Drawing on controls

ROOT
1

Dear ROOTers,

Is there a way to draw on top of GUI controls in ROOT? I have a TGListView that sometimes takes long to fill up from a TTree. Therefore I display it empty and than fill it in a separate thread. I would like to write on top of it a related message, larger and more visible than standard entry. Just painting a red text not taking into account control characteristics. Is it possible? I thought that maybe with TVirtualX, but that seems to paint only in Canvases.

2

Hi,

No, there is no simple way of doing this. But you can change the cursor to “wait” state, like it is done for example in TGFileBrowser:

[code]//_____________________________________________________________________________
//
// TCursorSwitcher
//
// Helper class used to change the cursor in a method and restore the
// original one when going out of the method scope.
//_____________________________________________________________________________

///////////////////////////////////////////////////////////////////////////////
class TCursorSwitcher {
private:
TGWindow *fW1;
TGWindow *fW2;
public:
TCursorSwitcher(TGWindow *w1, TGWindow *w2) : fW1(w1), fW2(w2) {
if (w1) gVirtualX->SetCursor(w1->GetId(), gVirtualX->CreateCursor(kWatch));
if (w2) gVirtualX->SetCursor(w2->GetId(), gVirtualX->CreateCursor(kWatch));
}
~TCursorSwitcher() {
if (fW1) gVirtualX->SetCursor(fW1->GetId(), gVirtualX->CreateCursor(kPointer));
if (fW2) gVirtualX->SetCursor(fW2->GetId(), gVirtualX->CreateCursor(kPointer));
}
};

[…]

//______________________________________________________________________________
void TGFileBrowser::Refresh(Bool_t /force/)
{
// Refresh content of the list tree.

TCursorSwitcher cursorSwitcher(this, fListTree);
[…]
}
[/code]
Cheers, Bertrand.