1 files changed, 191 insertions, 0 deletions
diff --git a/layout/base/DisplayItemClip.h b/layout/base/DisplayItemClip.h
new file mode 100644
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--- /dev/null
+++ b/layout/base/DisplayItemClip.h
@@ -0,0 +1,191 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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 DISPLAYITEMCLIP_H_
+#define DISPLAYITEMCLIP_H_
+
+#include "mozilla/RefPtr.h"
+#include "nsRect.h"
+#include "nsTArray.h"
+#include "nsStyleConsts.h"
+
+class gfxContext;
+class nsPresContext;
+class nsRegion;
+
+namespace mozilla {
+namespace gfx {
+class DrawTarget;
+class Path;
+} // namespace gfx
+} // namespace mozilla
+
+namespace mozilla {
+
+/**
+ * An DisplayItemClip represents the intersection of an optional rectangle
+ * with a list of rounded rectangles (which is often empty), all in appunits.
+ * It can represent everything CSS clipping can do to an element (except for
+ * SVG clip-path), including no clipping at all.
+ */
+class DisplayItemClip {
+  typedef mozilla::gfx::Color Color;
+  typedef mozilla::gfx::DrawTarget DrawTarget;
+  typedef mozilla::gfx::Path Path;
+
+public:
+  struct RoundedRect {
+    nsRect mRect;
+    // Indices into mRadii are the NS_CORNER_* constants in nsStyleConsts.h
+    nscoord mRadii[8];
+
+    RoundedRect operator+(const nsPoint& aOffset) const {
+      RoundedRect r = *this;
+      r.mRect += aOffset;
+      return r;
+    }
+    bool operator==(const RoundedRect& aOther) const {
+      if (!mRect.IsEqualInterior(aOther.mRect)) {
+        return false;
+      }
+
+      NS_FOR_CSS_HALF_CORNERS(corner) {
+        if (mRadii[corner] != aOther.mRadii[corner]) {
+          return false;
+        }
+      }
+      return true;
+    }
+    bool operator!=(const RoundedRect& aOther) const {
+      return !(*this == aOther);
+    }
+  };
+
+  // Constructs a DisplayItemClip that does no clipping at all.
+  DisplayItemClip() : mHaveClipRect(false) {}
+
+  void SetTo(const nsRect& aRect);
+  void SetTo(const nsRect& aRect, const nscoord* aRadii);
+  void SetTo(const nsRect& aRect, const nsRect& aRoundedRect, const nscoord* aRadii);
+  void IntersectWith(const DisplayItemClip& aOther);
+
+  // Apply this |DisplayItemClip| to the given gfxContext.  Any saving of state
+  // or clearing of other clips must be done by the caller.
+  // See aBegin/aEnd note on ApplyRoundedRectsTo.
+  void ApplyTo(gfxContext* aContext, nsPresContext* aPresContext,
+               uint32_t aBegin = 0, uint32_t aEnd = UINT32_MAX);
+
+  void ApplyRectTo(gfxContext* aContext, int32_t A2D) const;
+  // Applies the rounded rects in this Clip to aContext
+  // Will only apply rounded rects from aBegin (inclusive) to aEnd
+  // (exclusive) or the number of rounded rects, whichever is smaller.
+  void ApplyRoundedRectClipsTo(gfxContext* aContext, int32_t A2DPRInt32,
+                               uint32_t aBegin, uint32_t aEnd) const;
+
+  // Draw (fill) the rounded rects in this clip to aContext
+  void FillIntersectionOfRoundedRectClips(gfxContext* aContext,
+                                          const Color& aColor,
+                                          int32_t aAppUnitsPerDevPixel,
+                                          uint32_t aBegin,
+                                          uint32_t aEnd) const;
+  // 'Draw' (create as a path, does not stroke or fill) aRoundRect to aContext
+  already_AddRefed<Path> MakeRoundedRectPath(DrawTarget& aDrawTarget,
+                                                  int32_t A2D,
+                                                  const RoundedRect &aRoundRect) const;
+
+  // Returns true if the intersection of aRect and this clip region is
+  // non-empty. This is precise for DisplayItemClips with at most one
+  // rounded rectangle. When multiple rounded rectangles are present, we just
+  // check that the rectangle intersects all of them (but possibly in different
+  // places). So it may return true when the correct answer is false.
