Combo Box — worked example

A combo box is a dropdown selector. Each item can carry a hidden tag (a stable key) alongside its display text, and the control raises events when the list is opened and when the selection changes.

Verified by execution on KCML 06.00.88 (KClient direct mode).

What it demonstrates

• Populating with .Add(text$, tag$) in Enter().
• Pre-selecting with SetSelection(0).
• The Click() event (selection changed) and DropDown() event (list opened).
• Reading the selection's tag with GetTag$(.Index).

The program

01000 REM test_combobox - single combobox with tagged items
    : DIM result, msg$80, tag$10
01010 - DEFFORM ComboTest()=\
       {.form,.form$,.Style=0x50c000c4,.Width=300,.Height=160,.Text$="Combo Test",.Id=1024},\
       {.lblInfo,.static$,.Style=0x50000000,.Left=10,.Top=10,.Width=280,.Height=10,.Text$="Pick a colour from the list.",.Id=2000,.Font=.SegoeCtl},\
       {.cboColour,.combobox$,.Style=0x50210003,.Left=10,.Top=25,.Width=160,.Height=120,.Id=2001,.Font=.SegoeCtl},\
       {.lblPicked,.static$,.Style=0x50000000,.Left=10,.Top=50,.Width=280,.Height=10,.Text$="(nothing picked yet)",.Id=2002,.Font=.SegoeCtl},\
       {.btnClose,.button$,.Style=0x50010001,.Left=210,.Top=115,.Width=80,.Height=14,.Text$="Close",.Id=1,.Font=.SegoeCtl},\
       {.paneStatus,.status$,.Width=300,.Style=0x50000000,.Text$="Ready"},\
       {.SegoeCtl,.dlgfont$,.Name$="Segoe UI",.Size=10}
    :     + DEFEVENT ComboTest.Enter()
    :         .cboColour.Add("Red","R")
    :         .cboColour.Add("Green","G")
    :         .cboColour.Add("Blue","B")
    :         .cboColour.Add("Yellow","Y")
    :         .cboColour.SetSelection(0)
    :     END EVENT
    :     + DEFEVENT ComboTest.cboColour.Click()
    :         tag$ = RTRIM(.cboColour.GetTag$(.cboColour.Index))
    :         .lblPicked.Text$ = $PRINTF("Picked idx=%d text=[%s] tag=[%s]", .cboColour.Index, RTRIM(.cboColour.Text$), tag$)
    :     END EVENT
    :     + DEFEVENT ComboTest.cboColour.DropDown()
    :         .paneStatus.Text$ = "cboColour.DropDown fired"
    :     END EVENT
    : FORM END ComboTest
01020 result = ComboTest.Open()
    : $END

How it works

Tags vs text. .Add("Green", "G") shows Green but stores G. After a selection, GetTag$(.Index) returns the tag — branch your logic on that stable key, not the (possibly translated) display text.

Mind the index base — it is asymmetric. This is the single most common combo-box trap, verified by execution:

• SetSelection(n) is 0-based — SetSelection(0) selects the first item.
• .Index and GetTag$() are 1-based — selecting the 2nd item (Green) reports .Index = 2, and GetTag$(2) returns Green's tag.

The pattern GetTag$(.Index) is correct precisely because both sides are 1-based. Do not offset .Index before passing it to GetTag$().

Style. 0x50210003 is a drop-down with an editable field; 0x50210002 is a drop-down list (no typing). The Click() event fires on every selection change, keyboard or mouse.

See also

• combobox — full reference
• List Box worked example — same tag pattern, always-visible list