Start canonicalizing color for all A8 textblobs

gm/textblobcolortrans.cpp

Index: gm/textblobcolortrans.cpp
diff --git a/gm/textblobcolortrans.cpp b/gm/textblobcolortrans.cpp
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+++ b/gm/textblobcolortrans.cpp
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+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+
+#include "Resources.h"
+#include "SkCanvas.h"
+#include "SkGradientShader.h"
+#include "SkStream.h"
+#include "SkTextBlob.h"
+#include "SkTypeface.h"
+
+namespace skiagm {
+class TextBlobColorTrans : public GM {
+public:
+    // This gm tests that textblobs can be translated and have their colors regenerated
+    // correctly.  With smaller atlas sizes, it can also trigger regeneration of texture coords on
+    // the GPU backend
+    TextBlobColorTrans() { }
+
+protected:
+    void onOnceBeforeDraw() override {
+        SkTextBlobBuilder builder;
+
+        // make textblob
+        // Large text is used to trigger atlas eviction
+        SkPaint paint;
+        paint.setTextSize(256);
+        const char* text = "AB";
+        sk_tool_utils::set_portable_typeface(&paint);
+
+        SkRect bounds;
+        paint.measureText(text, strlen(text), &bounds);
+
+        SkScalar yOffset = bounds.height();
+        sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset - 30);
+
+        // A8
+        paint.setTextSize(28);
+        text = "The quick brown fox jumps over the lazy dog.";
+        paint.setSubpixelText(false);
+        paint.setLCDRenderText(false);
+        paint.measureText(text, strlen(text), &bounds);
+        sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset - 8);
+
+        // build
+        fBlob.reset(builder.build());
+    }
+
+    SkString onShortName() override {
+        return SkString("textblobcolortrans");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(kWidth, kHeight);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+
+        canvas->drawColor(SK_ColorGRAY);
+
+        SkPaint paint;
+        canvas->translate(10, 40);
+
+        SkRect bounds = fBlob->bounds();
+
+        // Colors were chosen to map to pairs of canonical colors.  The GPU Backend will cache A8
+        // Texture Blobs based on the canonical color they map to.  Canonical colors are used to
+        // create masks.  For A8 there are 8 of them.
+        SkColor colors[] = {SK_ColorCYAN, SK_ColorLTGRAY, SK_ColorYELLOW, SK_ColorWHITE};
+
+        size_t count = SK_ARRAY_COUNT(colors);
+        size_t colorIndex = 0;
+        for (int y = 0; y + SkScalarFloorToInt(bounds.height()) < kHeight;
+             y += SkScalarFloorToInt(bounds.height())) {
+            paint.setColor(colors[colorIndex++ % count]);
+            canvas->save();
+            canvas->translate(0, SkIntToScalar(y));
+            canvas->drawTextBlob(fBlob, 0, 0, paint);
+            canvas->restore();
+        }
+    }
+
+private:
+    SkAutoTUnref<const SkTextBlob> fBlob;
+
+    static const int kWidth = 675;
+    static const int kHeight = 1600;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return SkNEW(TextBlobColorTrans); )
+}