SkTextBlob

include/core/SkTextBlob.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTextBlob_DEFINED
+#define SkTextBlob_DEFINED
+
+#include "SkPaint.h"
+#include "SkRect.h"
+#include "SkRefCnt.h"
+#include "SkTDArray.h"
+
+class SkBaseDevice;
+class SkDraw;
+struct SkPoint;
+
+/** \class SkTextChunk
+
+    A text chunk is a sequence of (optionally positioned) glyphs sharing the same
+    font data/metrics.
+*/
+class SK_API SkTextChunk {
+public:
+    static const SkTextChunk* Create(const uint16_t* glyphs, size_t count, const SkPaint& paint,
+                                     const SkRect* bounds = NULL);
+    static const SkTextChunk* Create(const uint16_t* glyphs, size_t count, const SkScalar* pos,
+                                     const SkPaint& paint, const SkRect* bounds = NULL);
+    static const SkTextChunk* Create(const uint16_t* glyphs, size_t count, const SkPoint* pos,
+                                     const SkPaint& paint, const SkRect* bounds = NULL);
+
+    ~SkTextChunk();
+
+    void draw(SkBaseDevice*, const SkDraw&, const SkPaint&) const;
+
+    const SkRect& bounds() const;
+
+private:
+    SkTextChunk(const uint16_t* glyphs, size_t count, const SkScalar* pos, unsigned scalarsPerPos,
+                const SkPaint& paint, const SkRect* bounds);
+
+    friend class SkPictureRecord;
+
+    size_t         fGlyphCount;
+    uint16_t*      fGlyphs;
+    SkScalar*      fPos;  // FIXME: merge glyphs/pos storage?
+
+    SkPaint        fFont; // FIXME: SkFont
+
+    mutable SkRect fBounds;
+    mutable bool   fBoundsDirty;
+
+    unsigned short fScalarsPerPos;
+};
+
+/** \class SkTextBlob
+
+    SkTextBlob combines multiple text chunks into an immutable, ref-counted structure.
+*/
+class SK_API SkTextBlob : public SkRefCnt {
+public:
+    static const SkTextBlob* Create(const SkTextChunk* chunk);
+    static const SkTextBlob* Create(const SkTDArray<const SkTextChunk*>& chunks);
+
+    ~SkTextBlob();
+
+    uint32_t uniqueID() const;
+
+    class SK_API Iter {
+    public:
+        Iter(const SkTextBlob* blob) : fBlob(blob), fIndex(0) { SkASSERT(blob); }
+        const SkTextChunk* next() {
+            return (fIndex < fBlob->fChunks.count()) ? fBlob->fChunks[fIndex++] : NULL;
+        }
+
+    private:
+        const SkTextBlob* fBlob;
+        int fIndex;
+    };
+
+private:
+    SkTextBlob(const SkTDArray<const SkTextChunk*>& chunks);
+
+    const SkTDArray<const SkTextChunk*>  fChunks;
+    mutable uint32_t                     fUniqueID;
+};
+
+/** \class SkTextBlobBuilder
+
+    Helper class for constructing SkTextBlobs.
+*/
+class SK_API SkTextBlobBuilder {
+public:
+    SkTextBlobBuilder();
+    ~SkTextBlobBuilder();
+
+    void addChunk(const SkTextChunk* chunk);

[reed1, 2014/08/14 15:55:49]

Hmmm, I was imagining an alternate adder style:

uint16_t* addRun(int count, const SkPaint&, const SkRect* bounds = NULL);

This would return writable memory (only valid until the next call to addChunk)
so that the caller need not do their own allocation, only to have us also alloc
and memcpy. 

[f(malita), 2014/08/14 16:27:01]

I like this idea, and there's no reason not to have multiple adder variants.

A couple of wrinkles:

* this lowers the immutability guarantee some: clients could potentially hold on
to these pointers and mess with constructed chunks

* for positioned glyphs, we need to return two preallocated buffers -- the api
for it makes me cringe a little

Let me play with this and see how it turns out.

+
+    // FIXME: should we support glyph-wise ops? Not sure whether this is interesting
+    // for clients at this point -- they likely have a better idea of chunking.
+    /*
+    void addGlyph(uint16_t glyph, const SkPaint& font, const SkRect* bounds = NULL);
+    void addGlyph(uint16_t glyph, const SkScalar pos, const SkPaint& font,
+                  const SkRect* bounds = NULL);
+    void addGlyph(uint16_t glyph, const SkPoint pos, const SkPaint& font,
+                  const SkRect* bounds = NULL);
+    */
+
+    const SkTextBlob* build();
+
+private:
+
+    SkTDArray<const SkTextChunk*>  fChunks;
+};
+
+#endif // SkTextBlob_DEFINED