[Gambas-user] Clearing data from TextAreas & ListBoxes

[Tobias Boege]

On Mon, 02 Mar 2015, John Rose wrote:
> On 02/03/15 19:25, Tobias Boege wrote:
> > On Mon, 02 Mar 2015, John Rose wrote:
> >> I have a Click event on a Button. At runtime, clicking the button should
> >> cause clearing of the data from a TextArea & some ListBoxes. There's no
> >> way this 'clearance' cannot be executed as the Exec of a CL program
> >> (which definitely happens because it populates these controls) soon
> >> follows it. However, it doesn't seem to do so. Clearance coding:
> >> With StopListBox
> >>     .Clear
> >>     .Refresh
> >>   End With
> >>   With SteckersListBox
> >>     .Clear
> >>     .Refresh
> >>   End With
> >>   With ReflectorListBox
> >>     .Clear
> >>     .Refresh
> >>   End With
> >>   With RotorsListBox
> >>     .Clear
> >>     .Refresh
> >>   End With
> >>   With DetailTextArea
> >>     .Clear
> >>     .Refresh
> >>   End With
> >>
> >> Is the above the correct method of causing the clearance to happen on
> >> the screen immediately?
> >>  
> > That last word is important. Controls are refreshed during the event loop
> > which you can think of as the pause mode of the interpreter: it enters it
> > when there is no Gambas code to execute at present. The interpreter sits
> > there waiting for events to happen or does maintenance like redrawing the
> > GUI.
> >
> > You can force the interpreter to look at pending events (and to redraw the
> > controls by the way!) by using the Wait instruction without argument.
> > Calling Refresh() is not necessary here which saves you 3 lines per Clear()
> > call.
> >
> Tobi,
> 
> I changed coding to:
> Public Sub RunButton_Click()
> ...
> StopListBox.Clear
> SteckersListBox.Clear
> ReflectorListBox.Clear
> RotorsListBox.Clear
> DetailTextArea.Clear
> Wait

Here, the controls are cleared.

> ...
> aExecParameters = ["/opt/Enigma/turing_bombe_all_wheels", sMenuPath] 
> 'sMenuPath points to an input file
> pturing_bombe = Exec aExecParameters Wait For Read As "TuringBombeResultsDetail"
> ...
> PopulateListBoxesFromDetailsTextArea
> ...

Here, they are filled again with data from the external process.

> End
> 
> Public Sub TuringBombeResultsDetail_Read()
>   Dim sLine As String
>   Line Input #Last, sLine
>   Print "SO=" & sLine
>   DetailTextArea.Text &= sLine & "\n"
>   Wait
> End
> 
> It still did not clear the displayed contents of those controls. I
> clicked the button once (i.e. when the contents were already clear) and
> it populated the above controls as expected. I clicked the button again
> but it did not clear the DetailTextArea or the ListBoxes immediately.
> The CL program took a few seconds to run and interestingly when it
> finished it did not add to the controls' contents (i.e. it cleared them
> before populating them again). 
> 

Yes, that's precisely what the code above is meant to do, right? First you
clear all the controls, then you start an external process to fill them
anew. If you don't want to refill the controls, don't start the external
process which gives you the new data.

In case I'm misunderstanding here, the best practice seems to me to be:

 [ 0. don't top-post, ]
   1. send a *small* project which shows your problem (with one or two
      controls to clear and a call to "ls" or something),
   2. tell me exactly what you want to achieve

and I'll send you the corrected project, if I can accomplish it.

Regards,
Tobi

-- 
"There's an old saying: Don't change anything... ever!" -- Mr. Monk