Hot Tracking

This post will show you how easy it is to make item hot tracking in Better ListView.

First, create a global variable in your Form or Control-derived class to hold a Font instance we will use for hot tracked items:

C#

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private Font fontHot = new Font(“Segoe UI”, 12.0f, FontStyle.Bold);
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Visual Basic

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Private fontHot As New Font(“Segoe UI”, 12F, FontStyle.Bold)
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This is not necessary, but we will re-use the font and will not need to create and dispose Font instances during hot tracking.

Second, initialize a BetterListView instance:

C#

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var listView = new CustomListView();

// add some items in the list
listView.Items.AddRange(new string[] { “The Hobbit”, “The People’s Crisis”, “The Net” });

// set default font for the items
listView.FontItems = new Font(“Segoe UI”, 12.0f, FontStyle.Regular);

// add HitTestChanged event handler
listView.HitTestChanged += ListViewHitTestChanged;
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Visual Basic

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Dim listView = New CustomListView()

‘ add some items in the list
listView.Items.AddRange(New String() {“The Hobbit”, “The People’s Crisis”, “The Net”})

‘ set default font for the items
listView.FontItems = New Font(“Segoe UI”, 12F, FontStyle.Regular)

‘ add HitTestChanged event handler
listView.HitTestChanged += ListViewHitTestChanged
[/vb]

Finally, implement the HitTestChanged event handler:

C#

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private void ListViewHitTestChanged(object sender, BetterListViewHitTestChangedEventArgs eventArgs)
{
BetterListView listView = (sender as BetterListView);
BetterListViewItem itemCurrent = eventArgs.HitTestInfoCurrent.ItemDisplay;
BetterListViewItem itemNew = eventArgs.HitTestInfoNew.ItemDisplay;

if (!ReferenceEquals(itemCurrent, itemNew))
{
listView.BeginUpdate();

if (itemCurrent != null)
{
// reset colors and font to default
itemCurrent.BackColor = