Simplify range mapping computation in SVGTextQuery/SVGInlineTextBox

Source/core/layout/svg/line/SVGInlineTextBox.cpp

 /**
  * Copyright (C) 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 184 matching lines @@
     run.disableSpacing();
 
     // Propagate the maximum length of the characters buffer to the TextRun, even when we're only processing a substring.
     run.setCharactersLength(text->textLength() - fragment.characterOffset);
     ASSERT(run.charactersLength() >= run.length());
     return run;
 }
 
 bool SVGInlineTextBox::mapStartEndPositionsIntoFragmentCoordinates(const SVGTextFragment& fragment, int& startPosition, int& endPosition) const
 {
-    if (startPosition >= endPosition)
-        return false;
+    int fragmentOffsetInBox = static_cast<int>(fragment.characterOffset) - start();
 
-    int offset = static_cast<int>(fragment.characterOffset) - start();
-    int length = static_cast<int>(fragment.length);
+    // Compute positions relative to the fragment.

[Erik Dahlström (inactive), 2015/04/01 14:04:20]

This used to leave startPosition and endPosition untouched in some cases, are
the callers of this method expecting that the values will now potentially always
change?

[fs, 2015/04/01 14:16:24]

The common pattern in callers are:

int startPos = fullStartPos;
int endPos = fullEndPos;
if (!mapStartEndPositionsIntoFragmentCoordinates(fragment, startPos, endPos))
    continue;
<use startPos, endPos>

the single user where that's not the case instead uses the returned bool (and a
"range empty" test). So, no, there's no caller that uses the values for anything
if false was returned.

+    startPosition -= fragmentOffsetInBox;
+    endPosition -= fragmentOffsetInBox;
 
-    if (startPosition >= offset + length || endPosition <= offset)
-        return false;
+    // Intersect with the fragment range.
+    startPosition = std::max(startPosition, 0);
+    endPosition = std::min(endPosition, static_cast<int>(fragment.length));
 
-    if (startPosition < offset)
-        startPosition = 0;
-    else
-        startPosition -= offset;
-
-    if (endPosition > offset + length) {
-        endPosition = length;
-    } else {
-        ASSERT(endPosition >= offset);
-        endPosition -= offset;
-    }
-
-    ASSERT(startPosition < endPosition);
-    return true;
+    return startPosition < endPosition;
 }
 
 void SVGInlineTextBox::paintDocumentMarker(GraphicsContext*, const FloatPointWillBeLayoutPoint&, DocumentMarker*, const ComputedStyle&, const Font&, bool)
 {
     // SVG does not have support for generic document markers (e.g., spellchecking, etc).
 }
 
 void SVGInlineTextBox::paintTextMatchMarker(GraphicsContext* context, const FloatPointWillBeLayoutPoint& point, DocumentMarker* marker, const ComputedStyle& style, const Font& font)
 {
     SVGInlineTextBoxPainter(*this).paintTextMatchMarker(context, point.toFloatPoint(), marker, style, font);
@@ skipping 44 matching lines @@
                 layoutObject().updateHitTestResult(result, locationInContainer.point() - toLayoutSize(accumulatedOffset));
                 if (!result.addNodeToListBasedTestResult(layoutObject().node(), request, locationInContainer, rect.rawValue()))
                     return true;
             }
         }
     }
     return false;
 }
 
 } // namespace blink