interactively adding text annotations to Qt plots

[John W. Eaton]

With the following changeset

  http://hg.savannah.gnu.org/hgweb/octave/rev/908b68a98ba6

I sketched out an implementation of handling interactive text 
annotations in the Qt plotting widget.  It seems to work OK but it is 
limited.  There is no way to specify multi-line text, fonts, alignment, 
colors, etc.  Instead of a simple QInputDialog, we need a custom dialog 
box that allows all the properties for a text annotation object to be 
set interactively.  These are:

  position:

    4-element vector [x0, y0, width, height], defaults for x0 and y0 
are the position of the mouse click.  The width and the height can be 
anything since "fitboxtotext" is true by default.

  units:

    Only use if position is specified.  If taking the position from the 
mouse click coordinates, then use the default "normalized" units.

  backgroundcolor, edgecolor, linestyle, linewidth:

    Customize the box background color and edges appearance.

  font... properties, horizontalalignment, verticalalignment:

    Properties for the text itself.

  fitboxtotext:

    Control the size of the box.  If "on" (the default) the box limits 
are fit to the text extent.


I could use some help with creating this dialog.  Perhaps there is a 
simple way to do this job that I'm not aware of?  Any help would be 
greatly appreciated.

jwe