[Author: sail]

 Currently GTMFadeTruncatingTextFieldCell only supports truncating the tail of a string.

 It should also allow the head of a string to be truncated.

 I'd like to use this in Chromium. See http://crbug.com/69304

R=thomasvl
APPROVED=thomasvl
DELTA=238  (197 added, 17 deleted, 24 changed)

6 files changed, 198 insertions, 33 deletions

diff --git a/AppKit/GTMFadeTruncatingTextFieldCell.h b/AppKit/GTMFadeTruncatingTextFieldCell.h
index 76e7b1c..267d4b8 100644
--- a/AppKit/GTMFadeTruncatingTextFieldCell.h
+++ b/AppKit/GTMFadeTruncatingTextFieldCell.h
@@ -21,8 +21,26 @@
 
 #if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_5
 
-// A simple text field cell that truncates the right hand edge using a gradient
-@interface GTMFadeTruncatingTextFieldCell : NSTextFieldCell
+typedef enum {
+  GTMFadeTruncatingTail,
+  GTMFadeTruncatingHead,
+  GTMFadeTruncatingHeadAndTail,
+} GTMFadeTruncateMode;
+
+// A simple text field cell that can truncate at the beginning or the end
+// using a gradient. By default it truncates the end.
+@interface GTMFadeTruncatingTextFieldCell : NSTextFieldCell {
+ @private
+  NSUInteger desiredCharactersToTruncateFromHead_;
+  GTMFadeTruncateMode truncateMode_;
+}
+
+@property (nonatomic) GTMFadeTruncateMode truncateMode;
+
+// When truncating the head this specifies the maximum number of characters
+// that can be truncated. Setting this to 0 means that there is no maximum.
+@property (nonatomic) NSUInteger desiredCharactersToTruncateFromHead;
+
 @end
 
 #endif
diff --git a/AppKit/GTMFadeTruncatingTextFieldCell.m b/AppKit/GTMFadeTruncatingTextFieldCell.m
index 0e7344c..ec266a2 100644
--- a/AppKit/GTMFadeTruncatingTextFieldCell.m
+++ b/AppKit/GTMFadeTruncatingTextFieldCell.m
@@ -34,54 +34,167 @@
   return self;
 }
 
+- (void)drawTextGradientPart:(NSAttributedString *)attributedString
+                   titleRect:(NSRect)titleRect
+              backgroundRect:(NSRect)backgroundRect
+                    clipRect:(NSRect)clipRect
+                        mask:(NSGradient *)mask
+                 fadeToRight:(BOOL)fadeToRight {
+  // 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:clipRect];
+  CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];
+  CGContextBeginTransparencyLayerWithRect(context,
+                                          NSRectToCGRect(clipRect), 0);
+
+  if ([self drawsBackground]) {
+    [[self backgroundColor] set];
+    NSRectFillUsingOperation([self titleRectForBounds:backgroundRect],
+                             NSCompositeSourceOver);
+  }
+  [attributedString drawInRect:titleRect];
+
+  NSPoint startPoint;
+  NSPoint endPoint;
+  if (fadeToRight) {
+    startPoint = clipRect.origin;
+    endPoint = NSMakePoint(NSMaxX(clipRect), NSMinY(clipRect));
+  } else {
+    startPoint = NSMakePoint(NSMaxX(clipRect), NSMinY(clipRect));
+    endPoint = clipRect.origin;
+  }
+
+  // Draw the gradient mask
+  CGContextSetBlendMode(context, kCGBlendModeDestinationIn);
+  [mask drawFromPoint:startPoint
+              toPoint:endPoint
+              options:fadeToRight ? NSGradientDrawsBeforeStartingLocation :
+                                    NSGradientDrawsAfterEndingLocation];
+
+  CGContextEndTransparencyLayer(context);
+  [[NSGraphicsContext currentContext] restoreGraphicsState];
+}
+
 - (void)drawInteriorWithFrame:(NSRect)cellFrame inView:(NSView *)controlView {
-  NSSize size = [[self attributedStringValue] size];
+  NSRect titleRect = [self titleRectForBounds:cellFrame];
+  // For some reason the title rect is too far to the left.
+  titleRect.origin.x += 2;
+  titleRect.size.width -= 2;
+
+  NSAttributedString *attributedString = [self attributedStringValue];
+  NSSize size = [attributedString size];
 
