Develop Reference

WinrtXamlToolkit TreeView expand with single instead of double click

I am using the TreeView from the WinrtXamlToolkit. The default behavior of this control is to expand the nested items on double click of the header. The code responsible for this is here (TreeViewItem.cs line 1205).
private void OnHeaderMouseLeftButtonDown(object sender, PointerRoutedEventArgs e)
{
if (Interaction.AllowMouseLeftButtonDown(e))
{
// If the event hasn't already been handled and this item is
// focusable, then focus (and possibly expand if it was double
// clicked)
if (!e.Handled && IsEnabled)
{
if (Focus(FocusState.Programmatic))
{
e.Handled = true;
}
// Expand the item when double clicked
if (Interaction.ClickCount % 2 == 0)
{
bool opened = !IsExpanded;
UserInitiatedExpansion |= opened;
IsExpanded = opened;
e.Handled = true;
}
}
Interaction.OnMouseLeftButtonDownBase();
OnPointerPressed(e);
}
}
Is there a way to change this behavior to expand the items on single click or tap without actually copying the control and all it's related classes to my project?
It seems like an overkill to do this just to change a few lines of code.

I tried to do drag'n'drop stuff with that TreeView and was in a similar situation. My first move was to actually copy all the TreeView and its related classes and man there are a lot. There's a lot of internal stuff happening and I pretty much gave up interfering with it after a bunch of other stuff stopped working.
So my solution was to just have a specific control inside the ItemTemplate that handled dragging for me. For you this would be a Button whose Click you handle. In the eventhandler you will navigate up the visual tree to your TreeViewItem and change the IsExpanded.

Container UserControl - Handle and Modify Added Controls

I'm trying to create a custom container as UserControl.
My Goal: I want to be able to drag controls inside the designer and handle incoming controls inside the code of my usercontrol.
Example: I place my container somewhere and then add a button. In this momemt I want my usercontrol to automatically adjust the width and position of this button. Thats the point where Im stuck.
My code:
[Designer("System.Windows.Forms.Design.ParentControlDesigner, System.Design", typeof(IDesigner))]
public partial class ContactList : UserControl
{
public ContactList()
{
InitializeComponent();
}
private void ContactList_ControlAdded(object sender, ControlEventArgs e)
{
e.Control.Width = 200; // Nothing happens
e.Control.Height = 100; // Nothing happens
MessageBox.Show("Test"); // Firing when adding a control
}
}
The MessageBox is working well. The set width and height is ignored.
The question is just "why?".
EDIT
I've just noticed, when placing the button and recompiling with F6 the button gets resized to 200x100. Why isnt this working when placing?
I mean... the FlowLayoutPanel handles added controls right when you place it. Thats the exact behaviour im looking for.

Using OnControlAdded
To fix your code, when you drop a control on container and you want to set some properties in OnControlAdded you should set properties using BeginInvoke, this way the size of control will change but the size handles don't update. Then to update the designer, you should notify the designer about changing size of the control, using IComponentChangeService.OnComponentChanged.
Following code executes only when you add a control to the container. After that, it respects to the size which you set for the control using size grab handles. It's suitable for initialization at design-time.
protected override void OnControlAdded(ControlEventArgs e)
{
base.OnControlAdded(e);
if (this.IsHandleCreated)
{
base.BeginInvoke(new Action(() =>
{
e.Control.Size = new Size(100, 100);
var svc = this.GetService(typeof(IComponentChangeService))
as IComponentChangeService;
if (svc != null)
svc.OnComponentChanged(e.Control,
TypeDescriptor.GetProperties(e.Control)["Size"], null, null);
}));
}
}

How to use ctrl key + mouse click to select multiple controls?

