Revert "Remove devKerning"

This reverts commit c86c5c0144b85d0bc8ec791f9609ee2d4e7d835a.

Reason for revert: 4 of 5

Original change's description:
> Remove devKerning
> 
> Dev kerning is not supported by any scalers. This is
> mostly removed. The remaining fields fRsbDelta and
> fLsbDelta are kept to keep Android compiling.
> 
> Change-Id: If1a9ee9bb599d4e1bdf4b3751ac0c65246350809
> Reviewed-on: https://skia-review.googlesource.com/124921
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: Herb Derby <herb@google.com>

TBR=bungeman@google.com,herb@google.com,reed@google.com

Change-Id: If865f702868192a1b72cd811baa996dd1282bbce
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/125263
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

1 files changed, 28 insertions, 10 deletions

diff --git a/src/core/SkFindAndPlaceGlyph.h b/src/core/SkFindAndPlaceGlyph.h
index 00417152ab..d92edb6b17 100644
--- a/src/core/SkFindAndPlaceGlyph.h
+++ b/src/core/SkFindAndPlaceGlyph.h
@@ -9,6 +9,7 @@
 #define SkFindAndPositionGlyph_DEFINED
 
 #include "SkArenaAlloc.h"
+#include "SkAutoKern.h"
 #include "SkGlyph.h"
 #include "SkGlyphCache.h"
 #include "SkMatrixPriv.h"
@@ -319,8 +320,8 @@ private:
         virtual ~GlyphFindAndPlaceInterface() { }
 
         // findAndPositionGlyph calculates the position of the glyph, finds the glyph, and
-        // returns the position of where the next glyph will be using the glyph's advance. The
-        // returned position is used by drawText, but ignored by drawPosText.
+        // returns the position of where the next glyph will be using the glyph's advance and
+        // possibly kerning. The returned position is used by drawText, but ignored by drawPosText.
         // The compiler should prune all this calculation if the return value is not used.
         //
         // This should be a pure virtual, but some versions of GCC <= 4.8 have a bug that causes a
@@ -382,20 +383,31 @@ private:
         GlyphFinderInterface* fGlyphFinder;
     };
 
+    enum SelectKerning {
+        kNoKerning = false,
+        kUseKerning = true
+    };
+
     // GlyphFindAndPlaceFullPixel handles finding and placing glyphs when no sub-pixel
-    // positioning is requested.
-    template<typename ProcessOneGlyph, SkPaint::Align kTextAlignment>
+    // positioning is requested. The kUseKerning argument should be true for drawText, and false
+    // for drawPosText.
+    template<typename ProcessOneGlyph, SkPaint::Align kTextAlignment, SelectKerning kUseKerning>
     class GlyphFindAndPlaceFullPixel final : public GlyphFindAndPlaceInterface<ProcessOneGlyph> {
     public:
         explicit GlyphFindAndPlaceFullPixel(GlyphFinderInterface* glyphFinder)
             : fGlyphFinder(glyphFinder) {
+            // Kerning can only be used with SkPaint::kLeft_Align
+            static_assert(!kUseKerning || SkPaint::kLeft_Align == kTextAlignment,
+                          "Kerning can only be used with left aligned text.");
         }
 
         SkPoint findAndPositionGlyph(
             const char** text, SkPoint position, ProcessOneGlyph&& processOneGlyph) override {
             SkPoint finalPosition = position;
             const SkGlyph& glyph = fGlyphFinder->lookupGlyph(text);
-
+            if (kUseKerning) {
+                finalPosition += {fAutoKern.adjust(glyph), 0.0f};
+            }
             if (glyph.fWidth > 0) {
                 finalPosition -= TextAlignmentAdjustment(kTextAlignment, glyph);
                 processOneGlyph(glyph, finalPosition, {SK_ScalarHalf, SK_ScalarHalf});
@@ -406,6 +418,8 @@ private:
 
     private:
         GlyphFinderInterface* fGlyphFinder;
+
+        SkAutoKern fAutoKern;
     };
 
     template <typename ProcessOneGlyph, SkPaint::Align kTextAlignment>
@@ -432,12 +446,14 @@ private:
         SkScalar    x = 0, y = 0;
         const char* stop = text + byteLength;
 
+        SkAutoKern  autokern;
+
         while (text < stop) {
             // don't need x, y here, since all subpixel variants will have the
             // same advance
             const SkGlyph& glyph = glyphFinder->lookupGlyph(&text);
 
-            x += SkFloatToScalar(glyph.fAdvanceX);
+            x += autokern.adjust(glyph) + SkFloatToScalar(glyph.fAdvanceX);
             y += SkFloatToScalar(glyph.fAdvanceY);
         }
         SkASSERT(text == stop);
@@ -527,17 +543,18 @@ inline void SkFindAndPlaceGlyph::ProcessPosText(
         switch (textAlignment) {
             case SkPaint::kLeft_Align:
                 findAndPosition = arena.make<
-                    GlyphFindAndPlaceFullPixel<ProcessOneGlyph, SkPaint::kLeft_Align>>(glyphFinder);
+                    GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
+                        SkPaint::kLeft_Align, kNoKerning>>(glyphFinder);
                 break;
             case SkPaint::kCenter_Align:
                 findAndPosition = arena.make<
                     GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
-                        SkPaint::kCenter_Align>>(glyphFinder);
+                        SkPaint::kCenter_Align, kNoKerning>>(glyphFinder);
                 break;
             case SkPaint::kRight_Align:
                 findAndPosition = arena.make<
                     GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
-                        SkPaint::kRight_Align>>(glyphFinder);
+                        SkPaint::kRight_Align, kNoKerning>>(glyphFinder);
                 break;
         }
     }
@@ -578,7 +595,8 @@ inline void SkFindAndPlaceGlyph::ProcessText(
         findAndPosition = getSubpixel<ProcessOneGlyph, SkPaint::kLeft_Align>(
             &arena, axisAlignment, glyphFinder);
     } else {
-        using FullPixel = GlyphFindAndPlaceFullPixel<ProcessOneGlyph, SkPaint::kLeft_Align>;
+        using FullPixel =
+            GlyphFindAndPlaceFullPixel<ProcessOneGlyph, SkPaint::kLeft_Align, kUseKerning>;
         findAndPosition = arena.make<FullPixel>(glyphFinder);
     }