Bug 1330236 - Compute SVG getNumberOfChars() quicker in simple cases. r=longsonr+218550

MozReview-Commit-ID: FgwR9dxTefx

--HG--
extra : rebase_source : 5b1ba3aa727cdd278a4b40c24231ca446b8bc45d

dom/svg/SVGTextContentElement.cpp

@@ -5,9 +5,14 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/dom/SVGTextContentElement.h"
-#include "nsISVGPoint.h"
-#include "SVGTextFrame.h"
+
 #include "mozilla/dom/SVGIRect.h"
+#include "nsBidiUtils.h"
+#include "nsISVGPoint.h"
+#include "nsTextFragment.h"
+#include "nsTextFrameUtils.h"
+#include "nsTextNode.h"
+#include "SVGTextFrame.h"
 
 namespace mozilla {
 namespace dom {
@@ -32,14 +37,18 @@ SVGTextFrame*
 SVGTextContentElement::GetSVGTextFrame()
 {
   nsIFrame* frame = GetPrimaryFrame(FlushType::Layout);
-  while (frame) {
-    SVGTextFrame* textFrame = do_QueryFrame(frame);
-    if (textFrame) {
-      return textFrame;
-    }
-    frame = frame->GetParent();
-  }
-  return nullptr;
+  nsIFrame* textFrame =
+    nsLayoutUtils::GetClosestFrameOfType(frame, nsGkAtoms::svgTextFrame);
+  return static_cast<SVGTextFrame*>(textFrame);
+}
+
+SVGTextFrame*
+SVGTextContentElement::GetSVGTextFrameForNonLayoutDependentQuery()
+{
+  nsIFrame* frame = GetPrimaryFrame(FlushType::Frames);
+  nsIFrame* textFrame =
+    nsLayoutUtils::GetClosestFrameOfType(frame, nsGkAtoms::svgTextFrame);
+  return static_cast<SVGTextFrame*>(textFrame);
 }
 
 already_AddRefed<SVGAnimatedLength>
@@ -56,9 +65,62 @@ SVGTextContentElement::LengthAdjust()
 
 //----------------------------------------------------------------------
 
+template<typename T>
+static bool
+FragmentHasSkippableCharacter(const T* aBuffer, uint32_t aLength)
+{
+  for (uint32_t i = 0; i < aLength; i++) {
+    if (nsTextFrameUtils::IsSkippableCharacterForTransformText(aBuffer[i])) {
+      return true;
+    }
+  }
+  return false;
+}
+
+Maybe<int32_t>
+SVGTextContentElement::GetNonLayoutDependentNumberOfChars()
+{
+  SVGTextFrame* frame = GetSVGTextFrameForNonLayoutDependentQuery();
+  if (!frame || frame != GetPrimaryFrame()) {
+    // Only support this fast path on <text>, not child <tspan>s, etc.
+    return Some(0);
+  }
+
+  uint32_t num = 0;
+
+  for (nsINode* n = Element::GetFirstChild(); n; n = n->GetNextSibling()) {
+    if (!n->IsNodeOfType(nsINode::eTEXT)) {
+      return Nothing();
+    }
+
+    const nsTextFragment* text = static_cast<nsTextNode*>(n)->GetText();
+    uint32_t length = text->GetLength();
+
+    if (text->Is2b()) {
+      if (FragmentHasSkippableCharacter(text->Get2b(), length)) {
+        return Nothing();
+      }
+    } else {
+      auto buffer = reinterpret_cast<const uint8_t*>(text->Get1b());
+      if (FragmentHasSkippableCharacter(buffer, length)) {
+        return Nothing();
+      }
+    }
+
+    num += length;
+  }
+
+  return Some(num);
+}
+
 int32_t
 SVGTextContentElement::GetNumberOfChars()
 {
+  Maybe<int32_t> num = GetNonLayoutDependentNumberOfChars();
+  if (num) {
+    return *num;
+  }
+
   SVGTextFrame* textFrame = GetSVGTextFrame();
   return textFrame ? textFrame->GetNumberOfChars(this) : 0;
 }

dom/svg/SVGTextContentElement.h

@@ -52,6 +52,8 @@ protected:
   {}
 
   SVGTextFrame* GetSVGTextFrame();
+  SVGTextFrame* GetSVGTextFrameForNonLayoutDependentQuery();
+  mozilla::Maybe<int32_t> GetNonLayoutDependentNumberOfChars();
 
   enum { LENGTHADJUST };
   virtual nsSVGEnum* EnumAttributes() = 0;

layout/generic/nsTextFrameUtils.cpp

@@ -56,6 +56,36 @@ IsSpaceOrTabOrSegmentBreak(char16_t aCh)
   return IsSpaceOrTab(aCh) || IsSegmentBreak(aCh);
 }
 
