Revert "Revert "Add Atlas Text interface for rendering SDF glyphs.""

This reverts commit 9c2202ffc22b4293b48a4edeafa1b5d2bab8bb83.

Bug: skia:
Change-Id: I482ddf74f8e40d3d0908c840ba5c6ff981ccefbd
Reviewed-on: https://skia-review.googlesource.com/73345
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

4 files changed, 209 insertions, 0 deletions

diff --git a/include/atlastext/SkAtlasTextContext.h b/include/atlastext/SkAtlasTextContext.h
new file mode 100644
index 0000000000..bb5de52992
--- /dev/null
+++ b/include/atlastext/SkAtlasTextContext.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAtlasTextContext_DEFINED
+#define SkAtlasTextContext_DEFINED
+
+#include "SkRefCnt.h"
+
+class SkAtlasTextRenderer;
+class SkInternalAtlasTextContext;
+
+SkAtlasTextRenderer* SkGetAtlasTextRendererFromInternalContext(class SkInternalAtlasTextContext&);
+
+/**
+ * Class that Atlas Text client uses to register their SkAtlasTextRenderer implementation and
+ * to create one or more SkAtlasTextTargets (destination surfaces for text rendering).
+ */
+class SK_API SkAtlasTextContext : public SkRefCnt {
+public:
+    static sk_sp<SkAtlasTextContext> Make(sk_sp<SkAtlasTextRenderer>);
+
+    SkAtlasTextRenderer* renderer() const {
+        return SkGetAtlasTextRendererFromInternalContext(*fInternalContext);
+    }
+
+    SkInternalAtlasTextContext& internal() { return *fInternalContext; }
+
+private:
+    SkAtlasTextContext() = delete;
+    SkAtlasTextContext(const SkAtlasTextContext&) = delete;
+    SkAtlasTextContext& operator=(const SkAtlasTextContext&) = delete;
+
+    SkAtlasTextContext(sk_sp<SkAtlasTextRenderer>);
+
+    std::unique_ptr<SkInternalAtlasTextContext> fInternalContext;
+};
+
+#endif
diff --git a/include/atlastext/SkAtlasTextFont.h b/include/atlastext/SkAtlasTextFont.h
new file mode 100644
index 0000000000..a9e641f7ad
--- /dev/null
+++ b/include/atlastext/SkAtlasTextFont.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAtlasTextFont_DEFINED
+#define SkAtlasTextFont_DEFINED
+
+#include "SkRefCnt.h"
+#include "SkTypeface.h"
+
+/** Represents a font at a size. TODO: What else do we need here (skewX, scaleX, vertical, ...)? */
+class SK_API SkAtlasTextFont : public SkRefCnt {
+public:
+    static sk_sp<SkAtlasTextFont> Make(sk_sp<SkTypeface> typeface, SkScalar size) {
+        return sk_sp<SkAtlasTextFont>(new SkAtlasTextFont(std::move(typeface), size));
+    }
+
+    SkTypeface* typeface() const { return fTypeface.get(); }
+
+    sk_sp<SkTypeface> refTypeface() const { return fTypeface; }
+
+    SkScalar size() const { return fSize; }
+
+private:
+    SkAtlasTextFont(sk_sp<SkTypeface> typeface, SkScalar size)
+            : fTypeface(std::move(typeface)), fSize(size) {}
+
+    sk_sp<SkTypeface> fTypeface;
+    SkScalar fSize;
+};
+
+#endif
diff --git a/include/atlastext/SkAtlasTextRenderer.h b/include/atlastext/SkAtlasTextRenderer.h
new file mode 100644
index 0000000000..a78e270edb
--- /dev/null
+++ b/include/atlastext/SkAtlasTextRenderer.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPoint.h"
+#include "SkRefCnt.h"
+
+#ifndef SkAtlasTextRenderer_DEFINED
+#define SkAtlasTextRenderer_DEFINED
+
+/**
+ * This is the base class for a renderer implemented by the SkAtlasText client. The
+ * SkAtlasTextContext issues texture creations, deletions, uploads, and vertex draws to the
+ * renderer. The renderer must perform those actions in the order called to correctly render
+ * the text drawn to SkAtlasTextTargets.
+ */
+class SK_API SkAtlasTextRenderer : public SkRefCnt {
+public:
+    enum class AtlasFormat {
+        /** Unsigned normalized 8 bit single channel format. */
+        kA8
+    };
+
+    struct SDFVertex {
+        /** Position in device space (not normalized). */
+        SkPoint fPosition;
