How to ensure a tab appear as the leftmost tab in the space

Comments

• Eugene Balabuev (LMD)

  December 2022

  It is not possible while loading. You can do it right after, by re-docking the panel using DockControl method and specifying ATabIndex = 0.
• John Barrat

  December 2022

  I am probably doing this wrong but I am getting an access violation when I try and force it to tab position 0.

  This is the code I have used...
  

  p := OpenPage(s,false, hlPositron, OpenMain);// Creates a DockPanel containing a control and returns with the DockPanel.
  

  dsMain.DockControl(p,p.Zone,alClient,0);// This attempts to set the tab position but causes the access violation

  
  

  Could this be a timing issue, where the Control has not been created before the panel tab is re-positioned .
• Eugene Balabuev (LMD)

  December 2022

  Are you sure that p.Zone is not nil?
• John Barrat

  December 2022

  You are right, its nil.

  Attached is a reduced version of the Open Page code 

  
  

  Start from the bottom of the page where I open a file and force it to tab position 0

  I call open page, which calls add page which calls create dock.  If all works OK the created dock panel back through the chain to the original calling routine.

  
  

  How is it that the doc zone is initially valid but by the time it reaches the calling function its nil.

  
  

  John Barrat
• Eugene Balabuev (LMD)

  December 2022

  Looking at your code, I've realized that you loading files one by one (I've initially though that you want to load the whole docking layout). So, my first answer was wrong, and in this case you actually can specify tab position directly, without re-docking the panel second time.

  
  

  Try to specify zero for ATabIndex parameter of the DockControl method directly in your CreateDock method, like:

  
  

  //....
  if zn <> nil then
    DsMain.DockControl(Result, zn, alClient, 0 {<- here}, SelectPage)
  else
    Result := nil;
  //...
• John Barrat

  December 2022

  Thank you, that seems to get me to where I want to be.