Revert "Revert "long rect dash fix with guards""

This reverts commit fa6b6c2d1b613faf72071b99f4b404fa4ee5e076.

Reason for revert: Looks like this was actually caused by another change but happen to fail a test that looked very related to this

Original change's description:
> Revert "long rect dash fix with guards"
> 
> This reverts commit 93ceab1b59f06c828cf62aa6a700e7f81620f23d.
> 
> Reason for revert: breaking layout test
> 
> Original change's description:
> > long rect dash fix with guards
> > 
> > long rect dash with guards
> > 
> > check dash fix back in with
> > guards against changing
> > chrome layout test results
> > 
> > original change clipped against wrong rectangle
> > some of the time, causing tiled drawing to fail.
> > Always clip against outset rectangle.
> > 
> > original CL: skia-review.googlesource.com/c/skia/+/84862
> > 
> > efficiently dash very large rectangles and very long lines
> > Speed up dashing when lines and rects are absurdly large.
> > 
> > Prior to this CL, only horizontal lines were detected.
> > 
> > Also folded in a change to handle dashing of zero length lines.
> > 
> > TBR=egdaniel@google.com
> > Bug: skia:7311
> > Change-Id: Ic3c68ec8ea35d0597c892c3b26ba7bb077045990
> > Reviewed-on: https://skia-review.googlesource.com/87768
> > Reviewed-by: Cary Clark <caryclark@skia.org>
> > Commit-Queue: Cary Clark <caryclark@skia.org>
> 
> TBR=egdaniel@google.com,caryclark@skia.org
> 
> Change-Id: I56ef771ccb281887d7381c2bd8a2553acbd30621
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:7311
> Reviewed-on: https://skia-review.googlesource.com/88421
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,caryclark@skia.org

Change-Id: Iecdd072544e6623bc4de8d5aab1402378112512d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:7311
Reviewed-on: https://skia-review.googlesource.com/88424
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>

2 files changed, 161 insertions, 0 deletions

diff --git a/gm/strokes.cpp b/gm/strokes.cpp
index ed13d090ff..50b940a4ed 100644
--- a/gm/strokes.cpp
+++ b/gm/strokes.cpp
@@ -533,3 +533,33 @@ DEF_SIMPLE_GM(zerolinedash, canvas, 256, 256) {
 
     canvas->drawLine(100, 100, 100, 100, paint);
 }
+
+#ifdef PDF_IS_FIXED_SO_THIS_DOESNT_BREAK_IT
+DEF_SIMPLE_GM(longrect_dash, canvas, 250, 250) {
+    canvas->clear(SK_ColorWHITE);
+
+    SkPaint paint;
+    paint.setColor(SkColorSetARGB(255, 0, 0, 0));
+    paint.setStrokeWidth(5);
+    paint.setStrokeCap(SkPaint::kRound_Cap);
+    paint.setStrokeJoin(SkPaint::kBevel_Join);
+    paint.setStyle(SkPaint::kStroke_Style);
+    SkScalar dash_pattern[] = {1, 5};
+    paint.setPathEffect(SkDashPathEffect::Make(dash_pattern, 2, 0));
+    // try all combinations of stretching bounds
+    for (auto left : { 20.f, -100001.f } ) {
+        for (auto top : { 20.f, -100001.f } ) {
+            for (auto right : { 40.f, 100001.f } ) {
+                for (auto bottom : { 40.f, 100001.f } ) {
+                    canvas->save();
+                    canvas->clipRect({10, 10, 50, 50});
+                    canvas->drawRect({left, top, right, bottom}, paint);
+                    canvas->restore();
+                    canvas->translate(60, 0);
+               }
+            }
+            canvas->translate(-60 * 4, 60);
+        }
+    }
+}
+#endif
diff --git a/src/utils/SkDashPath.cpp b/src/utils/SkDashPath.cpp
index cbfc8f2168..8d6c3cf567 100644
--- a/src/utils/SkDashPath.cpp
+++ b/src/utils/SkDashPath.cpp
@@ -83,11 +83,95 @@ static void outset_for_stroke(SkRect* rect, const SkStrokeRec& rec) {
     rect->outset(radius, radius);
 }
 
