dont load docking in the OnFirstShow handler

This caused random cycles while auto-sizing, making dexed impossible
to start without deleting docking.xml

src/u_main.pas

@@ -457,6 +457,8 @@ type
     procedure updateFloatingWidgetOnTop(onTop: boolean);
     procedure widgetDockingChanged(sender: TDexedWidget; newState: TWidgetDockingState);
     procedure mnuOptsItemClick(sender: TObject);
+    procedure anchorDockingAddControlEvent(Sender: TObject; aName: string;
+                var AControl: TControl; DoDisableAutoSizing: boolean);
 
     // IMainMenu
     function singleServiceName: string;
@@ -1356,6 +1358,10 @@ begin
 
   fProcInputHandler := getprocInputHandler;
 
+  InitDocking;
+  if FileExists(getDocPath + 'docking.xml') then
+    LoadDocking();
+
   fInitialized := true;
 end;
 
@@ -1610,6 +1616,18 @@ begin
   fCleanIconIndex := loadIcon('CLEAN');
 end;
 
+procedure TMainForm.anchorDockingAddControlEvent(Sender: TObject; aName: string;
+            var AControl: TControl; DoDisableAutoSizing: boolean);
+var w : TDexedWidget;
+begin
+  for w in fWidgList do
+    if w.name = aName then
+    begin
+      AControl := w;
+      break;
+    end;
+end;
+
 procedure TMainForm.InitWidgets;
 var
   widg: TDexedWidget;
@@ -1617,6 +1635,9 @@ var
   itm: TMenuItem;
   idx: integer;
 begin
+
+  DockMaster.OnCreateControl := @anchorDockingAddControlEvent;
+
   fWidgList   := TWidgetList.Create;
   fMesgWidg   := TMessagesWidget.create(self);
   fEditWidg   := TEditorWidget.create(self);
@@ -2110,8 +2131,6 @@ var
 begin
   inherited;
 
-  InitDocking;
-
   // TODO-cbetterfix: clipboard doesn't work first time it's used on a reloaded doc.
   // see: http://forum.lazarus.freepascal.org/index.php/topic,30616.0.htm
   if fAppliOpts.reloadLastDocuments then
@@ -2129,11 +2148,6 @@ begin
       fInfoWidg.showWidget;
   end;
 
-  // see https://bugs.freepascal.org/view.php?id=29475
-  // reloading must be done here otherwise there are "jumps"
-  if FileExists(getDocPath + 'docking.xml') then
-    LoadDocking();
-
   if fAppliOpts.autoCheckUpdates then
   begin
     url := checkForUpdate;