gecko-dev/dom/canvas/CanvasPath.h
Lee Salzman b2d67698b9 Bug 1846079 - Ensure pruned point begins first sub-path if necessary. r=aosmond
The Canvas2D specification says that if a path has no active sub-paths, and a
primitive is drawn, that the first point of that primitive becomes the start of
the newly created sub-path that will be created for it.

So if we prune a point when a path has no active sub-paths, and then a new
primitive comes in that does not start with that same point, we risk not
installing the pruned point as the start of that new sub-path.

To solve this, we need to detect if a path has no active sub-paths while
we are building it. This adds PathBuilder::IsActive() to help with that.
Then before we go to add a primitive, we check if there is a pruned point
on a path that is not active yet, and if so, install the correct start
point with a MoveTo.

This also makes IsActive and IsEmpty required so to ensure all our path
implementations behave consistently rather than having any surprising
unimplemented behavior.

Differential Revision: https://phabricator.services.mozilla.com/D184891
2023-07-30 14:31:09 +00:00

98 lines
3.4 KiB
C++

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef CanvasPath_h
#define CanvasPath_h
#include "mozilla/Attributes.h"
#include "mozilla/RefPtr.h"
#include "nsWrapperCache.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/dom/BindingDeclarations.h"
namespace mozilla {
class ErrorResult;
namespace dom {
enum class CanvasWindingRule : uint8_t;
struct DOMMatrix2DInit;
class
UnrestrictedDoubleOrDOMPointInitOrUnrestrictedDoubleOrDOMPointInitSequence;
class CanvasPath final : public nsWrapperCache {
public:
NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(CanvasPath)
NS_DECL_CYCLE_COLLECTION_NATIVE_WRAPPERCACHE_CLASS(CanvasPath)
nsISupports* GetParentObject() { return mParent; }
JSObject* WrapObject(JSContext* aCx,
JS::Handle<JSObject*> aGivenProto) override;
static already_AddRefed<CanvasPath> Constructor(const GlobalObject& aGlobal);
static already_AddRefed<CanvasPath> Constructor(const GlobalObject& aGlobal,
CanvasPath& aCanvasPath);
static already_AddRefed<CanvasPath> Constructor(const GlobalObject& aGlobal,
const nsAString& aPathString);
void ClosePath();
void MoveTo(double x, double y);
void LineTo(double x, double y);
void QuadraticCurveTo(double cpx, double cpy, double x, double y);
void BezierCurveTo(double cp1x, double cp1y, double cp2x, double cp2y,
double x, double y);
void ArcTo(double x1, double y1, double x2, double y2, double radius,
ErrorResult& error);
void Rect(double x, double y, double w, double h);
void RoundRect(
double aX, double aY, double aW, double aH,
const UnrestrictedDoubleOrDOMPointInitOrUnrestrictedDoubleOrDOMPointInitSequence&
aRadii,
ErrorResult& aError);
void Arc(double x, double y, double radius, double startAngle,
double endAngle, bool anticlockwise, ErrorResult& error);
void Ellipse(double x, double y, double radiusX, double radiusY,
double rotation, double startAngle, double endAngle,
bool anticlockwise, ErrorResult& error);
void LineTo(const gfx::Point& aPoint);
void BezierTo(const gfx::Point& aCP1, const gfx::Point& aCP2,
const gfx::Point& aCP3);
already_AddRefed<gfx::Path> GetPath(const CanvasWindingRule& aWinding,
const gfx::DrawTarget* aTarget) const;
explicit CanvasPath(nsISupports* aParent);
// already_AddRefed arg because the return value from Path::CopyToBuilder()
// is passed directly and we can't drop the only ref to have a raw pointer.
CanvasPath(nsISupports* aParent,
already_AddRefed<gfx::PathBuilder> aPathBuilder);
void AddPath(CanvasPath& aCanvasPath, const DOMMatrix2DInit& aInit,
ErrorResult& aError);
private:
virtual ~CanvasPath() = default;
nsCOMPtr<nsISupports> mParent;
static gfx::Float ToFloat(double aValue) { return gfx::Float(aValue); }
mutable RefPtr<gfx::Path> mPath;
mutable RefPtr<gfx::PathBuilder> mPathBuilder;
// Whether an internal segment was zero-length.
mutable bool mPruned = false;
void EnsurePathBuilder() const;
void EnsureCapped() const;
void EnsureActive() const;
};
} // namespace dom
} // namespace mozilla
#endif /* CanvasPath_h */