Introduce MinikinFont abstraction

This commit removes the direct dependency on FreeType and replaces it
with a MinikinFont abstraction, which is designed to support both
FreeType and Skia fonts (and possibly others in the future).

Also adds a "total advance" to the Layout, with an API for retrieving
it.

Change-Id: If20f92db9a43fd15b0fe9794b761ba00fb21338c

5 files changed, 162 insertions, 23 deletions

diff --git a/include/minikin/FontCollection.h b/include/minikin/FontCollection.h
index 3aa2aca..a2a5391 100644
--- a/include/minikin/FontCollection.h
+++ b/include/minikin/FontCollection.h
@@ -19,12 +19,9 @@
 
 #include <vector>
 
-#include <ft2build.h>
-#include FT_FREETYPE_H
-#include FT_TRUETYPE_TABLES_H
-
-#include "SparseBitSet.h"
-#include "FontFamily.h"
+#include <minikin/MinikinFont.h>
+#include <minikin/SparseBitSet.h>
+#include <minikin/FontFamily.h>
 
 namespace android {
 
@@ -40,19 +37,19 @@ public:
         // Do copy constructor, assignment, destructor so it can be used in vectors
         Run() : font(NULL) { }
         Run(const Run& other): font(other.font), start(other.start), end(other.end) {
-            if (font) FT_Reference_Face(font);
+            if (font) font->Ref();
         }
         Run& operator=(const Run& other) {
-            if (other.font) FT_Reference_Face(other.font);
-            if (font) FT_Done_Face(font);
+            if (other.font) other.font->Ref();
+            if (font) font->Unref();
             font = other.font;
             start = other.start;
             end = other.end;
             return *this;
         }
-        ~Run() { if (font) FT_Done_Face(font); }
+        ~Run() { if (font) font->Unref(); }
 
-        FT_Face font;
+        MinikinFont* font;
         int start;
         int end;
     };
diff --git a/include/minikin/FontFamily.h b/include/minikin/FontFamily.h
index 01ea232..290220b 100644
--- a/include/minikin/FontFamily.h
+++ b/include/minikin/FontFamily.h
@@ -42,21 +42,21 @@ private:
 class FontFamily {
 public:
     // Add font to family, extracting style information from the font
-    bool addFont(FT_Face typeface);
+    bool addFont(MinikinFont* typeface);
 
-    void addFont(FT_Face typeface, FontStyle style);
-    FT_Face getClosestMatch(FontStyle style) const;
+    void addFont(MinikinFont* typeface, FontStyle style);
+    MinikinFont* getClosestMatch(FontStyle style) const;
 
     // API's for enumerating the fonts in a family. These don't guarantee any particular order
     size_t getNumFonts() const;
-    FT_Face getFont(size_t index) const;
+    MinikinFont* getFont(size_t index) const;
     FontStyle getStyle(size_t index) const;
 private:
     class Font {
     public:
-        Font(FT_Face typeface, FontStyle style) :
+        Font(MinikinFont* typeface, FontStyle style) :
             typeface(typeface), style(style) { }
-        FT_Face typeface;
+        MinikinFont* typeface;
         FontStyle style;
     };
     std::vector<Font> mFonts;
diff --git a/include/minikin/Layout.h b/include/minikin/Layout.h
index 7a6c6cf..fd0ed75 100644
--- a/include/minikin/Layout.h
+++ b/include/minikin/Layout.h
@@ -17,15 +17,13 @@
 #ifndef MINIKIN_LAYOUT_H
 #define MINIKIN_LAYOUT_H
 
-#include <ft2build.h>
-#include FT_FREETYPE_H
-
 #include <hb.h>
 
 #include <vector>
 
 #include <minikin/CssParse.h>
 #include <minikin/FontCollection.h>
+#include <minikin/MinikinFontFreeType.h>
 
 namespace android {
 
@@ -37,7 +35,7 @@ public:
     Bitmap(int width, int height);
     ~Bitmap();
     void writePnm(std::ofstream& o) const;
-    void drawGlyph(const FT_Bitmap& bitmap, int x, int y);
+    void drawGlyph(const GlyphBitmap& bitmap, int x, int y);
 private:
     int width;
     int height;
@@ -65,12 +63,14 @@ public:
     void draw(Bitmap*, int x0, int y0) const;
     void setProperties(const std::string css);
 
