SkPDF: Fastpath for clipstack flattening

BUG: chromium:837279

Change-Id: I79a675e7d9e713617711948e491e28babe06b1a2
Reviewed-on: https://skia-review.googlesource.com/132092
Auto-Submit: Hal Canary <halcanary@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>

1 files changed, 72 insertions, 22 deletions

diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index ced94ce9a9..1cf649c1a1 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -283,49 +283,99 @@ bool apply_clip(SkClipOp op, const SkPath& u, const SkPath& v, SkPath* r)  {
     }
 }
 
-// TODO(vandebo): Take advantage of SkClipStack::getSaveCount(), the PDF
-// graphic state stack, and the fact that we can know all the clips used
-// on the page to optimize this.
-void GraphicStackState::updateClip(const SkClipStack& clipStack,
-                                   const SkIRect& bounds) {
-    if (clipStack == currentEntry()->fClipStack) {
-        return;
-    }
-
-    while (fStackDepth > 0) {
-        pop();
-        if (clipStack == currentEntry()->fClipStack) {
-            return;
+static SkRect rect_intersect(SkRect u, SkRect v) {
+    if (u.isEmpty() || v.isEmpty()) { return {0, 0, 0, 0}; }
+    return u.intersect(v) ? u : SkRect{0, 0, 0, 0};
+}
+
+// Test to see if the clipstack is a simple rect, If so, we can avoid all PathOps code
+// and speed thing up.
+static bool is_rect(const SkClipStack& clipStack, const SkRect& bounds, SkRect* dst) {
+    SkRect currentClip = bounds;
+    SkClipStack::Iter iter(clipStack, SkClipStack::Iter::kBottom_IterStart);
+    while (const SkClipStack::Element* element = iter.next()) {
+        SkRect elementRect{0, 0, 0, 0};
+        switch (element->getDeviceSpaceType()) {
+            case SkClipStack::Element::DeviceSpaceType::kEmpty:
+                break;
+            case SkClipStack::Element::DeviceSpaceType::kRect:
+                elementRect = element->getDeviceSpaceRect();
+                break;
+            default:
+                return false;
+        }
+        switch (element->getOp()) {
+            case kReplace_SkClipOp:
+                currentClip = rect_intersect(bounds, elementRect);
+                break;
+            case SkClipOp::kIntersect:
+                currentClip = rect_intersect(currentClip, elementRect);
+                break;
+            default:
+                return false;
         }
     }
-    push();
+    *dst = currentClip;
+    return true;
+}
 
-    currentEntry()->fClipStack = clipStack;
+static void append_clip(const SkClipStack& clipStack,
+                        const SkIRect& bounds,
+                        SkWStream* wStream) {
+    // The bounds are slightly outset to ensure this is correct in the
+    // face of floating-point accuracy and possible SkRegion bitmap
+    // approximations.
+    SkRect outsetBounds = SkRect::Make(bounds.makeOutset(1, 1));
+
+    SkRect clipStackRect;
+    if (is_rect(clipStack, outsetBounds, &clipStackRect)) {
+        SkPDFUtils::AppendRectangle(clipStackRect, wStream);
+        wStream->writeText("W* n\n");
+        return;
+    }
 
     SkPath clipPath;
     (void)clipStack.asPath(&clipPath);
 
-    // The bounds are slightly outset to ensure this is correct in the
-    // face of floating-point accuracy and possible SkRegion bitmap
-    // approximations.
     SkPath clipBoundsPath;
-    clipBoundsPath.addRect(SkRect::Make(bounds.makeOutset(1, 1)));
+    clipBoundsPath.addRect(outsetBounds);
 
     if (Op(clipPath, clipBoundsPath, kIntersect_SkPathOp, &clipPath)) {
-        SkPDFUtils::EmitPath(clipPath, SkPaint::kFill_Style, fContentStream);
+        SkPDFUtils::EmitPath(clipPath, SkPaint::kFill_Style, wStream);
         SkPath::FillType clipFill = clipPath.getFillType();
         NOT_IMPLEMENTED(clipFill == SkPath::kInverseEvenOdd_FillType, false);
         NOT_IMPLEMENTED(clipFill == SkPath::kInverseWinding_FillType, false);
         if (clipFill == SkPath::kEvenOdd_FillType) {
-            fContentStream->writeText("W* n\n");
+            wStream->writeText("W* n\n");
         } else {
-            fContentStream->writeText("W n\n");
+            wStream->writeText("W n\n");
         }
     }
     // If Op() fails (pathological case; e.g. input values are
     // extremely large or NaN), emit no clip at all.
 }
 
+// TODO(vandebo): Take advantage of SkClipStack::getSaveCount(), the PDF
+// graphic state stack, and the fact that we can know all the clips used
+// on the page to optimize this.
+void GraphicStackState::updateClip(const SkClipStack& clipStack,
+                                   const SkIRect& bounds) {
+    if (clipStack == currentEntry()->fClipStack) {
+        return;
+    }
+
+    while (fStackDepth > 0) {
+        pop();
+        if (clipStack == currentEntry()->fClipStack) {
+            return;
+        }
+    }
+    push();
+
+    currentEntry()->fClipStack = clipStack;
+    append_clip(clipStack, bounds, fContentStream);
+}
+
 void GraphicStackState::updateMatrix(const SkMatrix& matrix) {
     if (matrix == currentEntry()->fMatrix) {
         return;