+#ifndef SK_SUPPORT_LEGACY_DASH_CULL_PATH
+// If line is zero-length, bump out the end by a tiny amount
+// to draw endcaps. The bump factor is sized so that
+// SkPoint::Distance() computes a non-zero length.
+// Offsets SK_ScalarNearlyZero or smaller create empty paths when Iter measures length.
+// Large values are scaled by SK_ScalarNearlyZero so significant bits change.
+static void adjust_zero_length_line(SkPoint pts[2]) {
+    SkASSERT(pts[0] == pts[1]);
+    pts[1].fX += SkTMax(1.001f, pts[1].fX) * SK_ScalarNearlyZero;
+}
+
+static bool clip_line(SkPoint pts[2], const SkRect& bounds, SkScalar intervalLength,
+                      SkScalar priorPhase) {
+    SkVector dxy = pts[1] - pts[0];
+
+    // only horizontal or vertical lines
+    if (dxy.fX && dxy.fY) {
+        return false;
+    }
+    int xyOffset = SkToBool(dxy.fY);  // 0 to adjust horizontal, 1 to adjust vertical
+
+    SkScalar minXY = (&pts[0].fX)[xyOffset];
+    SkScalar maxXY = (&pts[1].fX)[xyOffset];
+    bool swapped = maxXY < minXY;
+    if (swapped) {
+        SkTSwap(minXY, maxXY);
+    }
+
+    SkASSERT(minXY <= maxXY);
+    SkScalar leftTop = (&bounds.fLeft)[xyOffset];
+    SkScalar rightBottom = (&bounds.fRight)[xyOffset];
+    if (maxXY < leftTop || minXY > rightBottom) {
+        return false;
+    }
+
+    // Now we actually perform the chop, removing the excess to the left/top and
+    // right/bottom of the bounds (keeping our new line "in phase" with the dash,
+    // hence the (mod intervalLength).
+
+    if (minXY < leftTop) {
+        minXY = leftTop - SkScalarMod(leftTop - minXY, intervalLength);
+        if (!swapped) {
+            minXY -= priorPhase;  // for rectangles, adjust by prior phase
+        }
+    }
+    if (maxXY > rightBottom) {
+        maxXY = rightBottom + SkScalarMod(maxXY - rightBottom, intervalLength);
+        if (swapped) {
+            maxXY += priorPhase;  // for rectangles, adjust by prior phase
+        }
+    }
+
+    SkASSERT(maxXY >= minXY);
+    if (swapped) {
+        SkTSwap(minXY, maxXY);
+    }
+    (&pts[0].fX)[xyOffset] = minXY;
+    (&pts[1].fX)[xyOffset] = maxXY;
+
+    if (minXY == maxXY) {
+        adjust_zero_length_line(pts);
+    }
+    return true;
+}
+
+static bool contains_inclusive(const SkRect& rect, const SkPoint& pt) {
+    return rect.fLeft <= pt.fX && pt.fX <= rect.fRight &&
+            rect.fTop <= pt.fY && pt.fY <= rect.fBottom;
+}
+
+// Returns true is b is between a and c, that is: a <= b <= c, or a >= b >= c.
+// Can perform this test with one branch by observing that, relative to b,
+// the condition is true only if one side is positive and one side is negative.
+// If the numbers are very small, the optimization may return the wrong result
+// because the multiply may generate a zero where the simple compare does not.
+// For this reason the assert does not fire when all three numbers are near zero.
+static bool between(SkScalar a, SkScalar b, SkScalar c) {
+    SkASSERT(((a <= b && b <= c) || (a >= b && b >= c)) == ((a - b) * (c - b) <= 0)
+            || (SkScalarNearlyZero(a) && SkScalarNearlyZero(b) && SkScalarNearlyZero(c)));
+    return (a - b) * (c - b) <= 0;
+}
+#endif
+
 // Only handles lines for now. If returns true, dstPath is the new (smaller)
 // path. If returns false, then dstPath parameter is ignored.
 static bool cull_path(const SkPath& srcPath, const SkStrokeRec& rec,
                       const SkRect* cullRect, SkScalar intervalLength,
                       SkPath* dstPath) {
+#ifdef SK_SUPPORT_LEGACY_DASH_CULL_PATH
     if (nullptr == cullRect) {
         return false;
     }
@@ -146,6 +230,53 @@ static bool cull_path(const SkPath& srcPath, const SkStrokeRec& rec,
     if (minX == maxX) {
         pts[1].fX += maxX * FLT_EPSILON * 32;  // 16 instead of 32 does not draw; length stays zero
     }
+#else // !SK_SUPPORT_LEGACY_DASH_CULL_PATH
+    SkPoint pts[4];
+    if (nullptr == cullRect) {
+        if (srcPath.isLine(pts) && pts[0] == pts[1]) {
+            adjust_zero_length_line(pts);
+        } else {
+            return false;
+        }
+    } else {
+        SkRect bounds;
+        bool isLine = srcPath.isLine(pts);
+        bool isRect = !isLine && srcPath.isRect(nullptr);
+        if (!isLine && !isRect) {
+            return false;
+        }
+        bounds = *cullRect;
+        outset_for_stroke(&bounds, rec);
+        if (isRect) {
+            // break rect into four lines, and call each one separately
+            SkPath::Iter iter(srcPath, false);
+            SkAssertResult(SkPath::kMove_Verb == iter.next(pts));
+            SkScalar priorLength = 0;
+            while (SkPath::kLine_Verb == iter.next(pts)) {
+                SkVector v = pts[1] - pts[0];
+                // if line is entirely outside clip rect, skip it
+                if (v.fX ? between(bounds.fTop, pts[0].fY, bounds.fBottom) :
+                        between(bounds.fLeft, pts[0].fX, bounds.fRight)) {
+                    bool skipMoveTo = contains_inclusive(bounds, pts[0]);
+                    if (clip_line(pts, bounds, intervalLength,
+                                  SkScalarMod(priorLength, intervalLength))) {
+                        if (0 == priorLength || !skipMoveTo) {
+                            dstPath->moveTo(pts[0]);
+                        }
+                        dstPath->lineTo(pts[1]);
+                    }
+                }
+                // keep track of all prior lengths to set phase of next line
+                priorLength += SkScalarAbs(v.fX ? v.fX : v.fY);
+            }
+            return !dstPath->isEmpty();
+        }
+        SkASSERT(isLine);
+        if (!clip_line(pts, bounds, intervalLength, 0)) {
+            return false;
+        }
+    }
+#endif
     dstPath->moveTo(pts[0]);
     dstPath->lineTo(pts[1]);
     return true;