Would Like an Event when a user tabs to a different doc tab

John Barrat

I have a number of Tabbed Docs open.  When user moves from Tab to Tab is it possible to raise an event when the tab change has taken place with the new tab being passed in the event.  Since these changes don't seem to happen in the main thread the only way I have of detecting user has changed tabs is when the user clicks on the new document.

Eugene Balabuev (LMD)

All DockingPack code works in the main thread. There is TLMDDockSite.OnChange event, which should be fired when the layout is changed in any way, including the case when the user selects another tab. A reference to the current selected doc zone can be retrieved via:

pnl := MySite.SpaceZone.SelectedPage.Panel;

John Barrat

If I use the code above I just get an Access Violation.  This is my code.

procedure TfmIDEMain.dsMainChange(Sender: TObject);

var pnl: TLMDDockPanel;

begin

  if Assigned(dsMain.SpaceZone) then begin

    ActivePanel := dsMain.SpaceZone.SelectedPage.Panel;

    if Assigned(ActivePanel) then

      if TIDEPageType(ActivePanel.Tag) = ptEditor then

        TfmEditor(ActivePanel.Controls[0]).DocEnter(self);

  end;

end;

The Access Violation happens on start up even if there are no documents being opened. The occurs on the highlighted line.

The problem I'm trying to resolve only occurs when I am closing a tab.  If I click on the Close button on the tab the tab closes and calls the following routine:

procedure TfmIDEMain.SelectPrevTab;

Var dz,tz, prevz: TLMDDockZone;

    dp: TLMDDockPanel;

    i: Integer;

begin

  UpdateTitleBarCaption('');

  if Not MultifileLoad

  and Assigned(ActivePanel) then begin

    dp := ActivePanel;

    ActivePanel := nil;

    dz := dp.zone;

    if Assigned(dz) then begin

      i := dz.Index;

      tz := dz.parent;

      if Assigned(tz) and (i > 1) then begin

        prevz := tz[i-1];

        if Not prevz.IsEmpty then begin

          tz.SelectedPage := prevz;

          ActivePanel := tz.Panel;

        end;

      end;

    end;

  end;

end;

This then goes to the next open tab but the DocEnter for the new tab doesn't get triggered.  

If I write code to trigger DocEnter the panel returned from tz.SelectedPage is nil so I cannot access the DocEnter routine of the control.  

I assume this is because the switch hasn't taken place yet. 

So if I could get the code you suggested in your original reply to work without crashing using the DockSite OnChange event I would hope that this would solve the problem. 

Eugene Balabuev (LMD)

The code was only an example. In reality you should check all referenced objects for null:

MySite.SpaceZone <> nil

MySite.SpaceZone.SelectedPage <> nil

MySite.SpaceZone.SelectedPage.Panel <> nil

John Barrat

Thanks, I assumed that the if the highest level was unassigned then every thing below would have been unassigned.

It now works very well as I don't need to assign DocClose in my CreateNewTab routine.