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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * Notes on transforms in Mozilla and the SVG code.
+ *
+ * It's important to note that the matrix convention used in the SVG standard
+ * is the opposite convention to the one used in the Mozilla code or, more
+ * specifically, the convention used in Thebes code (code using gfxMatrix).
+ * Whereas the SVG standard uses the column vector convention, Thebes code uses
+ * the row vector convention. Thus, whereas in the SVG standard you have
+ * [M1][M2][M3]|p|, in Thebes you have |p|'[M3]'[M2]'[M1]'. In other words, the
+ * following are equivalent:
+ *
+ * / a1 c1 tx1 \ / a2 c2 tx2 \ / a3 c3 tx3 \ / x \
+ * SVG: | b1 d1 ty1 | | b2 d2 ty2 | | b3 d3 ty3 | | y |
+ * \ 0 0 1 / \ 0 0 1 / \ 0 0 1 / \ 1 /
+ *
+ * / a3 b3 0 \ / a2 b2 0 \ / a1 b1 0 \
+ * Thebes: [ x y 1 ] | c3 d3 0 | | c2 d2 0 | | c1 d1 0 |
+ * \ tx3 ty3 1 / \ tx2 ty2 1 / \ tx1 ty1 1 /
+ *
+ * Because the Thebes representation of a transform is the transpose of the SVG
+ * representation, our transform order must be reversed when representing SVG
+ * transforms using gfxMatrix in the SVG code. Since the SVG implementation
+ * stores and obtains matrices in SVG order, to do this we must pre-multiply
+ * gfxMatrix objects that represent SVG transforms instead of post-multiplying
+ * them as we would for matrices using SVG's column vector convention.
+ * Pre-multiplying may look wrong if you're only familiar with the SVG
+ * convention, but in that case hopefully the above explanation clears things
+ * up.
+ */
+
+#ifndef DOM_SVG_SVGMATRIX_H_
+#define DOM_SVG_SVGMATRIX_H_
+
+#include "DOMSVGTransform.h"
+#include "gfxMatrix.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+#include "mozilla/Attributes.h"
+
+namespace mozilla::dom {
+
+/**
+ * DOM wrapper for an SVG matrix.
+ */
+class SVGMatrix final : public nsWrapperCache {
+ public:
+ NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(SVGMatrix)
+ NS_DECL_CYCLE_COLLECTION_NATIVE_WRAPPERCACHE_CLASS(SVGMatrix)
+
+ /**
+ * Ctor for SVGMatrix objects that belong to a DOMSVGTransform.
+ */
+ explicit SVGMatrix(DOMSVGTransform& aTransform) : mTransform(&aTransform) {}
+
+ /**
+ * Ctors for SVGMatrix objects created independently of a DOMSVGTransform.
+ */
+ // Default ctor for gfxMatrix will produce identity mx
+ SVGMatrix() = default;
+
+ explicit SVGMatrix(const gfxMatrix& aMatrix) : mMatrix(aMatrix) {}
+
+ // WebIDL
+ DOMSVGTransform* GetParentObject() const;
+ JSObject* WrapObject(JSContext* aCx,
+ JS::Handle<JSObject*> aGivenProto) override;
+
+ float A() const { return static_cast<float>(GetMatrix()._11); }
+ void SetA(float aA, ErrorResult& rv);
+ float B() const { return static_cast<float>(GetMatrix()._12); }
+ void SetB(float aB, ErrorResult& rv);
+ float C() const { return static_cast<float>(GetMatrix()._21); }
+ void SetC(float aC, ErrorResult& rv);
+ float D() const { return static_cast<float>(GetMatrix()._22); }
+ void SetD(float aD, ErrorResult& rv);
+ float E() const { return static_cast<float>(GetMatrix()._31); }
+ void SetE(float aE, ErrorResult& rv);
+ float F() const { return static_cast<float>(GetMatrix()._32); }
+ void SetF(float aF, ErrorResult& rv);
+ already_AddRefed<SVGMatrix> Multiply(SVGMatrix& aMatrix);
+ already_AddRefed<SVGMatrix> Inverse(ErrorResult& aRv);
+ already_AddRefed<SVGMatrix> Translate(float x, float y);
+ already_AddRefed<SVGMatrix> Scale(float scaleFactor);
+ already_AddRefed<SVGMatrix> ScaleNonUniform(float scaleFactorX,
+ float scaleFactorY);
+ already_AddRefed<SVGMatrix> Rotate(float angle);
+ already_AddRefed<SVGMatrix> RotateFromVector(float x, float y,
+ ErrorResult& aRv);
+ already_AddRefed<SVGMatrix> FlipX();
+ already_AddRefed<SVGMatrix> FlipY();
+ already_AddRefed<SVGMatrix> SkewX(float angle, ErrorResult& rv);
+ already_AddRefed<SVGMatrix> SkewY(float angle, ErrorResult& rv);
+
+ private:
+ ~SVGMatrix() = default;
+
+ const gfxMatrix& GetMatrix() const {
+ return mTransform ? mTransform->Matrixgfx() : mMatrix;
+ }
+
+ void SetMatrix(const gfxMatrix& aMatrix) {
+ if (mTransform) {
+ mTransform->SetMatrix(aMatrix);
+ } else {
+ mMatrix = aMatrix;
+ }
+ }
+
+ bool IsAnimVal() const {
+ return mTransform ? mTransform->IsAnimVal() : false;
+ }
+
+ RefPtr<DOMSVGTransform> mTransform;
+
+ // Typically we operate on the matrix data accessed via mTransform but for
+ // matrices that exist independently of an DOMSVGTransform we use mMatrix
+ // below.
+ gfxMatrix mMatrix;
+};
+
+} // namespace mozilla::dom
+
+#endif // DOM_SVG_SVGMATRIX_H_