Rip that bandaid off!
This does the following, in one big, awkward jump:
- Replace all uses of `set_main_widget<Foo>()` with the `try` version.
- Remove `set_main_widget<Foo>()`.
- Rename the `try` version to just be `set_main_widget` because it's now
the only one.
The majority of places that call `set_main_widget<Foo>()` are inside
constructors, so this unfortunately gives us a big batch of new
`release_value_but_fixme_should_propagate_errors()` calls.
This PR adds resize ability to PixelPaint as per issue 11862.
The previous behaviour was to always rescale the canvas when
resizing an image. This adds a checkbox to toggle between
rescaling, and resizing which blits the existing canvas to
the top left of the new, resized canvas.
As part of this, a new ScalingMode is added to
LibGfx - None.
