2 GetMouseDelta(void)
     return delta;
 }
 
-// Set mouse offset
+// Set user's mouse offset
 // NOTE: Useful when rendering to different size targets
 void SetMouseOffset(int offsetX, int offsetY)
 {
     CORE.Input.Mouse.offset = (Vector2){ (float)offsetX, (float)offsetY };
 }
 
-// Set mouse scaling
+// Set user's mouse scaling
 // NOTE: Useful when rendering to different size targets
 void SetMouseScale(float scaleX, float scaleY)
 {