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// Copyright 2020 The Chromium Authors
// 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 <limits>
#include "build/build_config.h"
#include "cc/cc_export.h"
namespace gfx {
class Vector2dF;
class SizeF;
} // namespace gfx
namespace cc {
static constexpr int kPixelsPerLineStep = 40;
static constexpr float kMinFractionToStepWhenSnapPaging = 0.4f;
static constexpr float kMinFractionToStepWhenPaging = 0.875f;
#if BUILDFLAG(IS_MAC)
static constexpr int kMaxOverlapBetweenPages = 40;
#else
static constexpr int kMaxOverlapBetweenPages = std::numeric_limits<int>::max();
#endif // BUILDFLAG(IS_MAC)
// 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 on its
// scroller_size and viewport_size. Inputs and output must be in physical
// pixels. Currently used for converting kScrollByPage wheel scrolls
// (available on some platforms and can be enabled via the OS setting) that
// are handled on the compositor thread to pixel units.
static gfx::Vector2dF ResolveScrollPercentageToPixels(
const gfx::Vector2dF& scroll_delta,
const gfx::SizeF& scroller_size,
const gfx::SizeF& viewport_size);
static int CalculateMinPageSnap(int length);
static int CalculateMaxPageSnap(int length);
static int CalculatePageStep(int length);
// Calculates the length of the scrollbar thumb.
// |total_size| is the total size of the scrolled contents.
// |visible_size| is the visible size of the contents.
// |track_length| is the visible length of the scrollbar.
// |minimum_thumb_length| specifies the lower limit of the return value.
static int CalculateScrollbarThumbLength(int total_size,
int visible_size,
int track_length,
int minimum_thumb_length);
};
} // namespace cc
#endif // CC_INPUT_SCROLL_UTILS_H_
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