Mac: Make a stop-gap visual indicator for dropping URLs on the tab strip.

A.k.a. a present for pkasting. Eventually we'll probably want to do something more sophisticated (at the very least arrows should fade in/out), but for now this doesn't look (much?) worse than what's on Win/Chrome.

BUG=25405
TEST=Drag URLs to the tab strip, move around, make sure the ugly arrow appears in the right locations, dropping to confirm. Repeat with various themes to make sure arrow is reasonably visible.

Review URL: http://codereview.chromium.org/466051

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@33924 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 61 insertions, 0 deletions

diff --git a/chrome/browser/cocoa/tab_strip_view.mm b/chrome/browser/cocoa/tab_strip_view.mm
index 1dcd746..3eeef0a 100644
--- a/chrome/browser/cocoa/tab_strip_view.mm
+++ b/chrome/browser/cocoa/tab_strip_view.mm
@@ -9,6 +9,8 @@
 @implementation TabStripView
 
 @synthesize newTabButton = newTabButton_;
+@synthesize dropArrowShown = dropArrowShown_;
+@synthesize dropArrowPosition = dropArrowPosition_;
 
 - (id)initWithFrame:(NSRect)frame {
   self = [super initWithFrame:frame];
@@ -30,6 +32,65 @@
   [[NSColor colorWithCalibratedWhite:0.0 alpha:0.2] set];
 
   NSRectFillUsingOperation(borderRect, NSCompositeSourceOver);
+
+  // Draw drop-indicator arrow (if appropriate).
+  // TODO(viettrungluu): this is all a stop-gap measure.
+  if ([self dropArrowShown]) {
+    // Programmer art: an arrow parametrized by many knobs. Note that the arrow
+    // points downwards (so understand "width" and "height" accordingly).
+
+    // How many (pixels) to inset on the top/bottom.
+    const CGFloat kArrowTopInset = 1.5;
+    const CGFloat kArrowBottomInset = 1;
+
+    // What proportion of the vertical space is dedicated to the arrow tip,
+    // i.e., (arrow tip height)/(amount of vertical space).
+    const CGFloat kArrowTipProportion = 0.5;
+
+    // This is a slope, i.e., (arrow tip height)/(0.5 * arrow tip width).
+    const CGFloat kArrowTipSlope = 1.2;
+
+    // What proportion of the arrow tip width is the stem, i.e., (stem
+    // width)/(arrow tip width).
+    const CGFloat kArrowStemProportion = 0.33;
+
+    NSPoint arrowTipPos = [self dropArrowPosition];
+    arrowTipPos.y += kArrowBottomInset;  // Inset on the bottom.
+
+    // Height we have to work with (insetting on the top).
+    CGFloat availableHeight =
+        NSMaxY([self bounds]) - arrowTipPos.y - kArrowTopInset;
+    DCHECK(availableHeight >= 5);
+
+    // Based on the knobs above, calculate actual dimensions which we'll need
+    // for drawing.
+    CGFloat arrowTipHeight = kArrowTipProportion * availableHeight;
+    CGFloat arrowTipWidth = 2 * arrowTipHeight / kArrowTipSlope;
+    CGFloat arrowStemHeight = availableHeight - arrowTipHeight;
+    CGFloat arrowStemWidth = kArrowStemProportion * arrowTipWidth;
+    CGFloat arrowStemInset = (arrowTipWidth - arrowStemWidth) / 2;
+
+    // The line width is arbitrary, but our path really should be mitered.
+    NSBezierPath* arrow = [NSBezierPath bezierPath];
+    [arrow setLineJoinStyle:NSMiterLineJoinStyle];
+    [arrow setLineWidth:1];
+
+    // Define the arrow's shape! We start from the tip and go clockwise.
+    [arrow moveToPoint:arrowTipPos];
+    [arrow relativeLineToPoint:NSMakePoint(-arrowTipWidth / 2, arrowTipHeight)];
+    [arrow relativeLineToPoint:NSMakePoint(arrowStemInset, 0)];
+    [arrow relativeLineToPoint:NSMakePoint(0, arrowStemHeight)];
+    [arrow relativeLineToPoint:NSMakePoint(arrowStemWidth, 0)];
+    [arrow relativeLineToPoint:NSMakePoint(0, -arrowStemHeight)];
+    [arrow relativeLineToPoint:NSMakePoint(arrowStemInset, 0)];
+    [arrow closePath];
+
+    // Draw and fill the arrow.
+    [[NSColor colorWithCalibratedWhite:0 alpha:0.67] set];
+    [arrow stroke];
+    [[NSColor colorWithCalibratedWhite:1 alpha:0.67] setFill];
+    [arrow fill];
+  }
 }
 
 // We accept first mouse so clicks onto close/zoom/miniaturize buttons and