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LibGfx: Clip path rasterizer scanlines sooner

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This moves the clipping from per-pixel/draw command to a step before
the main drawing/plotting loop.
This commit is contained in:
MacDue 2024-01-06 13:45:45 +00:00 • committed by Andreas Kling
parent b1adabdac4
commit e2152a5b3d
2 changed files with 77 additions and 37 deletions
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83
Userland/Libraries/LibGfx/EdgeFlagPathRasterizer.cpp
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@ -235,6 +235,8 @@ Color EdgeFlagPathRasterizer<SamplesPerPixel>::scanline_color(int scanline, int
[&](auto& function) {
return function({ offset, scanline });
});
if (color.alpha() == 255)
return color.with_alpha(alpha);
return color.with_alpha(color.alpha() * alpha / 255);
}
@ -298,21 +300,21 @@ Detail::Edge* EdgeFlagPathRasterizer<SamplesPerPixel>::plot_edges_for_scanline(i
}
template<unsigned SamplesPerPixel>
void EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_even_odd_scanline(EdgeExtent edge_extent, auto sample_callback)
auto EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_even_odd_scanline(EdgeExtent edge_extent, auto init, auto sample_callback)
{
SampleType sample = 0;
SampleType sample = init;
for (int x = edge_extent.min_x; x <= edge_extent.max_x; x += 1) {
sample ^= m_scanline[x];
sample_callback(x, sample);
m_scanline[x] = 0;
}
return sample;
}
template<unsigned SamplesPerPixel>
void EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_non_zero_scanline(EdgeExtent edge_extent, auto sample_callback)
auto EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_non_zero_scanline(EdgeExtent edge_extent, auto init, auto sample_callback)
{
SampleType sample = 0;
WindingCounts sum_winding = {};
NonZeroAcc acc = init;
for (int x = edge_extent.min_x; x <= edge_extent.max_x; x += 1) {
if (auto edges = m_scanline[x]) {
// We only need to process the windings when we hit some edges.
@ -320,64 +322,81 @@ void EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_non_zero_scanline(EdgeE
auto subpixel_bit = 1 << y_sub;
if (edges & subpixel_bit) {
auto winding = m_windings[x].counts[y_sub];
auto previous_winding_count = sum_winding.counts[y_sub];
sum_winding.counts[y_sub] += winding;
auto previous_winding_count = acc.winding.counts[y_sub];
acc.winding.counts[y_sub] += winding;
// Toggle fill on change to/from zero.
if (bool(previous_winding_count) ^ bool(sum_winding.counts[y_sub]))
sample ^= subpixel_bit;
if (bool(previous_winding_count) ^ bool(acc.winding.counts[y_sub]))
acc.sample ^= subpixel_bit;
}
}
}
sample_callback(x, sample);
sample_callback(x, acc.sample);
m_scanline[x] = 0;
m_windings[x] = {};
}
return acc;
}
template<unsigned SamplesPerPixel>
template<Painter::WindingRule WindingRule, typename Callback>
void EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_scanline(EdgeExtent edge_extent, Callback callback)
auto EdgeFlagPathRasterizer<SamplesPerPixel>::accumulate_scanline(EdgeExtent edge_extent, auto init, Callback callback)
{
if constexpr (WindingRule == Painter::WindingRule::EvenOdd)
accumulate_even_odd_scanline(edge_extent, callback);
return accumulate_even_odd_scanline(edge_extent, init, callback);
else
accumulate_non_zero_scanline(edge_extent, callback);
return accumulate_non_zero_scanline(edge_extent, init, callback);
}
template<unsigned SamplesPerPixel>
void EdgeFlagPathRasterizer<SamplesPerPixel>::write_pixel(Painter& painter, int scanline, int offset, SampleType sample, auto& color_or_function)
void EdgeFlagPathRasterizer<SamplesPerPixel>::write_pixel(BitmapFormat format, ARGB32* scanline_ptr, int scanline, int offset, SampleType sample, auto& color_or_function)
{
if (!sample)
return;
auto dest = IntPoint { offset, scanline } + m_blit_origin;
if (!m_clip.contains_horizontally(dest.x()))
return;
auto dest_x = offset + m_blit_origin.x();
auto coverage = SubpixelSample::compute_coverage(sample);
