Comboboxes

ComboBox

How to set the dropdown list width

For default, the width of the dropdown list is the same as the combobox width.
You can change the width programatically.

To do this you will have to send a message to the Combobox and supply a new width in pixels.
Also the current width in pixels can be determined.
First you have to declare these constants

Number: CB_GETDROPPEDWIDTH   = 0x015F
Number: CB_SETDROPPEDWIDTH   = 0x0160

(More information on CB_GETDROPPEDWIDTH and CB_SETDROPPEDWIDTH)

The next piece of code sets the width of combobox cmbSample to 100 pixels

Call SalSendMsg( cmbSample, CB_SETDROPPEDWIDTH, 100, 0 )

The next piece of code gets the current width of combobox cmbSample in pixels

Set nWidth = SalSendMsg( cmbSample, CB_GETDROPPEDWIDTH, 0, 0 )

The next piece of code doubles the width of combobox cmbSample

Call SalSendMsg( cmbSample, CB_SETDROPPEDWIDTH, SalSendMsg( cmbSample, CB_GETDROPPEDWIDTH, 0, 0 )*2, 0 )

How to programatically open the dropdown list

Open (or close) the dropdown list of a combobox using

Call VisListSetDropDownState( hWndList, bState )

! bState = TRUE to open
! bState = FALSE to close

How to get the handles of the edit and list parts of a combobox

TODO -> CB_GETCOMBOBOXINFO.

How to set the vertical size of the dropdown list programatically

TODO -> CB_SETMINVISIBLE.

How to set the height of the edit portion and list entries programatically

The height of the edit control portion and the dropdown list entries can be changed.

To do this you will have to send a message to the Combobox and supply a new height in pixels.
Also the current height in pixels can be determined.
First you have to declare these constants

Number: CB_SETITEMHEIGHT     = 0x0153
Number: CB_GETITEMHEIGHT     = 0x0154

( More information on CB_SETITEMHEIGHT and CB_GETITEMHEIGHT )

To set the height of the edit control portion of combobox cmbSample to 30 pixels

Call SalSendMsg( cmbSample, CB_SETITEMHEIGHT , -1, 30 )

To set the height of the dropdown list entries of combobox cmbSample to 30 pixels

Call SalSendMsg( cmbSample, CB_SETITEMHEIGHT , 0, 30 )

To get the current height of the edit control portion and items of combobox cmbSample in pixels

Set nEditHeight = SalSendMsg( cmbSample, CB_GETITEMHEIGHT , -1, 0)
Set nItemHeight = SalSendMsg( cmbSample, CB_GETITEMHEIGHT , 0, 0)

How to prevent combobox dropdown

To prevent the combobox list popping up (dropdown) when clicking on the dropdown button, here is a solution.
The edit part of the combobox is unaffected.

First declare these constants

Number: WM_NCHITTEST   = 0x84
!
Number: HTNOWHERE      = 0

Now, trap WM_NCHITTEST on the combobox.

Combo Box: cmb1
    Message Actions
        On WM_NCHITTEST
            Return HTNOWHERE

Here you can download a sample:
WIKI_PreventComboboxDropdown.zip