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LibGfx: Fix some more antialiased line off-by-ones

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Turns out most things expect lines to include the endpoint,
e.g. 0,0 -> 3,0 is a 4px long line. But the fill_path() implementation
seems to expect the line to be the distance between the two points
(so the above example is a 3px line instead).

This now adds an option to pick between PointToPoint line length or
Distance line length and uses the latter for fill_path().
This commit is contained in:
MacDue 2022-12-02 00:22:53 +00:00 committed by Linus Groh
parent acc0fceaae
commit 40e978df85
Notes: sideshowbarker 2024-07-17 03:46:07 +09:00 
Author: https://github.com/MacDue
Commit: https://github.com/SerenityOS/serenity/commit/40e978df85
Pull-request: https://github.com/SerenityOS/serenity/pull/16280
3 changed files with 26 additions and 12 deletions
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14
Userland/Libraries/LibGfx/AntiAliasingPainter.cpp
View file

@ -19,7 +19,7 @@
namespace Gfx {
template<AntiAliasingPainter::FixmeEnableHacksForBetterPathPainting path_hacks>
void AntiAliasingPainter::draw_anti_aliased_line(FloatPoint actual_from, FloatPoint actual_to, Color color, float thickness, Painter::LineStyle style, Color)
void AntiAliasingPainter::draw_anti_aliased_line(FloatPoint actual_from, FloatPoint actual_to, Color color, float thickness, Painter::LineStyle style, Color, LineLengthMode line_length_mode)
{
// FIXME: Implement this :P
VERIFY(style == Painter::LineStyle::Solid);
@ -45,7 +45,7 @@ void AntiAliasingPainter::draw_anti_aliased_line(FloatPoint actual_from, FloatPo
auto mapped_from = m_transform.map(actual_from);
auto mapped_to = m_transform.map(actual_to);
auto distance = mapped_to.distance_from(mapped_from);
auto length = distance + 1;
auto length = distance + (line_length_mode == LineLengthMode::PointToPoint);
// Axis-aligned lines:
if (mapped_from.y() == mapped_to.y()) {
@ -107,7 +107,7 @@ void AntiAliasingPainter::draw_anti_aliased_line(FloatPoint actual_from, FloatPo
float x_error = 0;
float x_error_per_y = x_gradient - x_step;
auto y_offset = int_thickness;
auto y_offset = int_thickness + 1;
auto x_offset = int(x_gradient * y_offset);
int const line_start_x = mapped_from.x();
int const line_start_y = mapped_from.y();
@ -154,9 +154,9 @@ void AntiAliasingPainter::draw_anti_aliased_line(FloatPoint actual_from, FloatPo
}
}
void AntiAliasingPainter::draw_line_for_path(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Painter::LineStyle style, Color alternate_color)
void AntiAliasingPainter::draw_line_for_path(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Painter::LineStyle style, Color alternate_color, LineLengthMode line_length_mode)
{
draw_anti_aliased_line<FixmeEnableHacksForBetterPathPainting::Yes>(actual_from, actual_to, color, thickness, style, alternate_color);
draw_anti_aliased_line<FixmeEnableHacksForBetterPathPainting::Yes>(actual_from, actual_to, color, thickness, style, alternate_color, line_length_mode);
}
void AntiAliasingPainter::draw_dotted_line(IntPoint point1, IntPoint point2, Color color, int thickness)
@ -201,11 +201,11 @@ void AntiAliasingPainter::draw_dotted_line(IntPoint point1, IntPoint point2, Col
}
}
void AntiAliasingPainter::draw_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Painter::LineStyle style, Color alternate_color)
void AntiAliasingPainter::draw_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Painter::LineStyle style, Color alternate_color, LineLengthMode line_length_mode)
{
if (style == Painter::LineStyle::Dotted)
return draw_dotted_line(actual_from.to_rounded<int>(), actual_to.to_rounded<int>(), color, static_cast<int>(round(thickness)));
draw_anti_aliased_line<FixmeEnableHacksForBetterPathPainting::No>(actual_from, actual_to, color, thickness, style, alternate_color);
draw_anti_aliased_line<FixmeEnableHacksForBetterPathPainting::No>(actual_from, actual_to, color, thickness, style, alternate_color, line_length_mode);
}
void AntiAliasingPainter::fill_path(Path& path, Color color, Painter::WindingRule rule)

20
Userland/Libraries/LibGfx/AntiAliasingPainter.h
View file

@ -19,8 +19,20 @@ public:
{
}
void draw_line(FloatPoint const&, FloatPoint const&, Color, float thickness = 1, Painter::LineStyle style = Painter::LineStyle::Solid, Color alternate_color = Color::Transparent);
void draw_line_for_path(FloatPoint const&, FloatPoint const&, Color, float thickness = 1, Painter::LineStyle style = Painter::LineStyle::Solid, Color alternate_color = Color::Transparent);
enum class LineLengthMode {
// E.g. A line from 0,1 -> 2,1 is 3px long
PointToPoint,
// E.g. A line from 0,1 -> 2,1 is 2px long
Distance
};
void draw_line(FloatPoint const&, FloatPoint const&, Color, float thickness = 1, Painter::LineStyle style = Painter::LineStyle::Solid, Color alternate_color = Color::Transparent, LineLengthMode line_length_mode = LineLengthMode::PointToPoint);
void draw_line_for_path(FloatPoint const&, FloatPoint const&, Color, float thickness = 1, Painter::LineStyle style = Painter::LineStyle::Solid, Color alternate_color = Color::Transparent, LineLengthMode line_length_mode = LineLengthMode::PointToPoint);
void draw_line_for_fill_path(FloatPoint const& from, FloatPoint const& to, Color color, float thickness = 1)
{
draw_line_for_path(from, to, color, thickness, Painter::LineStyle::Solid, Color {}, LineLengthMode::Distance);
}
void fill_path(Path&, Color, Painter::WindingRule rule = Painter::WindingRule::Nonzero);
void stroke_path(Path const&, Color, float thickness);
void draw_quadratic_bezier_curve(FloatPoint const& control_point, FloatPoint const&, FloatPoint const&, Color, float thickness = 1, Painter::LineStyle style = Painter::LineStyle::Solid);
@ -81,8 +93,10 @@ private:
Yes,
No,
};
template<FixmeEnableHacksForBetterPathPainting path_hacks>
void draw_anti_aliased_line(FloatPoint, FloatPoint, Color, float thickness, Painter::LineStyle style, Color alternate_color);
void draw_anti_aliased_line(FloatPoint, FloatPoint, Color, float thickness, Painter::LineStyle style, Color alternate_color, LineLengthMode line_length_mode = LineLengthMode::PointToPoint);
void stroke_segment_intersection(FloatPoint const& current_line_a, FloatPoint const& current_line_b, FloatLine const& previous_line, Color, float thickness);
Painter& m_underlying_painter;

4
Userland/Libraries/LibGfx/FillPathImplementation.h
View file

@ -47,8 +47,8 @@ void fill_path(Painter& painter, Path const& path, Color color, Gfx::Painter::Wi
using GridCoordinateType = Conditional<fill_path_mode == FillPathMode::PlaceOnIntGrid, int, float>;
using PointType = Point<GridCoordinateType>;
auto draw_line = [&](auto... args) {
if constexpr (requires { painter.draw_line_for_path(args...); })
painter.draw_line_for_path(args...);
if constexpr (requires { painter.draw_line_for_fill_path(args...); })
painter.draw_line_for_fill_path(args...);
else
painter.draw_line(args...);
};