CODEWITHSUNDEEP
delphifocusmouse-cursorsetfocus
lkessler
lkessler

Reputation: 20132

How do I get the Control that is under the cursor in Delphi?

I need the opposite information that the question "How to get cursor position on a control?" asks.

Given the current cursor position, how can I find the form (in my application) and the control that the cursor is currently over? I need the handle to it so that I can use Windows.SetFocus(Handle).

For reference, I'm using Delphi 2009.

Upvotes: 3

Views: 12458

Answers (3)

Andrei Galatyn
Andrei Galatyn

Reputation: 3432

I experienced some problems with suggested solutions (Delphi XE6/Windows 8.1/x64):

  • FindVCLWindow doesn't search disabled controls (Enabled=False).
  • TWinControl.ControlAtPos doesn't search controls if they are disabled indirectly (for example if Button.Enabled=True, but Button.Parent.Enabled=False).

In my case it was a problem, because i need to find any visible control under the mouse cursor, so i have to use my own implementation of function FindControlAtPos:

function FindSubcontrolAtPos(AControl: TControl; AScreenPos, AClientPos: TPoint): TControl;
var
  i: Integer;
  C: TControl;
begin
  Result := nil;
  C := AControl;
  if (C=nil) or not C.Visible or not TRect.Create(C.Left, C.Top, C.Left+C.Width, C.Top+C.Height).Contains(AClientPos) then
    Exit;
  Result := AControl;
  if AControl is TWinControl then
    for i := 0 to TWinControl(AControl).ControlCount-1 do
    begin
      C := FindSubcontrolAtPos(TWinControl(AControl).Controls[i], AScreenPos, AControl.ScreenToClient(AScreenPos));
      if C<>nil then
        Result := C;
    end;
end;

function FindControlAtPos(AScreenPos: TPoint): TControl;
var
  i: Integer;
  f,m: TForm;
  p: TPoint;
  r: TRect;
begin
  Result := nil;
  for i := Screen.FormCount-1 downto 0 do
    begin
      f := Screen.Forms[i];
      if f.Visible and (f.Parent=nil) and (f.FormStyle<>fsMDIChild) and 
        TRect.Create(f.Left, f.Top, f.Left+f.Width, f.Top+f.Height).Contains(AScreenPos) 
      then
        Result := f; 
    end;
  Result := FindSubcontrolAtPos(Result, AScreenPos, AScreenPos);
  if (Result is TForm) and (TForm(Result).ClientHandle<>0) then
  begin
    WinAPI.Windows.GetWindowRect(TForm(Result).ClientHandle, r);
    p := TPoint.Create(AScreenPos.X-r.Left, AScreenPos.Y-r.Top);
    m := nil;
    for i := TForm(Result).MDIChildCount-1 downto 0 do
    begin
      f := TForm(Result).MDIChildren[i];
      if TRect.Create(f.Left, f.Top, f.Left+f.Width, f.Top+f.Height).Contains(p) then
        m := f; 
    end;
    if m<>nil then
      Result := FindSubcontrolAtPos(m, AScreenPos, p);
  end;
end;

Upvotes: 5

Johan
Johan

Reputation: 76567

If you want to know the control inside a form that is at a certain x,y coordinate

Use

function TWinControl.ControlAtPos(const Pos: TPoint; AllowDisabled: Boolean;
        AllowWinControls: Boolean = False; AllLevels: Boolean = False): TControl;

Given the fact that you seem only interested in forms inside your application, you can just query all forms.

Once you get a non-nil result, you can query the control for its Handle, with code like the following

Pseudo code

function HandleOfControlAtCursor: THandle;
const
  AllowDisabled = true;
  AllowWinControls = true;
  AllLevels = true;
var
  CursorPos: TPoint
  FormPos: TPoint;
  TestForm: TForm;
  ControlAtCursor: TControl;
begin
  Result:= THandle(0);
  GetCursorPos(CursorPos);
  for each form in my application do begin
    TestForm:= Form_to_test;
    FormPos:= TestForm.ScreenToClient(CursorPos);
    ControlAtCursor:= TestForm.ControlAtPos(FormPos,  AllowDisabled,
                                            AllowWinControls, AllLevels);
    if Assigned(ControlAtCursor) then break;
  end; {for each}
  //Break re-enters here
  if Assigned(ControlAtCursor) then begin
    while not(ControlAtCursor is TWinControl) do 
      ControlAtCursor:= ControlAtCursor.Parent;
    Result:= ControlAtCursor.Handle;
  end; {if}
end;

This also allows you to exclude certain forms from consideration should you so desire. If you're looking for simplicity I'd go with David and use FindVCLWindow.

P.S. Personally I'd use a goto rather than a break, because with a goto it's instantly clear where the break re-enters, but in this case it's not a big issue because there are no statements in between the break and the re-entry point.

Upvotes: 2

David Heffernan
David Heffernan

Reputation: 612954

I think FindVCLWindow will meet your needs. Once you have the windowed control under the cursor you can walk the parent chain to find the form on which the window lives.

Upvotes: 3

Related Questions