`Shift + Return` was not compatible with the ibusCandidatePopup.
So the only way to "validate" a text element is to click outside the text area.
Related to #56.
* Can browse and break lines anywhere
* Can past multi-line texts
* Do not need lineIndex anymore and grouped lines are preserved permanently
Related to #56
The drawing area is now a container and the layers are the proper drawing widgets. There is a separated layer for the current element so only the current element is redisplayed when drawing.
* Handle stage key events only when the area is reactive. Any reason to handle key events in other cases?
* Move `Escape` key handling to the stage `key-press-event` handler. So leaving the drawing mode with `Escape` is still possible when the overview mode has been entered inadvertently.
* "Undo(Redo) last brushstroke" -> "Undo(Redo)".
* Sync `_updateActionSensitivity` menu method with the new undo/redo behavior.
* Smooth button action is no longer destructive.
* Clean undone smooth transformations when doing a new smooth transformation.
The `undoable` transformation property is not preserved when the element is "stringified". So transformations cannot be undone, once the element is loaded from JSON.
Add intermediate points to make quick free drawings smoother.
Do not redisplay the area at this step (crashes).
Use device.get_coords rather than global.get_pointer because the later return rounded (floor) values.
Fix#45.
With old GS/GJS, some GType names were generated from class names without sanitizing it (e.g. Menu.ActionButton).
Instead of defining all GType names, sanitize all class name as it was GType name, and let GJS generated GType name securely when it is necessary.
Fix#46.
* Take scale factor into account.
* Put it in '_onMenuOpenStateChanged' so the max-height will be updated if the monitor size change.
See PanelMenu.Button.
abakkk
O. Giesmann