Probably this question has already an answer here but I was not able to find it..
I have a tabControl with a flowlayoutpanel in each tab page where I can add controls at run time. I can rearrange them, move them across tab pages.. How can I select multiple controls to be able to move them around using ctrl key + mouse click?
This is my drag event so far:
private void control_DragDrop(object sender, DragEventArgs e)
{
Control target = new Control();
target.Parent = sender as Control;
if (target != null)
{
int targetIndex = FindCSTIndex(target.Parent);
if (targetIndex != -1)
{
string cst_ctrl = typeof(CustomControl).FullName;
if (e.Data.GetDataPresent(cst_ctrl))
{
Button source = new Button();
source.Parent = e.Data.GetData(cst_ctrl) as CustomControl;
if (targetIndex != -1)
fl_panel = (FlowLayoutPanel)tabControl1.SelectedTab.Controls[0];
if (source.Parent.Parent.Name == target.Parent.Parent.Parent.Name)
{
this.fl_panel.Controls.SetChildIndex(source.Parent, targetIndex);
}
else
{
target.Parent.Parent.Parent.Controls.Add(source.Parent);
this.fl_panel.Controls.SetChildIndex(source.Parent, targetIndex);
}
}
}
}
}
private int FindCSTIndex(Control cst_ctr)
{
fl_panel = (FlowLayoutPanel)tabControl1.SelectedTab.Controls[0];
for (int i = 0; i < this.fl_panel.Controls.Count; i++)
{
CustomControl target = this.fl_panel.Controls[i] as CustomControl;
if (cst_ctr.Parent == target)
return i;
}
return -1;
}

This is not an easy, nor a common task. But surely doable and depending on preconditions could become trivial without need to spend multi-man-year effort on it ^^.
You have many options:
controls support selection;
container control support children controls selection;
overlay.
Handling selection is pretty easy: have a dictionary (or a control property, possibly using Tag) to store if control is selected or not, show selection somehow, when control is Ctrl-clicked invert selection. You can even provide Shift-key selection.
As #Hans Passant commented, you can use overlay window (invisible window on top of everything) to draw selection reticle there as well as handle selection and dragging itself. Or it could be a custom control with property IsSelected, setting which will draw something (border?) to indicate selection.
Easiest option would be to create SelectionPanel control, which can host any other controls inside, has IsSelected indication and is draggable. When children is added subscribe to MouseUp/MouseDown events or you can only allow to drag if special area of SelectionPanel is clicked. To example, you could have option Enable dragging in your software, when set all SelectionPanels will display special area (header?) which you can drag or Ctrl-click.

ListView scroll control - scroll to bottom if user isn't scrolling?

I have a .NET 3.5 WinForm that has a ListView with the View set in Details mode. It functions as a scrollable list of status items on a long background task. I have the most recent ListViewItem (status entry) added to the bottom. To assure that it is seen, I ensure the visibility of the new item after adding. This all works fine; the list view automatically scrolls to the bottom to show the most recent item.
private void AddListItem(DateTime timestamp, string message, int index)
{
var listItem = new ListViewItem(timestamp.ToString());
listItem.SubItems.Add(message);
statusList.Items.Insert(index, listItem);
statusList.Items[statusList.Items.Count - 1].EnsureVisible();
}
The problem is if the user is scrolling up to look at older messages, the ListView will be scrolled down to make the new item visible as it comes in. Is there a way to control this behavior to check if the user is interacting with the scrollbar (specifically, if they're holding down the mouse button on the scrollbar)? It is probably also acceptable to detected if the scroll is always at the bottom. if it is not at the bottom, then I would not ensure the visibility of the latest item. Something like:
private void AddListItem(DateTime timestamp, string message, int index)
{
var listItem = new ListViewItem(timestamp.ToString());
listItem.SubItems.Add(message);
statusList.Items.Insert(index, listItem);
if (!statusList.IsScrollbarUserControlled)
{
statusList.Items[statusList.Items.Count - 1].EnsureVisible();
}
}
What's strange is that when the user is holding down the scrollbar "handle" in place, the handle doesn't move (implying that the view is not actually being scrolled down programatically), but in infact is.
Update: Is it possible to detect the position of the scrollbar, i.e., if i'ts at the bottom or not?

Two steps to solving this problem:
The WinForms ListView doesn't have a Scrolled event. We'll need to define one.
Determining when the ListView is idle, and calling EnsureVisible only when it's been idle for awhile.
For the first problem, inherit a new class from ListView, override the Windows message pump, and raise an event when the user scrolls it:
public class MyListView : ListView
{
public event EventHandler<EventArgs> Scrolled;
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
const int wm_vscroll = 0x115;
if (m.Msg == wm_vscroll && Scrolled != null)
{
Scrolled(this, new EventArgs());
}
}
}
Now we know when the user scrolls the list view. Your next problem is to determine whether the list view is idle; that is, if the user hasn't scrolled it in awhile.
There are multiple ways to do that. For this purpose, I'm just going to use a time stamp to indicate the last scroll time:
private DateTime lastScrollTime;
...
listView.Scrolled += delegate { lastScrollTime = DateTime.Now };
...
private void AddListItem(DateTime timestamp, string message, int index)
{
var listItem = new ListViewItem(timestamp.ToString());
listItem.SubItems.Add(message);
statusList.Items.Insert(index, listItem);
// Scroll down only if the list view is idle.
var idleTime = TimeSpan.FromSeconds(5);
var isListViewIdle = DateTime.Now.Subtract(this.lastScrollTime) > idleTime;
if (isListViewIdle)
{
statusList.Items[statusList.Items.Count - 1].EnsureVisible();
}
}

