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Timothy Flynn 2024-11-09 12:25:08 -05:00 • committed by Andreas Kling
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Libraries/LibWeb/CSS/StyleValues/EasingStyleValue.cpp Normal file
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/*
* Copyright (c) 2018-2020, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2021, Tobias Christiansen <tobyase@serenityos.org>
* Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
* Copyright (c) 2022-2023, MacDue <macdue@dueutil.tech>
* Copyright (c) 2023, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "EasingStyleValue.h"
#include <AK/BinarySearch.h>
#include <AK/StringBuilder.h>
namespace Web::CSS {
// https://drafts.csswg.org/css-easing-1/#valdef-easing-function-linear
EasingStyleValue::Linear EasingStyleValue::Linear::identity()
{
static Linear linear { { { 0, {}, false }, { 1, {}, false } } };
return linear;
}
// NOTE: Magic cubic bezier values from https://www.w3.org/TR/css-easing-1/#valdef-cubic-bezier-easing-function-ease
EasingStyleValue::CubicBezier EasingStyleValue::CubicBezier::ease()
{
static CubicBezier bezier { 0.25, 0.1, 0.25, 1.0 };
return bezier;
}
EasingStyleValue::CubicBezier EasingStyleValue::CubicBezier::ease_in()
{
static CubicBezier bezier { 0.42, 0.0, 1.0, 1.0 };
return bezier;
}
EasingStyleValue::CubicBezier EasingStyleValue::CubicBezier::ease_out()
{
static CubicBezier bezier { 0.0, 0.0, 0.58, 1.0 };
return bezier;
}
EasingStyleValue::CubicBezier EasingStyleValue::CubicBezier::ease_in_out()
{
static CubicBezier bezier { 0.42, 0.0, 0.58, 1.0 };
return bezier;
}
EasingStyleValue::Steps EasingStyleValue::Steps::step_start()
{
static Steps steps { 1, Steps::Position::Start };
return steps;
}
EasingStyleValue::Steps EasingStyleValue::Steps::step_end()
{
static Steps steps { 1, Steps::Position::End };
return steps;
}
bool EasingStyleValue::CubicBezier::operator==(Web::CSS::EasingStyleValue::CubicBezier const& other) const
{
return x1 == other.x1 && y1 == other.y1 && x2 == other.x2 && y2 == other.y2;
}
// https://drafts.csswg.org/css-easing/#linear-canonicalization
EasingStyleValue::Linear::Linear(Vector<EasingStyleValue::Linear::Stop> stops)
{
// To canonicalize a linear() function’s control points, perform the following:
// 1. If the first control point lacks an input progress value, set its input progress value to 0.
if (!stops.first().input.has_value())
stops.first().input = 0;
// 2. If the last control point lacks an input progress value, set its input progress value to 1.
if (!stops.last().input.has_value())
stops.last().input = 1;
// 3. If any control point has an input progress value that is less than
// the input progress value of any preceding control point,
// set its input progress value to the largest input progress value of any preceding control point.
double largest_input = 0;
for (auto stop : stops) {
if (stop.input.has_value()) {
if (stop.input.value() < largest_input) {
stop.input = largest_input;
} else {
largest_input = stop.input.value();
}
}
}
// 4. If any control point still lacks an input progress value,
// then for each contiguous run of such control points,
// set their input progress values so that they are evenly spaced
// between the preceding and following control points with input progress values.
Optional<size_t> run_start_idx;
for (size_t idx = 0; idx < stops.size(); idx++) {
auto stop = stops[idx];
if (stop.input.has_value() && run_start_idx.has_value()) {
// Note: this stop is immediately after a run
// set inputs of [start, idx-1] stops to be evenly spaced between start-1 and idx
auto start_input = stops[run_start_idx.value() - 1].input.value();
auto end_input = stops[idx].input.value();
auto run_stop_count = idx - run_start_idx.value() + 1;
auto delta = (end_input - start_input) / run_stop_count;
for (size_t run_idx = 0; run_idx < run_stop_count; run_idx++) {
stops[run_idx + run_start_idx.value() - 1].input = start_input + delta * run_idx;
}
run_start_idx = {};
} else if (!stop.input.has_value() && !run_start_idx.has_value()) {
// Note: this stop is the start of a run
run_start_idx = idx;
}
}
this->stops = move(stops);
}
// https://drafts.csswg.org/css-easing/#linear-easing-function-output
double EasingStyleValue::Linear::evaluate_at(double input_progress, bool before_flag) const
{
// To calculate linear easing output progress for a given linear easing function func,
// an input progress value inputProgress, and an optional before flag (defaulting to false),
// perform the following:
// 1. Let points be func’s control points.
