Is it possible to determine if the text in a dbEdit is longer than what is visible?

问题

On some forms I have dbEdits that sometimes aren't wide enough to show all the text their fields may contain. For them I have the following code:

procedure Tgm12edLots.dbeLotNameMouseEnter(Sender: TObject);
begin
  with dbeLotName do begin
    ShowHint := True;
    Hint := Text;
  end;
end;

I'd like to avoid the hint showing if all the text is visible, but I don't how to test for that condition.

Thanks for any tips/suggestions!

回答1:

I think this should work...

function CanShowAllText(Edit: TDBEdit):Boolean;
var
    TextWidth:Integer;
    VisibleWidth: Integer;
    Bitmap: TBitmap;
const
//This could be worked out but without delphi I can't remember all that goes into it.
    BordersAndMarginsWidthEtc = 4;
begin
    Bitmap := TBitmap.Create;
    try
        Bitmap.Canvas.Font.Assign(Edit.Font);
        TextWidth := Bitmap.Canvas.TextWidth(Edit.Text);
        VisibleWidth := Edit.Width - BordersAndMarginsWidthEtc;
        Result := TextWidth < VisibleWidth;
    finally
        Bitmap.Free;
    end;
end;

回答2:

Here is a fast version (without a TBitmap overhead) that takes into account the Edit control's Margins (i.e. EM_SETMARGINS).

Use IsEditTextOverflow below to determine if the Text overflows the visible area.

type
  TCustomEditAccess = class(TCustomEdit);

function EditTextWidth(Edit: TCustomEdit): Integer;
var
  DC: HDC;
  Size: TSize;
  SaveFont: HFont;
begin
  DC := GetDC(0);
  SaveFont := SelectObject(DC, TCustomEditAccess(Edit).Font.Handle);
  GetTextExtentPoint32(DC, PChar(Edit.Text), Length(Edit.Text), Size);
  SelectObject(DC, SaveFont);
  ReleaseDC(0, DC);
  Result := Size.cx;
end;

function EditVisibleWidth(Edit: TCustomEdit): Integer;
var
  R: TRect;
begin
  SendMessage(Edit.Handle, EM_GETRECT, 0, LPARAM(@R));
  Result := R.Right - R.Left;
end;

function IsEditTextOverflow(Edit: TCustomEdit): Boolean;
begin
  Result := EditTextWidth(Edit) > EditVisibleWidth(Edit);
end;

来源：https://stackoverflow.com/questions/9941787/is-it-possible-to-determine-if-the-text-in-a-dbedit-is-longer-than-what-is-visib