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Correctly return zero vertices if clipping plane...

This commit is contained in:
Fedor 2019-09-20 13:10:17 +03:00
parent 94c6e51ff3
commit fdc0a37db5
2 changed files with 29 additions and 14 deletions
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42
gfx/2d/Matrix.h
View File

@ -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>
@ -734,7 +734,8 @@ public:
// Initialize a double-buffered array of points in homogenous space with
// the input rectangle, aRect.
Point4DTyped<UnknownUnits, F> points[2][kTransformAndClipRectMaxVerts];
Point4DTyped<UnknownUnits, F>* dstPoint = points[0];
Point4DTyped<UnknownUnits, F>* dstPointStart = points[0];
Point4DTyped<UnknownUnits, F>* dstPoint = dstPointStart;
*dstPoint++ = TransformPoint(Point4DTyped<UnknownUnits, F>(aRect.x, aRect.y, 0, 1));
*dstPoint++ = TransformPoint(Point4DTyped<UnknownUnits, F>(aRect.XMost(), aRect.y, 0, 1));
@ -750,16 +751,26 @@ 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 = points[plane & 1];
Point4DTyped<UnknownUnits, F>* srcPoint = dstPointStart;
Point4DTyped<UnknownUnits, F>* srcPointEnd = dstPoint;
dstPoint = points[~plane & 1];
Point4DTyped<UnknownUnits, F>* dstPointStart = dstPoint;
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)) {
@ -783,14 +794,16 @@ public:
}
if (dstPoint == dstPointStart) {
// No polygon points were produced, so the polygon has been
// completely clipped away by the current clipping plane. Exit.
break;
}
}
size_t dstPointCount = 0;
size_t srcPointCount = dstPoint - points[0];
for (Point4DTyped<UnknownUnits, F>* srcPoint = points[0]; srcPoint < points[0] + srcPointCount; srcPoint++) {
Point4DTyped<UnknownUnits, F>* srcPoint = dstPointStart;
Point4DTyped<UnknownUnits, F>* srcPointEnd = dstPoint;
size_t vertCount = 0;
while (srcPoint < srcPointEnd) {
PointTyped<TargetUnits, F> p;
if (srcPoint->w == 0.0) {
// If a point lies on the intersection of the clipping planes at
@ -800,12 +813,13 @@ public:
p = srcPoint->As2DPoint();
}
// Emit only unique points
if (dstPointCount == 0 || p != aVerts[dstPointCount - 1]) {
aVerts[dstPointCount++] = p;
if (vertCount == 0 || p != aVerts[vertCount - 1]) {
aVerts[vertCount++] = p;
}
srcPoint++;
}
return dstPointCount;
return vertCount;
}
static const int kTransformAndClipRectMaxVerts = 32;

1
gfx/tests/gtest/moz.build
View File

@ -17,6 +17,7 @@ UNIFIED_SOURCES += [
'TestGfxWidgets.cpp',
'TestJobScheduler.cpp',
'TestLayers.cpp',
'TestMatrix.cpp',
'TestMoz2D.cpp',
'TestPolygon.cpp',
'TestQcms.cpp',