Firemonkey draw over native elements

[CHackbart 12]

Hi,

 

since this is not working properly since the beginning I thought I try to do the following. A TLayout component which helds a transparent borderless TForm. All the layout children are rendered in the form on run time, while the native control behind stays behind. This works fine, but I got stuck in the issue that if I resize the main form, the position of the transparent form won't be updated. I could solve this by a timer which checks the position in the background but this is not the best idea I guess. I added a small example which plays a video stream and draws a icon over the stream. Maybe somebody has an idea how to achieve this without a timer.

 

Christian

example.zip

 

 

Edited November 4, 2021 by CHackbart

[Gustav Schubert 25]

OnResizeEnd ? ( RSP-18851 ) Not tested.

[CHackbart 12]

Thanks for the link, but this only works on windows. In this particular case I need it on almost all platforms, starting on a Mac. Frankly using a Timer is not the worst thing, but I hate the idea of polling on a high frequency as well as the fact that even a 1ms interval would have a delay while moving the main window and updating the content. 

[Gustav Schubert 25]

Did you consider OnIdle?

 

As I understand it, the issue is when dragging the main form by the title bar, then the location of the TImage is not updated; not while changing the position and not even after the drag operation has ended.

 

Using OnIdle can be a replacement for the missing OnResizeEnd event. It should work on a Mac but may not be good enough, as it is not called while dragging.
 

procedure TfrmMain.FormActivate(Sender: TObject);
begin
  OnActivate := nil;

  FOSD := TImageLayout.Create(self);
  FOSD.Parent := self;
  FOSD.Align := TAlignLayout.Contents;
  FOSD.Visible := true;

  imgPlay.Parent := FOSD;
  FOSD.Active := true;

  MediaPlayer.FileName := 'D:\...\TestGif.gif';
  MediaPlayer.Play;

  Application.OnIdle := DoOnIdle;
end;

procedure TfrmMain.DoOnIdle(Sender: TObject; var Handled: Boolean);
begin
  if (Left <> OldLeft) or (Top <> OldTop) then
  begin
    Inc(IdleCounter);
    OldLeft := Left;
    OldTop := Top;
    Caption := IntToStr(IdleCounter);
    FOSD.UpdateView;
  end;
  Handled := True;
end;

 

Update: Are we  in search of an event that is triggered when the form is repositioned?

procedure TfrmMain.FormActivate(Sender: TObject);
begin
  ...
{
OnTimer is the one to beat.
OnResize fails.
public property TControl.OnResized is not available in 10.1 Berlin (I cannot test).
OnResizeEnd is priate to myself.
OnIdle is not triggered while relocating.
OnCanResize does not exist in FMX (works in VCL).
}

  Timer.Interval := 1;
//  Self.OnResize := FormResize;
//  Self.OnResizeEnd := FormResizeEnd;
//  Application.OnIdle := DoOnIdle;
  Timer.OnTimer := FormResize;
end;

procedure TfrmMain.FormResize(Sender: TObject);
begin
  if FOSD <> nil then
    FOSD.UpdateView;
end;

 

Test result: I don't know.
 

Edited November 6, 2021 by Gustav Schubert
after testing out timer

[Gustav Schubert 25]

18 hours ago, Gustav Schubert said:

Are we  in search of an event that is triggered when the form is repositioned?

If so the test app can be simplified: MediaPlayer not needed. This topic has potential to become an interesting question. I wanted to reduce the amount of updates. Here we want frequent updates as the form is relocated, not resized. Resizing is not the problem. Correct me if I am wrong.

 

[CHackbart 12]

Yes of course, I just added the player to explain why I need this in particular. By reading the platform implementation for MacOS I found a solution which should work fine on all platforms:

 

The public SetBoundsF function which is part of the TCommonCustomForm is executed every time the window moved. 

procedure SetBoundsF(const ALeft, ATop, AWidth, AHeight: Single); override;

 

Christian

 

Edited November 6, 2021 by CHackbart

[Gustav Schubert 25]

3 hours ago, CHackbart said:

which should work fine on all platforms

Yes, it does on Windows. No event needed.