+template<typename CharT>
+/* static */ bool
+nsTextFrameUtils::IsSkippableCharacterForTransformText(CharT aChar)
+{
+  return aChar == ' ' ||
+         aChar == '\t' ||
+         aChar == '\n' ||
+         aChar == CH_SHY ||
+         (aChar > 0xFF && IsBidiControl(aChar));
+}
+
+#ifdef DEBUG
+template<typename CharT>
+static void AssertSkippedExpectedChars(const CharT* aText,
+                                       const gfxSkipChars& aSkipChars,
+                                       int32_t aSkipCharsOffset)
+{
+  gfxSkipCharsIterator it(aSkipChars);
+  it.AdvanceOriginal(aSkipCharsOffset);
+  while (it.GetOriginalOffset() < it.GetOriginalEnd()) {
+    CharT ch = aText[it.GetOriginalOffset() - aSkipCharsOffset];
+    MOZ_ASSERT(!it.IsOriginalCharSkipped() ||
+               nsTextFrameUtils::IsSkippableCharacterForTransformText(ch),
+               "skipped unexpected character; need to update "
+               "IsSkippableCharacterForTransformText?");
+    it.AdvanceOriginal(1);
+  }
+}
+#endif
+
 template<class CharT>
 static CharT*
 TransformWhiteSpaces(const CharT* aText, uint32_t aLength,
@@ -183,6 +213,9 @@ nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
 {
   uint32_t flags = 0;
   CharT* outputStart = aOutput;
+#ifdef DEBUG
+  int32_t skipCharsOffset = aSkipChars->GetOriginalCharCount();
+#endif
 
   bool lastCharArabic = false;
   if (aCompression == COMPRESS_NONE ||
@@ -303,12 +336,18 @@ nsTextFrameUtils::TransformText(const CharT* aText, uint32_t aLength,
     flags |= TEXT_WAS_TRANSFORMED;
   }
   *aAnalysisFlags = flags;
+
+#ifdef DEBUG
+  AssertSkippedExpectedChars(aText, *aSkipChars, skipCharsOffset);
+#endif
   return aOutput;
 }
+
 /*
- * NOTE: This template is part of public API of nsTextFrameUtils, while
- * its function body is not available in the header. It may stop working
- * (fail to resolve symbol in link time) once its callsites are moved to a
+ * NOTE: The TransformText and IsSkippableCharacterForTransformText template
+ * functions are part of the public API of nsTextFrameUtils, while
+ * their function bodies are not available in the header. They may stop working
+ * (fail to resolve symbol in link time) once their callsites are moved to a
  * different translation unit (e.g. a different unified source file).
  * Explicit instantiating this function template with `uint8_t` and `char16_t`
  * could prevent us from the potential risk.
@@ -327,6 +366,10 @@ nsTextFrameUtils::TransformText(const char16_t* aText, uint32_t aLength,
                                 uint8_t* aIncomingFlags,
                                 gfxSkipChars* aSkipChars,
                                 uint32_t* aAnalysisFlags);
+template bool
+nsTextFrameUtils::IsSkippableCharacterForTransformText(uint8_t aChar);
+template bool
+nsTextFrameUtils::IsSkippableCharacterForTransformText(char16_t aChar);
 
 uint32_t
 nsTextFrameUtils::ComputeApproximateLengthWithWhitespaceCompression(

layout/generic/nsTextFrameUtils.h

@@ -121,6 +121,16 @@ public:
                               gfxSkipChars* aSkipChars,
                               uint32_t* aAnalysisFlags);
 
+  /**
+   * Returns whether aChar is a character that nsTextFrameUtils::TransformText
+   * might mark as skipped.  This is used by
+   * SVGTextContentElement::GetNumberOfChars to know whether reflowing frames,
+   * so that we have the results of TransformText, is required, or whether we
+   * can use a fast path instead.
+   */
+  template<class CharT>
+  static bool IsSkippableCharacterForTransformText(CharT aChar);
+
   static void
   AppendLineBreakOffset(nsTArray<uint32_t>* aArray, uint32_t aOffset)
   {