VirtualTreeView: Fix header paint issue in gtk2.

(cherry picked from commit 8b9b6cd85d)

components/virtualtreeview/laz.virtualtrees.pas

@@ -294,6 +294,12 @@ var // Clipboard format IDs used in OLE drag'n drop and clipboard transfers.
 
   UtilityImageSize: Integer = cUtilityImageSize;
 
+{$ifdef gtk}
+// Workaround LCL bug 8553
+var
+  pf32bit: TPixelFormat = pfDevice;
+{$endif}
+
 type
   // The exception used by the trees.
   EVirtualTreeError = class(Exception);

examples/virtualtreeview/vst_advanced/DrawTreeDemo.lfm

@@ -7,8 +7,8 @@ object DrawTreeForm: TDrawTreeForm
   Caption = 'DrawTreeForm'
   ClientHeight = 453
   ClientWidth = 710
+  LCLVersion = '4.99.0.0'
   OnCreate = FormCreate
-  LCLVersion = '2.1.0.0'
   object Label7: TLabel
     Left = 8
     Height = 30
@@ -53,6 +53,7 @@ object DrawTreeForm: TDrawTreeForm
     AnchorSideBottom.Control = TrackBar1
     Left = 8
     Height = 361
+    Hint = '(dummy)'
     Top = 46
     Width = 694
     Anchors = [akTop, akLeft, akRight, akBottom]
@@ -111,6 +112,8 @@ object DrawTreeForm: TDrawTreeForm
     OnDrawHint = VDT1DrawHint
     OnDrawNode = VDT1DrawNode
     OnFreeNode = VDT1FreeNode
+    OnGetHint = VDT1GetHint
+    OnGetHintKind = VDT1GetHintKind
     OnGetHintSize = VDT1GetHintSize
     OnGetImageIndex = VDT1GetImageIndex
     OnGetNodeWidth = VDT1GetNodeWidth
@@ -129,9 +132,9 @@ object DrawTreeForm: TDrawTreeForm
     Top = 415
     Width = 197
     Max = 100
-    OnChange = TrackBar1Change
     Position = 50
     TickStyle = tsNone
+    OnChange = TrackBar1Change
     Anchors = [akLeft, akBottom]
     BorderSpacing.Left = 7
     TabOrder = 1

examples/virtualtreeview/vst_advanced/DrawTreeDemo.pas

@@ -379,8 +379,9 @@ begin
             Data.Properties := Data.Properties + ', 64K colors';
           pf24bit:
             Data.Properties := Data.Properties + ', 16M colors';
-          pf32bit:
-            Data.Properties := Data.Properties + ', 16M+ colors';
+          else
+            if Picture.Bitmap.PixelFormat = pf32bit then
+              Data.Properties := Data.Properties + ', 16M+ colors';
         end;
         if Cardinal(Data.Image.Height) + 4 > TLazVirtualDrawTree(Sender).DefaultNodeHeight then
             Sender.NodeHeight[Node] := Data.Image.Height + 4;