add helper to create fancy underlines

src/core/SkTextToPathIter.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTextToPathIter_DEFINED
 #define SkTextToPathIter_DEFINED
 
 #include "SkAutoKern.h"
 #include "SkPaint.h"
 
 class SkGlyphCache;
 
-class SkTextToPathIter {
-public:
-    SkTextToPathIter(const char text[], size_t length, const SkPaint& paint,
-                     bool applyStrokeAndPathEffects);
-    ~SkTextToPathIter();
+class SkTextBaseIter {
+protected:
+    SkTextBaseIter(const char text[], size_t length, const SkPaint& paint,
+                   bool applyStrokeAndPathEffects);
+    ~SkTextBaseIter();
 
-    const SkPaint&  getPaint() const { return fPaint; }
-    SkScalar        getPathScale() const { return fScale; }
-
-    struct Rec {
-        const SkPath*   fPath;  // may be null for "whitespace" glyphs
-        SkScalar        fXPos;
-    };
-
-    /**
-     *  Returns false when all of the text has been consumed
-     */
-    bool next(const SkPath** path, SkScalar* xpos);
-
-private:
     SkGlyphCache*   fCache;
     SkPaint         fPaint;
     SkScalar        fScale;
     SkFixed         fPrevAdvance;
     const char*     fText;
     const char*     fStop;
     SkMeasureCacheProc fGlyphCacheProc;
 
     SkScalar        fXPos;      // accumulated xpos, returned in next
     SkAutoKern      fAutoKern;
     int             fXYIndex;   // cache for horizontal -vs- vertical text
 };
 
+class SkTextToPathIter : SkTextBaseIter {
+public:
+    SkTextToPathIter(const char text[], size_t length, const SkPaint& paint,
+                     bool applyStrokeAndPathEffects)
+                     : SkTextBaseIter(text, length, paint, applyStrokeAndPathEffects) {
+    }
+
+    const SkPaint&  getPaint() const { return fPaint; }
+    SkScalar        getPathScale() const { return fScale; }
+
+    /**
+     *  Returns false when all of the text has been consumed
+     */
+    bool next(const SkPath** path, SkScalar* xpos);
+};
+
+class SkTextInterceptsIter : SkTextBaseIter {
+public:
+    enum class TextType {
+        kText,
+        kPosText
+    };
+
+    SkTextInterceptsIter(const char text[], size_t length, const SkPaint& paint,
+                         const SkScalar bounds[2], SkScalar x, SkScalar y, TextType textType)
+                         : SkTextBaseIter(text, length, paint, false)
+                         , fTextType(textType) {
+        fBoundsBase[0] = bounds[0];
+        fBoundsBase[1] = bounds[1];
+        this->setPosition(x, y);
+    }
+
+    /**
+     *  Returns false when all of the text has been consumed
+     */
+    bool next(SkScalar* array, int* count);
+
+    void setPosition(SkScalar x, SkScalar y) {
+        SkScalar xOffset = TextType::kText == fTextType && fXYIndex ? fXPos : 0;
+        if (TextType::kPosText == fTextType
+                && fPaint.getTextAlign() != SkPaint::kLeft_Align) { // need to measure first
+            const char* text = fText;
+            const SkGlyph& glyph = fGlyphCacheProc(fCache, &text);
+            SkScalar width = SkScalarMul(SkFixedToScalar((&glyph.fAdvanceX)[0]), fScale);
+            if (fPaint.getTextAlign() == SkPaint::kCenter_Align) {
+                width = SkScalarHalf(width);
+            }
+            xOffset = width;
+        }
+
+        for (int i = 0; i < (int) SK_ARRAY_COUNT(fBounds); ++i) {
+            SkScalar bound = fBoundsBase[i] - (fXYIndex ? x : y);
+            if (fXYIndex) {
+                bound += xOffset;
+            }
+            fBounds[i] = bound / fScale;
+        }
+
+        fXPos = xOffset + (fXYIndex ? y : x);
+        fPrevAdvance = 0;
+    }
+
+private:
+    SkScalar fBounds[2];
+    SkScalar fBoundsBase[2];
+    TextType fTextType;
+};
+
 #endif