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Fix a typo in CPGradient comment and attempt to better explain what's going on.

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Alexander Ljungberg
2012-03-12 12:04:34 +00:00
parent a069f2945b
commit 53334251b8
1 changed files with 7 additions and 4 deletions
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AppKit/CPGradient.j
+7 -4
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@@ -94,10 +94,13 @@ CPGradientDrawsAfterEndingLocation = kCGGradientDrawsAfterEndLocation;
// we want the opposite corner of the starting corner to just reach the final colour stop.
// So when the angle isn't a right angle, the segment has to extend beyond the edge of the
// rectangle just far enough. This is hard to describe without a picture but if we place
// another line through the opposite corner at -90 degrees, it'll cross through our
// gradient segment just where it should end and form a right triangle with the right edge.
// of the rect. One leg of this triangle is how far the gradient line should stick out,
// and the length of that leg is (in the first quadrant) width * cos(a) + height * sin(a).
// another line through the opposite corner at -90 degrees, it'll help form some triangles
// from which we can derive this formula:
//
// length = cos(angle) * (rectWidth + rectHeight * tan(angle))
//
// This simplifies down to (in the first quadrant) rectWidth * cos(a) + rectHeight * sin(a).
var radians = PI * angle / 180.0,
length = ABS(_CGRectGetWidth(rect) * COS(radians)) + ABS(_CGRectGetHeight(rect) * SIN(radians));