Avoid resetting the metrics-list/character offset for each text box

Source/core/layout/svg/SVGTextMetrics.h

Index: Source/core/layout/svg/SVGTextMetrics.h
diff --git a/Source/core/layout/svg/SVGTextMetrics.h b/Source/core/layout/svg/SVGTextMetrics.h
index cbddde0a789de8d820c0126cb091b7911c6558d2..0fb8de219a2b9b74339ca9adb0dfcb1e4b994d30 100644
--- a/Source/core/layout/svg/SVGTextMetrics.h
+++ b/Source/core/layout/svg/SVGTextMetrics.h
@@ -21,6 +21,7 @@
 #define SVGTextMetrics_h
 
 #include "platform/text/TextDirection.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
@@ -56,6 +57,34 @@ private:
     unsigned m_length;
 };
 
+class SVGTextMetricsIterator {

[f(malita), 2015/05/27 01:53:49]

nit: can this be a private nested class in SVGTextLayoutEngine?

[fs, 2015/05/27 12:53:14]

I have other possible uses in mind for this (SVGTextQuery), that would make that
a poor fit... (Not that this is a great fit, I also pondered putting this in
LayoutSVGInlineText, and given pdr's feedback maybe I should.) Ended up moving
it to LayoutSVGInlineText.h

+public:
+    SVGTextMetricsIterator() { reset(nullptr); }
+
+    void reset(const Vector<SVGTextMetrics>* metricsList)

[pdr., 2015/05/27 03:11:18]

I think this can be an internal detail of the iterator.

[fs, 2015/05/27 12:53:13]

I wanted to keep the interface of the iterator fairly low-level to avoid hiding
too much semantics in it (and to keep it simple and default-inlineable.)

+    {
+        m_metricsList = metricsList;
+        m_characterOffset = 0;
+        m_metricsListOffset = 0;
+    }
+
+    void next()
+    {
+        m_characterOffset += metrics().length();
+        ++m_metricsListOffset;
+    }
+
+    const SVGTextMetrics& metrics() const { return metricsList()[m_metricsListOffset]; }

[f(malita), 2015/05/27 01:53:49]

nit: ASSERT(m_metricsList && m_metricsListOffset < m_metricsList->size());?

[fs, 2015/05/27 12:53:14]

I've sort of been relying on the RELEASE_ASSERT in operator[] here - that and a
nullptr crash... Added as requested though.

+    const Vector<SVGTextMetrics>& metricsList() const { return *m_metricsList; }
+    unsigned metricsListOffset() const { return m_metricsListOffset; }
+    unsigned characterOffset() const { return m_characterOffset; }
+
+private:
+    const Vector<SVGTextMetrics>* m_metricsList;
+    unsigned m_metricsListOffset;
+    unsigned m_characterOffset;
+};
+
 } // namespace blink
 
 #endif