BBC BASIC Programmers' Reference

by Richard Russell, April 2011

A List View control has built-in support for tooltips, but this feature requires your program to respond to the LVN_EX_INFOTIP notification, and in BBC BASIC for Windows that is only possible using assembler code.

The program listed below uses an alternative technique that doesn't require assembler code. The position of the mouse cursor is constantly monitored, and when it moves over the List View control a tooltip is displayed. As shown, the displayed message depends only on what item (row) the mouse is hovering over, but it could easily be adapted so the message is specific to the subitem (column) as well.

The code requires v4.70 of the Windows Common Controls, so won't work on versions of Windows prior to XP. It is also necessary to ensure that the Use Windows XP visual styles option is selected if the program is compiled.

        REM. List View with tooltips, Richard Russell, 02-Apr-2011
 
        REM. Install libraries:
        INSTALL @lib$+"WINLIB5"
 
        nColumns% = 5
 
        REM!WC Windows constants:
        LVCF_FMT = 1
        LVCF_SUBITEM = 8
        LVCF_TEXT = 4
        LVCF_WIDTH = 2
        LVIF_PARAM = 4
        LVIF_STATE = 8
        LVIF_TEXT = 1
        LVM_GETITEMRECT = 4110
        LVM_GETTOOLTIPS = 4174
        LVM_INSERTCOLUMN = 4123
        LVM_INSERTITEM = 4103
        LVM_SETITEMTEXT = 4142
        LVM_SUBITEMHITTEST = 4153
        LVS_REPORT = 1
        TTM_ADDTOOL = &404
        TTM_NEWTOOLRECT = &406
        TTM_UPDATETIPTEXT = &40C
 
        ON ERROR SYS "MessageBox", @hwnd%, REPORT$, 0, 48 : PROCcleanup : QUIT
        ON CLOSE PROCcleanup : QUIT
 
        REM. Declare and initialise structures:
        DIM pt{x%,y%}, rc{l%,t%,r%,b%}
        DIM ti{cbSize%, uFlags%, hwnd%, uId%, rect{} = rc{}, hinst%, lpszText%}
        DIM lvh{pt{} = pt{}, flags%, iItem%, iSubItem%, iGroup%}
        DIM lvc{mask%, fmt%, cx%, pszText%, cchTextMax%, iSubItem%}
        DIM lvi{mask%, iItem%, iSubItem%, state%, stateMask%, pszText%, \
        \       cchTextMax%, iImage%, lParam%}
        lvc.mask% = LVCF_WIDTH OR LVCF_SUBITEM OR LVCF_FMT OR LVCF_TEXT
        lvi.mask% = LVIF_TEXT OR LVIF_STATE OR LVIF_PARAM
 
        REM. Create list view control:
        SYS "InitCommonControls"
        dx% =  @vdu.tr%
        dy% =  @vdu.tb%
        hwndLV% = FN_createwindow("SysListView32", "", 0, 0, dx%, dy%, 0, LVS_REPORT, 0)
        FOR col% = 0 TO nColumns%-1
          title$ = "Column " + STR$col% + " header" + CHR$0
          lvc.cx%         = dx% DIV nColumns%
          lvc.pszText%    = !^title$
          lvc.cchTextMax% = LEN(title$)
          lvc.iSubItem%   = col%
          SYS "SendMessage", hwndLV%, LVM_INSERTCOLUMN, col%, lvc{}
        NEXT
        SYS "SendMessage", hwndLV%, LVM_GETTOOLTIPS, 0, 0 TO hwndTT%
        ti.cbSize% = DIM(ti{})
        ti.hwnd% = hwndLV%
        SYS "SendMessage", hwndTT%, TTM_ADDTOOL, 0, ti{}
 
        REM. Populate list view control:
        FOR item% = 0 TO 10
          FOR col% = 0 TO nColumns%
            text$ = "Item " + STR$item% + " column " + STR$col% + CHR$0
            lvi.iItem%      = item%
            lvi.iSubItem%   = col%
            lvi.pszText%    = !^text$
            lvi.cchTextMax% = LEN(text$)
            IF col% THEN
              SYS "SendMessage", hwndLV%, LVM_SETITEMTEXT, item%, lvi{}
            ELSE
              SYS "SendMessage", hwndLV%, LVM_INSERTITEM, item%, lvi{}
            ENDIF
          NEXT col%
        NEXT item%
 
        REM. Polling loop, monitoring mouse position:
        oldx% = -1
        oldy% = -1
        REPEAT
          WAIT 1
          SYS "GetCursorPos", pt{}
          SYS "ScreenToClient", hwndLV%, pt{}
          IF pt.x%<>oldx% OR pt.y%<>oldy% THEN
            oldx% = pt.x%
            oldy% = pt.y%
            PROCtooltip(pt.x%, pt.y%)
          ENDIF
        UNTIL FALSE
 
        DEF PROCtooltip(x%, y%)
        LOCAL tip$
        lvh.pt.x% = x%
        lvh.pt.y% = y%
        SYS "SendMessage", hwndLV%, LVM_SUBITEMHITTEST, 0, lvh{}
        IF lvh.iItem% >= 0 THEN
          SYS "SendMessage", hwndLV%, LVM_GETITEMRECT, lvh.iItem%, rc{}
          tip$ = "Tooltip for item " + STR$(lvh.iItem%) + CHR$0
          ti.lpszText% = !^tip$
          ti.rect.l% = rc.l%
          ti.rect.r% = rc.r%
          ti.rect.t% = rc.t%
          ti.rect.b% = rc.b%
          SYS "SendMessage", hwndTT%, TTM_UPDATETIPTEXT, 0, ti{}
          SYS "SendMessage", hwndTT%, TTM_NEWTOOLRECT, 0, ti{}
        ENDIF
        ENDPROC
 
        DEF PROCcleanup
        hwndLV% += 0 : IF hwndLV% PROC_closewindow(hwndLV%) : hwndLV% = 0
        ENDPROC