Update hardstop_gradients GM to include more special cases

gm/hardstop_gradients.cpp

 /*
  * 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.
+ *                            | Clamp         Repeat          Mirror
+ * ___________________________|___________________________________________
+ * 2-color                    | rect00        rect01          rect02
+ * 3-color even               | rect10        rect11          rect12
+ * 3-color texture            | rect20        rect21          rect22

[tomhudson, 2016/08/03 14:14:36]

I can intuit meanings of most of these names if I squint and think hard and
remember personal conversations with you, but this one is too opaque. Consider
adding a half-dozen or so sentences defining these shorthands.

+ * 5-color hard stop          | rect30        rect31          rect32
+ * 4-color hard stop centered | rect40        rect41          rect42
+ * 3-color hard stop 001      | rect50        rect51          rect52
+ * 3-color hard stop 011      | rect60        rect61          rect62
  */
 
 #include "gm.h"
 
 #include "SkGradientShader.h"
 
 const int WIDTH  = 500;
 const int HEIGHT = 500;
 
-const int NUM_ROWS = 5;
+const int NUM_ROWS = 7;
 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);
+    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() {
 
     }
@@ skipping 11 matching lines @@
         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 row3[] = {0.00f, 0.25f, 1.00f};
+        SkScalar row4[] = {0.00f, 0.25f, 0.50f, 0.50f, 1.00f};
+        SkScalar row5[] = {0.00f, 0.50f, 0.50f, 1.00f};
+        SkScalar row6[] = {0.00f, 0.00f, 1.00f};
+        SkScalar row7[] = {0.00f, 1.00f, 1.00f};
 
-        SkScalar* positions[] = {
+        SkScalar* positions[NUM_ROWS] = {
             nullptr,
             nullptr,
             row3,
             row4,
             row5,
+            row6,
+            row7,
         };
 
-        int numGradientColors[] = {
+        int numGradientColors[NUM_ROWS] = {
             2,
             3,
+            3,
             5,
-            5,
-            5,
+            4,
+            3,
+            3,
         };
 
-        SkShader::TileMode tilemodes[] = {
+        SkShader::TileMode tilemodes[NUM_COLS] = {
             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;)