Mac: Add nice fade effect to overflowing bookmark buttons in the bookmark bar

Port magic from GTMFadeTruncatingTextFieldCell to Chrome's GradientButtonCell, used by buttons in the bookmark bar.  Any button that inherits from this class will now get overflowing titles truncated with a nice gradient (same as tab titles), rather than the default ellipsis.

Using GTMFadeTruncatingTextFieldCell in this case wasn't feasible because bookmark buttons are subclasses of NSButtonCell and already use a bunch of specialized behavior provided by it.

BUG=45104
TEST=Add a bookmark to the bookmark bar and increase the length of it's title.  Once you get past a certain length, rather than truncate the title should fade out nicely.  Exactly in the same way long tab titles do.  Bookmark buttons with titles that aren't truncated should look exactly the same. Also test with Dolce & Gabbana theme which has inverted contrast.

Review URL: http://codereview.chromium.org/2806066

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53773 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 74 insertions, 0 deletions

diff --git a/chrome/browser/cocoa/gradient_button_cell.mm b/chrome/browser/cocoa/gradient_button_cell.mm
index f924f1f..64e3f75 100644
--- a/chrome/browser/cocoa/gradient_button_cell.mm
+++ b/chrome/browser/cocoa/gradient_button_cell.mm
@@ -453,6 +453,80 @@ static const NSTimeInterval kAnimationHideDuration = 0.4;
   }
 }
 
+// Overriden from NSButtonCell so we can display a nice fadeout effect for
+// button titles that overflow.
+// This method is copied in the most part from GTMFadeTruncatingTextFieldCell,
+// the only difference is that here we draw the text ourselves rather than
+// calling the super to do the work.
+// We can't use GTMFadeTruncatingTextFieldCell because there's no easy way to
+// get it to work with NSButtonCell.
+// TODO(jeremy): Move this to GTM.
+- (NSRect)drawTitle:(NSAttributedString *)title
+          withFrame:(NSRect)cellFrame
+             inView:(NSView *)controlView {
+  NSSize size = [title size];
+
+  // Don't complicate drawing unless we need to clip
+  if (size.width <= NSWidth(cellFrame)) {
+    return [super drawTitle:title withFrame:cellFrame inView:controlView];
+  }
+
+  // Gradient is about twice our line height long.
+  CGFloat gradientWidth = MIN(size.height * 2, NSWidth(cellFrame) / 4);
+
+  NSRect solidPart, gradientPart;
+  NSDivideRect(cellFrame, &gradientPart, &solidPart, gradientWidth, NSMaxXEdge);
+
+  // Draw non-gradient part without transparency layer, as light text on a dark
+  // background looks bad with a gradient layer.
+  [[NSGraphicsContext currentContext] saveGraphicsState];
+  [NSBezierPath clipRect:solidPart];
+
+  // 11 is the magic number needed to make this match the native NSButtonCell's
+  // label display.
+  CGFloat textLeft = [[self image] size].width + 11;
+
+  // For some reason, the height of cellFrame as passed in is totally bogus.
+  // For vertical centering purposes, we need the bounds of the containing
+  // view.
+  NSRect buttonFrame = [[self controlView] frame];
+
+  // Off-by-one to match native NSButtonCell's version.
+  NSPoint textOffset = NSMakePoint(textLeft,
+                        (NSHeight(buttonFrame) - size.height)/2 + 1);
+  [title drawAtPoint:textOffset];
+  [[NSGraphicsContext currentContext] restoreGraphicsState];
+
+  // Draw the gradient part with a transparency layer. This makes the text look
+  // suboptimal, but since it fades out, that's ok.
+  [[NSGraphicsContext currentContext] saveGraphicsState];
+  [NSBezierPath clipRect:gradientPart];
+  CGContextRef context = static_cast<CGContextRef>(
+      [[NSGraphicsContext currentContext] graphicsPort]);
+  CGContextBeginTransparencyLayerWithRect(context,
+                                          NSRectToCGRect(gradientPart), 0);
+  [title drawAtPoint:textOffset];
+
+  // TODO(alcor): switch this to GTMLinearRGBShading if we ever need on 10.4
+  NSColor *color = [NSColor textColor]; //[self textColor];
+  NSColor *alphaColor = [color colorWithAlphaComponent:0.0];
+  NSGradient *mask = [[NSGradient alloc] initWithStartingColor:color
+                                                   endingColor:alphaColor];
+
+  // Draw the gradient mask
+  CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
+  [mask drawFromPoint:NSMakePoint(NSMaxX(cellFrame) - gradientWidth,
+                                  NSMinY(cellFrame))
+              toPoint:NSMakePoint(NSMaxX(cellFrame),
+                                  NSMinY(cellFrame))
+              options:NSGradientDrawsBeforeStartingLocation];
+  [mask release];
+  CGContextEndTransparencyLayer(context);
+  [[NSGraphicsContext currentContext] restoreGraphicsState];
+
+  return cellFrame;
+}
+
 - (NSBezierPath*)clipPathForFrame:(NSRect)cellFrame
                            inView:(NSView*)controlView {
   NSBezierPath* boundingPath = nil;