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LibWeb: Fix destination bitmap edge clip case in transform painting

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This fixes an edge case, where the destination rect falls partly
outside the painter, so is clipped to a smaller size in
`get_region_bitmap()` (which needs to be accounted for with an extra
offset).
This commit is contained in:
MacDue 2022-09-26 00:01:31 +01:00 • committed by Andreas Kling
parent bbaa05fcf9
commit f6264523b9
1 changed files with 13 additions and 8 deletions
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21
Userland/Libraries/LibWeb/Painting/StackingContext.cpp
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@ -303,12 +303,18 @@ void StackingContext::paint(PaintContext& context) const
// to the size of the source (which could add some artefacts, though just scaling the bitmap already does that).
// We need to copy the background at the destination because a bunch of our rendering effects now rely on
// being able to sample the painter (see border radii, shadows, filters, etc).
Gfx::FloatPoint destination_clipped_fixup {};
auto try_get_scaled_destination_bitmap = [&]() -> ErrorOr<NonnullRefPtr<Gfx::Bitmap>> {
auto bitmap = TRY(context.painter().get_region_bitmap(destination_rect, Gfx::BitmapFormat::BGRA8888, destination_rect));
Gfx::IntRect actual_destination_rect;
auto bitmap = TRY(context.painter().get_region_bitmap(destination_rect, Gfx::BitmapFormat::BGRA8888, actual_destination_rect));
// get_region_bitmap() may clip to a smaller region if the requested rect goes outside the painter, so we need to account for that.
destination_clipped_fixup = Gfx::FloatPoint { destination_rect.location() - actual_destination_rect.location() };
destination_rect = actual_destination_rect;
if (source_rect.size() != transformed_destination_rect.size()) {
bitmap = TRY(bitmap->scaled(
static_cast<float>(source_rect.width()) / transformed_destination_rect.width(),
static_cast<float>(source_rect.height()) / transformed_destination_rect.height()));
auto sx = static_cast<float>(source_rect.width()) / transformed_destination_rect.width();
auto sy = static_cast<float>(source_rect.height()) / transformed_destination_rect.height();
bitmap = TRY(bitmap->scaled(sx, sy));
destination_clipped_fixup.scale_by(sx, sy);
}
return bitmap;
};
@ -318,13 +324,12 @@ void StackingContext::paint(PaintContext& context) const
return;
auto bitmap = bitmap_or_error.release_value_but_fixme_should_propagate_errors();
Gfx::Painter painter(bitmap);
painter.translate(-paintable().absolute_paint_rect().location().to_rounded<int>());
painter.translate((-paintable().absolute_paint_rect().location() + destination_clipped_fixup).to_rounded<int>());
auto paint_context = context.clone(painter);
paint_internal(paint_context);
// NOTE: If the destination and source rects are the same size, we round the source rect to ensure that it's pixel-aligned.
if (transformed_destination_rect.size() == source_rect.size())
context.painter().draw_scaled_bitmap(destination_rect, *bitmap, bitmap->rect(), opacity);
if (destination_rect.size() == bitmap->size())
context.painter().blit(destination_rect.location(), *bitmap, bitmap->rect(), opacity);
else
context.painter().draw_scaled_bitmap(destination_rect, *bitmap, bitmap->rect(), opacity, Gfx::Painter::ScalingMode::BilinearBlend);
} else {