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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.
#ifndef CC_INPUT_SCROLL_UTILS_H_
#define CC_INPUT_SCROLL_UTILS_H_
#include "cc/cc_export.h"
namespace gfx {
class Vector2dF;
class SizeF;
} // namespace gfx
namespace cc {
static constexpr int kPixelsPerLineStep = 40;
static constexpr float kMinFractionToStepWhenPaging = 0.875f;
// Each directional scroll for percentage-based units should scroll 1/8th of
// the scrollable area.
static constexpr float kPercentDeltaForDirectionalScroll = 0.125f;
// Scroll deltas are lower-bounded by 16 physical pixels in percent-based
// scrolls.
static constexpr float kMinPixelDeltaForPercentBasedScroll = 16;
// Class for scroll helper methods in cc and blink.
class CC_EXPORT ScrollUtils {
public:
// Transforms a |scroll_delta| in percent units to pixel units based in its
// |scroller_size|. Clamps it by 16 pixels to avoid too small deltas for tiny
// scrollers and 12.5% of |viewport_size| to avoid too large deltas.
// Inputs and output muest be in physical pixels.
static gfx::Vector2dF ResolveScrollPercentageToPixels(
const gfx::Vector2dF& scroll_delta,
const gfx::SizeF& scroller_size,
const gfx::SizeF& viewport_size);
};
} // namespace cc
#endif // CC_INPUT_SCROLL_UTILS_H_
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