How to access design position on non-visual Delphi components? - delphi

Question

When designing a form in the IDE, non-visual components (eg TMainMenus, TDatamodules) can be freely placed and positioned. The position is persisted, so that on reloading the form these components appear in the correct place.
But, TComponent does not have Top or Left properties!
So, how can my code access the 'designed position' of non visual components?

Answer 1

This can be accessed at runtime, but it's sort of a hack. (Mostly because it's implemented as sort of a hack.)
The Left and Top properties are set up as Word-size values, and the two of them are packed together into a Longint called TComponent.FDesignInfo. You can obtain its value with the DesignInfo property. Have a look at TComponent.DefineProperties to get a look into how it's used.

Answer 2

And also:
How to set DesignInfo to a point like (-100,-100)?
Objective: Put the icon out of visual area, hide it on design-time.
Note: It is very usefull when for example creating simple visual components derived directly from TComponent, i have in mind a very simple label (taht is allways aligned to top, has allways left=0, top is auto-calculated, bla bla bla) that only stores it's caption property into the .dfm file; and also any localizer will only see that caption property.
SOLUTION is to Override ReadState with code like this:
procedure TMyComponent.ReadState(Reader:TReader);
var
NewDesignInfo:LongRec;
begin
inherited ReadState(Reader);
NewDesignInfo.Hi:=Word(-100); // Hide design-time icon (top position = -100)
NewDesignInfo.Lo:=Word(-100); // Hide design-time icon (left position = -100)
DesignInfo:=Longint(NewDesignInfo); // Set the design-icon position out of visual area
end;
Hope help others!

Answer 3

This worked for me. Source: CnPack CnAlignSizeWizard.pas.
procedure SetNonVisualPos(Form: TCustomForm; Component: TComponent; X, Y: Integer);
const
NonvisualClassNamePattern = 'TContainer';
csNonVisualSize = 28;
csNonVisualCaptionSize = 14;
csNonVisualCaptionV = 30;
var
P: TSmallPoint;
H1, H2: HWND;
Offset: TPoint;
function HWndIsNonvisualComponent(hWnd: hWnd): Boolean;
var
AClassName: array[0..256] of Char;
begin
AClassName[GetClassName(hWnd, #AClassName, SizeOf(AClassName) - 1)] := #0;
Result := string(AClassName) = NonvisualClassNamePattern;
end;
procedure GetComponentContainerHandle(AForm: TCustomForm; L, T: Integer; var H1, H2: hWnd; var Offset: TPoint);
var
R1, R2: TRect;
P: TPoint;
ParentHandle: hWnd;
AControl: TWinControl;
I: Integer;
begin
ParentHandle := AForm.Handle;
AControl := AForm;
if AForm.ClassNameIs('TDataModuleForm') then // ÊÇ DataModule
begin
for I := 0 to AForm.ControlCount - 1 do
if AForm.Controls[I].ClassNameIs('TComponentContainer')
and (AForm.Controls[I] is TWinControl) then
begin
AControl := AForm.Controls[I] as TWinControl;
ParentHandle := AControl.Handle;
Break;
end;
end;
H2 := 0;
H1 := GetWindow(ParentHandle, GW_CHILD);
H1 := GetWindow(H1, GW_HWNDLAST);
while H1 <> 0 do
begin
if HWndIsNonvisualComponent(H1) and GetWindowRect(H1, R1) then
begin
P.x := R1.Left;
P.y := R1.Top;
P := AControl.ScreenToClient(P);
if (P.x = L) and (P.y = T) and (R1.Right - R1.Left = csNonVisualSize)
and (R1.Bottom - R1.Top = csNonVisualSize) then
begin
H2 := GetWindow(ParentHandle, GW_CHILD);
H2 := GetWindow(H2, GW_HWNDLAST);
while H2 <> 0 do
begin
if HWndIsNonvisualComponent(H2) and GetWindowRect(H2, R2) then
begin
if (R2.Top - R1.Top = csNonVisualCaptionV) and (Abs(R2.Left + R2.Right - R1.Left - R1.Right) <= 1)
and (R2.Bottom - R2.Top = csNonVisualCaptionSize) then
begin
Offset.x := R2.Left - R1.Left;
Offset.y := R2.Top - R1.Top;
Break;
end;
end;
H2 := GetWindow(H2, GW_HWNDPREV);
end;
Exit;
end;
end;
H1 := GetWindow(H1, GW_HWNDPREV);
end;
end;
begin
P := TSmallPoint(Component.DesignInfo);
GetComponentContainerHandle(Form, P.x, P.y, H1, H2, Offset);
Component.DesignInfo := Integer(PointToSmallPoint(Point(X, Y)));
if H1 <> 0 then
SetWindowPos(H1, 0, X, Y, 0, 0, SWP_NOSIZE or SWP_NOZORDER);
if H2 <> 0 then
SetWindowPos(H2, 0, X + Offset.x, Y + Offset.y, 0, 0, SWP_NOSIZE or SWP_NOZORDER);
end;
Use sample:
SetNonVisualPos(TCustomForm(Designer.Root),MyComponent,10,10);