[Author: thomasvl]

Nicer drawing of text by not using the gradient where it isn't needed,
  helps where light text is drawn on a dark background.

Patch from thakis - http://codereview.appspot.com/159060/show

R=thakis,dmaclach
DELTA=79  (54 added, 7 deleted, 18 changed)

4 files changed, 58 insertions, 21 deletions

diff --git a/AppKit/GTMFadeTruncatingTextFieldCell.m b/AppKit/GTMFadeTruncatingTextFieldCell.m
index 98eac8c..0e7344c 100644
--- a/AppKit/GTMFadeTruncatingTextFieldCell.m
+++ b/AppKit/GTMFadeTruncatingTextFieldCell.m
@@ -35,33 +35,53 @@
 }
 
 - (void)drawInteriorWithFrame:(NSRect)cellFrame inView:(NSView *)controlView {
-  CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];
-  CGContextBeginTransparencyLayer(context, 0);
+  NSSize size = [[self attributedStringValue] size];
+
+  // Don't complicate drawing unless we need to clip
+  if (size.width <= NSWidth(cellFrame)) {
+    [super drawInteriorWithFrame:cellFrame inView:controlView];
+    return;
+  }
+
+  // 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];
   [super drawInteriorWithFrame:cellFrame inView:controlView];
+  [[NSGraphicsContext currentContext] restoreGraphicsState];
 
-  // Don't complicate drawing unless we need to clip
-  NSSize size = [[self attributedStringValue] size];
-  if (size.width > cellFrame.size.width) {
-    // Gradient is about twice our line height long
-    CGFloat width = MIN(size.height * 2, NSWidth(cellFrame) / 4);
+  // 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 = [[NSGraphicsContext currentContext] graphicsPort];
+  CGContextBeginTransparencyLayerWithRect(context,
+                                          NSRectToCGRect(gradientPart), 0);
 
-    // TODO(alcor): switch this to GTMLinearRGBShading if we ever need on 10.4
-    NSColor *color = [self textColor];
-    NSGradient *mask = [[NSGradient alloc]
-        initWithStartingColor:color
-                  endingColor:[color colorWithAlphaComponent:0.0]];
+  [super drawInteriorWithFrame:cellFrame inView:controlView];
 
-    // Draw the gradient mask
-    CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
-    [mask drawFromPoint:NSMakePoint(NSMaxX(cellFrame) - width,
-                                    NSMinY(cellFrame))
-                toPoint:NSMakePoint(NSMaxX(cellFrame),
-                                    NSMinY(cellFrame))
-                options:NSGradientDrawsBeforeStartingLocation];
-    [mask release];
-  }
+  // TODO(alcor): switch this to GTMLinearRGBShading if we ever need on 10.4
+  NSColor *color = [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];
 }
 
 @end
diff --git a/AppKit/GTMFadeTruncatingTextFieldCellTest.m b/AppKit/GTMFadeTruncatingTextFieldCellTest.m
index d3f328f..5957269 100644
--- a/AppKit/GTMFadeTruncatingTextFieldCellTest.m
+++ b/AppKit/GTMFadeTruncatingTextFieldCellTest.m
@@ -31,6 +31,7 @@
                          NSMakeRect(0, 0, 100, 16)] autorelease];
   [field setCell:[[[GTMFadeTruncatingTextFieldCell alloc] initTextCell:@""]
                   autorelease]];
+
   [field setStringValue:@"A very long string that won't fit"];
   GTMAssertObjectImageEqualToImageNamed(field,
                                         @"GTMFadeTruncatingTextFieldCellTest1",
@@ -39,6 +40,22 @@
   GTMAssertObjectImageEqualToImageNamed(field,
                                         @"GTMFadeTruncatingTextFieldCellTest2",
                                         nil);
+
+  // Dark background, light text (force the background to draw (which is odd
+  // for a text cell), but this is to make sure the support for light on dark
+  // is tested.
+  [field setTextColor:[NSColor whiteColor]];
+  [field setDrawsBackground:YES];
+  [field setBackgroundColor:[NSColor blackColor]];
+
+  [field setStringValue:@"A very long string that won't fit"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest3",
+                                        nil);
+  [field setStringValue:@"A short string"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest4",
+                                        nil);
 }
 
 @end
diff --git a/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest3.tiff b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest3.tiff
new file mode 100644
index 0000000..6d7563a
--- /dev/null
+++ b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest3.tiff
diff --git a/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest4.tiff b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest4.tiff
new file mode 100644
index 0000000..77c03de
--- /dev/null
+++ b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest4.tiff