Fixed a bug with linear gradient PDF matrices and added test cases

gm/gradient_matrix.cpp

Index: gm/gradient_matrix.cpp
diff --git a/gm/gradient_matrix.cpp b/gm/gradient_matrix.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..756e6e6ee0d98e7f667424e8489b6223d653ef18
--- /dev/null
+++ b/gm/gradient_matrix.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2013 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 "SkGradientShader.h"
+
+SkColor gColors[] = {
+    SK_ColorRED, SK_ColorYELLOW
+};
+
+// these arrays define the gradient stop points
+// as x1, y1, x2, y2 per gradient to draw
+SkScalar linearPts[] = {
+    0, 0, 1, 0,
+    0, 0, 0, 1,
+    1, 0, 0, 0,
+    0, 1, 0, 0,
+
+    0, 0, 1, 1,
+    1, 1, 0, 0,
+    1, 0, 0, 1,
+    0, 1, 1, 0
+};
+
+const SkScalar TESTGRID_X = 200;    // pixels allocated to each image in x dimension
+const SkScalar TESTGRID_Y = 200;    // pixels allocated to each image in y dimension
+
+const int IMAGES_X = 4;             // number of images per row
+
+static SkShader* make_linear_gradient(SkPoint pts[2]) {
+    return SkGradientShader::CreateLinear(pts, gColors, NULL, SK_ARRAY_COUNT(gColors),
+                                          SkShader::kClamp_TileMode, NULL);
+}
+
+void draw_gradients(SkCanvas* canvas, SkShader* (*makeShader)(SkPoint[2]),
+                   SkScalar* ptsArray, int numImages) {

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

nit: indent

[ducky, 2013/06/11 23:18:17]

Done.

+    for (int i = 0; i < numImages; i++) {
+        // advance line if necessary
+        if (i % IMAGES_X == 0 && i != 0) {
+            canvas->restore();
+            canvas->translate(0, TESTGRID_Y);
+            canvas->save();
+        }
+
+        // unpack points, setup shader, draw
+        SkPoint pts[2] = {

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

You shouldn't need this bit.

[ducky, 2013/06/11 23:18:17]

Done.

+            { *(ptsArray+0), *(ptsArray+1) },
+            { *(ptsArray+2), *(ptsArray+3) }
+        };
+        ptsArray += 4;
+
+        SkMatrix shaderMat = SkMatrix();

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

Pull this stuff above the loop.

[ducky, 2013/06/11 23:18:17]

Done.

+        shaderMat.setAll(138, 0,   43,
+                         0,   106, 61,
+                         0,   0,   1);
+        SkRect rectGrad = { 43, 61, 181, 167 }; // some nice prime numbers
+
+        SkShader* shader = makeShader(pts);

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

use SkAutoTUnref

[ducky, 2013/06/11 23:18:17]

Done.

+        shader->setLocalMatrix(shaderMat);
+
+        SkPaint paint;
+        paint.setShader(shader);
+        canvas->drawRect(rectGrad, paint);
+
+        shader->unref();
+
+        // advance to next position
+        canvas->translate(TESTGRID_X, 0);
+    }
+}
+
+namespace skiagm {
+
+class GradientMatrixGM : public GM {
+public:
+    GradientMatrixGM() {
+        this->setBGColor(0xFFDDDDDD);
+    }
+
+protected:
+    SkString onShortName() {
+        return SkString("gradient_matrix");
+    }
+
+    virtual SkISize onISize() {
+        return SkISize::Make(800, 800);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        canvas->save();

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

Do the save restore around the for loop instead of here.

[ducky, 2013/06/11 23:18:17]

Done.

+
+        draw_gradients(canvas, &make_linear_gradient,
+                      linearPts, sizeof(linearPts) / sizeof(linearPts[0]) / 4);

[vandebo (ex-Chrome), 2013/06/11 22:11:05]

SK_ARRAY_COUNT()

[ducky, 2013/06/11 23:18:17]

Done.

+
+        canvas->restore();
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+static GM* MyFactory(void*) { return new GradientMatrixGM; }
+static GMRegistry reg(MyFactory);
+}