I have a TreeView which holds approximately 100,000 TreeNodes or even more, I have optimized everything related to loading or unloading them on deserialization process but now I'm stuck with an issue I can't overcome.
Its important to mention I decided not to use the LabelEdit default event given by the control since its pretty tricky to make it work as I wanted to, Its widely known that there are a lot of "problems" with this particular event which have pushed many devs to implement their own custom TreeViews.
In my case I am using a ContextMenu which has a Rename option, this brings a textbox right in front of the TreeNode and then I just simply change the TreeNode.Text property to whatever the user input was in the TextBox keydown event, once we trigger this event, the whole GUI freezes for a couple of seconds (4-5), I'm not doing any Depth search over the TreeNodeCollection or anything, I am directly accessing the TreeNode and modifying the property...
So, any thoughts on what could be wrong here? I already tried BeginUpdate / SuspendLayout / or even a custom solution found here How do I suspend painting for a control and its children? and nothing seems to help.
The first thing that comes to mind is that when the text is changed on the node, it must be redrawing the entire treeview.
In this situation, suspendlayout will not help, as the control isn't laying its contents.
I think beginupdate stops the drawing when nodes are being added to the list, but the text changed might bypass this.
Have you considered not using the keydown, and just updating the text once the user has dismissed the textbox? (i.e. done editing). Not ideal, but will limit the performance hit to once, instead of every key stroke?
Related
Currently I am stuck with a problem that is simple on the first sight. Its about automated GUI testing.
I want to make a row/cell of a WPF DatGrid completely visible by scrolling using ScrollIntoView(row) and then accessing the row/cell directly after. Unfortunately scrolling in ScrollViewer seems to happen asynchronously. This means I need to wait for the scrolling to finish before accessing the row/cell. For this purpose I found the ScrollChanged event I can subscribe.
There is only one detail I can not solve: If the row/cell I want to access is already visible (and no scrolling is necessary) I do not get that event and the algorithm gets stuck. I was not able to find a reliable way to predict if a call to ScrollIntoView(row) actually scrolls.
Any idea how to solve this?
To make sure layout is updated call UIElement.UpdateLayout after you ScrollIntoView and before you want to use item. Quoting MSDN it
Ensures that all visual child elements of this element are properly updated for layout.
I have a treeview and a textbox. As I type in the text box it updates the tree view in real time (filtering by what I type and matching against the objects in the tree view).
The problem is it starts freezing a bit as I'm typing in the box. ie. while the treeview is updating the text box freezes. I have put the logic that populates the treeview in another thread hoping this would make it run a bit faster - which it did, but not enough. I believe it is the actual UI updating which is causing the responsiveness to diminish.
What are some ways that I can tackle this problem? Is it possible to have different UI elements (in this case, the treeview and the textbox) handled in different threads - rather than just the logic which is the case now?
Thanks
Your problem is that only one UI thread exists!
A possible solution to your problem is to filter the treeview after a few milliseconds after the user has made a text input.
Another possibility is to make the filtering in a separate task and the result of the Treview reassign.
I hope this helps you with your problem.
I have implemented a custom Undo/Redo stack and Im trying to get it to work with the WPF TextBox.
I have turned off the built in Undo-mechanism and hooked up my custom Undo on Ctrl+Z. Everything works fine accept that the caret in the TextBox is always being moved to index 0 on every undo/redo. The question is how to solve this?
I have tried having a custom behaviour on the TextBox which listens to TextChanged and is localizing the last change in the text-string. But this only works unless you start typing the same letter several times in a row. The my method breaks down.
What I ideally want is some kind of behaviour that only makes actual changes to the TextBox.Text-property. As it is now it is updated completely for every Undo, even if its only the last entered letter that is removed. This is of course no suprise since it listens to the Text-property on my PresentationModel which is triggering PropertyChanged on Undo.
