OPENGL: Smooth mouse experience when black bars are visible.

This gets rid of the feeling of the mouse sticking to black borders by using
the full output resolution as area for tracking game mouse movement. The same
behavior is present in plain SDL output with SDL2.

backends/graphics/opengl/opengl-graphics.cpp

@@ -551,11 +551,8 @@ void OpenGLGraphicsManager::warpMouse(int x, int y) {
 			return;
 		}
 
-		x = (x * _displayWidth)  / _gameScreen->getWidth();
-		y = (y * _displayHeight) / _gameScreen->getHeight();
-
-		x += _displayX;
-		y += _displayY;
+		x = (x * _outputScreenWidth)  / _gameScreen->getWidth();
+		y = (y * _outputScreenHeight) / _gameScreen->getHeight();
 	}
 
 	setMousePosition(x, y);
@@ -946,18 +943,11 @@ void OpenGLGraphicsManager::adjustMousePosition(int16 &x, int16 &y) {
 			y = (y * _overlay->getHeight()) / _outputScreenHeight;
 		}
 	} else if (_gameScreen) {
-		x -= _displayX;
-		y -= _displayY;
-
 		const int16 width  = _gameScreen->getWidth();
 		const int16 height = _gameScreen->getHeight();
 
-		x = (x * width)  / (int)_displayWidth;
-		y = (y * height) / (int)_displayHeight;
-
-		// Make sure we only supply valid coordinates.
-		x = CLIP<int16>(x, 0, width - 1);
-		y = CLIP<int16>(y, 0, height - 1);
+		x = (x * width)  / (int)_outputScreenWidth;
+		y = (y * height) / (int)_outputScreenHeight;
 	}
 }
 
@@ -975,8 +965,8 @@ void OpenGLGraphicsManager::setMousePosition(int x, int y) {
 		_cursorDisplayX = x;
 		_cursorDisplayY = y;
 	} else {
-		_cursorDisplayX = CLIP<int>(x, _displayX, _displayX + _displayWidth  - 1);
-		_cursorDisplayY = CLIP<int>(y, _displayY, _displayY + _displayHeight - 1);
+		_cursorDisplayX = _displayX + (x * _displayWidth)  / _outputScreenWidth;
+		_cursorDisplayY = _displayY + (y * _displayHeight) / _outputScreenHeight;
 	}
 }