1 files changed, 45 insertions, 0 deletions
diff --git a/chromium/cc/input/scroll_utils.cc b/chromium/cc/input/scroll_utils.cc
new file mode 100644
index 00000000000..e9c036e3896
--- /dev/null
+++ b/chromium/cc/input/scroll_utils.cc
@@ -0,0 +1,45 @@
+// Copyright 2020 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 "cc/input/scroll_utils.h"
+
+#include "base/numerics/ranges.h"
+#include "ui/gfx/geometry/size_f.h"
+#include "ui/gfx/geometry/vector2d_f.h"
+
+namespace cc {
+
+// static
+gfx::Vector2dF ScrollUtils::ResolveScrollPercentageToPixels(
+    const gfx::Vector2dF& delta,
+    const gfx::SizeF& scroller,
+    const gfx::SizeF& viewport) {
+  // Work with unsigned values and keep sign information in sign_x / sign_y.
+  float sign_x = std::signbit(delta.x()) ? -1 : 1;
+  float sign_y = std::signbit(delta.y()) ? -1 : 1;
+  float delta_x = std::abs(delta.x());
+  float delta_y = std::abs(delta.y());
+
+  // Resolved deltas in percent based scrolling are clamped at min by 16 pixels.
+  float min = kMinPixelDeltaForPercentBasedScroll;
+
+  // Resolve and clamp horizontal scroll
+  if (delta_x > 0) {
+    delta_x = delta_x * std::min(scroller.width(), viewport.width());
+    if (delta_x < min)
+      delta_x = min;
+  }
+
+  // Resolve and clamps vertical scroll.
+  if (delta_y > 0) {
+    delta_y = delta_y * std::min(scroller.height(), viewport.height());
+    if (delta_y < min)
+      delta_y = min;
+  }
+
+  return gfx::Vector2dF(std::copysign(delta_x, sign_x),
+                        std::copysign(delta_y, sign_y));
+}
+
+}  // namespace cc