text: /*
   * Copyright 2017 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/SkFilterQuality.h"
  #include "include/core/SkImage.h"
  #include "include/core/SkMatrix.h"
  #include "include/core/SkPaint.h"
  #include "include/core/SkRect.h"
  #include "include/core/SkRefCnt.h"
  #include "include/core/SkShader.h"
  #include "include/core/SkSurface.h"
  #include "include/core/SkTileMode.h"
  
  // This GM reproduces skia:6783, which demonstrated a bug in repeat and mirror
  // image sampling tiling modes as implemented in software.  We want to tile to
  // [0,limit), and the old incorrect logic was:
  //
  //    limit = ulp_before(limit)
  //    val = val - floor(val/limit)*limit    (This is repeat; mirror is similar.)
  //
  // while the correct logic is more like:
  //
  //    val = val - floor(val/limit)*limit
  //    val = min(val, ulp_before(limit))
  //
  // You would see ugly jaggies on the blue/yellow edge near the bottom left if
  // the bug were still present.  All stripes should now look roughly the same.
  
  DEF_SIMPLE_GM(bug6783, canvas, 500, 500) {
    sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(100, 100);
  
    SkPaint p;
    p.setColor(SK_ColorYELLOW);
    surface->getCanvas()->drawPaint(p);
    p.setColor(SK_ColorBLUE);
    surface->getCanvas()->drawRect(SkRect::MakeWH(50, 100), p);
  
    sk_sp<SkImage> img = surface->makeImageSnapshot();
  
    SkMatrix m = SkMatrix::Translate(25, 214) * SkMatrix::Scale(2, 2);
    m.preSkew(0.5f, 0.5f);
  
    // The bug was present at all filter levels, but you might not notice it at kNone.
    p.setFilterQuality(kLow_SkFilterQuality);
  
    // It's only important to repeat or mirror in x to show off the bug.
    p.setShader(img->makeShader(SkTileMode::kRepeat, SkTileMode::kClamp, &m));
    canvas->drawPaint(p);
  }
  