change convex scan converter to be defensive
ran convex_path_* nanobench, with no appreciable perf loss
(for the cases tested)
Bug: 899689
Bug: skia:8606
Change-Id: Ida253c5057f38b90cda86a1717a8bb7c4a6155dc
Reviewed-on: https://skia-review.googlesource.com/c/175832
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
diff --git a/src/core/SkPath.cpp b/src/core/SkPath.cpp
index 09badf5..4eafc1b 100644
--- a/src/core/SkPath.cpp
+++ b/src/core/SkPath.cpp
@@ -1863,6 +1863,11 @@
// convex after a transformation, so mark it as unknown here.
// However, some transformations are thought to be safe:
// axis-aligned values under scale/translate.
+ //
+ // See skbug.com/8606
+ // If we can land a robust convex scan-converter, we may be able to relax/remove this
+ // check, and keep convex paths marked as such after a general transform...
+ //
if (matrix.isScaleTranslate() && SkPathPriv::IsAxisAligned(*this)) {
dst->setConvexity(convexity);
} else {
diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp
index 7fdef96..2120343 100644
--- a/src/core/SkScan_Path.cpp
+++ b/src/core/SkScan_Path.cpp
@@ -210,9 +210,17 @@
return true;
}
-static void walk_convex_edges(SkEdge* prevHead, SkPath::FillType,
- SkBlitter* blitter, int start_y, int stop_y,
- PrePostProc proc) {
+// Unexpected conditions for which we need to return
+#define ASSERT_RETURN(cond) \
+ do { \
+ if (!(cond)) { \
+ SkASSERT(false); \
+ return; \
+ } \
+ } while (0)
+
+// Needs Y to only change once (looser than convex in X)
+static void walk_simple_edges(SkEdge* prevHead, SkBlitter* blitter, int start_y, int stop_y) {
validate_sort(prevHead->fNext);
SkEdge* leftE = prevHead->fNext;
@@ -222,31 +230,29 @@
// our edge choppers for curves can result in the initial edges
// not lining up, so we take the max.
int local_top = SkMax32(leftE->fFirstY, riteE->fFirstY);
- SkASSERT(local_top >= start_y);
+ ASSERT_RETURN(local_top >= start_y);
- for (;;) {
+ while (local_top < stop_y) {
SkASSERT(leftE->fFirstY <= stop_y);
SkASSERT(riteE->fFirstY <= stop_y);
- if (leftE->fX > riteE->fX || (leftE->fX == riteE->fX &&
- leftE->fDX > riteE->fDX)) {
- using std::swap;
- swap(leftE, riteE);
- }
-
int local_bot = SkMin32(leftE->fLastY, riteE->fLastY);
local_bot = SkMin32(local_bot, stop_y - 1);
- SkASSERT(local_top <= local_bot);
+ ASSERT_RETURN(local_top <= local_bot);
SkFixed left = leftE->fX;
SkFixed dLeft = leftE->fDX;
SkFixed rite = riteE->fX;
SkFixed dRite = riteE->fDX;
int count = local_bot - local_top;
- SkASSERT(count >= 0);
+ ASSERT_RETURN(count >= 0);
+
if (0 == (dLeft | dRite)) {
int L = SkFixedRoundToInt(left);
int R = SkFixedRoundToInt(rite);
+ if (L > R) {
+ std::swap(L, R);
+ }
if (L < R) {
count += 1;
blitter->blitRect(L, local_top, R - L, count);
@@ -256,6 +262,9 @@
do {
int L = SkFixedRoundToInt(left);
int R = SkFixedRoundToInt(rite);
+ if (L > R) {
+ std::swap(L, R);
+ }
if (L < R) {
blitter->blitH(L, local_top, R - L);
}
@@ -274,26 +283,19 @@
if (!update_edge(leftE, local_bot)) {
if (currE->fFirstY >= stop_y) {
- break;
+ return; // we're done
}
leftE = currE;
currE = currE->fNext;
+ ASSERT_RETURN(leftE->fFirstY == local_top);
}
if (!update_edge(riteE, local_bot)) {
if (currE->fFirstY >= stop_y) {
- break;
+ return; // we're done
}
riteE = currE;
currE = currE->fNext;
- }
-
- SkASSERT(leftE);
- SkASSERT(riteE);
-
- // check our bottom clip
- SkASSERT(local_top == local_bot + 1);
- if (local_top >= stop_y) {
- break;
+ ASSERT_RETURN(riteE->fFirstY == local_top);
}
}
}
@@ -467,7 +469,7 @@
// count >= 2 is required as the convex walker does not handle missing right edges
if (path.isConvex() && (nullptr == proc) && count >= 2) {
- walk_convex_edges(&headEdge, path.getFillType(), blitter, start_y, stop_y, nullptr);
+ walk_simple_edges(&headEdge, blitter, start_y, stop_y);
} else {
walk_edges(&headEdge, path.getFillType(), blitter, start_y, stop_y, proc,
shiftedClip.right());
@@ -733,8 +735,7 @@
if (clipRect && start_y < clipRect->fTop) {
start_y = clipRect->fTop;
}
- walk_convex_edges(&headEdge, SkPath::kEvenOdd_FillType, blitter, start_y, stop_y, nullptr);
-// walk_edges(&headEdge, SkPath::kEvenOdd_FillType, blitter, start_y, stop_y, nullptr);
+ walk_simple_edges(&headEdge, blitter, start_y, stop_y);
}
void SkScan::FillTriangle(const SkPoint pts[], const SkRasterClip& clip,
