Re: [gtkmm] configure_event in drawing area

[Daniel <dss home se>]

> AFAIK, GtkNotebook will only realize widgets that are to be shown, in
> order to speed up the display of the whole widget[1]. This would lead to
> the problem you seem to have, as on_configure_event will only be called
> *after* you click on the "Drawing Area" tab.
>

Yes this is my problem. I want to be able to draw to the pixmap before it is shown to the user for the first time (think about a couple of different plots in a notebook, the user might or might not look at all of them). I would like to modify my code so that I can draw to the pixmap before on_configure_event...
 
> If the drawing you have to perform in add_line is relatively light, you
> could perform it directly in the expose handler. If it is computationally
> intensive, you should set some defaults (for example in the default size
> of the draing area) and create your pixmap based on them.
> 

I want to draw to the pixmap in the add_line-functions since it depends on pretty heavy calculations (an external program is executed and data is read from a file).

> If the user resizes the window, the pixmap will be recreated, losing all
> its contents. Are you prepared to redraw all the pixmap contents?
> 
> As an aside note, if you want to receive Expose events on the drawing
> area, you will need to modify your constructor to be
>     MyDrawingArea() {add_events(Gdk::EXPOSURE_MASK);};
> 

I used a drawingarea in several applications without this. Why is this important? Shouldn't it be in the example then?

> Also, note that many of the default GCs will not do what you want, as they
> will be set/modified by themes.
> 
> Also, consider initializing the newly created pixmap to some color, as
> it may contain junk.
>

The attached file was just an example to illustrate the segfault. However, the GC-initalization stuff is from my program. I would like to do this the proper way but it is difficult to find information on how to do this.

/Daniel
 
> Tassos
> [1] Note that notebooks are notorious for having many subwidgets, think
>     property dialogs or preferences.
> 
> -- 
> Bassoukos Tassos   +30 31 996011 / +30 93 7109954       IT Generalist
> 
> Unix:        Your gun, Your bullet, Your foot, Your choice.
> M$-CE/ME/NT: Same as Unix, BUT: No choice, and We Aim Higher.
>                          -- From the Linux S/390 mailing list
> 
>