"Fix" for hairline corner bugs
https://codereview.chromium.org/23708036/
git-svn-id: http://skia.googlecode.com/svn/trunk@11365 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrAAHairLinePathRenderer.cpp b/src/gpu/GrAAHairLinePathRenderer.cpp
index 5078467..66cb80d 100644
--- a/src/gpu/GrAAHairLinePathRenderer.cpp
+++ b/src/gpu/GrAAHairLinePathRenderer.cpp
@@ -28,8 +28,16 @@
static const int kVertsPerQuad = 5;
static const int kIdxsPerQuad = 9;
+// lines are rendered as:
+// *______________*
+// |\ -_______ /|
+// | \ \ / |
+// | *--------* |
+// | / ______/ \ |
+// */_-__________\*
+// For: 6 vertices and 18 indices (for 6 triangles)
static const int kVertsPerLineSeg = 6;
-static const int kIdxsPerLineSeg = 12;
+static const int kIdxsPerLineSeg = 18;
static const int kNumQuadsInIdxBuffer = 256;
static const size_t kQuadIdxSBufize = kIdxsPerQuad *
@@ -90,32 +98,41 @@
data = SkNEW_ARRAY(uint16_t, kNumLineSegsInIdxBuffer * kIdxsPerLineSeg);
}
for (int i = 0; i < kNumLineSegsInIdxBuffer; ++i) {
- // Each line segment is rendered as two quads, with alpha = 1 along the
- // spine of the segment, and alpha = 0 along the outer edges, represented
- // horizontally (i.e., the line equation is t*(p1-p0) + p0)
+ // Each line segment is rendered as two quads and two triangles.
+ // p0 and p1 have alpha = 1 while all other points have alpha = 0.
+ // The four external points are offset 1 pixel perpendicular to the
+ // line and half a pixel parallel to the line.
//
// p4 p5
- // p0 p1
+ // p0 p1
// p2 p3
//
- // Each is drawn as four triangles specified by these 12 indices:
+ // Each is drawn as six triangles specified by these 18 indices:
int baseIdx = i * kIdxsPerLineSeg;
uint16_t baseVert = (uint16_t)(i * kVertsPerLineSeg);
- data[0 + baseIdx] = baseVert + 0; // p0
- data[1 + baseIdx] = baseVert + 1; // p1
- data[2 + baseIdx] = baseVert + 2; // p2
+ data[0 + baseIdx] = baseVert + 0;
+ data[1 + baseIdx] = baseVert + 1;
+ data[2 + baseIdx] = baseVert + 3;
- data[3 + baseIdx] = baseVert + 2; // p2
- data[4 + baseIdx] = baseVert + 1; // p1
- data[5 + baseIdx] = baseVert + 3; // p3
+ data[3 + baseIdx] = baseVert + 0;
+ data[4 + baseIdx] = baseVert + 3;
+ data[5 + baseIdx] = baseVert + 2;
- data[6 + baseIdx] = baseVert + 0; // p0
- data[7 + baseIdx] = baseVert + 5; // p5
- data[8 + baseIdx] = baseVert + 1; // p1
+ data[6 + baseIdx] = baseVert + 0;
+ data[7 + baseIdx] = baseVert + 4;
+ data[8 + baseIdx] = baseVert + 5;
- data[9 + baseIdx] = baseVert + 0; // p0
- data[10+ baseIdx] = baseVert + 4; // p4
- data[11+ baseIdx] = baseVert + 5; // p5
+ data[9 + baseIdx] = baseVert + 0;
+ data[10+ baseIdx] = baseVert + 5;
+ data[11+ baseIdx] = baseVert + 1;
+
+ data[12 + baseIdx] = baseVert + 0;
+ data[13 + baseIdx] = baseVert + 2;
+ data[14 + baseIdx] = baseVert + 4;
+
+ data[15 + baseIdx] = baseVert + 1;
+ data[16 + baseIdx] = baseVert + 5;
+ data[17 + baseIdx] = baseVert + 3;
}
if (tempData) {
bool ret = lIdxBuffer->updateData(data, kLineSegIdxSBufize);
@@ -649,31 +666,33 @@
}
void add_line(const SkPoint p[2],
- int rtHeight,
const SkMatrix* toSrc,
GrColor coverage,
