Scale test

cc/tiles/tile_manager_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/run_loop.h"
 #include "base/thread_task_runner_handle.h"
 #include "cc/playback/display_list_raster_source.h"
@@ skipping 1942 matching lines @@
                         true /* partial_raster_enabled */);
 }
 
 // Ensures that the tile manager does not attempt to reuse tiles when partial
 // raster is disabled.
 TEST_F(TileManagerTest, PartialRasterSuccessfullyDisabled) {
   RunPartialRasterCheck(std::move(host_impl_),
                         false /* partial_raster_enabled */);
 }
 
+#define PRECISION (15)
+void TestScale(float lw, float lh, float s) {
+  long slw = std::lround(lw * s);
+  long slh = std::lround(lh * s);
+
+  std::cout << "\nGiven Scale = " << std::setprecision(PRECISION) << s;
+  std::cout << "\nLayer Size = " << lw << " x " << lh;
+  std::cout << "\nScaled Layer Size = " << std::setprecision(PRECISION)
+            << (lw * s) << " x " << std::setprecision(PRECISION) << (lh * s);
+  std::cout << "\nRounded Scaled Layer Size = " << slw << " x " << slh;
+  std::cout << "\nApproximated Scale [sx, sy] = ["
+            << std::setprecision(PRECISION) << (slw / lw) << ", "
+            << std::setprecision(PRECISION) << (slh / lh) << "] <====";
+
+  std::cout << "\n\n";
+}
+
+TEST_F(TileManagerTest, ScaleTestSmallLayerSize) {
+  // Almost equal scales.
+  float scale1 = 7.33907556533813f;
+  float scale2 = 7.33907508850098f;
+  TestScale(501.f, 502.f, scale1);
+  TestScale(501.f, 502.f, scale2);
+}
+
+TEST_F(TileManagerTest, ScaleTestVeryBigLayerSize) {
+  // Almost equal scales.
+  float scale1 = 7.33907556533813f;
+  float scale2 = 7.33907508850098f;
+  TestScale(5010000.f, 5020000.f, scale1);
+  TestScale(5010000.f, 5020000.f, scale2);
+}
+
 }  // namespace
 }  // namespace cc