From e2330261a704e2db762e2de0d297bf8b4dc510f1 Mon Sep 17 00:00:00 2001
From: Mike Reed <reed@google.com>
Date: Fri, 12 Jan 2018 12:06:40 -0500
Subject: [PATCH] relax path bounds check so we can draw larger paths

Bug:800804
Change-Id: Ief0679de95887d8e11aa5853228c2bdef27d07a2
Reviewed-on: https://skia-review.googlesource.com/94100
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Mike Reed <reed@google.com>
---
 gm/hugepath.cpp              | 31 ++++++++++++++++++++-----------
 src/core/SkScan_AntiPath.cpp | 32 +++++++++++---------------------
 2 files changed, 31 insertions(+), 32 deletions(-)

diff --git a/gm/hugepath.cpp b/gm/hugepath.cpp
index dbca413093..83dff9ec3e 100644
--- a/gm/hugepath.cpp
+++ b/gm/hugepath.cpp
@@ -9,20 +9,29 @@
 #include "SkCanvas.h"
 #include "SkPath.h"
 
-DEF_SIMPLE_GM(path_huge_crbug_800804, canvas, 30, 600) {
+DEF_SIMPLE_GM(path_huge_crbug_800804, canvas, 50, 600) {
     SkPaint paint;
     paint.setAntiAlias(true);
-
     paint.setStyle(SkPaint::kStroke_Style);
-    paint.setStrokeWidth(1);
-    SkPath path;
-    path.moveTo(-1000,12345678901234567890.f);
-    path.lineTo(10.5f,200);
-    canvas->drawPath(path, paint);
 
-    path.reset();
-    path.moveTo(20.5f,400);
-    path.lineTo(1000,-9.8765432109876543210e+19f);
-    canvas->drawPath(path, paint);
+    // exercise various special-cases (e.g. hairlines or not)
+    const float widths[] = { 0.9f, 1.0f, 1.1f };
+
+    SkPath path;
+    for (float w : widths) {
+        paint.setStrokeWidth(w);
+
+        path.reset();
+        path.moveTo(-1000,12345678901234567890.f);
+        path.lineTo(10.5f,200);
+        canvas->drawPath(path, paint);
+
+        path.reset();
+        path.moveTo(30.5f,400);
+        path.lineTo(1000,-9.8765432109876543210e+19f);
+        canvas->drawPath(path, paint);
+
+        canvas->translate(3, 0);
+    }
 }
 
diff --git a/src/core/SkScan_AntiPath.cpp b/src/core/SkScan_AntiPath.cpp
index f903a4fd5c..28a6cfc5fc 100644
--- a/src/core/SkScan_AntiPath.cpp
+++ b/src/core/SkScan_AntiPath.cpp
@@ -630,12 +630,6 @@ void SkScan::SAAFillPath(const SkPath& path, SkBlitter* blitter, const SkIRect&
     }
 }
 
-static bool fitsInsideLimit(const SkRect& r, SkScalar max) {
-    const SkScalar min = -max;
-    return  r.fLeft > min && r.fTop > min &&
-            r.fRight < max && r.fBottom < max;
-}
-
 static int overflows_short_shift(int value, int shift) {
     const int s = 16 + shift;
     return (SkLeftShift(value, s) >> s) - value;
@@ -659,14 +653,17 @@ static int rect_overflows_short_shift(SkIRect rect, int shift) {
            overflows_short_shift(rect.fBottom, shift);
 }
 
-static bool safeRoundOut(const SkRect& src, SkIRect* dst, int32_t maxInt) {
-    const SkScalar maxScalar = SkIntToScalar(maxInt);
+static SkIRect safeRoundOut(const SkRect& src) {
+    // roundOut will pin huge floats to max/min int
+    SkIRect dst = src.roundOut();
 
-    if (fitsInsideLimit(src, maxScalar)) {
-        src.roundOut(dst);
-        return true;
-    }
-    return false;
+    // intersect with a smaller huge rect, so the rect will not be considered empty for being
+    // too large. e.g. { -SK_MaxS32 ... SK_MaxS32 } is considered empty because its width
+    // exceeds signed 32bit.
+    const int32_t limit = SK_MaxS32 >> 1;
+    (void)dst.intersect({ -limit, -limit, limit, limit});
+
+    return dst;
 }
 
 void SkScan::AntiFillPath(const SkPath& path, const SkRegion& origClip,
@@ -676,12 +673,7 @@ void SkScan::AntiFillPath(const SkPath& path, const SkRegion& origClip,
     }
 
     const bool isInverse = path.isInverseFillType();
-    SkIRect ir;
-
-    if (!safeRoundOut(path.getBounds(), &ir, SK_MaxS32 >> SHIFT)) {
-        // Bounds can't fit in SkIRect; we'll return without drawing
-        return;
-    }
+    SkIRect ir = safeRoundOut(path.getBounds());
     if (ir.isEmpty()) {
         if (isInverse) {
             blitter->blitRegion(origClip);
@@ -745,8 +737,6 @@ void SkScan::AntiFillPath(const SkPath& path, const SkRegion& origClip,
         sk_blit_above(blitter, ir, *clipRgn);
     }
 
-    SkASSERT(SkIntToScalar(ir.fTop) <= path.getBounds().fTop);
-
     if (forceDAA || ShouldUseDAA(path)) {
         SkScan::DAAFillPath(path, blitter, ir, clipRgn->getBounds(), forceRLE);
     } else if (ShouldUseAAA(path)) {