skia2/gm/pixelsnap.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 "SkShader.h"
// This class of GMs test how edges/verts snap near rounding boundaries in device space without
// anti-aliaing.
class PixelSnapGM : public skiagm::GM {
public:
PixelSnapGM() {}
protected:
// kTrans should be even or checkboards wont agree in different test cases.
static constexpr int kTrans = 14;
static constexpr int kLabelPad = 4;
// The inverse of this value should be a perfect SkScalar.
static constexpr int kSubPixelSteps = 8;
static constexpr int kLabelTextSize = 9;
static_assert(kSubPixelSteps < 99, "label_offset_too_small");
static constexpr int kLabelOffsetX = 2 * kLabelTextSize + kLabelPad;
static constexpr int kLabelOffsetY = kLabelTextSize + kLabelPad;
SkISize onISize() override {
return SkISize::Make((kSubPixelSteps + 1) * kTrans + kLabelOffsetX + kLabelPad,
(kSubPixelSteps + 1) * kTrans + kLabelOffsetY + kLabelPad);
}
void onDraw(SkCanvas* canvas) override {
SkPaint bgPaint;
bgPaint.setShader(
sk_tool_utils::create_checkerboard_shader(
sk_tool_utils::color_to_565(0xFFAAAAAA),
sk_tool_utils::color_to_565(0xFF777777), 1));
canvas->drawPaint(bgPaint);
SkString offset;
SkPaint labelPaint;
labelPaint.setAntiAlias(true);
labelPaint.setColor(SK_ColorWHITE);
labelPaint.setTextSize(SkIntToScalar(kLabelTextSize));
sk_tool_utils::set_portable_typeface(&labelPaint);
SkPaint linePaint;
linePaint.setColor(SK_ColorWHITE);
// Draw row labels
canvas->save();
canvas->translate(0, SkIntToScalar(kLabelOffsetY));
for (int i = 0; i <= kSubPixelSteps; ++i) {
offset.printf("%d", i);
canvas->drawText(offset.c_str(), offset.size(),
0, i * kTrans + labelPaint.getTextSize(),
labelPaint);
}
canvas->restore();
// Draw col labels
canvas->save();
canvas->translate(SkIntToScalar(kLabelOffsetX), 0);
for (int i = 0; i <= kSubPixelSteps; ++i) {
offset.printf("%d", i);
canvas->drawText(offset.c_str(), offset.size(),
i * SkIntToScalar(kTrans), labelPaint.getTextSize(),
labelPaint);
}
canvas->restore();
canvas->translate(SkIntToScalar(kLabelOffsetX), SkIntToScalar(kLabelOffsetY));
// Draw test case grid lines (Draw them all at pixel centers to hopefully avoid any
// snapping issues).
for (int i = 0; i <= kSubPixelSteps + 1; ++i) {
canvas->drawLine(0.5f,
i * SkIntToScalar(kTrans) + 0.5f,
SkIntToScalar(kTrans) * (kSubPixelSteps + 1) + 0.5f,
i * SkIntToScalar(kTrans) + 0.5f,
linePaint);
canvas->drawLine(i * SkIntToScalar(kTrans) + 0.5f,
0.5f,
i * SkIntToScalar(kTrans) + 0.5f,
SkIntToScalar(kTrans) * (kSubPixelSteps + 1) + 0.5f,
linePaint);
}
for (int i = 0; i <= kSubPixelSteps; ++i) {
for (int j = 0; j <= kSubPixelSteps; ++j) {
canvas->save();
// +1's account for the grid lines around each test case.
canvas->translate(j * (kTrans + 1.f/kSubPixelSteps) + 1,
i * (kTrans + 1.f/kSubPixelSteps) + 1);
this->drawElement(canvas);
canvas->restore();
}
}
}
virtual void drawElement(SkCanvas*) = 0;
private:
typedef skiagm::GM INHERITED;
};
class PointSnapGM : public PixelSnapGM {
protected:
SkString onShortName() override { return SkString("pixel_snap_point"); }
void drawElement(SkCanvas* canvas) override { canvas->drawPoint(1, 1, SK_ColorBLUE); }
private:
typedef PixelSnapGM INHERITED;
};
class LineSnapGM : public PixelSnapGM {
protected:
SkString onShortName() override { return SkString("pixel_snap_line"); }
void drawElement(SkCanvas* canvas) override {
SkPaint paint;
paint.setColor(SK_ColorGREEN);
// Draw a horizontal and vertical line, each length 3.
canvas->drawLine(1, 1, 4, 1, paint);
canvas->drawLine(6, 1, 6, 4, paint);
}
private:
typedef PixelSnapGM INHERITED;
};
class RectSnapGM : public PixelSnapGM {
protected:
SkString onShortName() override { return SkString("pixel_snap_rect"); }
void drawElement(SkCanvas* canvas) override {
SkPaint paint;
paint.setColor(SK_ColorRED);
canvas->drawRect(SkRect::MakeXYWH(1, 1, 3, 3), paint);
}
private:
typedef PixelSnapGM INHERITED;
};
class ComboSnapGM : public PixelSnapGM {
protected:
SkString onShortName() override { return SkString("pixel_snap_combo"); }
void drawElement(SkCanvas* canvas) override {
SkPaint paint;
paint.setAntiAlias(false);
// A rectangle that exactly covers a pixel, a point at each corner, 8 horiz/vert lines
// at rect corners (two at each corner, extending away from rect). They are drawn in this
// order lines (green), points (blue), rect(red).
SkRect rect = SkRect::MakeXYWH(3, 3, 1, 1);
paint.setColor(SK_ColorGREEN);
canvas->drawLine(3, 3, 0, 3, paint);
canvas->drawLine(3, 3, 3, 0, paint);
canvas->drawLine(4, 3, 7, 3, paint);
canvas->drawLine(4, 3, 4, 0, paint);
canvas->drawLine(3, 4, 0, 4, paint);
canvas->drawLine(3, 4, 3, 7, paint);
canvas->drawLine(4, 4, 7, 4, paint);
canvas->drawLine(4, 4, 4, 7, paint);
canvas->drawPoint(4, 3, SK_ColorBLUE);
canvas->drawPoint(4, 4, SK_ColorBLUE);
canvas->drawPoint(3, 3, SK_ColorBLUE);
canvas->drawPoint(3, 4, SK_ColorBLUE);
paint.setColor(SK_ColorRED);
canvas->drawRect(rect, paint);
}
private:
typedef PixelSnapGM INHERITED;
};
//////////////////////////////////////////////////////////////////////////////
DEF_GM(return new PointSnapGM;)
DEF_GM(return new LineSnapGM;)
DEF_GM(return new RectSnapGM;)
DEF_GM(return new ComboSnapGM;)