// 2. If points holds only a single item, return the output progress value of that item.
if (stops.size() == 1)
return stops[0].output;
// 3. If inputProgress matches the input progress value of the first point in points,
// and the before flag is true, return the first point’s output progress value.
if (input_progress == stops[0].input.value() && before_flag)
return stops[0].output;
// 4. If inputProgress matches the input progress value of at least one point in points,
// return the output progress value of the last such point.
auto maybe_match = stops.last_matching([&](auto& stop) { return input_progress == stop.input.value(); });
if (maybe_match.has_value())
return maybe_match->output;
// 5. Otherwise, find two control points in points, A and B, which will be used for interpolation:
Stop A;
Stop B;
if (input_progress < stops[0].input.value()) {
// 1. If inputProgress is smaller than any input progress value in points,
// let A and B be the first two items in points.
// If A and B have the same input progress value, return A’s output progress value.
A = stops[0];
B = stops[1];
if (A.input == B.input)
return A.output;
} else if (input_progress > stops.last().input.value()) {
// 2. If inputProgress is larger than any input progress value in points,
// let A and B be the last two items in points.
// If A and B have the same input progress value, return B’s output progress value.
A = stops[stops.size() - 2];
B = stops[stops.size() - 1];
if (A.input == B.input)
return B.output;
} else {
// 3. Otherwise, let A be the last control point whose input progress value is smaller than inputProgress,
// and let B be the first control point whose input progress value is larger than inputProgress.
A = stops.last_matching([&](auto& stop) { return stop.input.value() < input_progress; }).value();
B = stops.first_matching([&](auto& stop) { return stop.input.value() > input_progress; }).value();
}
// 6. Linearly interpolate (or extrapolate) inputProgress along the line defined by A and B, and return the result.
auto factor = (input_progress - A.input.value()) / (B.input.value() - A.input.value());
return A.output + factor * (B.output - A.output);
}
// https://drafts.csswg.org/css-easing/#linear-easing-function-serializing
String EasingStyleValue::Linear::to_string() const
{
// The linear keyword is serialized as itself.
if (*this == identity())
return "linear"_string;
// To serialize a linear() function:
// 1. Let s be the string "linear(".
StringBuilder builder;
builder.append("linear("sv);
// 2. Serialize each control point of the function,
// concatenate the results using the separator ", ",
// and append the result to s.
bool first = true;
for (auto stop : stops) {
if (first) {
first = false;
} else {
builder.append(", "sv);
}
// To serialize a linear() control point:
// 1. Let s be the serialization, as a <number>, of the control point’s output progress value.
builder.appendff("{}", stop.output);
// 2. If the control point originally lacked an input progress value, return s.
// 3. Otherwise, append " " (U+0020 SPACE) to s,
// then serialize the control point’s input progress value as a <percentage> and append it to s.
if (stop.had_explicit_input) {
builder.appendff(" {}%", stop.input.value() * 100);
}
// 4. Return s.
}
// 4. Append ")" to s, and return it.
builder.append(')');
return MUST(builder.to_string());
}
double EasingStyleValue::CubicBezier::evaluate_at(double input_progress, bool) const
{
constexpr static auto cubic_bezier_at = [](double x1, double x2, double t) {
auto a = 1.0 - 3.0 * x2 + 3.0 * x1;
auto b = 3.0 * x2 - 6.0 * x1;
auto c = 3.0 * x1;
auto t2 = t * t;
auto t3 = t2 * t;
return (a * t3) + (b * t2) + (c * t);
};
// https://www.w3.org/TR/css-easing-1/#cubic-bezier-algo
// For input progress values outside the range [0, 1], the curve is extended infinitely using tangent of the curve
// at the closest endpoint as follows:
// - For input progress values less than zero,
if (input_progress < 0.0) {
// 1. If the x value of P1 is greater than zero, use a straight line that passes through P1 and P0 as the
// tangent.
if (x1 > 0.0)
return y1 / x1 * input_progress;
// 2. Otherwise, if the x value of P2 is greater than zero, use a straight line that passes through P2 and P0 as
// the tangent.
if (x2 > 0.0)
return y2 / x2 * input_progress;
// 3. Otherwise, let the output progress value be zero for all input progress values in the range [-∞, 0).
return 0.0;
}
// - For input progress values greater than one,
if (input_progress > 1.0) {
// 1. If the x value of P2 is less than one, use a straight line that passes through P2 and P3 as the tangent.
if (x2 < 1.0)
return (1.0 - y2) / (1.0 - x2) * (input_progress - 1.0) + 1.0;
// 2. Otherwise, if the x value of P1 is less than one, use a straight line that passes through P1 and P3 as the
// tangent.
if (x1 < 1.0)
return (1.0 - y1) / (1.0 - x1) * (input_progress - 1.0) + 1.0;
// 3. Otherwise, let the output progress value be one for all input progress values in the range (1, ∞].
return 1.0;
}
// Note: The spec does not specify the precise algorithm for calculating values in the range [0, 1]:
// "The evaluation of this curve is covered in many sources such as [FUND-COMP-GRAPHICS]."
