TCanvas::Emit("Closed") executed twice?

ROOT
1

Hi rooters,
seems to me that TCanvas::Emit(“Closed”)
is called twice. (root 6.12.04 and earlier)
Attached a little macro:
.L mycanvas.C+
MyCanvas *mc = new MyCanvas()
then close canvas with WM cross.
Same happens if the canvas is deleted from the command line.
Cheers
Otto
mycanvas.C (1.1 KB)

2

run-in in debug I see that

MyCanvas::CanvasClosed()

is called twice from:

  1. void TCanvas::Closed()
  2. void TPad::Close(Option_t *)
3

Hi,
in TPad::Close(Option_t *) line: 985 we have:

// emit signal
if (IsA() != TCanvas::Class())
Closed();

so in this case (TCanvas) the signal should be suppressed.
Otto

4

But it seems that’s what this code does: in case the object is a TCanvas, Closed() is not called … right ?

5 
in TPad::Close(Option_t *) line: 985 we have:

// emit signal
if (IsA() != TCanvas::Class())  Closed();

The conditional statement is ineffective in this case. TPad::Close is called from the TPad destructor which is called as a base destructor from the TCanvas destructror. By the time the TPad destructor starts, the object has (on some platform) ‘forgotten’ that it once was a TCanvas.

6

ok, I understand.
The question is:
Do we need the Emit(“Closed”) in TCanvas.cxx:802 at all
if it is emitted in TPad anyway.

I use for the moment a workaround:
When I receive “Closed” I do a Disconnect(“Closed”…
then I dont see another one.

Otto

7

Hi Otto,

Hard to tell if deleting it will generate side effects or not. It seems it was introduced 13 years ago by this patch.