Disabling keyboard focus for a control (TButton especially)?
lazarus / 31-LCL

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dahaiou · 2012-07-27 09:58

Is it possible to disable focus for a control (TButton especially)?

I have already set Tabstop := False for all these buttons,
and it works in the sense that they are passed over when
the Tab-key is pressed.

But when I use the arrow-keys, it seems these buttons still
receive focus, and the button faces are annoyingly focus-
highlighted one after the other as I keep hitting an arrow key.

I am using the arrows for specific things in the program and
have them intercepted by the main form. This is working as
I want, but it's unrelated to the buttons on the form, and
I don't want to see them flickering as I press the arrows.

There is a TabOrder property that holds an Integer value.
I was trying to take the buttons out of the TabOrder
sequence entirely by setting this to an empty string
but the IDE won't allow it. I might be missing something
vary basic here (?).

Note: There is no problem with the functionality of the
buttons as such. I am intercepting the enter-key as well
and a button press is never generated from the keyboard.
It's just the annnoying highlighting I need to get rid of.

How can I prevent it?

PS. In case it matters, I am using Lazarus 0.9.30.4/32bit under
Win7-64.

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dahaiou · 2012-07-27 12:38

An afterthought: If focus cannot be disabled, just disabling the
hightlighting would do too.

Is this a tough one perhaps, since no-one has come up with anything?
Any ideas?

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Zoran · 2012-07-27 13:00

I don't know if it can be done.
Anyway, the workaround for you is using TSpeedButton instead of
TButton controls. TSpeedButton does not descend from TWinControl, so
it never receives focus.

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dahaiou · 2012-07-27 14:31

Thanks, I changed them all to TSpeedButton and it seems to do the
trick.
No more highlighting.

Only thing that happens now, when I use the Up/Down arrow keys, is
that once in a while all these buttons flicker briefly, like they are
redrawn for no reason.

I guess this might be an effect of the parent TGroupBox receiving
focus. This is a smaller nuisance than the highlighting though. And
it's only happening with the Up/Down arrow keys, not Left/Right.
Strange.

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CM630 · 2017-03-16 10:03

A few years later- maybe there is already asolution for that?
I want to fully disable changing focus with the arrows on the form
components.
Maybe I could put something in the OnKeyDown event of the form (I have
keypreview enabled).

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Zoran · 2017-03-16 11:03

Quote from: CM630 on March 16, 2017, 11:03:27 am
A few years later- maybe there is already asolution for that?
I want to fully disable changing focus with the arrows on the form
components.
Maybe I could put something in the OnKeyDown event of the form (I have
keypreview enabled).

To disable changing focus only with arrows set Form1.KeyPreview to
True and Form1.OnKeyDown to this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState 
);begin  if Key in [VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN] then    Key :=
0;end; 
The focus will still change with Tab. If you want to disable tab as
well, add VK_TAB in the set.

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CM630 · 2017-03-16 13:11

Thanks, it works!
I only changed it to if (Key >36) and (key <41) then  Key := 0;
because VK_ requred uses  ... windows... which causes some problems.

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Zoran · 2017-03-16 20:21

Quote from: CM630 on March 16, 2017, 02:11:55 pmThanks, it works!
I only changed it to if (Key >36) and (key <41) then  Key := 0;
because VK_ requred uses  ... windows... which causes some problems.
No, VK constants can be found in LCLType unit.
There is even a FAQ about it
http://wiki.lazarus.freepascal.org/Lazarus_Faq#Virtual_key_constants

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Thaddy · 2017-03-16 20:30

Correct. I often wonder why people never read documentation.