We only called `get_bitmap_pixels` when creating a `BitmapData`
for an SWF-provided `Bitmap`. We now store the initial pixels
in `Character::Bitmap`, and use them to initialize a `BitmapData`
when needed.
This lets us simplify the wgpu backend, which no longer needs
to store a `Bitmap` object. In addition to saving space for
`BitmapData` objects that lack an SWF `Bitmap`, this will make
it easier to move data from `bitmap_registry` into `BitmapHandle`
itself.
Currently, we rely on ShapeTessellator being able to get a BitmapHandle
without a RenderBackend. With the upcoming BitmapData refactor,
we will always need a RenderBackend to get a BitmapHandle, which creates
borrow-checker issues in ShapeTessellator (which is stored in a
RenderBackend).
To solve this, we split BitmapSource.bitmap into two methods -
BitmapSource.bitmap and BitmapSource.bitmap_handle. ShapeTessellator
continues to use BitmapSource.bitmap, and uses the u16 bitmap id
instead of a BitmapHandle. The BitmapSource.bitmap_handle method
is used inside each render backend to convert the id to a BitmapHandle,
avoiding borrow-checker issues.
This PR fixes a numbe of interconnected bugs:
* We weren't consistently uploading a dirty BitmapData to the render
backend before drawing to/from it.
* BitmapData.draw should *not* add a fill color - it should draw over
the current contents of the BitmapData
* After drawing to a non-transparent BitmapData, we need to manually
set the opacity back to 255 for each pixel (the drawing process
takes transparency into account, but the opacity information is
thrown away at the end).