I am not very experienced with the TVirtualStringTree component yet, so maybe I forgot something trivial.
My application collects information about a file into a record (file_name, path, size) and displays the data in a virtual row tree.
Now that there are many nodes (200K +), I am experiencing a strong slowdown, the whole tree is basically lagging. I know that the amount of memory is quite large only with the recording data, but I found that the lag is caused by the OnGetText method for VST. It doesn’t matter if this method reads the actual data or sets CellText to a static line (for example, CellText: = 'Test';), the slowdown is significant. If I exit OnGetText without installing CellText, it works great - even with an integer of 1,000,000 nodes in my tree. Also, if I destroy Tree (FullCollapse) by hiding this method, 90% of my nodes, OnGetText behaves normally, or at least is much better.
As far as I understand, OnGetText is called only for really visible screen nodes, so I don’t understand why this is such a problem with a large number of nodes in the tree.
Does anyone have any clues for me to point me in the direction?
EDIT:
Delphi Version: D2010 VST Version: 4.8.6
My code in its simplest test form basically looks like this:
var
SkipGetText : boolean;
procedure TXForm.VSTGetText(Sender: TBaseVirtualTree;
Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType; var CellText: string);
begin
if SkipGetText then exit;
CellText := 'TEST';
// actual code commented out to reduce complications
end;
If I installed CellText, it lags; if I exit, it is not. Oddly enough, further scrolling down worsens.
Here is what is assigned as NodeData:
type
PVSData = ^Fi;
Fi = Packed Record
Name, Dir, Ext: String;
Size: Int64;
end;
procedure TXForm.AddFile( const RootFolder:string; const SR: TSearchRec );
var
FileInfo: PVSData;
FileSize: Int64;
Node: PVirtualNode;
begin
Node := VST.AddChild(nil);
INC(AllFiles);
FileInfo := VST.GetNodeData(Node);
FileInfo^.Name := SR.Name;
FileInfo^.Dir := RootFolder;
Int64Rec(FileSize).Hi := SR.FindData.nFileSizeHigh;
Int64Rec(FileSize).Lo := SR.FindData.nFileSizeLow;
FileInfo^.Size := FileSize;
end;
procedure TXForm.VSTPaintText(Sender: TBaseVirtualTree;
const TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType);
begin
if SkipPaintText then exit;
case ListView.GetNodeLevel(Node) of
0: TargetCanvas.Font.Color := Color1;
else TargetCanvas.Font.Color := Color2;
end;
end;
procedure TXForm.VSTBeforeCellPaint(Sender: TBaseVirtualTree;
TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
CellPaintMode: TVTCellPaintMode; CellRect: TRect; var ContentRect: TRect);
begin
case ListView.GetNodeLevel(Node) of
0: TargetCanvas.Font.Color := Color1;
else TargetCanvas.Font.Color := Color2;
end;
end;
I noticed that expanding / collapsing and re-expanding somehow seems to improve the situation, but it's outside of me to understand why this can really affect.