1 files changed, 101 insertions, 0 deletions
diff --git a/dom/svg/SVGLengthListSMILType.h b/dom/svg/SVGLengthListSMILType.h
new file mode 100644
index 000000000..10321b585
--- /dev/null
+++ b/dom/svg/SVGLengthListSMILType.h
@@ -0,0 +1,101 @@
+/* -*- 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/. */
+
+#ifndef MOZILLA_SVGLENGTHLISTSMILTYPE_H_
+#define MOZILLA_SVGLENGTHLISTSMILTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "nsISMILType.h"
+
+class nsSMILValue;
+
+namespace mozilla {
+
+////////////////////////////////////////////////////////////////////////
+// SVGLengthListSMILType
+//
+// Operations for animating an SVGLengthList.
+//
+class SVGLengthListSMILType : public nsISMILType
+{
+public:
+  // Singleton for nsSMILValue objects to hold onto.
+  static SVGLengthListSMILType sSingleton;
+
+protected:
+  // nsISMILType Methods
+  // -------------------
+
+  /**
+   * When this method initializes the SVGLengthListAndInfo for its nsSMILValue
+   * argument, it has to blindly set its mCanZeroPadList to true despite
+   * the fact that some attributes can't be zero-padded. (See the explaination
+   * that follows.) SVGAnimatedLengthList::SMILAnimatedLengthList's
+   * GetBaseValue() and ValueFromString() methods then override this for the
+   * nsSMILValue objects that they create to set this flag to the appropriate
+   * value for the attribute in question.
+   *
+   * The reason that we default to setting the mCanZeroPadList to true is
+   * because the SMIL engine creates "zero" valued nsSMILValue objects for
+   * intermediary calculations, and may pass such an nsSMILValue (along with an
+   * nsSMILValue from an animation element - that is an nsSMILValue created by
+   * SVGAnimatedLengthList::SMILAnimatedLengthList's GetBaseValue() or
+   * ValueFromString() methods) into the Add(), ComputeDistance() or
+   * Interpolate() methods below. Even in the case of animation of list
+   * attributes that may *not* be padded with zeros (such as 'x' and 'y' on the
+   * <text> element), we need to allow zero-padding of these "zero" valued
+   * nsSMILValue's lists. One reason for this is illustrated by the following
+   * example:
+   *
+   *   <text x="2 4">foo
+   *      <animate by="2 2" .../>
+   *   </text>
+   *
+   * In this example there are two SMIL animation layers to be sandwiched: the
+   * base layer, and the layer created for the <animate> element. The SMIL
+   * engine calculates the result of each layer *independently*, before
+   * compositing the results together. Thus for the <animate> sandwich layer
+   * the SMIL engine interpolates between a "zero" nsSMILValue that it creates
+   * (since there is no explicit "from") and the "2 2", before the result of
+   * that interpolation is added to the "2 4" from the base layer. Clearly for
+   * the interpolation between the "zero" nsSMILValue and "2 2" to work, the
+   * "zero" nsSMILValue's SVGLengthListAndInfo must be zero paddable - hence
+   * why this method always sets mCanZeroPadList to true.
+   *
+   * (Since the Add(), ComputeDistance() and Interpolate() methods may be
+   * passed two input nsSMILValue objects for which CanZeroPadList() returns
+   * opposite values, these methods must be careful what they set the flag to
+   * on the nsSMILValue that they output. If *either* of the input nsSMILValues
+   * has an SVGLengthListAndInfo for which CanZeroPadList() returns false,
+   * then they must set the flag to false on the output nsSMILValue too. If
+   * the methods failed to do that, then when the result nsSMILValue objects
+   * from each sandwich layer are composited together, we could end up allowing
+   * animation between lists of different length when we should not!)
+   */
+  virtual void     Init(nsSMILValue& aValue) const override;
+
+  virtual void     Destroy(nsSMILValue& aValue) const override;
+  virtual nsresult Assign(nsSMILValue& aDest, const nsSMILValue& aSrc) const override;
+  virtual bool     IsEqual(const nsSMILValue& aLeft,
+                           const nsSMILValue& aRight) const override;
+  virtual nsresult Add(nsSMILValue& aDest, const nsSMILValue& aValueToAdd,
+                       uint32_t aCount) const override;
+  virtual nsresult ComputeDistance(const nsSMILValue& aFrom,
+                                   const nsSMILValue& aTo,
+                                   double& aDistance) const override;
+  virtual nsresult Interpolate(const nsSMILValue& aStartVal,
+                               const nsSMILValue& aEndVal,
+                               double aUnitDistance,
+                               nsSMILValue& aResult) const override;
+
+private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SVGLengthListSMILType() {}
+};
+
+} // namespace mozilla
+
+#endif // MOZILLA_SVGLENGTHLISTSMILTYPE_H_