Fixed issue #760: TVirtualTreeColumns.GetFirstVisibleColumn() cause A…

…V if called between BeginUpdate() and EndUpdate()

CHANGES.txt

@@ -4,6 +4,7 @@
 	- We do no longer test on Windows XP/2003
 	- We may accept pull request for XP support if the code quality is sufficient.
 	- We recommend to use the V6 branch on Windows XP
+  * Fixed issue #760: TVirtualTreeColumns.GetFirstVisibleColumn() cause AV if called between BeginUpdate() and EndUpdate()
   * Fixed issue #759: TBaseVirtualTree.InitNode() overrides check state of top level nodes set in OnInitNode event handler
   * Fixed issue #757: Header popup menu opens twice
   * Fixed issue #758: The OnColumnVisibilityChanged event is not always fired

Source/VirtualTrees.pas

@@ -8914,6 +8914,8 @@ function TVirtualTreeColumns.GetFirstVisibleColumn(ConsiderAllowFocus: Boolean =
 
 begin
   Result := InvalidColumn;
+  if (UpdateCount > 0) or (csLoading in Header.TreeView.ComponentState) then
+    exit; // See issue #760
   for I := 0 to Count - 1 do
     if (coVisible in Items[FPositionToIndex[I]].FOptions) and
        ( (not ConsiderAllowFocus) or
@@ -8938,6 +8940,8 @@ function TVirtualTreeColumns.GetLastVisibleColumn(ConsiderAllowFocus: Boolean =
 
 begin
   Result := InvalidColumn;
+  if (UpdateCount > 0) or (csLoading in Header.TreeView.ComponentState) then
+    exit; // See issue #760
   for I := Count - 1 downto 0 do
     if (coVisible in Items[FPositionToIndex[I]].FOptions) and
        ( (not ConsiderAllowFocus) or