But wouldnt it be great if there was some more fine-detailed way of telling exactly what had changed with the property-value, that only one or a couple of letters where inserted/removed in the string value. Then the TextBox could change only that without having to refresh its entire Text-value. Is there any such way of telling the TextBox this allready or could it be possible to make a custom TextBox that behaved in this way? Then it would be possible to pinpoint the exact location for the new caret without having it go straight back to 0 for every propertychange-update!
I am using a standard TreeView in a WinForms application and everything works fine except for one issue:
Parts of the system need to change depending on the selected TreeNode, which works fine using the AfterSelect event.
However, sometimes the TreeView will get cleared completely resulting in an empty selection which does not trigger this event.
At the momemnt I am calling the event callback manually to fix this issue.
This is obviously dangerous, since I will forget to call this function somewhere. Is there a "correct" way to do this?
Thank You!
This is by design. The underlying native Windows controls only generate notifications for things you cannot figure out yourself. The ListBox control for example doesn't have any event that tells you an item got added or removed. Which is because there is no way for the user to add or remove items. Similarly, there's no way for the user to remove the nodes from a tree view.
These kinds of changes requires code that you write. Since it is your code, you cannot not know that these changes happened. If you want an event then you'll have to raise it yourself. Beware that this is harder than it looks, the TreeNodeCollection class doesn't reliably let you generate an event for programmatic changes to the node collection. It doesn't behave like an ObservableCollection. You are definitely better off by not needing this event.
We've created a new, quite complex, WPF application from the ground up and have run into a performance problem as the number of commands registered with the CommandManager increase. We're using simple lightweight commands in our MVVM implementation, however the third party controls we're using (Infragistics) do not, and call CommandManager.RegisterClassCommandBinding liberally to add RoutedCommands. The performance problem manifests itself as a perceived sluggishness in the UI when responding to user input, for example tabbing between controls is slow, text input is 'jerky' and popup animation is 'clunky'. When the app is first fired up the UI is snappy. As more screens containing Infragistics grids are opened the performance deteriorates.
Internally, the CommandManager has a private field named _requerySuggestedHandlers, which is a List< WeakReference>. I've used reflection to get a reference to this collection, and I've noticed that when I call .Clear(), the responsiveness of the UI improves back to its initial state. Obviously I don't want to go round clearing collections that I know little about, especially using reflection (!) but I did it to see if it would cure the performance problems, and voila it did.
Normally, this situation would clean itself up after a certain amount of time passes. However, the collection of WeakReferences (_requerySuggestedHandlers) will only get trimmed once a garbage collection is initiated, which is non-deterministic. Because of this, when we close down windows containing grids (Infragistics XamDataGrid), the CanExecute property for 'dead' grid commands continue to be evaluated unnecessarily, long after the window is closed. This also means that if we close down a number of windows, the performance is still sluggish until a garbage collect is initiated. I understand that this can happen on allocation, and I've seen that myself because if I open a further window this causes the initial memory (from the disposed Windows) to be collected and performance returns to normal.
So, given the above, here are my questions:
How, and from where, does CommandManager.InvalidateRequerySuggested() get called? I haven't found any documentation on MSDN that explains this in any great detail. I hooked up to the CommandManager.RequerySuggested event and it looks like it's being called whenever controls lose focus.
Is is possible to suppress CommandManager.InvalidateRequerySuggested() being called in response to user input?
Has anyone else run into this issue, and if so, how have you avoided it?
Thanks!
This sounds like one of the rare cases where deterministically calling GC.Collect() is the right thing to do. The ordinary argument against it is that the garbage collector is smarter than you are. But when you're dealing with WeakReference objects, you enter territory where you may know something that the garbage collector doesn't. Kicking off garbage collection is certainly better than clearing _requerySuggestedHandlers - among other things, it won't do anything to the WeakReference objects that point to controls that are still alive.
I'd choose this over trying to figure out how to suppress RequerySuggested, since that would screw up the behavior of those commands that you still care about.