Detecting checkbox flip in treeview

[Shannon David Larratt]

I understand that when a checkbox (or anything) is clicked inside a treeview, I will get a %WM_NOTIFY, and that if I grab CBLPARAM.idfrom it will match the handle of my treeview, and that if I look at CBLPARAM.hdr.Code, it will match %NM_CLICK... but I'm sort of lost at that point in getting the handle of the item that was clicked on.

I assumed CBLPARAM.itemNew.hItem or something like that, but no luck.

What I'm trying to do is detect when a checkbox has been flipped on a treeview. Previously I was just scanning the entire thing for changes every time there was a click, but there has to be an easier way to do it.

[Shannon David Larratt]

Sorry, using version 9...

CASE %WM_NOTIFY
IF CB.NMID = %IDC_CITIESTREE THEN
IF CB.NMCODE = %NM_CLICK THEN
...if we get here, the treeview IDC_CITIESTREE has been clicked on, but how do I know which of the elements has been clicked on?

[Michael Mattias]

Do you want to know if it has been clicked, or do you want to know if that click has changed the selected item? (This came up here not too long ago).

Depending on which one you want, you process WM_NOTIFY/NM_CLICK or WM_NOTIFY/TVN_SELCHANGED ( or TVN_SELCHANGING if you want to disallow the selection of this item)

FWIW, you get TVN_SELCHANGED when the user uses the keyboard as well as the mouse to change selection.

If it's really "click" you want, you have to figure out where the click occured, then use the Treeview_HitTest function to figure out where on which item (if any) the cursor was when the mouse was clicked. .. then you can use Treeview_getCheckState to query the check status.

(I can't find a TVN_ITEMCHANGED which handles state changes! There must be one somewhere!)

HINT:
THis will be about ten lines of code. You will probably want to put it into a reusable function such as "Treeview_WhereWasClick" so you only have to do it ONCE.

HINT#2
I am sure the code is posted here, but not in the source code forum.


MCM

[Shannon David Larratt]

Thanks -- I want to know which one was clicked on. So it sounds like there's no simple one-call return function... I'm surprised, I would have though there would be something that returned a handle to the item that was clicked on, and some of the data structures implied that was what they could do.

I have another Treeview question while we're at it -- if I want to select all or deselect all (of the the checkboxes), how can I do that in bulk, without flicker issues? Can I temporarily turn off redrawing and then make all the changes and then turn it back on.

[Michael Mattias]

So it sounds like there's no simple one-call return function... I'm surprised, I would have though there would be something that returned a handle to the item that was clicked

There will be - after you write it. Here's a start:

FUNCTION OnWhichItemDidClickHappen (hTV AS LONG, NMH NMHDR) AS LONG
'  Return: hItem on which click occurred, or null if click occurred 
'             on the control BUT NOT ON AN ITEM AND YES THIS HAPPENS

END FUNCTION

BTW, make sure you want CLICKS and not "CHANGE OF SELECTION BY EITHER CLICK OR KEYBOARD." Last thing you want is for the user to complain about 'keys don't work' (and you KNOW that is how it will come back to you!)

Also, "selected" with a treeview does NOT mean "the checkbox is checked". You can have only one selection at a time, but many items may be checked!

(I know someone posted a tree view with check boxes demo here. Try a search on "TVS_CHECKBOXES" and you should find it, since that style had to be included)

MCM

[Shannon David Larratt]

Hahaha... I can't tell if you're messing with me or if you're giving me useful advice or both. It's the guts of that function that I'm stuck on, not its declaration.

[Michael Mattias]

I don't mess with people. All statements above are feither fact as I know it or my honest "best guess" at what you should do next. If my facts are shown to be wrong, I will promptly acknowledge and correct.

However, I am in no position to judge if the suggestions or advice I offer are useful.

>It's the guts of that function that I'm stuck on

I wasn't about to pre-empt the fun you will have creating it. That would not be nice at all, would it?

[Shannon David Larratt]

Thanks, admittedly I am under no particular deadline so I have been having fun slowly figuring it all out. I do console apps 99% of the time, so I'm still fairly unfamiliar with GUI programming.

[colin glenn]

PB will give you the rudiments of the event, there's a lot more buried in the structure which is passed to the window via the NMHDR Structure, AKA in PB it's CB.NMHDR, and that header is common across a bunch of notification systems, for the treeview control, you need to:

LOCAL pnmtv                 AS NM_TREEVIEW POINTER

and there's something to note here, the CB.NMHDR is a pointer, CB.NMCODE, CB.NMHWND, & CB.NMID are all derived from the structure, alias:

TYPE NMHDR
  hwndFrom AS DWORD
  idfrom AS DWORD
  CODE AS LONG    ' used for messages, so needs to be LONG, not DWORD...
END TYPE

And when you look at NM_TREEVIEW:

TYPE NM_TREEVIEW
    hdr     AS NMHDR
    action  AS DWORD
    itemOld AS TV_ITEM
    itemNew AS TV_ITEM
    ptDrag  AS POINTAPI
END TYPE

See? And if you're following along;

