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* 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/gm.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColor.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkShader.h"
#include "include/core/SkTileMode.h"
#include "include/core/SkTypes.h"
#include "include/effects/SkGradientShader.h"
constexpr SkColor gColors[] = {
// These annoying defines are necessary, because the only other alternative
// is to use SkIntToScalar(...) everywhere.
constexpr SkScalar sZero = 0;
constexpr SkScalar sHalf = SK_ScalarHalf;
constexpr SkScalar sOne = SK_Scalar1;
// These arrays define the gradient stop points
// as x1, y1, x2, y2 per gradient to draw.
constexpr SkPoint linearPts[][2] = {
{{sZero, sZero}, {sOne, sZero}},
{{sZero, sZero}, {sZero, sOne}},
{{sOne, sZero}, {sZero, sZero}},
{{sZero, sOne}, {sZero, sZero}},
{{sZero, sZero}, {sOne, sOne}},
{{sOne, sOne}, {sZero, sZero}},
{{sOne, sZero}, {sZero, sOne}},
{{sZero, sOne}, {sOne, sZero}}
constexpr SkPoint radialPts[][2] = {
{{sZero, sHalf}, {sOne, sHalf}},
{{sHalf, sZero}, {sHalf, sOne}},
{{sOne, sHalf}, {sZero, sHalf}},
{{sHalf, sOne}, {sHalf, sZero}},
{{sZero, sZero}, {sOne, sOne}},
{{sOne, sOne}, {sZero, sZero}},
{{sOne, sZero}, {sZero, sOne}},
{{sZero, sOne}, {sOne, sZero}}
// These define the pixels allocated to each gradient image.
constexpr SkScalar TESTGRID_X = SkIntToScalar(200);
constexpr SkScalar TESTGRID_Y = SkIntToScalar(200);
constexpr int IMAGES_X = 4; // number of images per row
static sk_sp<SkShader> make_linear_gradient(const SkPoint pts[2], const SkMatrix& localMatrix) {
return SkGradientShader::MakeLinear(pts, gColors, nullptr, std::size(gColors),
SkTileMode::kClamp, 0, &localMatrix);
static sk_sp<SkShader> make_radial_gradient(const SkPoint pts[2], const SkMatrix& localMatrix) {
SkPoint center;
center.set(SkScalarAve(pts[0].fX, pts[1].fX),
SkScalarAve(pts[0].fY, pts[1].fY));
float radius = (center - pts[0]).length();
return SkGradientShader::MakeRadial(center, radius, gColors, nullptr, std::size(gColors),
SkTileMode::kClamp, 0, &localMatrix);
static void draw_gradients(SkCanvas* canvas,
sk_sp<SkShader> (*makeShader)(const SkPoint[2], const SkMatrix&),
const SkPoint ptsArray[][2], int numImages) {
// Use some nice prime numbers for the rectangle and matrix with
// different scaling along the x and y axes (which is the bug this
// test addresses, where incorrect order of operations mixed up the axes)
SkRect rectGrad = {
SkIntToScalar(43), SkIntToScalar(61),
SkIntToScalar(181), SkIntToScalar(167) };
SkMatrix shaderMat;
shaderMat.setScale(rectGrad.width(), rectGrad.height());
for (int i = 0; i < numImages; i++) {
// Advance line downwards if necessary.
if (i % IMAGES_X == 0 && i != 0) {
canvas->translate(0, TESTGRID_Y);
SkPaint paint;
paint.setShader(makeShader(*ptsArray, shaderMat));
canvas->drawRect(rectGrad, paint);
// Advance to next position.
canvas->translate(TESTGRID_X, 0);
DEF_SIMPLE_GM_BG(gradient_matrix, canvas, 800, 800, 0xFFDDDDDD) {
draw_gradients(canvas, &make_linear_gradient,
linearPts, std::size(linearPts));
canvas->translate(0, TESTGRID_Y);
draw_gradients(canvas, &make_radial_gradient,
radialPts, std::size(radialPts));