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-rw-r--r--gfx/2d/Matrix.h18
-rw-r--r--gfx/tests/gtest/TestMatrix.cpp61
-rw-r--r--gfx/tests/gtest/moz.build1
3 files changed, 77 insertions, 3 deletions
diff --git a/gfx/2d/Matrix.h b/gfx/2d/Matrix.h
index 84c9a5280..d6835c8e6 100644
--- a/gfx/2d/Matrix.h
+++ b/gfx/2d/Matrix.h
@@ -723,7 +723,7 @@ public:
* The resulting vertices are populated in aVerts. aVerts must be
* pre-allocated to hold at least kTransformAndClipRectMaxVerts Points.
* The vertex count is returned by TransformAndClipRect. It is possible to
- * emit fewer that 3 vertices, indicating that aRect will not be visible
+ * emit fewer than 3 vertices, indicating that aRect will not be visible
* within aClip.
*/
template<class F>
@@ -751,8 +751,10 @@ public:
planeNormals[3] = Point4DTyped<UnknownUnits, F>(0.0, -1.0, 0.0, aClip.YMost());
// Iterate through each clipping plane and clip the polygon.
- // In each pass, we double buffer, alternating between points[0] and
- // points[1].
+ // For each clipping plane, we intersect the plane with all polygon edges.
+ // Each pass can increase or decrease the number of points that make up the
+ // current clipped polygon. We double buffer that set of points, alternating
+ // between points[0] and points[1].
for (int plane=0; plane < 4; plane++) {
planeNormals[plane].Normalize();
Point4DTyped<UnknownUnits, F>* srcPoint = dstPointStart;
@@ -761,6 +763,14 @@ public:
dstPointStart = points[~plane & 1];
dstPoint = dstPointStart;
+ // Iterate over the polygon edges. In each iteration the current edge is
+ // the edge from prevPoint to srcPoint. If the two end points lie on
+ // different sides of the plane, we have an intersection. Otherwise, the
+ // edge is either completely "inside" the half-space created by the
+ // clipping plane, and we add srcPoint, or it is completely "outside", and
+ // we discard srcPoint.
+ // We may create duplicated points in the polygon. We keep those around
+ // until all clipping is done and then filter out duplicates at the end.
Point4DTyped<UnknownUnits, F>* prevPoint = srcPointEnd - 1;
F prevDot = planeNormals[plane].DotProduct(*prevPoint);
while (srcPoint < srcPointEnd && ((dstPoint - dstPointStart) < kTransformAndClipRectMaxVerts)) {
@@ -784,6 +794,8 @@ public:
}
if (dstPoint == dstPointStart) {
+ // No polygon points were produced, so the polygon has been
+ // completely clipped away by the current clipping plane. Exit.
break;
}
}
diff --git a/gfx/tests/gtest/TestMatrix.cpp b/gfx/tests/gtest/TestMatrix.cpp
new file mode 100644
index 000000000..bc2f9e63c
--- /dev/null
+++ b/gfx/tests/gtest/TestMatrix.cpp
@@ -0,0 +1,61 @@
+/* -*- 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/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/gfx/Matrix.h"
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+
+static Rect NudgedToInt(const Rect& aRect) {
+ Rect r(aRect);
+ r.NudgeToIntegers();
+ return r;
+}
+
+TEST(Matrix, TransformAndClipRect)
+{
+ Rect c(100, 100, 100, 100);
+ Matrix4x4 m;
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 50, 20, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(250, 50, 20, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(250, 250, 20, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 250, 20, 20), c).IsEmpty());
+
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 50, 100, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(150, 50, 100, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 250, 100, 20), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(150, 250, 100, 20), c).IsEmpty());
+
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 50, 20, 100), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(50, 150, 20, 100), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(250, 50, 20, 100), c).IsEmpty());
+ EXPECT_TRUE(m.TransformAndClipBounds(Rect(250, 150, 20, 100), c).IsEmpty());
+
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 50, 100, 100), c))
+ .IsEqualInterior(Rect(100, 100, 50, 50)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(150, 50, 100, 100), c))
+ .IsEqualInterior(Rect(150, 100, 50, 50)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(150, 150, 100, 100), c))
+ .IsEqualInterior(Rect(150, 150, 50, 50)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 150, 100, 100), c))
+ .IsEqualInterior(Rect(100, 150, 50, 50)));
+
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(110, 110, 80, 80), c))
+ .IsEqualInterior(Rect(110, 110, 80, 80)));
+
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 50, 200, 200), c))
+ .IsEqualInterior(Rect(100, 100, 100, 100)));
+
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 50, 200, 100), c))
+ .IsEqualInterior(Rect(100, 100, 100, 50)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 150, 200, 100), c))
+ .IsEqualInterior(Rect(100, 150, 100, 50)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(50, 50, 100, 200), c))
+ .IsEqualInterior(Rect(100, 100, 50, 100)));
+ EXPECT_TRUE(NudgedToInt(m.TransformAndClipBounds(Rect(150, 50, 100, 200), c))
+ .IsEqualInterior(Rect(150, 100, 50, 100)));
+}
diff --git a/gfx/tests/gtest/moz.build b/gfx/tests/gtest/moz.build
index 23b019d1b..ea18c1e3b 100644
--- a/gfx/tests/gtest/moz.build
+++ b/gfx/tests/gtest/moz.build
@@ -17,6 +17,7 @@ UNIFIED_SOURCES += [
'TestGfxWidgets.cpp',
'TestJobScheduler.cpp',
'TestLayers.cpp',
+ 'TestMatrix.cpp',
'TestMoz2D.cpp',
'TestPolygon.cpp',
'TestQcms.cpp',