COMBOBOX tip..

[Jules Marchildon]

Borje;

Yes, I understand the trade-offs between the standard control and the
extended control w/wo OwnerDraw, but just wanted to add one more point...

ComboBoxEx have same problem, it triggers last
selection when one tries to ignore.

If you are trapping the old messages via WM_COMMAND then yes, same
problem exist. But using the new messages via WM_NOTIFY, the %CBEN_ENDEDIT
will allow you to look at the NMCBEENDEDIT structure member .iWhy for
either of the following values;

CBENF_DROPDOWN
CBENF_ESCAPE
CBENF_KILLFOCUS
CBENF_RETURN

and you can return false to allow the control to display the selected item or
return true to abort the edit selection in the case Esc/Killfocus.

Regards,
Jules

[Borje Hagsten]

ComboBoxEx has nice ability to easily insert images, but still don't
like it. Don't like MS way to draw selection around text only. Can be
confusing for some users.

Better to use ownerdrawn combo and have better control of things. Did
quick test and see that ComboBoxEx have same problem, it triggers last
selection when one tries to ignore.


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[Jules Marchildon]

Borje;

Have you looked at using the ComboBoxEx() from the common controls instead?
This will send a %CBEN_ENDEDIT via %WM_NOTIFY and by using the structure passed
to you, you can determine if you need to return a False to process the notification
or True to ignore it and preserves the last action.

Regards,
Jules

[Borje Hagsten]

Okay, found a working way by looking at coordinates. Could have been so simple,
if only MS had provided the correct info. Found that %CB_GETDROPPEDCONTROLRECT
returns a rect that starts from entire control's top, including edit part - down
to height given at creation time, not visible list's real height. Typical MS logic..

So, one has to grab both window rect, number of items, item height and cursor
pos, then calculate real list rect from this for compare. How important is this?
Depends on importance of code, of course. If combobox selection starts a nuclear
plant in different ways, I guess it can be a bit important..

Okay, so we know that MS combobox does not always ignore properly if we click
outside list or press Escape - instead it repeats last selection. Following
fixes this stupid and potentially dangerous behaviour:

                 CASE %CBN_SELENDOK
                    LOCAL itemCount AS LONG, itemHeight AS LONG, visItems AS LONG
                    LOCAL rc AS RECT, rc2 AS RECT, pt AS POINTAPI
 
                    GetCursorPos pt
                    GetWindowRect CBLPARAM, rc2
                    itemCount  = SendMessage(CBLPARAM, %CB_GETCOUNT, 0, 0)
                    itemHeight = SendMessage(CBLPARAM, %CB_GETITEMHEIGHT, 0, 0)
                    SendMessage CBLPARAM, %CB_GETDROPPEDCONTROLRECT, 0, VARPTR(rc)
 
                    'calculate visible dropdown list's real rect
                    rc.nTop    = rc.nTop + rc2.nBottom - rc2.nTop
                    visItems   = MIN&(itemCount, (rc.nBottom - rc.nTop) \ itemHeight)
                    rc.nBottom = rc.nTop + visItems * itemHeight
 
                    IF PtInRect(rc, pt.x, pt.y) = 0 OR _
                       (GetKeyState(%VK_ESCAPE) AND &H8000) THEN EXIT FUNCTION
 
                    BEEP 'or start a space shuttle to Mars, whatever..

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[Semen Matusovski]

Borje --
"Canceled" means Esc ?
If so, you can subclass - WM_CHAR exactly will be before SELENDOK.

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E-MAIL: [email protected]

[Borje Hagsten]

Okay, tested with other code and got different result. Lance is right
as usual, message order cannot be trusted and result may be that if one
really selects something, one has to repeat selection to make it work.

So, bad tip - ignore! See it works in own editor because I use sub-classed
combo and do other stunts on select. But even then, I get unpredictable
result when I switch between documents and a new list is created.

Ah well, back to the drawing board again..


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[Borje Hagsten]

Only thing guaranteed is that nothing is guaranteed. Edwin's solution
can be better in some situations, but what if we want to reselect last
item again?

Like in PBedit's case - sometimes we just want to look at list, and
sometimes we want to repeat selection to go to beginning of a sub
or function again. Have implemented "flag-way" in my own editor and
am pleased with result so far..


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[Edwin Knoppert]

You can also store the last selected index and compare that.

Not the same..

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http://www.hellobasic.com

[Lance Edmonds]

Is the message order guaranteed in that situation?

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Borje Hagsten]

A tip for handling ignored selections in a combobox. Background: If a
combobox list is dropped in order to change a selection, but action is
cancelled by clicking beside the list, whatever, previous selection is
reinstated and a %CBN_SELENDOK notification message still is triggered.
Nothing has changed, but since a %CBN_SELENDOK is triggered, code there
also will be activated (like, repeated).

We can see this in for example PBedit's sub/function finder combo, where
this behaviour can cause some frustration, because an ignored selection
still triggers latest one and cursor jumps back to start of that one. Not
fun if we were doing work elsewhere and just wanted to have a look in the
sub/function finder list..

Not PBedit's fault - it's default Windows behaviour, but sometimes we want
to decide behaviour ourselves, and then following simple way can be used.

I looked at message order and found that a %CBN_SELENDCANCEL is sent before
%CBN_SELENDOK, so by using this, one can make sure the ignore is respected
all the way. Just set a static flag in %CBN_SELENDCANCEL and let this flag
decide action in %CBN_SELENDOK, like:

CALLBACK FUNCTION DlgProc
  SELECT CASE CBMSG  'wMsg
     CASE %WM_INITDIALOG
        STATIC gCBflag AS BYTE
 
     CASE %WM_COMMAND
        SELECT CASE CBCTL  'LOWRD(wParam)
           CASE %IDCOMBO
              SELECT CASE CBCTLMSG  'HIWRD(wParam)
                 CASE %CBN_SELENDCANCEL 'trap this one to enable proper ignore
                    gCBflag = 1
 
                 CASE %CBN_SELENDOK
                    IF gCBflag THEN     'if user cancels, really ignore
                       gCBflag = 0 : EXIT FUNCTION
                    END IF
                    BEEP   'whatever..
              END SELECT
        END SELECT
  END SELECT
END FUNCTION

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