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Bug 944704, part 4 - Fix PathBuilderCG::Arc to sweep in the correct direction. r=Bas

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This commit is contained in:
Jonathan Watt 2013-12-14 11:09:36 +00:00
parent da3a4828db
commit 452b6c3fcf
1 changed files with 9 additions and 1 deletions
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10
gfx/2d/PathCG.cpp
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@ -68,12 +68,20 @@ void
PathBuilderCG::Arc(const Point &aOrigin, Float aRadius, Float aStartAngle,
Float aEndAngle, bool aAntiClockwise)
{
// Core Graphic's initial coordinate system is y-axis up, whereas Moz2D's is
// y-axis down. Core Graphics therefore considers "clockwise" to mean "sweep
// in the direction of decreasing angle" whereas Moz2D considers it to mean
// "sweep in the direction of increasing angle". In other words if this
// Moz2D method is instructed to sweep anti-clockwise we need to tell
// CGPathAddArc to sweep clockwise, and vice versa. Hence why we pass the
// value of aAntiClockwise directly to CGPathAddArc's "clockwise" bool
// parameter.
CGPathAddArc(mCGPath, nullptr,
aOrigin.x, aOrigin.y,
aRadius,
aStartAngle,
aEndAngle,
!aAntiClockwise);
aAntiClockwise);
}
Point