auto x = input_progress;
auto solve = [&](auto t) {
auto x = cubic_bezier_at(x1, x2, t);
auto y = cubic_bezier_at(y1, y2, t);
return CubicBezier::CachedSample { x, y, t };
};
if (m_cached_x_samples.is_empty())
m_cached_x_samples.append(solve(0.));
size_t nearby_index = 0;
if (auto found = binary_search(m_cached_x_samples, x, &nearby_index, [](auto x, auto& sample) {
if (x - sample.x >= NumericLimits<double>::epsilon())
return 1;
if (x - sample.x <= NumericLimits<double>::epsilon())
return -1;
return 0;
}))
return found->y;
if (nearby_index == m_cached_x_samples.size() || nearby_index + 1 == m_cached_x_samples.size()) {
// Produce more samples until we have enough.
auto last_t = m_cached_x_samples.last().t;
auto last_x = m_cached_x_samples.last().x;
while (last_x <= x && last_t < 1.0) {
last_t += 1. / 60.;
auto solution = solve(last_t);
m_cached_x_samples.append(solution);
last_x = solution.x;
}
if (auto found = binary_search(m_cached_x_samples, x, &nearby_index, [](auto x, auto& sample) {
if (x - sample.x >= NumericLimits<double>::epsilon())
return 1;
if (x - sample.x <= NumericLimits<double>::epsilon())
return -1;
return 0;
}))
return found->y;
}
// We have two samples on either side of the x value we want, so we can linearly interpolate between them.
auto& sample1 = m_cached_x_samples[nearby_index];
auto& sample2 = m_cached_x_samples[nearby_index + 1];
auto factor = (x - sample1.x) / (sample2.x - sample1.x);
return sample1.y + factor * (sample2.y - sample1.y);
}
String EasingStyleValue::CubicBezier::to_string() const
{
StringBuilder builder;
if (*this == CubicBezier::ease()) {
builder.append("ease"sv);
} else if (*this == CubicBezier::ease_in()) {
builder.append("ease-in"sv);
} else if (*this == CubicBezier::ease_out()) {
builder.append("ease-out"sv);
} else if (*this == CubicBezier::ease_in_out()) {
builder.append("ease-in-out"sv);
} else {
builder.appendff("cubic-bezier({}, {}, {}, {})", x1, y1, x2, y2);
}
return MUST(builder.to_string());
}
double EasingStyleValue::Steps::evaluate_at(double input_progress, bool before_flag) const
{
// https://www.w3.org/TR/css-easing-1/#step-easing-algo
// 1. Calculate the current step as floor(input progress value × steps).
auto current_step = floor(input_progress * number_of_intervals);
// 2. If the step position property is one of:
// - jump-start,
// - jump-both,
// increment current step by one.
if (position == Steps::Position::JumpStart || position == Steps::Position::Start || position == Steps::Position::JumpBoth)
current_step += 1;
// 3. If both of the following conditions are true:
// - the before flag is set, and
// - input progress value × steps mod 1 equals zero (that is, if input progress value × steps is integral), then
// decrement current step by one.
auto step_progress = input_progress * number_of_intervals;
if (before_flag && trunc(step_progress) == step_progress)
current_step -= 1;
// 4. If input progress value ≥ 0 and current step < 0, let current step be zero.
if (input_progress >= 0.0 && current_step < 0.0)
current_step = 0.0;
// 5. Calculate jumps based on the step position as follows:
// jump-start or jump-end -> steps
// jump-none -> steps - 1
// jump-both -> steps + 1
auto jumps = number_of_intervals;
if (position == Steps::Position::JumpNone) {
jumps--;
} else if (position == Steps::Position::JumpBoth) {
jumps++;
}
// 6. If input progress value ≤ 1 and current step > jumps, let current step be jumps.
if (input_progress <= 1.0 && current_step > jumps)
current_step = jumps;
// 7. The output progress value is current step / jumps.
return current_step / jumps;
}
String EasingStyleValue::Steps::to_string() const
{
StringBuilder builder;
if (*this == Steps::step_start()) {
builder.append("step-start"sv);
} else if (*this == Steps::step_end()) {
builder.append("step-end"sv);
} else {
auto position = [&] -> Optional<StringView> {
switch (this->position) {
case Steps::Position::JumpStart:
return "jump-start"sv;
case Steps::Position::JumpNone:
return "jump-none"sv;
case Steps::Position::JumpBoth:
return "jump-both"sv;
case Steps::Position::Start:
return "start"sv;
default:
return {};
}
}();
if (position.has_value()) {
builder.appendff("steps({}, {})", number_of_intervals, position.value());
} else {
builder.appendff("steps({})", number_of_intervals);
}
}
return MUST(builder.to_string());
}
double EasingStyleValue::Function::evaluate_at(double input_progress, bool before_flag) const
{
return visit(
[&](auto const& curve) {
return curve.evaluate_at(input_progress, before_flag);
});
}
String EasingStyleValue::Function::to_string() const
{
return visit(
[&](auto const& curve) {
return curve.to_string();
});
}
}