+  bool MayIntersect(const nsRect& aRect) const;
+
+  // Return a rectangle contained in the intersection of aRect with this
+  // clip region. Tries to return the largest possible rectangle, but may
+  // not succeed.
+  nsRect ApproximateIntersectInward(const nsRect& aRect) const;
+
+  /*
+   * Computes a region which contains the clipped area of this DisplayItemClip,
+   * or if aOldClip is non-null, the union of the clipped area of this
+   * DisplayItemClip with the clipped area of aOldClip translated by aShift.
+   * The result is stored in aCombined. If the result would be infinite
+   * (because one or both of the clips does no clipping), returns false.
+   */
+  bool ComputeRegionInClips(DisplayItemClip* aOldClip,
+                            const nsPoint& aShift,
+                            nsRegion* aCombined) const;
+
+  // Returns false if aRect is definitely not clipped by a rounded corner in
+  // this clip. Returns true if aRect is clipped by a rounded corner in this
+  // clip or it can not be quickly determined that it is not clipped by a
+  // rounded corner in this clip.
+  bool IsRectClippedByRoundedCorner(const nsRect& aRect) const;
+
+  // Returns false if aRect is definitely not clipped by anything in this clip.
+  // Fast but not necessarily accurate.
+  bool IsRectAffectedByClip(const nsRect& aRect) const;
+  bool IsRectAffectedByClip(const nsIntRect& aRect, float aXScale, float aYScale, int32_t A2D) const;
+
+  // Intersection of all rects in this clip ignoring any rounded corners.
+  nsRect NonRoundedIntersection() const;
+
+  // Intersect the given rects with all rects in this clip, ignoring any
+  // rounded corners.
+  nsRect ApplyNonRoundedIntersection(const nsRect& aRect) const;
+
+  // Gets rid of any rounded corners in this clip.
+  void RemoveRoundedCorners();
+
+  // Adds the difference between Intersect(*this + aPoint, aBounds) and
+  // Intersect(aOther, aOtherBounds) to aDifference (or a bounding-box thereof).
+  void AddOffsetAndComputeDifference(uint32_t aStart, const nsPoint& aPoint, const nsRect& aBounds,
+                                     const DisplayItemClip& aOther, uint32_t aOtherStart, const nsRect& aOtherBounds,
+                                     nsRegion* aDifference);
+
+  bool operator==(const DisplayItemClip& aOther) const {
+    return mHaveClipRect == aOther.mHaveClipRect &&
+           (!mHaveClipRect || mClipRect.IsEqualInterior(aOther.mClipRect)) &&
+           mRoundedClipRects == aOther.mRoundedClipRects;
+  }
+  bool operator!=(const DisplayItemClip& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool HasClip() const { return mHaveClipRect; }
+  const nsRect& GetClipRect() const
+  {
+    NS_ASSERTION(HasClip(), "No clip rect!");
+    return mClipRect;
+  }
+
+  void MoveBy(nsPoint aPoint);
+
+  nsCString ToString() const;
+
+  /**
+   * Find the largest N such that the first N rounded rects in 'this' are
+   * equal to the first N rounded rects in aOther, and N <= aMax.
+   */
+  uint32_t GetCommonRoundedRectCount(const DisplayItemClip& aOther,
+                                     uint32_t aMax) const;
+  uint32_t GetRoundedRectCount() const { return mRoundedClipRects.Length(); }
+  void AppendRoundedRects(nsTArray<RoundedRect>* aArray, uint32_t aCount) const;
+
+  static const DisplayItemClip& NoClip();
+
+  static void Shutdown();
+
+private:
+  nsRect mClipRect;
+  nsTArray<RoundedRect> mRoundedClipRects;
+  // If mHaveClipRect is false then this object represents no clipping at all
+  // and mRoundedClipRects must be empty.
+  bool mHaveClipRect;
+};
+
+} // namespace mozilla
+
+#endif /* DISPLAYITEMCLIP_H_ */