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Bug 944704, part 1 - Extend Moz2D's ArcToBezier helper so that it can draw ellipse arcs in addition to circle arcs. r=Bas

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This commit is contained in:
Jonathan Watt 2013-12-13 12:14:36 +00:00
parent 8167b5ca6f
commit f47e1b2989
4 changed files with 16 additions and 14 deletions
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2
gfx/2d/Path.cpp
View File

@ -121,7 +121,7 @@ void
FlattenedPath::Arc(const Point &aOrigin, float aRadius, float aStartAngle,
float aEndAngle, bool aAntiClockwise)
{
ArcToBezier(this, aOrigin, aRadius, aStartAngle, aEndAngle, aAntiClockwise);
ArcToBezier(this, aOrigin, Size(aRadius, aRadius), aStartAngle, aEndAngle, aAntiClockwise);
}
Float

2
gfx/2d/PathCairo.cpp
View File

@ -113,7 +113,7 @@ void
PathBuilderCairo::Arc(const Point &aOrigin, float aRadius, float aStartAngle,
float aEndAngle, bool aAntiClockwise)
{
ArcToBezier(this, aOrigin, aRadius, aStartAngle, aEndAngle, aAntiClockwise);
ArcToBezier(this, aOrigin, Size(aRadius, aRadius), aStartAngle, aEndAngle, aAntiClockwise);
}
Point

24
gfx/2d/PathHelpers.h
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@ -13,11 +13,11 @@ namespace mozilla {
namespace gfx {
template <typename T>
void ArcToBezier(T* aSink, const Point &aOrigin, float aRadius, float aStartAngle,
float aEndAngle, bool aAntiClockwise)
void ArcToBezier(T* aSink, const Point &aOrigin, const Size &aRadius,
float aStartAngle, float aEndAngle, bool aAntiClockwise)
{
Point startPoint(aOrigin.x + cos(aStartAngle) * aRadius,
aOrigin.y + sin(aStartAngle) * aRadius);
Point startPoint(aOrigin.x + cos(aStartAngle) * aRadius.width,
aOrigin.y + sin(aStartAngle) * aRadius.height);
aSink->LineTo(startPoint);
@ -56,23 +56,25 @@ void ArcToBezier(T* aSink, const Point &aOrigin, float aRadius, float aStartAngl
currentEndAngle = currentStartAngle + arcSweepLeft * sweepDirection;
}
Point currentStartPoint(aOrigin.x + cos(currentStartAngle) * aRadius,
aOrigin.y + sin(currentStartAngle) * aRadius);
Point currentEndPoint(aOrigin.x + cos(currentEndAngle) * aRadius,
aOrigin.y + sin(currentEndAngle) * aRadius);
Point currentStartPoint(aOrigin.x + cos(currentStartAngle) * aRadius.width,
aOrigin.y + sin(currentStartAngle) * aRadius.height);
Point currentEndPoint(aOrigin.x + cos(currentEndAngle) * aRadius.width,
aOrigin.y + sin(currentEndAngle) * aRadius.height);
// Calculate kappa constant for partial curve. The sign of angle in the
// tangent will actually ensure this is negative for a counter clockwise
// sweep, so changing signs later isn't needed.
Float kappa = (4.0f / 3.0f) * tan((currentEndAngle - currentStartAngle) / 4.0f) * aRadius;
Float kappaFactor = (4.0f / 3.0f) * tan((currentEndAngle - currentStartAngle) / 4.0f);
Float kappaX = kappaFactor * aRadius.width;
Float kappaY = kappaFactor * aRadius.height;
Point tangentStart(-sin(currentStartAngle), cos(currentStartAngle));
Point cp1 = currentStartPoint;
cp1 += tangentStart * kappa;
cp1 += Point(tangentStart.x * kappaX, tangentStart.y * kappaY);
Point revTangentEnd(sin(currentEndAngle), -cos(currentEndAngle));
Point cp2 = currentEndPoint;
cp2 += revTangentEnd * kappa;
cp2 += Point(revTangentEnd.x * kappaX, revTangentEnd.y * kappaY);
aSink->BezierTo(cp1, cp2, currentEndPoint);

2
gfx/2d/PathSkia.cpp
View File

@ -88,7 +88,7 @@ void
PathBuilderSkia::Arc(const Point &aOrigin, float aRadius, float aStartAngle,
float aEndAngle, bool aAntiClockwise)
{
ArcToBezier(this, aOrigin, aRadius, aStartAngle, aEndAngle, aAntiClockwise);
ArcToBezier(this, aOrigin, Size(aRadius, aRadius), aStartAngle, aEndAngle, aAntiClockwise);
}
Point