[changeset] - improve clf() compatibility

[John W. Eaton]

On 21-Oct-2008, David Bateman wrote:

| There are also other issues related to hidden children such as the 
| "BaseLine" of stem series, etc that cause issues with the "legend" 
| function as they aren't currently invisible.. So yes, I'd also like to 
| see this issue addressed. Could you give more information about what 
| exactly doesn't work with your patch?

This appears to work properly:

  octave:1> get (gca (), "children")
  ans = [](0x1)
  octave:2> h = allchild (gca ())
  h =

    -5.4293
    -4.2588
    -3.3136
    -2.2985

  octave:3> get (h, "type")
  ans =

  {
    [1,1] = text
    [1,2] = text
    [1,3] = text
    [1,4] = text
  }

But the first example from "rundemos plot" fails with the following
error:

  /home/jwe/src/octave/scripts/plot/axis.m example 1: failed
  get: invalid handle (= -3.2606)
  error: get: invalid handle (= -2.92254)
  error: called from:
  error:   /home/jwe/src/octave/scripts/plot/__go_draw_axes__.m at line 77, column 9
  error:   /home/jwe/src/octave/scripts/plot/__go_draw_figure__.m at line 56, column 8
  error:   /home/jwe/src/octave/scripts/plot/gnuplot_drawnow.m at line 68, column 5
  error: input: reading user-input failed!
  error:   /home/jwe/src/octave/scripts/testfun/demo.m at line 111, column 7
  error:   /home/jwe/src/octave/scripts/testfun/rundemos.m at line 65, column 2
  error:   /home/jwe/src/octave/scripts/testfun/rundemos.m at line 52, column 5

I'll try to take a look at this now.

jwe