OmniboxPopupViewMac refactoring Part 3 (truncation)

chrome/browser/ui/cocoa/omnibox/omnibox_popup_cell.mm

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/omnibox/omnibox_popup_cell.h"
 
+#include <algorithm>
 #include <cmath>
 
+#include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
+
 namespace {
 
 // How far to offset image column from the left.
 const CGFloat kImageXOffset = 5.0;
 
 // How far to offset the text column from the left.
 const CGFloat kTextXOffset = 28.0;
 
+// Maximum fraction of the popup width that can be used to display match
+// contents.
+const CGFloat kMaxContentsFraction = 0.7;
+
 // Rounding radius of selection and hover background on popup items.
 const CGFloat kCellRoundingRadius = 2.0;
 
-NSColor* SelectedBackgroundColor() {
-  return [NSColor selectedControlColor];
-}
-NSColor* HoveredBackgroundColor() {
-  return [NSColor controlHighlightColor];
+void DrawFadeTruncatingTitle(NSAttributedString* title,
+                             NSRect titleRect) {
+  NSSize size = [title size];
+
+  // Empirically, Cocoa will draw an extra 2 pixels past NSWidth(titleRect)
+  // before it clips the text.
+  const CGFloat kOverflowBeforeClip = 2;

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

2.0

[sail, 2013/06/28 18:41:16]

Done.

+  BOOL clipping =
+      std::floor(size.width) > NSWidth(titleRect) + kOverflowBeforeClip;
+
+  // Gradient is about twice our line height long.
+  CGFloat gradientWidth = MIN(size.height * 2, NSWidth(titleRect) / 4);

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

std::min().

[sail, 2013/06/28 18:41:16]

Done.

+
+  NSRect solidPart, gradientPart;
+  NSDivideRect(titleRect, &gradientPart, &solidPart, gradientWidth, NSMaxXEdge);
+
+  NSPoint textOffset;
+  textOffset.x = NSMinX(titleRect);
+  textOffset.y =
+      NSMinY(titleRect) + roundf((NSHeight(titleRect) - size.height) / 2.0) - 1;

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

Sigh.  No std::round until c++11.

+
+  // Draw non-gradient part without transparency layer, as light text on a dark
+  // background looks bad with a gradient layer.
+  {
+    gfx::ScopedNSGraphicsContextSaveGState scopedGState;
+    if (clipping)
+      [NSBezierPath clipRect:solidPart];
+    [title drawAtPoint:textOffset];
+  }
+
+  if (!clipping)

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

Couldn't this result in incorrect drawing if the text reaches to w/in
gradientWidth of NSMaxX(titleRect), but is not clipped?  Perhaps an else
-clipRect:titleRect above in that case?

[sail, 2013/06/28 18:41:16]

Done.
This part is not relevant anymore now that I removed the transparency layer.

+    return;
+
+  // Draw the gradient part with a transparency layer. This makes the text look
+  // suboptimal, but since it fades out, that's ok.

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

This seems complicated.  Something like this using NSCompositeSourceOver seems
easier:
   http://lists.apple.com/archives/cocoa-dev/2009/Mar/msg00797.html
it would involve a different approach - draw the text, then blend over from
transparent to opaque.

[sail, 2013/06/28 18:41:16]

Done.
Yep, I just draw the full string and then draw the gradient from 0 alpha to 1.0
alpha.

+  gfx::ScopedNSGraphicsContextSaveGState scopedGState;
+  [NSBezierPath clipRect:gradientPart];
+  CGContextRef context = static_cast<CGContextRef>(
+      [[NSGraphicsContext currentContext] graphicsPort]);
+  CGContextBeginTransparencyLayerWithRect(context,
+                                          NSRectToCGRect(gradientPart), 0);
+  [title drawAtPoint:textOffset];
+
+  NSColor *color = [NSColor 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(titleRect) - gradientWidth,
+                                  NSMinY(titleRect))
+              toPoint:NSMakePoint(NSMaxX(titleRect),
+                                  NSMinY(titleRect))
+              options:NSGradientDrawsBeforeStartingLocation];
+  [mask release];

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

Why not scoped_ptr<>?  Does the mask require specific lifetime?

[sail, 2013/06/28 18:41:16]

Done.

