Bugs: undo & redo

The bug depends on what attributes are changed.

chips-1> x = 10**np.linspace(-1,1,20)
chips-2> y = x**2
chips-3> add_curve(x, y)
chips-4> get_plot_range()
         [-0.395, 10.495, -4.9895000000000005, 104.9995]
chips-5> log_scale(X_AXIS)
chips-6> get_plot_range()
         [0.07943282347242815, 12.589254117941673, -4.9895000000000005, 104.9995]
chips-7> set_axis(["pad", 0])
chips-8> get_plot_range()
         [0.1, 10.0, 0.010000000000000002, 100.0]
chips-9> undo()
chips-10> get_plot_range()
          [0.1, 10.0, 0.010000000000000002, 100.0]

The plot and ranges have not been reverted to the state at line chips-6. Calling log_scale on the axis again fixes up the plot:

chips-11> log_scale(X_AXIS)
chips-12> get_plot_range()
          [0.07943282347242815, 12.589254117941673, -4.9895000000000005, 104.9995]

If an undo buffer block is nested in another undo buffer block and the inside block ends with a discard_undo_buffer, but the outside block ends with a close_undo_buffer, the discard_undo_buffer will not clear out the commands from the inside block. The inside block will be executed.

However, to increase speed the contents of the chips window are not refreshed. So while nothing is drawn to the window, if the window is obscured by another window, the obscured pixels are lost and will not be refreshed if the obscured part is made visible again. That part of the chips window will be black.

Calling undo after deleting a window which had its redraw parameter set to False will re-create the window but display all its contents on screen.