The original method just selected the first encountered vertex in some
epsilon-neighborhood of the mouse cursor. Now the closest one is
picked. This is done in O(number_of_vertices) and could be someday
improved by more efficient nearest neighbor using k-d tree.

Add edit/copy/delete actions to menu, so that their shortcuts are
available as well.

Copy line/fill color when duplicating shapes.

Fix off by one error in double click event handler and refactor closing
and finalising code.

The closed attribute of the new shape was not copied

Move the copied shape slightly, so that it stands out.

Undo close and Delete shape were partially broken.

Mostly working, vertex highlighting needs a bit of tweaking. The code
could use a refactoring as well.

Also change the way vertices are drawn (fill color).

Remove some duplicated code.

Also switch to round nodes, they seem more appealing.

Bound movement of shapes inside the pixmap area. Movement could be a bit
more accurate, but it currently breaks bounding.

Refactor some of the shape and main window code accordingly.

context menu , copy , delete and add new shape

Draw the image in the same painter as the shapes.

Center the image inside the widget and transform the painter so that any
drawing is done relative to the pixmap, and any scaling is applied to both.

Added the code to do that in canvas
Added select shape , when the user click on any shape it's choosen and the outline becomes white
(done that in canavas and shape)

Make point shape and size class variables, so that changing them will
affect all shapes.

Re-add the last point when double clicking, so that it is consistent
with the point list created normally, and because it is also used to
when checking if a path is closed.

small change in canvas

This approach seems much cleaner and more intuitive than the previous
one.

Take the opportunity to refactor the code.