LineVertex** vert) {
const SkPoint& a = p[0];
const SkPoint& b = p[1];
- SkVector orthVec = b;
- orthVec -= a;
+ SkVector ortho, vec = b;
+ vec -= a;
- if (orthVec.setLength(SK_Scalar1)) {
- orthVec.setOrthog(orthVec);
+ if (vec.setLength(SK_ScalarHalf)) {
+ // Create a vector orthogonal to 'vec' and of unit length
+ ortho.fX = 2.0f * vec.fY;
+ ortho.fY = -2.0f * vec.fX;
- for (int i = 0; i < kVertsPerLineSeg; ++i) {
- (*vert)[i].fPos = (i & 0x1) ? b : a;
- if (i & 0x2) {
- (*vert)[i].fPos += orthVec;
- (*vert)[i].fCoverage = 0;
- } else if (i & 0x4) {
- (*vert)[i].fPos -= orthVec;
- (*vert)[i].fCoverage = 0;
- } else {
- (*vert)[i].fCoverage = coverage;
- }
- }
+ (*vert)[0].fPos = a;
+ (*vert)[0].fCoverage = coverage;
+ (*vert)[1].fPos = b;
+ (*vert)[1].fCoverage = coverage;
+ (*vert)[2].fPos = a - vec + ortho;
+ (*vert)[2].fCoverage = 0;
+ (*vert)[3].fPos = b + vec + ortho;
+ (*vert)[3].fCoverage = 0;
+ (*vert)[4].fPos = a - vec - ortho;
+ (*vert)[4].fCoverage = 0;
+ (*vert)[5].fPos = b + vec - ortho;
+ (*vert)[5].fCoverage = 0;
+
if (NULL != toSrc) {
toSrc->mapPointsWithStride(&(*vert)->fPos,
sizeof(LineVertex),
@@ -709,15 +728,13 @@
};
-bool GrAAHairLinePathRenderer::createLineGeom(
- const SkPath& path,
- GrDrawTarget* target,
- const PtArray& lines,
- int lineCnt,
- GrDrawTarget::AutoReleaseGeometry* arg,
- SkRect* devBounds) {
+bool GrAAHairLinePathRenderer::createLineGeom(const SkPath& path,
+ GrDrawTarget* target,
+ const PtArray& lines,
+ int lineCnt,
+ GrDrawTarget::AutoReleaseGeometry* arg,
+ SkRect* devBounds) {
GrDrawState* drawState = target->drawState();
- int rtHeight = drawState->getRenderTarget()->height();
const SkMatrix& viewM = drawState->getViewMatrix();
@@ -725,8 +742,8 @@
int vertCnt = kVertsPerLineSeg * lineCnt;
- target->drawState()->setVertexAttribs<gHairlineLineAttribs>(SK_ARRAY_COUNT(gHairlineLineAttribs));
- SkASSERT(sizeof(LineVertex) == target->getDrawState().getVertexSize());
+ drawState->setVertexAttribs<gHairlineLineAttribs>(SK_ARRAY_COUNT(gHairlineLineAttribs));
+ SkASSERT(sizeof(LineVertex) == drawState->getVertexSize());
if (!arg->set(target, vertCnt, 0)) {
return false;
@@ -744,7 +761,7 @@
}
devBounds->set(lines.begin(), lines.count());
for (int i = 0; i < lineCnt; ++i) {
- add_line(&lines[2*i], rtHeight, toSrc, drawState->getCoverage(), &verts);
+ add_line(&lines[2*i], toSrc, drawState->getCoverage(), &verts);
}
// All the verts computed by add_line are within unit distance of the end points. Add a little
// extra to account for vector normalization precision.
@@ -910,7 +927,7 @@
GrDrawTarget::AutoStateRestore asr;
- // createGeom transforms the geometry to device space when the matrix does not have
+ // createLineGeom transforms the geometry to device space when the matrix does not have
// perspective.
if (target->getDrawState().getViewMatrix().hasPerspective()) {
asr.set(target, GrDrawTarget::kPreserve_ASRInit);
@@ -933,8 +950,8 @@
kVertsPerLineSeg*lines, // startV
0, // startI
kVertsPerLineSeg*n, // vCount
- kIdxsPerLineSeg*n,
- &devBounds); // iCount
+ kIdxsPerLineSeg*n, // iCount
+ &devBounds);
lines += n;
}
}