Currently, in CPU painter, border painting is implemented by building
a Gfx::Path that is filled by Gfx::AntiAliasingPainter. In the GPU
painter, we will likely want to do something different, and with a
special command, it becomes possible.
Also, by making this change, the CPU executor also benefits because now
we can skip building paths for borders that are out of the viewport.
The current set of stacking context commands do not encode the
information needed to correctly paint the stacking context, instead,
they're based on the limitations of the current CPU renderer.
Stacking contexts should be able to be transformed by an arbitrary
3D transformation matrix, not just scaled from a source to a destination
rect. The `_with_mask()` stacking context also should not be separate
from the regular stacking context.
```c++
push_stacking_context(
bool semitransparent_or_has_non_identity_transform,
float opacity, Gfx::FloatRect const& source_rect,
Gfx::FloatRect const& transformed_destination_rect,
Gfx::IntPoint const& painter_location);
pop_stacking_context(
bool semitransparent_or_has_non_identity_transform,
Gfx::Painter::ScalingMode scaling_mode);
push_stacking_context_with_mask(
Gfx::IntRect const& paint_rect);
pop_stacking_context_with_mask(
Gfx::IntRect const& paint_rect,
RefPtr<Gfx::Bitmap> const& mask_bitmap,
Gfx::Bitmap::MaskKind mask_kind, float opacity);
```
This patch replaces this APIs with just:
```c++
push_stacking_context(
float opacity,
bool is_fixed_position,
Gfx::IntRect const& source_paintable_rect,
Gfx::IntPoint post_transform_translation,
CSS::ImageRendering image_rendering,
StackingContextTransform transform,
Optional<StackingContextMask> mask);
pop_stacking_context()
```
And moves the implementation details into the executor, this should
allow future backends to implement stacking contexts without these
limitations.
Representing a text run panting command as a vector of glyphs, rather
than as a string simplifies collecting of unique glyphs which is a
prerequisite for `prepare_glyphs_texture()` call.
