Re: file selection interacting with drawing area

["Amadeus W. M." <amadeus84 cablespeed com>]

On Sun, 14 May 2006 11:25:13 -0600, Timothy M. Shead wrote:

> On Sun, 2006-05-14 at 12:42 -0400, Amadeus W. M. wrote:
>> I have an unusual problem. I have a window (MainWindow) which contains a
>> drawing area (Darea) and some buttons. The user can draw various things
>> with the mouse. E.g. a segment is being drawn/updated continuously when
>> the user moves the mouse with button 1 pressed. The final position of the
>> segment is recorded when button 1 is released, so there is an
>> on_Darea_button_release() callback, which also draws the segment.
>> 
>> Enter the file selection dialog. When the user selects a file by
>> double-clicking, the dialog terminates upon the second button PRESS. The
>> event immediately following the second button press is a button RELEASE,
>> but that's now caught by the Darea, because the file selector is gone.
>> Bad things happen: the Darea, of course, tries to store and draw a segment,
>> because on_Darea_button_release() has been called.
>> 
>> What do I do?
>> 
>> I'm thinking about introducing a
>> 
>> bool loading_file;
>> 
>> which is set to 1 when the file chooser is being popped up,
>> and inspected within on_Darea_button_release(): only draw/store the
>> segment if and only if loading_file=0; if loading_file happens to be 1,
>> set it to 0. Something like this:
>> 
>> bool on_Darea_button_release(GdkEventButton * ev)
>> {
>> 
>>     if(loading_file){
>>        loading_file=0;
>>        return 0;
>>     }
>> 
>>     // if we've survived...
>> 
>>     // set the segment from ev->x, ev->y.
>>     Darea.queue_draw(); 
>>     return 0;
>> }
>> 
>> This seems awkward and prone to error though. Is there a more natural/Gtk
>> way?
> 
> I wouldn't make this conditional on the file dialog, since other
> dialog(s) added later may cause the same problem.  

That's exactly why I didn't like it.

You just need to keep
> track of whether you caught a button press event, and ignore the button
> release if you didn't - add an on_Darea_button_press() handler and set a
> flag there - then test it in on_Darea_button_release().
> 

Yes, it's more robust to set the bool flag to 1 in
on_Darea_button_press_event(), rather than make it contingent upon the
file selection dialog. Then, in on_Darea_button_release_event(), just
return if the flag is not 1. But I can't avoid the flag thing, can I?

Thanks!