PBDLL: Label Editing in Listview Control

[LRantanen]

hi,

i'm learning to use listview control from pb/dll. based on examples from these forums - mainly i have used peter redei's posting

pddll5: generic listview example


i have come up with following test program

<font face="courier new, courier" size="3"><pre>

'------------------------------------------------------------------------------
'
' testing listview common control
'
' based on sample by peter redei
'
' include file "listview.bas" can be found in peter's posting
' pddll5: generic listview example
'
'------------------------------------------------------------------------------
'
' ** eliminate unnecessary macros
%noanimate = 1
%nodraglist = 1
%noheader = 1
%noimagelist = 1
'%nolistview = 1
%notabcontrol = 1
%notrackbar = 1
%notreeview = 1
%noupdown = 1

#compile exe
#include "win32api.inc"
#include "commctrl.inc"
#include "listview.bas"

%idok = 1
%idlistview = 101

global hlistview as long
global lviewsort as integer

'------------------------------------------------------------------------------
function compare(byval lparam1 as long, byval lparam2 as long, byval lparamsort as long) as integer
' written by peter redei

local value1 as asciiz * 300
local value2 as asciiz * 300
local j as integer

value1 = retrievelvdata(hlistview, lparam1, lparamsort)
value2 = retrievelvdata(hlistview, lparam2, lparamsort)

select case lviewsort
case 0 'ascending
j = 1
case else 'descending
j = -1
end select

if value1 < value2 then
function = -1 * j
elseif value1 = value2 then
function = 0
else
function = 1 * j
end if
end function

'------------------------------------------------------------------------------
callback function okbutton_proc()
dialog end cbhndl, 0
end function

'------------------------------------------------------------------------------
callback function dialog_proc()
local hdlg as long
local my_lplvnm as nm_listview ptr
local stext as string

hdlg = cbhndl
select case cbmsg
case %wm_notify
select case lowrd(cbwparam)
case %idlistview
my_lplvnm = cblparam
select case @my_lplvnm.hdr.code
case %lvn_endlabeledit
msgbox "done editing!"
case %lvn_columnclick
if (@my_lplvnm.isubitem <> -1) then
'toggle ascending/descending
lviewsort = not lviewsort
listview_sortitems hlistview, _
codeptr(compare), _
@my_lplvnm.isubitem
'lparam was set to the original 'recordnumber'
'now this changed, we need to set it to the new position
resetlparam hlistview
end if
case %nm_dblclk
stext = retrievelvdata(hlistview, @my_lplvnm.iitem, @my_lplvnm.isubitem)
msgbox stext,48,"just for test purposes"
end select
end select
end select
end function

'------------------------------------------------------------------------------
function pbmain () as long

$register none

local hdlg as long
local icc as init_common_controlsex
local r as long
local c as long
local lstyle as long
%numcols = 5
%numrows = 20
local ldata as listdata
dim rec(%numcols) as string

' init listview control
icc.dwicc = %icc_listview_classes
icc.dwsize = sizeof(icc)
initcommoncontrolsex icc

' create a new dialog template
dialog new 0, "listview test", ,, 315, 182, 0, 0 to hdlg

' add controls to it
control add "syslistview32", _
hdlg, %idlistview,", _
0,0,315,161, _
%ws_border or %ws_child or %ws_visible or %ws_tabstop or _
%lvs_report or %lvs_showselalways or %lvs_editlabels, _
%ws_ex_clientedge

control add button, _
hdlg, %idok, "&ok", _
137, 164, 40, 14, _
%ws_tabstop _
call okbutton_proc

' set some extended style flags for listview control
control handle hdlg,%idlistview to hlistview
lstyle = sendmessage(hlistview, %lvm_getextendedlistviewstyle, 0, 0)
lstyle = lstyle or %lvs_ex_fullrowselect or %lvs_ex_gridlines
call sendmessage(hlistview, %lvm_setextendedlistviewstyle, 0, byval lstyle)

' set column headers
ldata.columns = %numcols
ldata.fields(0).fname = "item #"
ldata.fields(0).size = 90
for c = 1 to %numcols - 1
ldata.fields(c).fname = "property #" + format$(c)
ldata.fields(c).size = 90
ldata.fields(c).alignment = %lvcfmt_left
next
setlistview hlistview, ldata