+  CGContextEndTransparencyLayer(context);
 }
 
 }  // namespace
 
 @implementation OmniboxPopupCell
 
 - (id)init {
-  self = [super init];
-  if (self) {
+  if ((self = [super init])) {
     [self setImagePosition:NSImageLeft];
     [self setBordered:NO];
     [self setButtonType:NSRadioButton];
 
     // Without this highlighting messes up white areas of images.
     [self setHighlightsBy:NSNoCellMask];
   }
   return self;
 }
 
-// The default NSButtonCell drawing leaves the image flush left and
-// the title next to the image.  This spaces things out to line up
-// with the star button and autocomplete field.
+- (NSAttributedString*)contentText {
+  return contentText_;
+}
+
+- (void)setContentText:(NSAttributedString*)contentText {
+  contentText_.reset([contentText retain]);
+}
+
+- (NSAttributedString*)descriptionText {
+  return descriptionText_;
+}
+
+- (void)setDescriptionText:(NSAttributedString*)descriptionText {
+  descriptionText_.reset([descriptionText retain]);
+}
+
 - (void)drawInteriorWithFrame:(NSRect)cellFrame inView:(NSView *)controlView {
   if ([self state] == NSOnState || [self isHighlighted]) {
     if ([self state] == NSOnState)
-      [SelectedBackgroundColor() set];
+      [[NSColor selectedControlColor] set];
     else
-      [HoveredBackgroundColor() set];
+      [[NSColor controlHighlightColor] set];
     NSBezierPath* path =
         [NSBezierPath bezierPathWithRoundedRect:cellFrame
                                         xRadius:kCellRoundingRadius
                                         yRadius:kCellRoundingRadius];
     [path fill];
   }
 
   // Put the image centered vertically but in a fixed column.
   NSImage* image = [self image];
   if (image) {
     NSRect imageRect = cellFrame;
     imageRect.size = [image size];
     imageRect.origin.y +=
         std::floor((NSHeight(cellFrame) - NSHeight(imageRect)) / 2.0);
     imageRect.origin.x += kImageXOffset;
     [image drawInRect:imageRect
              fromRect:NSZeroRect  // Entire image
             operation:NSCompositeSourceOver
              fraction:1.0
        respectFlipped:YES
                 hints:nil];
   }
 
   // Adjust the title position to be lined up under the field's text.
-  NSAttributedString* title = [self attributedTitle];
-  if (title && [title length]) {
-    NSRect titleRect = cellFrame;
-    titleRect.size.width -= kTextXOffset;
-    titleRect.origin.x += kTextXOffset;
-    [self drawTitle:title withFrame:titleRect inView:controlView];
+  if ([contentText_ length]) {
+    CGFloat availableWidth = NSWidth(cellFrame) - kTextXOffset;
+    CGFloat contentWidth = [contentText_ size].width;
+    CGFloat descriptionWidth = 0;
+    if ([descriptionText_ length])
+      descriptionWidth = [descriptionText_ size].width;
+
+    if (contentWidth + descriptionWidth > availableWidth) {
+      if (contentWidth > kMaxContentsFraction * availableWidth) {
+        if (descriptionWidth > (1.0 - kMaxContentsFraction) * availableWidth)
+          descriptionWidth = (1.0 - kMaxContentsFraction) * availableWidth;

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

std::min?

[sail, 2013/06/28 18:41:16]

Done.

+        contentWidth =
+            std::min(contentWidth, availableWidth - descriptionWidth);
+      } else {
+        descriptionWidth = availableWidth - contentWidth;
+      }
+    }

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

I think this entire if() can be replaced with something like:
  tempDescWidth = std::min(descriptionWidth, (1.0 - kMax) * availableWidth);
  contentWidth = std::min(contentWidth, availableWidth - tempDescWidth);
  descriptionWidth = std::min(descriptionWidth, availableWidth - contentWidth);
I'm not sure it's less confusing, though a better name for tempDescWidth might
help.  I'm also not sure it's more confusing :-).

[sail, 2013/06/28 18:41:16]

Done.

+
+    NSRect contentRect = cellFrame;
+    contentRect.origin.x = kTextXOffset;
+    contentRect.size.width = contentWidth;
+    DrawFadeTruncatingTitle(contentText_, contentRect);
+
+    NSRect descriptionRect = cellFrame;

[Scott Hess - ex-Googler, 2013/06/28 01:02:48]

if ([descriptionText_ length]){...} around this?

[sail, 2013/06/28 18:41:16]

Done.

+    descriptionRect.origin.x = NSMaxX(contentRect);
+    descriptionRect.size.width = descriptionWidth;
+    DrawFadeTruncatingTitle(descriptionText_, descriptionRect);
   }
 }
 
 @end