MacViews: Add native drop shadow to dialogs on OSX < 10.10.

ui/views/cocoa/bridged_content_view.mm

Index: ui/views/cocoa/bridged_content_view.mm
diff --git a/ui/views/cocoa/bridged_content_view.mm b/ui/views/cocoa/bridged_content_view.mm
index 56e53abe4eaf4e947ae921953083f16ada4f8924..deb211faa5e3675d76b1315b5961e800bff87350 100644
--- a/ui/views/cocoa/bridged_content_view.mm
+++ b/ui/views/cocoa/bridged_content_view.mm
@@ -5,6 +5,7 @@
 #import "ui/views/cocoa/bridged_content_view.h"
 
 #include "base/logging.h"
+#import "base/mac/mac_util.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "skia/ext/skia_utils_mac.h"
@@ -16,6 +17,9 @@
 #import "ui/events/keycodes/keyboard_code_conversion_mac.h"
 #include "ui/gfx/canvas_paint_mac.h"
 #include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/path.h"
+#import "ui/gfx/path_mac.h"
+#include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 #include "ui/strings/grit/ui_strings.h"
 #include "ui/views/controls/menu/menu_config.h"
 #include "ui/views/controls/menu/menu_controller.h"
@@ -26,6 +30,17 @@ using views::MenuController;
 
 namespace {
 
+// Returns true if all four corners of |rect| are contained inside |path|.
+bool IsRectInsidePath(NSRect rect, NSBezierPath* path) {
+  return [path containsPoint:rect.origin] &&
+         [path containsPoint:NSMakePoint(rect.origin.x + rect.size.width,
+                                         rect.origin.y)] &&
+         [path containsPoint:NSMakePoint(rect.origin.x,
+                                         rect.origin.y + rect.size.height)] &&
+         [path containsPoint:NSMakePoint(rect.origin.x + rect.size.width,
+                                         rect.origin.y + rect.size.height)];
+}
+
 // Convert a |point| in |source_window|'s AppKit coordinate system (origin at
 // the bottom left of the window) to |target_window|'s content rect, with the
 // origin at the top left of the content area.
@@ -117,6 +132,20 @@ bool DispatchEventToMenu(views::Widget* widget, ui::KeyboardCode key_code) {
                owner:self
             userInfo:nil]);
     [self addTrackingArea:cursorTrackingArea_.get()];
+
+    // Get Notified whenever the view bounds or frame change.
+    [self setPostsBoundsChangedNotifications:YES];
+    [self setPostsFrameChangedNotifications:YES];
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(boundsDidChangeNotification:)
+               name:NSViewBoundsDidChangeNotification
+             object:self];
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(boundsDidChangeNotification:)
+               name:NSViewFrameDidChangeNotification
+             object:self];
   }
   return self;
 }
@@ -306,6 +335,15 @@ bool DispatchEventToMenu(views::Widget* widget, ui::KeyboardCode key_code) {
   hostedView_->SetSize(gfx::Size(newSize.width, newSize.height));
 }
 
+- (void)viewDidEndLiveResize {
+  // We prevent updating the window mask and clipping the border around the
+  // view, during a live resize. Hence update the window mask and redraw the
+  // view after resize has completed.
+  [super viewDidEndLiveResize];

[karandeepb, 2016/02/04 03:39:28]

This optimisation to prevent drawing during a live resize leads to rectangular
corners during a resize. Should we go ahead with it? 

+  [self setWindowMask];
+  [self setNeedsDisplay:YES];
+}
+
 - (void)drawRect:(NSRect)dirtyRect {
   // Note that BridgedNativeWidget uses -[NSWindow setAutodisplay:NO] to
   // suppress calls to this when the window is known to be hidden.
@@ -320,6 +358,31 @@ bool DispatchEventToMenu(views::Widget* widget, ui::KeyboardCode key_code) {
                                      yRadius:radius] fill];
   }
 
+  // On OS versions earlier than Yosemite, to generate a drop shadow, we set an
+  // opaque background. This distorts windows with non rectangular shapes. To
+  // get around this, fill the path outside the window boundary with clearColor
+  // and tell Cococa to regenerate drop shadow. See crbug.com/543671.
+  if (windowMask_ && ![self inLiveResize] &&
+      !IsRectInsidePath(dirtyRect, windowMask_)) {
+    gfx::ScopedNSGraphicsContextSaveGState state;
+    DLOG(WARNING) << "Drawing\n";
+    // The outer rectangular path corresponding to the window.
+    NSBezierPath* outerPath = [NSBezierPath bezierPathWithRect:[self bounds]];
+
+    [outerPath appendBezierPath:windowMask_];
+    [outerPath setWindingRule:NSEvenOddWindingRule];
+    [[NSGraphicsContext currentContext]
+        setCompositingOperation:NSCompositeCopy];
+    [[NSColor clearColor] set];
+
+    // Fill the region between windowMask_ and its outer rectangular path
+    // with clear color. This causes the window to have the shape described
+    // by windowMask_.
+    [outerPath fill];
+    // Regerate drop shadow around the window boundary.
+    [[self window] invalidateShadow];
+  }
+
   // If there's a layer, painting occurs in BridgedNativeWidget::OnPaintLayer().
   if (hostedView_->GetWidget()->GetLayer())
     return;
@@ -741,4 +804,42 @@ bool DispatchEventToMenu(views::Widget* widget, ui::KeyboardCode key_code) {
   return [hostedView_->GetNativeViewAccessible() accessibilityHitTest:point];
 }
 
+// Update windowMask_ depending on the current view bounds.
+- (void)setWindowMask {
+  // Ensure a live resize is not in progress.
+  DCHECK(![self inLiveResize]);
+
+  views::Widget* widget = hostedView_->GetWidget();
+  if (widget->non_client_view() && base::mac::IsOSMavericksOrEarlier()) {
+    const NSRect frameRect = [self bounds];
+    gfx::Path mask;
+    widget->non_client_view()->GetWindowMask(gfx::Size(frameRect.size), &mask);
+    if (!mask.isEmpty()) {
+      windowMask_.reset([gfx::CreateNSBezierPathFromSkPath(mask) retain]);
+
+      // Convert to AppKit coordinate system.
+      NSAffineTransform* flipTransform = [NSAffineTransform transform];
+      [flipTransform translateXBy:0.0 yBy:frameRect.size.height];
+      [flipTransform scaleXBy:1.0 yBy:-1.0];
+      [windowMask_ transformUsingAffineTransform:flipTransform];
+    }
+  }
+}
+
+// Called whenever the view's bounds or frame change. Used to update
+// windowMask_.
+- (void)boundsDidChangeNotification:(NSNotification*)notification {
+  // Ensure that the notification was posted by this object.
+  DCHECK_EQ(notification.object, self);
+  // We don't update the window mask during a live resize, instead it is done
+  // after the resize is completed in viewDidEndLiveResize:.
+  if (![self inLiveResize])
+    [self setWindowMask];
+}
+
+- (void)dealloc {
+  [[NSNotificationCenter defaultCenter] removeObserver:self];
+  [super dealloc];
+}
+
 @end