+    float getAdvance() const;
+
     // This must be called before any invocations.
 	// TODO: probably have a factory instead
     static void init();
 private:
     // Find a face in the mFaces vector, or create a new entry
-    int findFace(FT_Face face);
+    int findFace(MinikinFont* face, MinikinPaint* paint);
 
     CssProperties mProps;  // TODO: want spans
     std::vector<LayoutGlyph> mGlyphs;
@@ -80,8 +80,9 @@ private:
     // But for the time being, it should be ok to have just one
     // per layout.
     const FontCollection *mCollection;
-    std::vector<FT_Face> mFaces;
+    std::vector<MinikinFont *> mFaces;
     std::vector<hb_font_t *> mHbFonts;
+    float mAdvance;
 };
 
 }  // namespace android
diff --git a/include/minikin/MinikinFont.h b/include/minikin/MinikinFont.h
new file mode 100644
index 0000000..2c265c3
--- /dev/null
+++ b/include/minikin/MinikinFont.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MINIKIN_FONT_H
+#define MINIKIN_FONT_H
+
+// An abstraction for platform fonts, allowing Minikin to be used with
+// multiple actual implementations of fonts.
+
+namespace android {
+
+class MinikinFont;
+
+// Possibly move into own .h file?
+struct MinikinPaint {
+    MinikinFont *font;
+    float size;
+    // todo: skew, stretch, hinting
+};
+
+class MinikinFontFreeType;
+
+class MinikinFont {
+public:
+    void Ref() { mRefcount_++; }
+    void Unref() { if (--mRefcount_ == 0) { delete this; } }
+
+    //MinikinFont();
+    virtual ~MinikinFont() = 0;
+
+    virtual bool GetGlyph(uint32_t codepoint, uint32_t *glyph) const = 0;
+
+    virtual float GetHorizontalAdvance(uint32_t glyph_id,
+        const MinikinPaint &paint) const = 0;
+
+    // If buf is NULL, just update size
+    virtual bool GetTable(uint32_t tag, uint8_t *buf, size_t *size) = 0;
+
+    virtual int32_t GetUniqueId() const = 0;
+
+    static uint32_t MakeTag(char c1, char c2, char c3, char c4) {
+        return ((uint32_t)c1 << 24) | ((uint32_t)c2 << 16) |
+            ((uint32_t)c3 << 8) | (uint32_t)c4;
+    }
+
+    // This is used to implement a downcast without RTTI
+    virtual MinikinFontFreeType* GetFreeType() {
+        return NULL;
+    }
+
+private:
+    int mRefcount_;
+};
+
+}  // namespace android
+
+#endif  // MINIKIN_FONT_H
diff --git a/include/minikin/MinikinFontFreeType.h b/include/minikin/MinikinFontFreeType.h
new file mode 100644
index 0000000..7051831
--- /dev/null
+++ b/include/minikin/MinikinFontFreeType.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MINIKIN_FONT_FREETYPE_H
+#define MINIKIN_FONT_FREETYPE_H
+
+#include <ft2build.h>
+#include FT_FREETYPE_H
+#include FT_TRUETYPE_TABLES_H
+
+#include <minikin/MinikinFont.h>
+
+// An abstraction for platform fonts, allowing Minikin to be used with
+// multiple actual implementations of fonts.
+
+namespace android {
+
+struct GlyphBitmap {
+    uint8_t *buffer;
+    int width;
+    int height;
+    int left;
+    int top;
+};
+
+class MinikinFontFreeType : public MinikinFont {
+public:
+    explicit MinikinFontFreeType(FT_Face typeface);
+
+    ~MinikinFontFreeType();
+
+    bool GetGlyph(uint32_t codepoint, uint32_t *glyph) const;
+
+    float GetHorizontalAdvance(uint32_t glyph_id,
+        const MinikinPaint &paint) const;
+
+    // If buf is NULL, just update size
+    bool GetTable(uint32_t tag, uint8_t *buf, size_t *size);
+
+    int32_t GetUniqueId() const;
+
+    // Not a virtual method, as the protocol to access rendered
+    // glyph bitmaps is probably different depending on the
+    // backend.
+    bool Render(uint32_t glyph_id,
+        const MinikinPaint &paint, GlyphBitmap *result);
+
+    MinikinFontFreeType* GetFreeType();
+
+private:
+    FT_Face mTypeface;
+    int32_t mUniqueId;
+    static int32_t sIdCounter;
+};
+
+}  // namespace android
+
+#endif  // MINIKIN_FONT_FREETYPE_H