   // Don't complicate drawing unless we need to clip
-  if (size.width <= NSWidth(cellFrame)) {
+  if (size.width <= NSWidth(titleRect)) {
     [super drawInteriorWithFrame:cellFrame inView:controlView];
     return;
   }
 
+  // Clip the string by drawing it to the left by |offsetX|.
+  CGFloat offsetX = 0;
+  switch (truncateMode_) {
+    case GTMFadeTruncatingTail:
+      break;
+    case GTMFadeTruncatingHead:
+      offsetX = size.width - titleRect.size.width;
+      break;
+    case GTMFadeTruncatingHeadAndTail: {
+      if (desiredCharactersToTruncateFromHead_ > 0) {
+        NSAttributedString *clippedHeadString =
+            [attributedString attributedSubstringFromRange:
+                NSMakeRange(0, desiredCharactersToTruncateFromHead_)];
+        NSSize clippedHeadSize = [clippedHeadString size];
+
+        // Clip the desired portion from the beginning of the string.
+        offsetX = clippedHeadSize.width;
+
+        CGFloat delta = size.width - titleRect.size.width;
+        if (offsetX > delta)
+          offsetX = delta;
+      } else {
+        // Center the string and clip equal portions of the head and tail.
+        offsetX = round((size.width - titleRect.size.width) / 2.0);
+      }
+      break;
+    }
+  }
+
+  NSRect offsetTitleRect = titleRect;
+  offsetTitleRect.origin.x -= offsetX;
+  offsetTitleRect.size.width += offsetX;
+  BOOL isTruncatingHead = offsetX > 0;
+  BOOL isTruncatingTail = (size.width - titleRect.size.width) > offsetX;
+
   // Gradient is about twice our line height long
-  CGFloat gradientWidth = MIN(size.height * 2, NSWidth(cellFrame) / 4);
+  CGFloat gradientWidth = MIN(size.height * 2, round(NSWidth(cellFrame) / 4));
+  NSRect solidPart = cellFrame;
+  NSRect headGradientPart = NSZeroRect;
+  NSRect tailGradientPart = NSZeroRect;
+  if (isTruncatingHead)
+    NSDivideRect(solidPart, &headGradientPart, &solidPart,
+                 gradientWidth, NSMinXEdge);
+  if (isTruncatingTail)
+    NSDivideRect(solidPart, &tailGradientPart, &solidPart,
+                 gradientWidth, NSMaxXEdge);
 
-  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.
+  NSRect backgroundRect = [self drawingRectForBounds:cellFrame];
   [[NSGraphicsContext currentContext] saveGraphicsState];
   [NSBezierPath clipRect:solidPart];
-  [super drawInteriorWithFrame:cellFrame inView:controlView];
+  if ([self drawsBackground]) {
+    [[self backgroundColor] set];
+    NSRectFillUsingOperation(backgroundRect, NSCompositeSourceOver);
+  }
+  // We draw the text ourselves because [super drawInteriorWithFrame:inView:]
+  // doesn't draw correctly if the cell draws its own background.
+  [attributedString drawInRect:offsetTitleRect];
   [[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 = [[NSGraphicsContext currentContext] graphicsPort];
-  CGContextBeginTransparencyLayerWithRect(context,
-                                          NSRectToCGRect(gradientPart), 0);
-
-  [super drawInteriorWithFrame:cellFrame inView:controlView];
+  NSColor *startColor = [self textColor];;
+  NSColor *endColor = [startColor colorWithAlphaComponent:0.0];
+  NSGradient *mask = [[NSGradient alloc] initWithStartingColor:startColor
+                                                   endingColor:endColor];
 
-  // 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];
+  if (isTruncatingHead)
+    [self drawTextGradientPart:attributedString
+                     titleRect:offsetTitleRect
+                backgroundRect:backgroundRect
+                      clipRect:headGradientPart
+                          mask:mask
+                   fadeToRight:NO];
+  if (isTruncatingTail)
+    [self drawTextGradientPart:attributedString
+                     titleRect:offsetTitleRect
+                backgroundRect:backgroundRect
+                      clipRect:tailGradientPart
+                          mask:mask
+                   fadeToRight:YES];
 
