Minimal changes for SampleApp to be HiDPI aware on Mac.

src/views/mac/SkNSView.mm

Index: src/views/mac/SkNSView.mm
===================================================================
--- src/views/mac/SkNSView.mm	(revision 9805)
+++ src/views/mac/SkNSView.mm	(working copy)
@@ -13,6 +13,9 @@
 SK_COMPILE_ASSERT(SK_SUPPORT_GPU, not_implemented_for_non_gpu_build);
 
 //#define FORCE_REDRAW
+// Can be dropped when we no longer support 10.6.
+#define RETINA_API_AVAILABLE (defined(MAC_OS_X_VERSION_10_7) && \
+                              MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7)
 @implementation SkNSView
 @synthesize fWind, fTitle, fOptionsDelegate, fGLContext;
 
@@ -33,15 +36,26 @@
 }
 
 - (id)initWithDefaults {
+#if RETINA_API_AVAILABLE
+    [self setWantsBestResolutionOpenGLSurface:YES];
+#endif
     fRedrawRequestPending = false;
     fWind = NULL;
     return self;
 }
 
 - (void)setUpWindow {
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                          selector:@selector(backingPropertiesChanged:)
+                                          name:@"NSWindowDidChangeBackingPropertiesNotification"
+                                          object:[self window]];
     if (NULL != fWind) {
         fWind->setVisibleP(true);
-        fWind->resize((int) self.frame.size.width, (int) self.frame.size.height, 
+        NSSize size = self.frame.size;
+#if RETINA_API_AVAILABLE
+        size = [self convertSizeToBacking:self.frame.size];
+#endif
+        fWind->resize((int) size.width, (int) size.height,
                       SkBitmap::kARGB_8888_Config);
     }
 }
@@ -54,13 +68,49 @@
     return YES;
 }
 
+- (float)scaleFactor {
+    NSWindow *window = [self window];
+#if RETINA_API_AVAILABLE
+    if (window) {
+        return [window backingScaleFactor];
+    }
+    return [[NSScreen mainScreen] backingScaleFactor];
+#else
+    if (window) {
+        return [window userSpaceScaleFactor];
+    }
+    return [[NSScreen mainScreen] userSpaceScaleFactor];
+#endif
+}
+
+- (void)backingPropertiesChanged:(NSNotification *)notification {
+    CGFloat oldBackingScaleFactor = [
+        [notification.userInfo objectForKey:@"NSBackingPropertyOldScaleFactorKey"] doubleValue
+    ];
+    CGFloat newBackingScaleFactor = [self scaleFactor];
+    if (oldBackingScaleFactor == newBackingScaleFactor) {
+        return;
+    }
+    
+    // TODO: need a better way to force a refresh (that works).
+    // [fGLContext update] does not appear to update if the point size has not changed,
+    // even if the backing size has changed.
+    [self setFrameSize:NSMakeSize(self.frame.size.width + 1, self.frame.size.height + 1)];
+}
+
 - (void)resizeSkView:(NSSize)newSize {
-    if (NULL != fWind && (fWind->width() != newSize.width || fWind->height() != newSize.height)) {
+#if RETINA_API_AVAILABLE
+    newSize = [self convertSizeToBacking:newSize];
+#endif
+    if (NULL != fWind &&
+            (fWind->width()  != newSize.width ||
+             fWind->height() != newSize.height))
+    {
         fWind->resize((int) newSize.width, (int) newSize.height);
         if (NULL != fGLContext) {
             glClear(GL_STENCIL_BUFFER_BIT);
+            [fGLContext update];
         }
-        [fGLContext update];
     }
 }
 
@@ -219,6 +269,10 @@
 
     if ([self mouse:p inRect:[self bounds]] && NULL != fWind) {
         NSPoint loc = [self convertPoint:p fromView:nil];
+#if RETINA_API_AVAILABLE
+        loc = [self convertPointToBacking:loc]; //y-up
+        loc.y = -loc.y;
+#endif
         fWind->handleClick((int) loc.x, (int) loc.y,
                            SkView::Click::kDown_State, self, modi);
     }
@@ -230,6 +284,10 @@
 
     if ([self mouse:p inRect:[self bounds]] && NULL != fWind) {
         NSPoint loc = [self convertPoint:p fromView:nil];
+#if RETINA_API_AVAILABLE
+        loc = [self convertPointToBacking:loc]; //y-up
+        loc.y = -loc.y;
+#endif
         fWind->handleClick((int) loc.x, (int) loc.y,
                            SkView::Click::kMoved_State, self, modi);
     }
@@ -241,6 +299,10 @@
     
     if ([self mouse:p inRect:[self bounds]] && NULL != fWind) {
         NSPoint loc = [self convertPoint:p fromView:nil];
+#if RETINA_API_AVAILABLE
+        loc = [self convertPointToBacking:loc]; //y-up
+        loc.y = -loc.y;
+#endif
         fWind->handleClick((int) loc.x, (int) loc.y,
                            SkView::Click::kMoved_State, self, modi);
     }
@@ -252,6 +314,10 @@
     
     if ([self mouse:p inRect:[self bounds]] && NULL != fWind) {
         NSPoint loc = [self convertPoint:p fromView:nil];
+#if RETINA_API_AVAILABLE
+        loc = [self convertPointToBacking:loc]; //y-up
+        loc.y = -loc.y;
+#endif
         fWind->handleClick((int) loc.x, (int) loc.y,
                            SkView::Click::kUp_State, self, modi);
     }
@@ -329,7 +395,11 @@
     CGLPixelFormatObj format = CGLGetPixelFormat((CGLContextObj)[fGLContext CGLContextObj]);
     CGLDescribePixelFormat(format, 0, kCGLPFASamples, &info->fSampleCount);
     CGLDescribePixelFormat(format, 0, kCGLPFAStencilSize, &info->fStencilBits);
-    glViewport(0, 0, (int) self.bounds.size.width, (int) self.bounds.size.width);
+    NSSize size = self.bounds.size;
+#if RETINA_API_AVAILABLE
+    size = [self convertSizeToBacking:size];
+#endif
+    glViewport(0, 0, (int) size.width, (int) size.height);
     glClearColor(0, 0, 0, 0);
     glClearStencil(0);
     glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);