        CASE %WM_NOTIFY
            IF ISTRUE isLoading THEN EXIT FUNCTION
            SELECT CASE CB.NMID
                CASE %IDTV_FOXTREE
                    IF CB.NMCODE = %TVN_SELCHANGED THEN
                        ' make image here
                        SELECT CASE CB.NMID
                            CASE %IDTV_FOXTREE
                                DisplaySelectedImage CB.HNDL, CB.NMID, CB.NMHDR

My code sets up a function call at this point, but in the function, I then use the above pointer declaration to gain access to the itemOld and itemNew elements of the structure:

SUB DisplaySelectedImage(hDialog AS DWORD, idControl AS DWORD, pnmhdr AS DWORD)
LOCAL pnmtv                 AS NM_TREEVIEW POINTER
LOCAL pitem                 AS TV_ITEM
LOCAL BumpX                 AS LONG
LOCAL hControl, hBitmap     AS DWORD
LOCAL KeyControl            AS INTEGER

    KeyControl = (GetKeyState(%VK_CONTROL) AND &H8000)
    IF ISTRUE SetCurrentShape(hDialog, idControl) THEN
        pnmtv = pnmhdr
        IF @pnmtv.action = %TVC_BYMOUSE THEN
            CONTROL HANDLE hDialog, %IDTV_FOXTREE TO hControl
            IF (ISTRUE @pnmtv.itemOld.hItem) AND (ISFALSE KeyControl) THEN
                pitem.hItem = @pnmtv.itemOld.hItem
                pitem.mask = %TVIF_STATE
                pitem.stateMask = %TVIS_BOLD
                BumpX = TreeView_GetItem(hControl, pitem)
                pitem.state = pitem.state AND (NOT %TVIS_BOLD)
                BumpX = TreeView_SetItem(hControl, pitem)
            END IF
            IF ISTRUE @pnmtv.itemNew.hItem THEN
                pitem.hItem = @pnmtv.itemNew.hItem
                pitem.mask = %TVIF_STATE
                pitem.stateMask = %TVIS_BOLD
                BumpX = TreeView_GetItem(hControl, pitem)
                pitem.state = pitem.state OR %TVIS_BOLD
                BumpX = TreeView_SetItem(hControl, pitem)
            END IF
        END IF
        hBitmap = MakeFshBitmap(CurrentShape, CurrentFrame, Fox)
        CONTROL SEND hDialog, %idf_imagedisplay, %UM_SETIMAGE, _
            hBitmap, Fox.ComboPosition(CurrentShape, CurrentFrame)
    END IF

END SUB

[Michael Mattias]

I think what you are going to need to do here is two things...

1. On click, check to see of the click was an item or not
2. On <spacebar> (use WM_NOTIFY/TVN_KEYDOWN) check to see what item was currently selected.

I think the checkbox status will be toggled automatically on either, meaning you really don't have to do anything vis-a-vis toggling the check state.

But we really don't know what it is you want to do when the user clicks (or selects?)

MCM

[colin glenn]

I think the checkbox status will be toggled automatically on either, meaning you really don't have to do anything vis-a-vis toggling the check state.

It's automatic.

[Jeff Blakeney]

Well, my first google search using the phrase "treeview using tvs_checkboxes" return this link. It says that when a user clicks on the state icon that an NM_CLICK notification is sent and the TVM_HITTEST message will return TVHT_ONITEMSTATEICON. Unfortunately, the treeview doesn't actually change the state until after the NM_CLICK notification is sent so you can't just check the state on an NM_CLICK.

His suggestion is to send a custom message to your dialog procedure when you get an NM_CLICK and TVM_HITTEST returns TVHT_ONITEMSTATEICON.

Here is my conversion of the code at the above linked converted to PB:

' make sure you have these includes
#INCLUDE "Win32API.inc"
#INCLUDE "CommCtrl.inc"

' add this equate to the start of your program
%UM_CHECKSTATECHANGE = %WM_USER + 100

' add these variable declarations in your dialog procedure
LOCAL dPos  AS DWORD
LOCAL tHTI  AS TVHITTESTINFO

' add the following case to your SELECT CASE CB.MSG
CASE %WM_NOTIFY
    SELECT CASE CB.NMID
        CASE %IDC_TREEVIEW1
            IF CB.NMCODE = %NM_CLICK THEN
                dPos = GetMessagePos
                tHTI.pt.x = LO(WORD, dPos)
                tHTI.pt.y = HI(WORD, dPos)
                MapWindowPoints %HWND_DESKTOP, CB.NMHWND, tHTI.pt, 1
                TreeView_HitTest CB.NMHWND, tHTI
                IF tHTI.flags AND %TVHT_ONITEMSTATEICON THEN
                    PostMessage CB.HNDL, %UM_CHECKSTATECHANGE, 0, tHTI.hItem
                END IF
            END IF
    END SELECT

CASE %UM_CHECKSTATECHANGE
    hItemChanged = CB.LPARAM ' handle of the item whose state icon was clicked
    ' you can now get the state of the item

Hopefully I ddin't screw anything up as I didn't test this code.

[Dave Biggs]

send a custom message to your dialog procedure when you get an NM_CLICK and TVM_HITTEST returns TVHT_ONITEMSTATEICON.

There's a good example of this technique in the Three State Checkbox Treeview example posted in the Source Code forum by Steve Mc Gregor..

http://www.powerbasic.com/support/pbforums/showpost.php?p=167445

Actually that example addresses just about all the questions raised by this thread