+        /** Color, same value for all four corners of a glyph quad. */
+        uint32_t fColor;
+        /** Texture coordinate (in texel units, not normalized). */
+        SkIPoint16 fTextureCoord;
+    };
+
+    virtual ~SkAtlasTextRenderer() = default;
+
+    /**
+     * Create a texture of the provided format with dimensions 'width' x 'height'
+     * and return a unique handle.
+     */
+    virtual void* createTexture(AtlasFormat, int width, int height) = 0;
+
+    /**
+     * Delete the texture with the passed handle.
+     */
+    virtual void deleteTexture(void* textureHandle) = 0;
+
+    /**
+     * Place the pixel data specified by 'data' in the texture with handle
+     * 'textureHandle' in the rectangle ['x', 'x' + 'width') x ['y', 'y' + 'height').
+     * 'rowBytes' specifies the byte offset between successive rows in 'data' and will always be
+     * a multiple of the number of bytes per pixel.
+     * The pixel format of data is the same as that of 'textureHandle'.
+     */
+    virtual void setTextureData(void* textureHandle, const void* data, int x, int y, int width,
+                                int height, size_t rowBytes) = 0;
+
+    /**
+     * Draws glyphs using SDFs. The SDF data resides in 'textureHandle'. The array
+     * 'vertices' provides interleaved device-space positions, colors, and
+     * texture coordinates. There are are 4 * 'quadCnt' entries in 'vertices'.
+     */
+    virtual void drawSDFGlyphs(void* targetHandle, void* textureHandle, const SDFVertex vertices[],
+                               int quadCnt) = 0;
+
+    /** Called when a SkAtlasTextureTarget is destroyed. */
+    virtual void targetDeleted(void* targetHandle) = 0;
+};
+
+#endif
diff --git a/include/atlastext/SkAtlasTextTarget.h b/include/atlastext/SkAtlasTextTarget.h
new file mode 100644
index 0000000000..0859afde39
--- /dev/null
+++ b/include/atlastext/SkAtlasTextTarget.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAtlasTextTarget_DEFINED
+#define SkAtlasTextTarget_DEFINED
+
+#include <memory>
+#include "SkRefCnt.h"
+#include "SkScalar.h"
+
+class SkAtlasTextContext;
+class SkAtlasTextFont;
+
+/** Represents a client-created renderable surface and is used to draw text into the surface. */
+class SK_API SkAtlasTextTarget {
+public:
+    virtual ~SkAtlasTextTarget();
+
+    /**
+     * Creates a text drawing target. ‘handle’ is used to identify this rendering surface when
+     * draws are flushed to the SkAtlasTextContext's SkAtlasTextRenderer.
+     */
+    static std::unique_ptr<SkAtlasTextTarget> Make(sk_sp<SkAtlasTextContext>, int width, int height,
+                                                   void* handle);
+
+    /**
+     * Enqueues a text draw in the target. The meaning of 'color' here is interpreted by the
+     * client's SkAtlasTextRenderer when it actually renders the text.
+     */
+    virtual void drawText(const void* text, size_t byteLength, SkScalar x, SkScalar y,
+                          uint32_t color, const SkAtlasTextFont& font) = 0;
+
+    /** Issues all queued text draws to SkAtlasTextRenderer. */
+    virtual void flush() = 0;
+
+    int width() const { return fWidth; }
+    int height() const { return fHeight; }
+
+    void* handle() const { return fHandle; }
+
+    SkAtlasTextContext* context() const { return fContext.get(); }
+
+protected:
+    SkAtlasTextTarget(sk_sp<SkAtlasTextContext>, int width, int height, void* handle);
+
+    void* const fHandle;
+    const sk_sp<SkAtlasTextContext> fContext;
+    const int fWidth;
+    const int fHeight;
+
+private:
+    SkAtlasTextTarget() = delete;
+    SkAtlasTextTarget(const SkAtlasTextContext&) = delete;
+    SkAtlasTextTarget& operator=(const SkAtlasTextContext&) = delete;
+};
+
+#endif