[Gambas-user] Paint misbehaves on QT when a ValueBox.value is changed (v3.5.4)

[T Lee Davidson]

On 10/18/2014 04:06 PM, Benoît Minisini wrote:
>> Well that's a little disappointing that you weren't able to replicate
>> >the issue on your system. On mine, the red line is drawn and then when
>> >it comes time for the blue line to be drawn, the red line disappears as
>> >if the DrawingArea has been cleared. It's a mystery to me.
>> >
>> >But, thank you for looking into it.
>> >
>> >Lee
>> >
> Did the 3.6 version fix your probelm or not?
>
> -- Benoît Minisini

I was curious about that too, Benoît. And, it was the first thing I 
tested after getting 3.6 installed. I didn't report my findings, because 
I had no idea that you would have remembered. But you did! :-)

Did 3.6 fix the problem?

Partially. DrawingArea.Clear now works with both QT4 and GTK(2).

But I still need to call DrawingArea.Show to get the drawing to display 
properly after any modification of a TextBox or ValueBox control's Value 
property. (Note: DrawingArea.Cache = True)

Just FYI: If I wrap each line draw in a Paint.Begin/End structure, the 
first line will be displayed until the second line's Paint.End is 
called. As so in pseudo-code:
Paint.Begin
   Draw red line
Paint.End
Modify ValueBox.Value
Paint.Begin
   Draw blue line
Paint.End 'The red line disappears here and blue line is not displayed

If I do not wrap each line in its own block as in:
Paint.Begin
   Draw red line
   Modify ValueBox.Value
   Draw blue line
Paint.End

then nothing is displayed unless I call DrawingArea.Show after Painting.

I can provide a project if you wish, but I think calling 
DrawingArea.Show is a very workable solution.

And, thank you for remembering.


-- 
Lee
__________

"Artificial Intelligence is no match for natural stupidity."