TCustomCombo.SelStart Property

Specifies the position of the first selected character in the edit portion of the combo box.

Pascal

property SelStart: Integer;

C++

__property int SelStart;

Description

Read SelStart to determine where the selection starts in the Text property. The first character is designated with 0, the second with 1, and so on. When SelLength is 0, SelStart is the position of the cursor.

Set SelStart to position the cursor in the edit region of the combo box. Setting SelStart to 0 positions the cursor before the first character, setting SelStart to 1 positions the cursor before the second character, and so on.

Note: Setting SelStart changes the SelLength property to 0. When using SelStart and SelLength to programmatically select a portion of the text in the edit region, set SelStart before setting SelLength.

Note: The SelStart property is only valid when the combo box has focus. When the combo box does not have focus, reading SelStart always yields a value of 0, and setting it has no effect.

C++ Examples:

Copy Code

/*
The following example shows how to complete partial strings
typed into a combo box. The code represents the OnKeyPress
event handler of the combo box, which performs most of the
default keystroke handling before finding a matching list
item and updating the text.
Note:   This OnKeyPress event handler does not deal with the
case when the user types the Delete key. That case must be
caught in the OnKeyDown event handler instead.
*/
void __fastcall TForm1::ComboBox1KeyPress(TObject *Sender, char &Key)
{
  // first, process the keystroke to obtain the current string
  // This code requires all items in list to be uppercase
  if (Key >= 'a' && Key <= 'z')
    Key -= 32; // Force Uppercase only!
  TComboBox *pCB = (TComboBox *)Sender;
  AnsiString TmpStr;
  bool BackSpace = (Key == (char)VK_BACK);
  if (BackSpace && pCB->SelLength)
    TmpStr = pCB->Text.SubString(1,pCB->SelStart)+
             pCB->Text.SubString(pCB->SelLength+pCB->SelStart+1,255);
  else if (BackSpace) // SelLength == 0
    TmpStr = pCB->Text.SubString(1,pCB->SelStart-1)+
             pCB->Text.SubString(pCB->SelStart+1,255);
  else //Key is a visible character
    TmpStr = pCB->Text.SubString(1,pCB->SelStart)+ Key +
             pCB->Text.SubString(pCB->SelLength+pCB->SelStart+1,255);
  if (TmpStr.IsEmpty())
    return;
  // set SelSt to the current insertion point
  int SelSt = pCB->SelStart;
  if (BackSpace && SelSt > 0)
    SelSt--;
  else if (!BackSpace)
    SelSt++;
  Key = 0; // indicate that key was handled
  if (SelSt == 0)
  {
    pCB->Text = "";
    return;
  }
  // Now that TmpStr is the currently typed string, see if we can locate a match
  bool Found = false;
  for (int i = 1; i < pCB->Items->Count; i++)
    if (TmpStr == pCB->Items->Strings[i-1].SubString(1,TmpStr.Length()))
    {
      pCB->Text = pCB->Items->Strings[i-1]; // update to the match that was found
      pCB->ItemIndex = i-1;
      Found = true;
      break;
    }
  if (Found) // select the untyped end of the string
  {
    pCB->SelStart = SelSt;
    pCB->SelLength = pCB->Text.Length() - SelSt;
  }
  else Beep();
}
//---------------------------------------------------------------------------
TStringList *CharSetList;

void __fastcall TForm1::AddCharacterSet(AnsiString S)
{
  CharSetList->Add(S);
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
CharSetList = new TStringList();
GetCharsetValues(AddCharacterSet);
CharSetList->Sort();
ComboBox1->Items = CharSetList;
}