Add GM for hard stop gradients
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2087273002
Review-Url: https://codereview.chromium.org/2087273002
diff --git a/gm/hardstop_gradients.cpp b/gm/hardstop_gradients.cpp
new file mode 100644
index 0000000..c1baa2f
--- /dev/null
+++ b/gm/hardstop_gradients.cpp
@@ -0,0 +1,145 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/*
+ * This GM presents a variety of different gradients with different
+ * tile modes. Each entry in the table is a rectangle with a linear
+ * gradient that spans from its left edge to its right edge. The rows
+ * in the table represent different color/position configurations,
+ * while the columns in the table represent different tile modes. In
+ * order to highlight the differences between tile modes, the gradient
+ * starts and ends at 30 pixel inset from either side of the rectangle.
+ *
+ * | Clamp Repeat Mirror
+ * _____________________|___________________________________________
+ * 2-color | rect00 rect01 rect02
+ * 3-color | rect10 rect11 rect12
+ * 5-color hard stop | rect20 rect21 rect22
+ * 5-color edge case 1 | rect30 rect31 rect32
+ * 5-color edge case 2 | rect40 rect41 rect42
+ *
+ * The LAST two t-values in edge case 1 are the same, while the FIRST
+ * two t-values in edge case 2 are the same.
+ */
+
+#include "gm.h"
+
+#include "SkGradientShader.h"
+
+const int WIDTH = 500;
+const int HEIGHT = 500;
+
+const int NUM_ROWS = 5;
+const int NUM_COLS = 3;
+
+const int CELL_WIDTH = WIDTH / NUM_COLS;
+const int CELL_HEIGHT = HEIGHT / NUM_ROWS;
+
+const int PAD_WIDTH = 3;
+const int PAD_HEIGHT = 3;
+
+const int RECT_WIDTH = CELL_WIDTH - (2 * PAD_WIDTH);
+const int RECT_HEIGHT = CELL_HEIGHT - (2 * PAD_HEIGHT);
+
+static void shade_rect(SkCanvas* canvas, sk_sp<SkShader> shader, int cellRow, int cellCol) {
+ SkPaint paint;
+ paint.setShader(shader);
+
+ SkRect rect = SkRect::MakeXYWH(SkIntToScalar(cellCol * CELL_WIDTH + PAD_WIDTH),
+ SkIntToScalar(cellRow * CELL_HEIGHT + PAD_HEIGHT),
+ SkIntToScalar(RECT_WIDTH),
+ SkIntToScalar(RECT_HEIGHT));
+
+ canvas->drawRect(rect, paint);
+}
+
+static void create_gradient_points(int cellRow, int cellCol, SkPoint points[2]) {
+ const int X_OFFSET = 30;
+
+ auto x0 = SkIntToScalar(cellCol * CELL_WIDTH + PAD_WIDTH + X_OFFSET);
+ auto x1 = SkIntToScalar((cellCol+1) * CELL_WIDTH - PAD_WIDTH - X_OFFSET);
+ auto y = SkIntToScalar(cellRow * CELL_HEIGHT + PAD_HEIGHT + RECT_HEIGHT/2);
+
+ points[0] = SkPoint::Make(x0, y);
+ points[1] = SkPoint::Make(x1, y);
+}
+
+class HardstopGradientShaderGM : public skiagm::GM {
+public:
+ HardstopGradientShaderGM() {
+
+ }
+
+protected:
+ SkString onShortName() override {
+ return SkString("hardstop_gradients");
+ }
+
+ SkISize onISize() override {
+ return SkISize::Make(512, 512);
+ }
+
+ void onDraw(SkCanvas* canvas) override {
+ SkPoint points[2];
+
+ SkColor colors[] = {
+ SK_ColorRED,
+ SK_ColorGREEN,
+ SK_ColorBLUE,
+ SK_ColorYELLOW,
+ SK_ColorMAGENTA,
+ };
+
+ SkScalar row3[] = {0.00f, 0.25f, 0.50f, 0.50f, 1.00f};
+ SkScalar row4[] = {0.00f, 0.25f, 0.50f, 1.00f, 1.00f};
+ SkScalar row5[] = {0.00f, 0.00f, 0.50f, 0.50f, 1.00f};
+
+ SkScalar* positions[] = {
+ nullptr,
+ nullptr,
+ row3,
+ row4,
+ row5,
+ };
+
+ int numGradientColors[] = {
+ 2,
+ 3,
+ 5,
+ 5,
+ 5,
+ };
+
+ SkShader::TileMode tilemodes[] = {
+ SkShader::kClamp_TileMode,
+ SkShader::kRepeat_TileMode,
+ SkShader::kMirror_TileMode,
+ };
+
+ for (int cellRow = 0; cellRow < NUM_ROWS; cellRow++) {
+ for (int cellCol = 0; cellCol < NUM_COLS; cellCol++) {
+ create_gradient_points(cellRow, cellCol, points);
+
+ auto shader = SkGradientShader::MakeLinear(
+ points,
+ colors,
+ positions[cellRow],
+ numGradientColors[cellRow],
+ tilemodes[cellCol],
+ 0,
+ nullptr);
+
+ shade_rect(canvas, shader, cellRow, cellCol);
+ }
+ }
+ }
+
+private:
+ typedef skiagm::GM INHERITED;
+};
+
+DEF_GM(return new HardstopGradientShaderGM;)