SDL: Scale the joystick mouse speed with the vertical window size

The mouse cursor now moves across the screen in a similar amount of time
irrespective of the display resolution.

2 files changed, 52 insertions, 40 deletions

diff --git a/backends/events/sdl/sdl-events.cpp b/backends/events/sdl/sdl-events.cpp
index a3dee67f22..a3c0087b94 100644
--- a/backends/events/sdl/sdl-events.cpp
+++ b/backends/events/sdl/sdl-events.cpp
@@ -212,46 +212,7 @@ bool SdlEventSource::handleKbdMouse(Common::Event &event) {
 				}
 			}
 
-			int16 speedFactor = 25;
-
-			if (g_system->hasFeature(OSystem::kFeatureKbdMouseSpeed)) {
-				switch (ConfMan.getInt("kbdmouse_speed")) {
-				// 0.25 keyboard pointer speed
-				case 0:
-					speedFactor = 100;
-					break;
-				// 0.5 speed
-				case 1:
-					speedFactor = 50;
-					break;
-				// 0.75 speed
-				case 2:
-					speedFactor = 33;
-					break;
-				// 1.0 speed
-				case 3:
-					speedFactor = 25;
-					break;
-				// 1.25 speed
-				case 4:
-					speedFactor = 20;
-					break;
-				// 1.5 speed
-				case 5:
-					speedFactor = 17;
-					break;
-				// 1.75 speed
-				case 6:
-					speedFactor = 14;
-					break;
-				// 2.0 speed
-				case 7:
-					speedFactor = 12;
-					break;
-				default:
-					speedFactor = 25;
-				}
-			}
+			int16 speedFactor = computeJoystickMouseSpeedFactor();
 
 			// - The modifier key makes the mouse movement slower
 			// - The extra factor "delay/speedFactor" ensures velocities 
@@ -300,6 +261,51 @@ bool SdlEventSource::handleKbdMouse(Common::Event &event) {
 	return false;
 }
 
+int16 SdlEventSource::computeJoystickMouseSpeedFactor() const {
+	int16 speedFactor;
+
+	switch (ConfMan.getInt("kbdmouse_speed")) {
+	// 0.25 keyboard pointer speed
+	case 0:
+		speedFactor = 100;
+		break;
+	// 0.5 speed
+	case 1:
+		speedFactor = 50;
+		break;
+	// 0.75 speed
+	case 2:
+		speedFactor = 33;
+		break;
+	// 1.0 speed
+	case 3:
+		speedFactor = 25;
+		break;
+	// 1.25 speed
+	case 4:
+		speedFactor = 20;
+		break;
+	// 1.5 speed
+	case 5:
+		speedFactor = 17;
+		break;
+	// 1.75 speed
+	case 6:
+		speedFactor = 14;
+		break;
+	// 2.0 speed
+	case 7:
+		speedFactor = 12;
+		break;
+	default:
+		speedFactor = 25;
+	}
+
+	// Scale the mouse cursor speed with the display size so moving across
+	// the screen takes a reasonable amount of time at higher resolutions.
+	return speedFactor * 480 / _km.y_max;
+}
+
 void SdlEventSource::SDLModToOSystemKeyFlags(SDLMod mod, Common::Event &event) {
 
 	event.kbd.flags = 0;
diff --git a/backends/events/sdl/sdl-events.h b/backends/events/sdl/sdl-events.h
index f5bbfeb15c..c4c2ab406d 100644
--- a/backends/events/sdl/sdl-events.h
+++ b/backends/events/sdl/sdl-events.h
@@ -152,6 +152,12 @@ protected:
 	virtual bool handleAxisToMouseMotion(int16 xAxis, int16 yAxis);
 
 	/**
+	 * Compute the virtual mouse movement speed factor according to the 'kbdmouse_speed' setting.
+	 * The speed factor is scaled with the display size.
+	 */
+	int16 computeJoystickMouseSpeedFactor() const;
+
+	/**
 	 * Assigns the mouse coords to the mouse event. Furthermore notify the
 	 * graphics manager about the position change.
 	 */