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path: root/AppKit/GTMFadeTruncatingTextFieldCell.m
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//  GTMFadeTruncatingTextFieldCell.m
//
//  Copyright 2009 Google Inc.
//
//  Licensed under the Apache License, Version 2.0 (the "License"); you may not
//  use this file except in compliance with the License.  You may obtain a copy
//  of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
//  License for the specific language governing permissions and limitations under
//  the License.
//

#import "GTMFadeTruncatingTextFieldCell.h"

#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_5

@implementation GTMFadeTruncatingTextFieldCell
- (void)awakeFromNib {
  // Force to clipping
  [self setLineBreakMode:NSLineBreakByClipping];
}

- (id)initTextCell:(NSString *)aString {
  self = [super initTextCell:aString];
  if (self) {
    // Force to clipping
    [self setLineBreakMode:NSLineBreakByClipping];
  }
  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 {
  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(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, 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);

  // 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];
  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];

  NSColor *startColor = [self textColor];;
  NSColor *endColor = [startColor colorWithAlphaComponent:0.0];
  NSGradient *mask = [[NSGradient alloc] initWithStartingColor:startColor
                                                   endingColor:endColor];

  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];

  [mask release];
}

- (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

#endif