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/*
* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Debug.h>
#include <AK/QuickSort.h>
#include <LibGfx/Color.h>
#include <LibGfx/Painter.h>
#include <LibGfx/Path.h>
namespace Gfx::Detail {
[[maybe_unused]] inline static void approximately_place_on_int_grid(FloatPoint ffrom, FloatPoint fto, IntPoint& from, IntPoint& to, Optional<IntPoint> previous_to)
{
auto diffs = fto - ffrom;
// Truncate all first (round down).
from = ffrom.to_type<int>();
to = fto.to_type<int>();
// There are 16 possible configurations, by deciding to round each
// coord up or down (and there are four coords, from.x from.y to.x to.y)
// we will simply choose one which most closely matches the correct slope
// with the following heuristic:
// - if the x diff is positive or zero (that is, a right-to-left slant), round 'from.x' up and 'to.x' down.
// - if the x diff is negative (that is, a left-to-right slant), round 'from.x' down and 'to.x' up.
// Note that we do not need to touch the 'y' attribute, as that is our scanline.
if (diffs.x() >= 0) {
from.set_x(from.x() + 1);
} else {
to.set_x(to.x() + 1);
}
if (previous_to.has_value() && from.x() != previous_to.value().x()) // The points have to line up, since we're using these lines to fill a shape.
from.set_x(previous_to.value().x());
}
enum class FillPathMode {
PlaceOnIntGrid,
AllowFloatingPoints,
};
template<FillPathMode fill_path_mode, typename Painter>
void fill_path(Painter& painter, Path const& path, Color color, Gfx::Painter::WindingRule winding_rule)
{
using GridCoordinateType = Conditional<fill_path_mode == FillPathMode::PlaceOnIntGrid, int, float>;
using PointType = Point<GridCoordinateType>;
auto draw_line = [&](auto... args) {
if constexpr (requires { painter.draw_aliased_line(args...); })
painter.draw_aliased_line(args...);
else
painter.draw_line(args...);
};
auto const& segments = path.split_lines();
if (segments.size() == 0)
return;
Vector<Path::SplitLineSegment> active_list;
active_list.ensure_capacity(segments.size());
// first, grab the segments for the very first scanline
GridCoordinateType first_y = path.bounding_box().bottom_right().y() + 1;
GridCoordinateType last_y = path.bounding_box().top_left().y() - 1;
float scanline = first_y;
size_t last_active_segment { 0 };
for (auto& segment : segments) {
if (segment.maximum_y != scanline)
break;
active_list.append(segment);
++last_active_segment;
}
auto is_inside_shape = [winding_rule](int winding_number) {
if (winding_rule == Gfx::Painter::WindingRule::Nonzero)
return winding_number != 0;
if (winding_rule == Gfx::Painter::WindingRule::EvenOdd)
return winding_number % 2 == 0;
VERIFY_NOT_REACHED();
};
auto increment_winding = [winding_rule](int& winding_number, PointType const& from, PointType const& to) {
if (winding_rule == Gfx::Painter::WindingRule::EvenOdd) {
++winding_number;
return;
}
if (winding_rule == Gfx::Painter::WindingRule::Nonzero) {
if (from.dy_relative_to(to) < 0)
++winding_number;
else
--winding_number;
return;
}
VERIFY_NOT_REACHED();
};
while (scanline >= last_y) {
Optional<PointType> previous_to;
if (active_list.size()) {
// sort the active list by 'x' from right to left
quick_sort(active_list, [](auto const& line0, auto const& line1) {
return line1.x < line0.x;
});
if constexpr (fill_path_mode == FillPathMode::PlaceOnIntGrid && FILL_PATH_DEBUG) {
if ((int)scanline % 10 == 0) {
painter.draw_text(Gfx::Rect<GridCoordinateType>(active_list.last().x - 20, scanline, 20, 10), String::number((int)scanline));
}
}
if (active_list.size() > 1) {
auto winding_number { winding_rule == Gfx::Painter::WindingRule::Nonzero ? 1 : 0 };
for (size_t i = 1; i < active_list.size(); ++i) {
auto& previous = active_list[i - 1];
auto& current = active_list[i];
PointType from, to;
PointType truncated_from { previous.x, scanline };
PointType truncated_to { current.x, scanline };
if constexpr (fill_path_mode == FillPathMode::PlaceOnIntGrid) {
approximately_place_on_int_grid({ previous.x, scanline }, { current.x, scanline }, from, to, previous_to);
} else {
from = truncated_from;
to = truncated_to;
}
if (is_inside_shape(winding_number)) {
// The points between this segment and the previous are
// inside the shape
dbgln_if(FILL_PATH_DEBUG, "y={}: {} at {}: {} -- {}", scanline, winding_number, i, from, to);
draw_line(from, to, color, 1);
}
auto is_passing_through_maxima = scanline == previous.maximum_y
|| scanline == previous.minimum_y
|| scanline == current.maximum_y
|| scanline == current.minimum_y;
auto is_passing_through_vertex = false;
if (is_passing_through_maxima) {
is_passing_through_vertex = previous.x == current.x;
}
if (!is_passing_through_vertex || previous.inverse_slope * current.inverse_slope < 0)
increment_winding(winding_number, truncated_from, truncated_to);
// update the x coord
active_list[i - 1].x -= active_list[i - 1].inverse_slope;
}
active_list.last().x -= active_list.last().inverse_slope;
} else {
auto point = PointType(active_list[0].x, scanline);
draw_line(point, point, color);
// update the x coord
active_list.first().x -= active_list.first().inverse_slope;
}
}
--scanline;
// remove any edge that goes out of bound from the active list
for (size_t i = 0, count = active_list.size(); i < count; ++i) {
if (scanline <= active_list[i].minimum_y) {
active_list.remove(i);
--count;
--i;
}
}
for (size_t j = last_active_segment; j < segments.size(); ++j, ++last_active_segment) {
auto& segment = segments[j];
if (segment.maximum_y < scanline)
break;
if (segment.minimum_y >= scanline)
continue;
active_list.append(segment);
}
}
if constexpr (FILL_PATH_DEBUG) {
size_t i { 0 };
for (auto& segment : segments) {
draw_line(PointType(segment.from), PointType(segment.to), Color::from_hsv(i++ * 360.0 / segments.size(), 1.0, 1.0), 1);
}
}
}
}
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