-  // 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];
+}
+
+- (void)setTruncateMode:(GTMFadeTruncateMode)mode {
+  if (truncateMode_ != mode) {
+    truncateMode_ = mode;
+    [[self controlView] setNeedsDisplay:YES];
+  }
+}
+
+- (GTMFadeTruncateMode)truncateMode {
+  return truncateMode_;
+}
+
+- (void)setDesiredCharactersToTruncateFromHead:(NSUInteger)length {
+  if (desiredCharactersToTruncateFromHead_ != length) {
+    desiredCharactersToTruncateFromHead_ = length;
+    [[self controlView] setNeedsDisplay:YES];
+  }
+}
+
+- (NSUInteger)desiredCharactersToTruncateFromHead {
+  return desiredCharactersToTruncateFromHead_;
 }
 
 @end
diff --git a/AppKit/GTMFadeTruncatingTextFieldCellTest.m b/AppKit/GTMFadeTruncatingTextFieldCellTest.m
index a42e22e..a1bf937 100644
--- a/AppKit/GTMFadeTruncatingTextFieldCellTest.m
+++ b/AppKit/GTMFadeTruncatingTextFieldCellTest.m
@@ -28,7 +28,7 @@
 
 @implementation GTMFadeTruncatingTextFieldCellTest
 
-- (void)testFadeCell {
+- (void)testFadeCellRight {
   NSTextField *field = [[[NSTextField alloc] initWithFrame:
                          NSMakeRect(0, 0, 100, 16)] autorelease];
   [field setCell:[[[GTMFadeTruncatingTextFieldCell alloc] initTextCell:@""]
@@ -38,6 +38,7 @@
   GTMAssertObjectImageEqualToImageNamed(field,
                                         @"GTMFadeTruncatingTextFieldCellTest1",
                                         nil);
+
   [field setStringValue:@"A short string"];
   GTMAssertObjectImageEqualToImageNamed(field,
                                         @"GTMFadeTruncatingTextFieldCellTest2",
@@ -60,6 +61,39 @@
                                         nil);
 }
 
+- (void)testFadeCellLeftAndRight {
+  NSTextField *field = [[[NSTextField alloc] initWithFrame:
+                         NSMakeRect(0, 0, 100, 16)] autorelease];
+  GTMFadeTruncatingTextFieldCell *cell =
+      [[[GTMFadeTruncatingTextFieldCell alloc] initTextCell:@""] autorelease];
+  [cell setTruncateMode:GTMFadeTruncatingHeadAndTail];
+  [cell setDesiredCharactersToTruncateFromHead:5];
+  [field setCell:cell];
+
+  [field setStringValue:@"Fade on both left and right AAAA"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest5",
+                                        nil);
+
+  [field setStringValue:@"Fade on left only AA"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest6",
+                                        nil);
+
+  [field setStringValue:@"A short string"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest2",
+                                        nil);
+
+  // Test the case where the number of characters to truncate from head is not
+  // specified. This should cause the string to be drawn centered.
+  [cell setDesiredCharactersToTruncateFromHead:0];
+  [field setStringValue:@"Fade on both left and right AAAA"];
+  GTMAssertObjectImageEqualToImageNamed(field,
+                                        @"GTMFadeTruncatingTextFieldCellTest7",
+                                        nil);
+}
+
 @end
 
 #endif  // MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_5
diff --git a/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest5.tiff b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest5.tiff
new file mode 100644
index 0000000..f360479
--- /dev/null
+++ b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest5.tiff
diff --git a/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest6.tiff b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest6.tiff
new file mode 100644
index 0000000..d704a81
--- /dev/null
+++ b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest6.tiff
diff --git a/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest7.tiff b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest7.tiff
new file mode 100644
index 0000000..ac1dca6
--- /dev/null
+++ b/AppKit/TestData/GTMFadeTruncatingTextFieldCellTest7.tiff