This patch begins the transition away from the global menu towards
per-window menus instead.
The global menu looks neat, but has always felt clunky, and there
are a number of usability problems with it, especially in programs
with multiple windows.
You can now call GUI::Window::set_menubar() to add a menubar to
your window. It will be specific to that one window only.
Tool windows are secondary windows with a smaller title bar. The sit on
the layer above normal windows, and cannot be minimized.
These are intended for complex yet non-modal interactions with the
content of a primary window, such as find/replace windows, property
windows, etc.
We weren't properly handling switching between having a shadow and
not having a shadow when switching themes. This allows an empty string
in the theme configuration for a shadow path, meaning no shadow should
be rendered.
Since theme changes may change geometrics, which are also affected by
window shadows, we need to recompute occlusions as well as re-render
window frames.
We only really need to re-render the simple window shadow when
the size of the frame changes. So, for all other cases only re-render
the window frame without rendering the shadow.
This implements simple window shadows around most windows, including
tooltips. Because this method uses a bitmap for the shadow bits,
it is limited to rectangular window frames. For non-rectangular
window frames we'll need to implement a more sophisticated algorithm.
This only renders the window frame once until the size of the window
changes, or some other event requires re-rendering. It is rendered
to a temporary bitmap, and then the top and bottom part is stored
in one bitmap as well as the left and right part. This also adds
an opacity setting, allowing it to be rendered with a different
opacity.
This makes it easier to enhance window themes and allows using
arbitrary bitmaps with e.g. alpha channels for e.g. shadows.