Compare to, say, SysInternals' ProcMon. Add a checkbox labeled "Auto scroll" so the user can turn it off.

smooth scrolling .net forms

Hi I am using forms in .net and i am adding lots of linked labels dynamically during runtime,
I am adding these linklabels to panel and adding that panel to the winform. When the no of linklabels increases the form puts out an auto scrollbar(vertical)...
Now when i scroll down using that autoscroll the form is not updating its view as i scroll, the form gets refreshed only when i stop scrolling...
Also when it refresh it looks too bad.. i can see how it draws slowly....
Has anyone dealt with this before??
I tried form.refresh() in scroll event handler but that doesn't seem to help..
Any clues?

Pop this into your class (UserControl, Panel, etc) , then it will work with thumb drag.
private const int WM_HSCROLL = 0x114;
private const int WM_VSCROLL = 0x115;
protected override void WndProc (ref Message m)
{
if ((m.Msg == WM_HSCROLL || m.Msg == WM_VSCROLL)
&& (((int)m.WParam & 0xFFFF) == 5))
{
// Change SB_THUMBTRACK to SB_THUMBPOSITION
m.WParam = (IntPtr)(((int)m.WParam & ~0xFFFF) | 4);
}
base.WndProc (ref m);
}

If you don't want to use WinAPI calls, you can do this:
// Add event handler to an existing panel
MyPanel.Scroll += new EventHandler(MyPanelScroll_Handler);
// Enables immediate scrolling of contents
private void MyPanelScroll_Handler(System.Object sender, System.Windows.Forms.ScrollEventArgs e)
{
Panel p = sender As Panel;
if (e.ScrollOrientation == ScrollOrientation.HorizontalScroll) {
p.HorizontalScroll.Value = e.NewValue;
} else if (e.ScrollOrientation == ScrollOrientation.VerticalScroll) {
p.VerticalScroll.Value = e.NewValue;
}
}

Try setting your form's DoubleBuffered property to True.
Update: actually, that probably won't do anything since your controls are on a Panel on your Form. The built-in Panel control doesn't have an exposed DoubleBuffered property, so the way to do it is to add a UserControl name DBPanel to your project, and change the code so that it inherits from Panel instead of UserControl (you can change this manually in the CS file after you add it). When you add the UserControl, the code will look like this:
public partial class DBPanel : UserControl
{
public DBPanel()
{
InitializeComponent();
}
}
Edit it so that it looks like this (change UserControl to Panel and add the "this.DoubleBuffered = true;" line to the constructor):
public partial class DBPanel : Panel
{
public DBPanel()
{
InitializeComponent();
this.DoubleBuffered = true;
}
}
When you build the project, the compiler will barf on a line that begins with "this.AutoScaleMode ... ". Delete this line and rebuild.
You can now use the DBPanel control on your form in place of a regular Panel, and this should take care of your flicker problem.
Update 2: sorry, I didn't read your question closely enough. You're right, the Panel doesn't redraw itself until you let go of the scrollbar's thumb. I think to achieve this effect you'll just have to create your own UserControl.
Basically you'd just have a UserControl with a VScrollBar docked on the right, and a Panel with AutoScroll = false docked on the left taking up the remainder of the space. The Scroll and ValueChanged events of the VScrollBar fire as you move the thumb up and down, so after adding a bunch of LinkLabels to the inner Panel you can use these events to change the Top position of the Panel, and thus achieve the dynamic scrolling effect you're looking for.
It's kind of irritating that the Panel doesn't work this way by default, or even have a setting that enables it.

The simplest way is to refresh the panel during the scroll event.
private void panel1_Scroll(object sender, ScrollEventArgs e)
{
panel1.Refresh();
}