auto paint_color = scanline_color(scanline, offset, coverage_to_alpha(coverage), color_or_function);
painter.set_physical_pixel(dest, paint_color, true);
scanline_ptr[dest_x] = color_for_format(format, scanline_ptr[dest_x]).blend(paint_color).value();
}
template<unsigned SamplesPerPixel>
void EdgeFlagPathRasterizer<SamplesPerPixel>::fast_fill_solid_color_span(Painter& painter, int scanline, int start, int end, Color color)
void EdgeFlagPathRasterizer<SamplesPerPixel>::fast_fill_solid_color_span(ARGB32* scanline_ptr, int start, int end, Color color)
{
auto dest_y = scanline + m_blit_origin.y();
auto start_x = max(m_clip.left(), start + m_blit_origin.x());
auto end_x = min(m_clip.right() - 1, end + m_blit_origin.x());
if (start_x > end_x)
return;
auto* dest_ptr = painter.target()->scanline(dest_y) + start_x;
fast_u32_fill(dest_ptr, color.value(), end_x - start_x + 1);
auto start_x = start + m_blit_origin.x();
auto end_x = end + m_blit_origin.x();
fast_u32_fill(scanline_ptr + start_x, color.value(), end_x - start_x + 1);
}
template<unsigned SamplesPerPixel>
template<Painter::WindingRule WindingRule>
void EdgeFlagPathRasterizer<SamplesPerPixel>::write_scanline(Painter& painter, int scanline, EdgeExtent edge_extent, auto& color_or_function)
{
// Handle scanline clipping.
auto left_clip = m_clip.left() - m_blit_origin.x();
auto right_clip = m_clip.right() - m_blit_origin.x() - 1;
EdgeExtent clipped_extent { max(left_clip, edge_extent.min_x), min(right_clip, edge_extent.max_x) };
if (clipped_extent.min_x > clipped_extent.max_x) {
// Fully clipped. Unfortunately we still need to zero the scanline data (before the right clip).
EdgeExtent zero_extent { edge_extent.min_x, clipped_extent.max_x };
zero_extent.memset_extent(m_scanline.data(), 0);
if constexpr (WindingRule == Painter::WindingRule::Nonzero)
zero_extent.memset_extent(m_windings.data(), 0);
return;
}
// Accumulate non-visible section (without plotting pixels).
auto acc = accumulate_scanline<WindingRule>(EdgeExtent { edge_extent.min_x, left_clip - 1 }, initial_acc<WindingRule>(), [](int, SampleType) {
// Do nothing!
});
// Get pointer to current scanline pixels.
auto dest_format = painter.target()->format();
auto dest_ptr = painter.target()->scanline(scanline + m_blit_origin.y());
// Simple case: Handle each pixel individually.
// Used for PaintStyle fills and semi-transparent colors.
auto write_scanline_pixelwise = [&](auto& color_or_function) {
accumulate_scanline<WindingRule>(edge_extent, [&](int x, SampleType sample) {
write_pixel(painter, scanline, x, sample, color_or_function);
accumulate_scanline<WindingRule>(clipped_extent, acc, [&](int x, SampleType sample) {
write_pixel(dest_format, dest_ptr, scanline, x, sample, color_or_function);
});
};
// Fast fill case: Track spans of solid color and set the entire span via a fast_u32_fill().
@ -387,20 +406,20 @@ void EdgeFlagPathRasterizer<SamplesPerPixel>::write_scanline(Painter& painter, i
return write_scanline_pixelwise(color);
constexpr SampleType full_converage = NumericLimits<SampleType>::max();
int full_converage_count = 0;
accumulate_scanline<WindingRule>(edge_extent, [&](int x, SampleType sample) {
accumulate_scanline<WindingRule>(clipped_extent, acc, [&](int x, SampleType sample) {
if (sample == full_converage) {
full_converage_count++;
return;
} else {
write_pixel(painter, scanline, x, sample, color);
write_pixel(dest_format, dest_ptr, scanline, x, sample, color);
}
if (full_converage_count > 0) {
fast_fill_solid_color_span(painter, scanline, x - full_converage_count, x - 1, color);
fast_fill_solid_color_span(dest_ptr, x - full_converage_count, x - 1, color);
full_converage_count = 0;
}
});
if (full_converage_count > 0)
fast_fill_solid_color_span(painter, scanline, edge_extent.max_x - full_converage_count + 1, edge_extent.max_x, color);
fast_fill_solid_color_span(dest_ptr, clipped_extent.max_x - full_converage_count + 1, clipped_extent.max_x, color);
};
switch_on_color_or_function(
color_or_function, write_scanline_with_fast_fills, write_scanline_pixelwise);