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LibGfx: Add fast path to AA line drawing with simple 2D transform

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If the effective 2D transform is just a basic translation, we now simply
translate the underlying painter before & after drawing AA lines.

This avoids all the extra math that otherwise has to happen when mapping
points through an affine transform.

This noticeably increase "mousing around" performance on Wikipedia. :^)
This commit is contained in:
Andreas Kling 2022-04-10 18:41:24 +02:00
parent b4c3882d9c
commit 908d42d0ba
2 changed files with 31 additions and 8 deletions
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35
Userland/Libraries/LibGfx/AntiAliasingPainter.cpp
View file

@ -12,8 +12,8 @@
// Base algorithm from https://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm,
// because there seems to be no other known method for drawing AA'd lines (?)
template<Gfx::AntiAliasingPainter::AntiAliasPolicy policy>
void Gfx::AntiAliasingPainter::draw_anti_aliased_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Gfx::Painter::LineStyle style, Color)
template<Gfx::AntiAliasingPainter::AntiAliasPolicy policy, typename TransformPoint>
void Gfx::AntiAliasingPainter::draw_anti_aliased_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Gfx::Painter::LineStyle style, Color, TransformPoint transform_point)
{
// FIXME: Implement this :P
VERIFY(style == Painter::LineStyle::Solid);
@ -21,8 +21,8 @@ void Gfx::AntiAliasingPainter::draw_anti_aliased_line(FloatPoint const& actual_f
auto corrected_thickness = thickness > 1 ? thickness - 1 : thickness;
auto size = IntSize(corrected_thickness, corrected_thickness);
auto plot = [&](int x, int y, float c) {
auto center = m_transform.map(Gfx::IntPoint(x, y)).to_type<int>();
m_underlying_painter.fill_rect(IntRect::centered_on(center, size), color.with_alpha(color.alpha() * c));
transform_point(x, y, m_transform);
m_underlying_painter.fill_rect(IntRect::centered_on({ x, y }, size), color.with_alpha(color.alpha() * c));
};
auto integer_part = [](float x) { return floorf(x); };
@ -112,14 +112,37 @@ void Gfx::AntiAliasingPainter::draw_anti_aliased_line(FloatPoint const& actual_f
draw_line(actual_from.x(), actual_from.y(), actual_to.x(), actual_to.y());
}
static ALWAYS_INLINE void no_transform(int&, int&, Gfx::AffineTransform const&)
{
}
static ALWAYS_INLINE void full_transform(int& x, int& y, Gfx::AffineTransform const& transform)
{
auto mapped = transform.map(Gfx::IntPoint { x, y });
x = mapped.x();
y = mapped.y();
}
void Gfx::AntiAliasingPainter::draw_aliased_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Gfx::Painter::LineStyle style, Color alternate_color)
{
draw_anti_aliased_line<AntiAliasPolicy::OnlyEnds>(actual_from, actual_to, color, thickness, style, alternate_color);
if (m_transform.is_identity_or_translation()) {
m_underlying_painter.translate(m_transform.e(), m_transform.f());
draw_anti_aliased_line<AntiAliasPolicy::OnlyEnds>(actual_from, actual_to, color, thickness, style, alternate_color, no_transform);
m_underlying_painter.translate(-m_transform.e(), -m_transform.f());
} else {
draw_anti_aliased_line<AntiAliasPolicy::OnlyEnds>(actual_from, actual_to, color, thickness, style, alternate_color, full_transform);
}
}
void Gfx::AntiAliasingPainter::draw_line(FloatPoint const& actual_from, FloatPoint const& actual_to, Color color, float thickness, Gfx::Painter::LineStyle style, Color alternate_color)
{
draw_anti_aliased_line<AntiAliasPolicy::Full>(actual_from, actual_to, color, thickness, style, alternate_color);
if (m_transform.is_identity_or_translation()) {
m_underlying_painter.translate(m_transform.e(), m_transform.f());
draw_anti_aliased_line<AntiAliasPolicy::Full>(actual_from, actual_to, color, thickness, style, alternate_color, no_transform);
m_underlying_painter.translate(-m_transform.e(), -m_transform.f());
} else {
draw_anti_aliased_line<AntiAliasPolicy::Full>(actual_from, actual_to, color, thickness, style, alternate_color, full_transform);
}
}
void Gfx::AntiAliasingPainter::fill_path(Path& path, Color color, Painter::WindingRule rule)