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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.
#include "cc/input/scroll_utils.h"
#include <algorithm>
#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());
// Resolve and clamp horizontal scroll
if (delta_x > 0)
delta_x =
std::max(1.0f, delta_x * std::min(scroller.width(), viewport.width()));
// Resolve and clamps vertical scroll.
if (delta_y > 0)
delta_y = std::max(
1.0f, delta_y * std::min(scroller.height(), viewport.height()));
return gfx::Vector2dF(std::copysign(delta_x, sign_x),
std::copysign(delta_y, sign_y));
}
// static
int ScrollUtils::CalculateMinPageSnap(int length) {
const int min_page_step = length * kMinFractionToStepWhenSnapPaging;
return std::max(min_page_step, 1);
}
// static
int ScrollUtils::CalculateMaxPageSnap(int length) {
return std::max(length, 1);
}
// static
int ScrollUtils::CalculatePageStep(int length) {
const int min_page_step = length * kMinFractionToStepWhenPaging;
const int page_step =
std::max(min_page_step, length - kMaxOverlapBetweenPages);
return std::max(page_step, 1);
}
// static
int ScrollUtils::CalculateScrollbarThumbLength(int total_size,
int visible_size,
int track_length,
int minimum_thumb_length) {
float proportion = 0.0f;
if (total_size > 0) {
proportion = static_cast<float>(visible_size) / total_size;
}
int length = round(proportion * track_length);
length = std::max(length, minimum_thumb_length);
if (length > track_length) {
length = track_length;
}
return length;
}
} // namespace cc
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