' show random data
randomize
for r = 1 to %numrows
rec(0) = format$(1000+r)
for c = 1 to %numcols - 1
rec(c) = chr$(rnd(asc("a"),asc("z"))) + trim$(str$(rnd(1000,2000)))
next c
appendlistview hlistview, rec()
next r

' display the dialog
dialog show modal hdlg call dialog_proc

end function

[/CODE]

the lvn_endlabeledit part is the first test in this matter - very incomplete, i know. however, i don't understand why program behaves as it does:

1. first click on a cell selects the row containing the cell - ok.
2. second click somewhere on the same row opens edit window in the first column (the item of this row), cell text is entered there and all the text is selected - ok.
3. a click somewhere outside the edit control shows message "done editing!" (notification message lvn_endlabeledit got processed) and the contents of the item cell do no change - ok.
4. selecting text in the edit box w/mouse works ok.
5. selecting text w/keys works ok. also ctrl+c copies text to clipboard.
6. right clicking w/mouse opens context menu - ok.
7. try to change the text - keyboard entry, del key etc. - and the program crashes -

can anybody give me any hints why it does it? there i have an edit window w/focus and can do everything else with it except change it- that i don't understand.

following is quote from ms' docs.

a list view control that has the lvs_editlabels window style enables a user to edit item labels in place. the user begins editing by clicking the label of an item that has the focus. alternatively, an application can begin editing automatically by using the lvm_editlabel message. the list view control notifies the parent window when editing begins and when it is canceled or completed. when editing is completed, the parent window is responsible for updating the item's label, if appropriate.

when label editing begins, an edit control is created, positioned, and initialized. before it is displayed, the list view control sends its parent window an lvn_beginlabeledit notification message. if you need to modify the label editing process, you can implement a handler for this notification.

the way i read this is that there is no need to implement a handler for lvn_beginlabeledit notification message, i.e. you should be able to edit the text in the edit window right away.

another quote

when label editing is canceled or completed, a list view control sends its parent window an lvn_endlabeledit notification message. the lparam parameter is the address of an nmlvdispinfo structure. the item member of this structure is an lvitem structure whose iitem member identifies the item. if editing is canceled, the psztext member of the lvitem structure is null; otherwise, psztext is the address of the edited text. the parent window is responsible for updating the item's label if it wishes to keep the new label.

again i read this so that if i every time (as in the sample program) want to discard the possible edits, i don't have to do anything.

regards
lasse rantanen
[email protected]

[LRantanen]

Hi,

done some further digging and found the reason - one of the most bizarre features of Windows' controls.

In "Listview Bugs and Problems" http://www.wdj.com/notgone/706art.htm Ron Burke explains:

Sure enough, the listview control located this flaw in my code for me, due to an "interesting" part of its design. When I started to edit an item in the listview control, as soon as I pressed a key my dialog disappeared! This was indeed mysterious, and I did a lot of head scratching before I finally realized that somebody was generating a notification for either my IDOK button or my IDCANCEL button. Further inspection revealed that the notification code was either 0x0300 or 0x0400. That's when the awful truth hit me.

When you edit a listview item, the listview control secretly creates its own edit control, positioned above the item being edited. Apparently, the listview control designer decided it would be nice to pass that edit control's notification messages on to the parent dialog. All well and good, but what control ID should be associated with those notifications? In a better world, the designer might have allocated a new reserved control ID (e.g., ID_LISTVIEWEDIT), adding to the existing reserved IDs such as IDOK and IDCANCEL. Instead, the designer decided just to use IDOK for the control ID of the edit control. After all, the edit control notifications, such as EN_CHANGE (0x0300) and EN_UPDATE (0x0400), happen to lie numerically above any possible button notifications.

Like so many aspects of the Windows API, this feature of the listview control is not documented. That could indicate Microsoft does not want to guarantee support for the feature in future versions, or it could just be a symptom of the generally incomplete documentation. Either way, be aware that notifications from unrelated controls may be stacked upon your IDOK button -- notifications aren't really guaranteed by the documentation to be there in future versions of the listview control.

OK, that was my problem, too. I had equate %IDOK=1 in my code. Changing it to %ID_OK=100 gotthings working as expected.

I hope this will help somebody else struggling with in-place editing.

Regards
Lasse Rantanen
[email protected]