[PDF] Fixes the cases where SkPDFDevice::finishContentEntry is called with empty content.

src/pdf/SkPDFDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPDFDevice.h"
 
 #include "SkAnnotation.h"
@@ skipping 1857 matching lines @@
         entry->fNext.reset(contentEntries->detach());
         contentEntries->reset(entry);
     } else {
         lastContentEntry->fNext.reset(entry);
         setLastContentEntry(entry);
     }
     newEntry.detach();
     return entry;
 }
 
-void SkPDFDevice::finishContentEntry(const SkXfermode::Mode xfermode,
+void SkPDFDevice::finishContentEntry(SkXfermode::Mode xfermode,
                                      SkPDFFormXObject* dst,
                                      SkPath* shape) {
     if (xfermode != SkXfermode::kClear_Mode       &&
             xfermode != SkXfermode::kSrc_Mode     &&
+            xfermode != SkXfermode::kDstOver_Mode &&
             xfermode != SkXfermode::kSrcIn_Mode   &&
             xfermode != SkXfermode::kDstIn_Mode   &&
             xfermode != SkXfermode::kSrcOut_Mode  &&
             xfermode != SkXfermode::kDstOut_Mode  &&
             xfermode != SkXfermode::kSrcATop_Mode &&
             xfermode != SkXfermode::kDstATop_Mode &&
             xfermode != SkXfermode::kModulate_Mode) {
         SkASSERT(!dst);
         return;
     }
+    if (xfermode == SkXfermode::kDstOver_Mode) {
+        SkASSERT(!dst);
+        ContentEntry* firstContentEntry = getContentEntries()->get();
+        if (firstContentEntry->fContent.getOffset() == 0) {
+            // For DstOver, an empty content entry was inserted before the rest
+            // of the content entries. If nothing was drawn, it needs to be
+            // removed.
+            SkAutoTDelete<ContentEntry>* contentEntries = getContentEntries();
+            contentEntries->reset(firstContentEntry->fNext.detach());
+        }
+        return;
+    }
     if (!dst) {
         SkASSERT(xfermode == SkXfermode::kSrc_Mode ||
                  xfermode == SkXfermode::kSrcOut_Mode);
         return;
     }
 
     ContentEntry* contentEntries = getContentEntries()->get();
     SkASSERT(dst);
     SkASSERT(!contentEntries->fNext.get());
     // We have to make a copy of these here because changing the current
     // content into a form-xobject will destroy them.
     SkClipStack clipStack = contentEntries->fState.fClipStack;
     SkRegion clipRegion = contentEntries->fState.fClipRegion;
 
+    SkMatrix identity;
+    identity.reset();
+    SkPaint stockPaint;
+
     SkAutoTUnref<SkPDFFormXObject> srcFormXObject;
     if (isContentEmpty()) {
-        SkASSERT(xfermode == SkXfermode::kClear_Mode);
+        // If nothing was drawn and there's no shape, then the draw was a
+        // no-op, but dst needs to be restored for that to be true.
+        // If there is shape, then an empty source with Src, SrcIn, SrcOut,
+        // DstIn, DstAtop or Modulate reduces to Clear and DstOut or SrcAtop
+        // reduces to Dst.
+        if (shape == NULL || xfermode == SkXfermode::kDstOut_Mode ||
+                xfermode == SkXfermode::kSrcATop_Mode) {
+            ScopedContentEntry content(this, &clipStack, clipRegion, identity,
+                                       stockPaint);
+            SkPDFUtils::DrawFormXObject(this->addXObjectResource(dst),
+                                        &content.entry()->fContent);
+            return;
+        } else {
+            xfermode = SkXfermode::kClear_Mode;
+        }
     } else {
         SkASSERT(!fContentEntries->fNext.get());
         srcFormXObject.reset(createFormXObjectFromDevice());
     }
 
-    SkMatrix identity;
-    identity.reset();
-
     // TODO(vandebo) srcFormXObject may contain alpha, but here we want it
     // without alpha.
     if (xfermode == SkXfermode::kSrcATop_Mode) {
         // TODO(vandebo): In order to properly support SrcATop we have to track
         // the shape of what's been drawn at all times. It's the intersection of
         // the non-transparent parts of the device and the outlines (shape) of
         // all images and devices drawn.
         drawFormXObjectWithMask(addXObjectResource(srcFormXObject.get()), dst,
                                 &clipStack, clipRegion,
                                 SkXfermode::kSrcOver_Mode, true);
@@ skipping 11 matching lines @@
             filledPaint.setStyle(SkPaint::kFill_Style);
             this->drawPath(d, *shape, filledPaint, NULL, true);
 
             dstMaskStorage.reset(createFormXObjectFromDevice());
             dstMask = dstMaskStorage.get();
         }
         drawFormXObjectWithMask(addXObjectResource(dst), dstMask, &clipStack,
                                 clipRegion, SkXfermode::kSrcOver_Mode, true);
     }
 
-    SkPaint stockPaint;
-
-    if (xfermode == SkXfermode::kSrcATop_Mode) {
-        ScopedContentEntry content(this, &clipStack, clipRegion, identity,
-                                   stockPaint);
-        if (content.entry()) {
-            SkPDFUtils::DrawFormXObject(this->addXObjectResource(dst),
-                                        &content.entry()->fContent);
-        }
-    } else if (xfermode == SkXfermode::kClear_Mode || !srcFormXObject.get()) {
+    if (xfermode == SkXfermode::kClear_Mode) {
         return;
     } else if (xfermode == SkXfermode::kSrc_Mode ||
             xfermode == SkXfermode::kDstATop_Mode) {
         ScopedContentEntry content(this, &clipStack, clipRegion, identity,
                                    stockPaint);
         if (content.entry()) {
             SkPDFUtils::DrawFormXObject(
                     this->addXObjectResource(srcFormXObject.get()),
                     &content.entry()->fContent);
         }
         if (xfermode == SkXfermode::kSrc_Mode) {
             return;
         }
+    } else if (xfermode == SkXfermode::kSrcATop_Mode) {
+        ScopedContentEntry content(this, &clipStack, clipRegion, identity,
+                                   stockPaint);
+        if (content.entry()) {
+            SkPDFUtils::DrawFormXObject(this->addXObjectResource(dst),
+                                        &content.entry()->fContent);
+        }
     }
 
     SkASSERT(xfermode == SkXfermode::kSrcIn_Mode   ||
              xfermode == SkXfermode::kDstIn_Mode   ||
              xfermode == SkXfermode::kSrcOut_Mode  ||
              xfermode == SkXfermode::kDstOut_Mode  ||
              xfermode == SkXfermode::kSrcATop_Mode ||
              xfermode == SkXfermode::kDstATop_Mode ||
              xfermode == SkXfermode::kModulate_Mode);
 
@@ skipping 322 matching lines @@
 }
 
 bool SkPDFDevice::onReadPixels(const SkBitmap& bitmap, int x, int y,
                                SkCanvas::Config8888) {
     return false;
 }
 
 bool SkPDFDevice::allowImageFilter(SkImageFilter*) {
     return false;
 }