Vanishing label
lazarus / 31-LCL

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timppl · 2014-01-17 07:19

Hi all

There appears to be a bug in the attached project.

There are 2 labels in a TGroupBox. Both labels are AutoSize = True;

When the caption of Label3 is changed, the label disappears. However
if the commented out code in the function Button1MouseUp is enabled
then Label3 works correctly.

The code works correctly with Lazarus 1.0.14 ( FPC 2.6.2 ) but does
not work with  Lazarus 1.2RC2  ( FPC 2.6.2 ) or with Lazarus 1.3  (
FPC 2.7.1 )

It is possible that I have done something stupid, but if it is really
a bug I will put it on Mantis

Regards

Tim

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howardpc · 2014-01-17 08:34

As far as I can see your code accomplishes exactly what you specify:
when the button is clicked you set label3's caption to a new value
which is correctly displayed, irrespective of Label1's caption value.
I see no difference with different Lazarus versions. No bug at all (at
least on Win32, the only platform I tested).

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wp · 2014-01-17 10:00

Maybe you are concerned about the labels vanishing while the mouse
button is pressed. Use the OnClick event of the button to get an
immediate response.

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timppl · 2014-01-20 07:08

Thanks for the replies

What concerns me is that on linux/gtk2, this line
Code: [Select]Label3.Caption:='RefreshedLabel';
does not work if it is the last item in the method.

@WP If I use On click the problem is still there. The caption of
label3 does not display.  

If Label3 is set to Autosize:= False then Label3 works correctly.

So to restate the steps to see the different behaviour of Label3

1)  Compile and run the project 
2) Click the 'Change Text' button  -  Label3 caption does not display

3)  Set Autosize to False ( you may need to resize the label to
display its initial caption correctly )
4) Compile and run the project
5) Click the 'Change Text' button  -  Label3 caption shows correctly
i.e 'Refreshed Label'

An alternative way of showing the problem is to set the colour of
Label3 without changing anything else in the project.  When the
'Change Text' button is clicked the label is no longer visible.

@Howardpc  As you said, it works correctly on windows, the problem
appears to be with gtk2 on linux, and only with versions of lazarus
from 1.2RC2 onwards ie the code perform identically on windows and
linux with Lazarus 1.0.14 ( fpc 2.6.2 )  but performs differently with
lazarus 1.2RC ( fpc 2.6.2 ) and 1.3 ( fpc 2.7.1 )

Regards

Tim

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Martin_fr · 2014-01-20 12:13

I can reproduce it on gtk2 indeed (only tested with current 1.3 / not
tested 1.0.14)

Please report, and mention it is a regression.

I also noted, that the designer shows "shadows" of the selection
indicators. (see image, only the ONE label is selected). Do you get
those too?

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timppl · 2014-01-21 07:55

Thanks Martin_fr

I have reported it on Mantis.

I have just had a look and I dont seem to be able to get the shadowed
selection indicators.

Regards

Tim