The button bevel was rendered upside down, which happens due to some
weird double y-axis inversion, which goes away when passing the QWidget
pointer to the style. When using the Qt backend, we can do that.
When the PM_LayoutHorizontalSpacing pixel metric is negative, we're supposed to call
layoutSpacing() on the style. Until we have a detailed
overview over the controls, a default spacing is better than -1 :-)
Set QStyle::State_Active conditional to whether the window is active,
which maps to Qt's active window concept and winit's has-focus (until we
render popups differently).
We apply a default window background from the palette to all `Window`
elements, and likewise we need to apply the default text color to Text
elements to ensure a readable contrast.
This also fixes the default text color when using Qt/native style in
dark mode on macOS.
* Change SharedVector::as_mut_slice() to SharedVector::make_mut_slice()
* SharedPixelBuffer::as_mut_slice and SharedPixelBuffer::make_mut_slice()
* SharedPixelBuffer::as_bytes_mut() to SharedPixelBuffer::make_mut_bytes()
This is consistent with Rc::make_mut() and is supposed to emphasize
that, unlike the usual as_* operations, it is not a free operation but
may involve work (detaching the data by cloning it).
Amends commit 7384ebdc32
