Send less transform data when drawing text with nvpr

Before this change, GrStencilAndCoverTextContext would send 6-float
affine transforms to drawPaths for every glyph. This updates it to
concat the text scale onto the context matrix, and then only send
2-float translates (or 1-float x-translates when possible).

Also adds a glyph_pos_align test to gm that exercises the newly added
codepaths, and starts ignoring a few gm tests with benign pixel diffs
until we can rebaseline.

BUG=skia:
R=bsalomon@google.com, kkinnunen@nvidia.com, jvanverth@google.com, bungeman@google.com

Author: cdalton@nvidia.com

Review URL: https://codereview.chromium.org/406523003

1 files changed, 99 insertions, 0 deletions

diff --git a/gm/glyph_pos_align.cpp b/gm/glyph_pos_align.cpp
new file mode 100644
index 0000000000..9a94e75b92
--- /dev/null
+++ b/gm/glyph_pos_align.cpp
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2014 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 "SkCanvas.h"
+#include "SkGradientShader.h"
+
+/**
+ * This test exercises drawPosTextH and drawPosText with every text align.
+ */
+static const int kWidth = 480;
+static const int kHeight = 600;
+static const SkScalar kTextHeight = 64.0f;
+static const int kMaxStringLength = 12;
+
+namespace skiagm {
+
+class GlyphPosAlignGM : public GM {
+protected:
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        return kSkipTiled_Flag;
+    }
+
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("glyph_pos_align");
+    }
+
+    virtual SkISize onISize() { return SkISize::Make(kWidth, kHeight); }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        canvas->clear(SK_ColorBLACK);
+
+        SkPaint paint;
+        paint.setTextSize(kTextHeight);
+        paint.setFakeBoldText(true);
+        const SkColor colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE };
+        const SkPoint pts[] = {{0, 0}, {kWidth, kHeight}};
+        SkAutoTUnref<SkShader> grad(SkGradientShader::CreateLinear(pts, colors, NULL,
+                                                                   SK_ARRAY_COUNT(colors),
+                                                                   SkShader::kMirror_TileMode));
+        paint.setShader(grad);
+
+
+        paint.setTextAlign(SkPaint::kRight_Align);
+        drawTestCase(canvas, "Right Align", kTextHeight, paint);
+
+        paint.setTextAlign(SkPaint::kCenter_Align);
+        drawTestCase(canvas, "Center Align", 4 * kTextHeight, paint);
+
+        paint.setTextAlign(SkPaint::kLeft_Align);
+        drawTestCase(canvas, "Left Align", 7 * kTextHeight, paint);
+    }
+
+    void drawTestCase(SkCanvas* canvas, const char* text, SkScalar y, const SkPaint& paint) {
+        SkScalar widths[kMaxStringLength];
+        SkScalar posX[kMaxStringLength];
+        SkPoint pos[kMaxStringLength];
+        int length = strlen(text);
+        SkASSERT(length <= kMaxStringLength);
+
+        paint.getTextWidths(text, length, widths);
+
+        float originX;
+        switch (paint.getTextAlign()) {
+            case SkPaint::kRight_Align: originX = 1; break;
+            case SkPaint::kCenter_Align: originX = 0.5f; break;
+            case SkPaint::kLeft_Align: originX = 0; break;
+            default: SkFAIL("Invalid paint origin"); return;
+        }
+
+        float x = kTextHeight;
+        for (int i = 0; i < length; ++i) {
+            posX[i] = x + originX * widths[i];
+            pos[i].set(posX[i], i ? pos[i - 1].y() + 3 : y + kTextHeight);
+            x += widths[i];
+        }
+
+        canvas->drawPosTextH(text, length, posX, y, paint);
+        canvas->drawPosText(text, length, pos, paint);
+    }
+
+private:
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* GlyphPosAlignFactory(void*) {
+    return new GlyphPosAlignGM();
+}
+
+static GMRegistry reg(GlyphPosAlignFactory);
+
+}