Finalise implementation of HiDPI mode for OS X

doc/lwjgl_hidden_switches.text

@@ -22,4 +22,7 @@ org.lwjgl.opengl.Window.undecorated
 Whether to create an undecorated window (no title bar)
 
 org.lwjgl.input.Mouse.allowNegativeMouseCoords
-Usually mouse is clamped to 0,0 - setting this to true will cause you to get negative values if dragging outside and below or left of window
+Usually mouse is clamped to 0,0 - setting this to true will cause you to get negative values if dragging outside and below or left of window
+
+org.lwjgl.opengl.Display.enableHighDPI
+Enable high DPI mode where available

src/java/org/lwjgl/opengl/Display.java

@@ -1358,8 +1358,9 @@ public final class Display {
 	 * not be scaled to match the Display window size.
 	 * 
 	 * OpenGL methods that require pixel dependent values e.g. glViewport, glTexImage2D,
-	 * glReadPixels, etc can convert the scaled Display and Mouse coordinates to the 
-	 * correct high resolution value by multiplying them by the pixel scale factor.
+	 * glReadPixels, glScissor, glLineWidth, glRenderbufferStorage, etc can convert the 
+	 * scaled Display and Mouse coordinates to the correct high resolution value by 
+	 * multiplying them by the pixel scale factor.
 	 * 
 	 * e.g. Display.getWidth() * Display.getPixelScaleFactor() will return the high DPI
 	 * width of the OpenGL frame buffer. Whereas Display.getWidth() will be the same as

src/java/org/lwjgl/opengl/MacOSXDisplay.java

@@ -91,6 +91,10 @@ final class MacOSXDisplay implements DisplayImplementation {
 	private boolean updateNativeCursor = false;
 	
 	private long currentNativeCursor = 0;
+	
+	private boolean enableHighDPI = false;
+	
+	private float scaleFactor = 1.0f;
 
 	MacOSXDisplay() {
 		
@@ -136,7 +140,7 @@ final class MacOSXDisplay implements DisplayImplementation {
 											!Display.getPrivilegedBoolean("org.lwjgl.opengl.Display.disableOSXFullscreenModeAPI");
 		
 		// OS X high DPI mode is only available on OS X 10.7+
-		boolean enableHighDPI = LWJGLUtil.isMacOSXEqualsOrBetterThan(10, 7) && parent == null &&
+		enableHighDPI = LWJGLUtil.isMacOSXEqualsOrBetterThan(10, 7) && parent == null &&
 											Display.getPrivilegedBoolean("org.lwjgl.opengl.Display.enableHighDPI");
 		
 		if (parented) this.canvas = parent;
@@ -191,6 +195,12 @@ final class MacOSXDisplay implements DisplayImplementation {
 		}
 		updateNativeCursor = true;
 	}
+	
+	public void setScaleFactor(float scale) {
+		synchronized (this) {
+			scaleFactor = scale;
+		}
+	}
 
 	public native void nDestroyCALayer(ByteBuffer peer_info_handle);
 	
@@ -624,7 +634,7 @@ final class MacOSXDisplay implements DisplayImplementation {
 	}
 	
 	public float getPixelScaleFactor() {
-		return 1f;
+		return (enableHighDPI && !Display.isFullscreen()) ? scaleFactor : 1f;
 	}
 
 }

src/native/macosx/org_lwjgl_opengl_Display.m

@@ -74,6 +74,9 @@ static NSUInteger lastModifierFlags = 0;
 	window_info->view = [[MacOSXOpenGLView alloc] initWithFrame:view_rect pixelFormat:peer_info->pixel_format];
 	[window_info->view setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
 
+    // Inform the view of its parent window info;
+	[window_info->view setParent:window_info];
+	
 	if (window_info->enableHighDPI) {
 		// call method using runtime selector as its a 10.7+ api and allows compiling on older SDK's
 		[window_info->view performSelector:NSSelectorFromString(@"setWantsBestResolutionOpenGLSurface:") withObject:YES];
@@ -134,9 +137,6 @@ static NSUInteger lastModifierFlags = 0;
 		[window_info->view setBoundsSize:newBounds];
 	}
 	
-	// Inform the view of its parent window info;
-	[window_info->view setParent:window_info];
-	
 	if (window_info->enableFullscreenModeAPI && window_info->resizable) {
 		// manually create OS X 10.7+ mask to allow compilation on previous OS X versions
 		NSUInteger NSWindowCollectionBehaviorFullScreenPrimary = 1 << 7;
@@ -499,6 +499,30 @@ static NSUInteger lastModifierFlags = 0;
 	}
 }
 
+- (void)viewDidChangeBackingProperties {
+	JNIEnv *env = attachCurrentThread();
+	if (env == nil || _parent == nil || _parent->jdisplay == nil) {
+		return;
+	}
+	
+	jclass display_class = (*env)->GetObjectClass(env, _parent->jdisplay);
+	jmethodID setScaleFactor_callback = (*env)->GetMethodID(env, display_class, "setScaleFactor", "(F)V");
+	
+	CGFloat scaleFactor;
+	
+	// call method using runtime selector as its a 10.7+ api and allows compiling on older SDK's
+	SEL selector = NSSelectorFromString(@"backingScaleFactor");
+	
+	// as we are using a runtime selector, we need to use NSInvocations to get a CGFloat value back from it
+	NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[[[self window] class] instanceMethodSignatureForSelector:selector]];
+	[invocation setSelector:selector];
+	[invocation setTarget:[self window]];
+	[invocation invoke];
+	[invocation getReturnValue:&scaleFactor];
+	
+	(*env)->CallVoidMethod(env, _parent->jdisplay, setScaleFactor_callback, scaleFactor);
+}
+
 -(void)updateTrackingAreas {
 	if(_trackingArea != nil) {
 		[self removeTrackingArea:_trackingArea];