SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
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.
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.
