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..8915b1699c709c2cc2afe36897c47801ba77eddf
--- /dev/null
+++ b/gm/gradient_matrix.cpp
@@ -0,0 +1,111 @@
+/*
+ * 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"
+
+static const SkColor gColors[] = {
+    SK_ColorRED, SK_ColorYELLOW
+};
+static const SkScalar gPosAll[] = {
+    0, SK_Scalar1
+};
+
+static SkShader* SimpleGradient(const SkPoint pts[2]) {

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

static helper functions are named in hacker case: simple_gradient()

[ducky, 2013/06/11 21:35:32]

Done.

+    return SkGradientShader::CreateLinear(pts, gColors, gPosAll,
+                                          2, SkShader::kClamp_TileMode, NULL);

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

nit: put "2" on the previous line.

[ducky, 2013/06/11 21:35:32]

Done.

+}
+
+namespace skiagm {
+
+class GradientMatrixGM : public GM {
+public:
+  GradientMatrixGM() {
+        this->setBGColor(0xFFDDDDDD);
+    }
+
+protected:
+    SkString onShortName() {
+        return SkString("gradient_matrix");
+    }
+
+    virtual SkISize onISize() { return make_isize(800, 400); }

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

line wrap.

[ducky, 2013/06/11 21:35:32]

Done.

+
+    virtual void onDraw(SkCanvas* canvas) {
+        const int TESTGRID_X = 200;

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

Should be SkScalar instead of int (applies in multiple places).

[ducky, 2013/06/11 21:35:32]

Done.

+        const int TESTGRID_Y = 200;
+
+        canvas->save();
+
+        testGrad(canvas, 0, 0, 1, 0);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 0, 0, 0, 1);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 1, 0, 0, 0);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 0, 1, 0, 0);
+
+        canvas->restore();
+        canvas->translate(0, TESTGRID_Y);
+        canvas->save();
+
+        testGrad(canvas, 0, 0, 1, 1);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 1, 1, 0, 0);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 1, 0, 0, 1);
+        canvas->translate(TESTGRID_X, 0);
+        testGrad(canvas, 0, 1, 1, 0);
+    }
+
+    virtual void simpleGrad(SkCanvas* canvas) {

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

This method is unused, remove.

[ducky, 2013/06/11 21:35:32]

Done.

+        SkPoint pts[2] = {
+            { 100, 0 },
+            { 0, 0 }
+        };
+        SkMatrix shaderMat = SkMatrix();
+        shaderMat.setAll(1, 0, 0,
+                         0, 1, 0,
+                         0, 0, 1);
+        SkRect rectGrad = { 0, 0, 100, 100 }; // very simple numbers
+
+        SkShader* shader = SimpleGradient(pts);
+        shader->setLocalMatrix(shaderMat);
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setShader(shader);
+        canvas->drawRect(rectGrad, paint);
+        shader->unref();
+    }
+
+    virtual void testGrad(SkCanvas* canvas, int x1, int y1, int x2, int y2) {

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

not virtual.  In fact, it can be a static helper function.

[ducky, 2013/06/11 21:35:32]

Done.

+        SkPoint pts[2] = {

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

why not just pass SkPoints[2] ?

[ducky, 2013/06/11 21:35:32]

Done.

+            { x1, y1 },
+            { x2, y2 }
+        };
+        SkMatrix shaderMat = SkMatrix();
+        shaderMat.setAll(138, 0, 43,
+                         0, 106, 61,
+                         0, 0, 1);
+        SkRect rectGrad = { 43, 61, 181, 167 }; // some nice prime numbers
+
+        SkShader* shader = SimpleGradient(pts);
+        shader->setLocalMatrix(shaderMat);
+        SkPaint paint;
+        paint.setAntiAlias(true);

[vandebo (ex-Chrome), 2013/06/11 05:15:10]

remove - not needed for this test.

[ducky, 2013/06/11 21:35:32]

Done.

+        paint.setShader(shader);
+        canvas->drawRect(rectGrad, paint);
+        shader->unref();
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+static GM* MyFactory(void*) { return new GradientMatrixGM; }
+static GMRegistry reg(MyFactory);
+
+}