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// 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
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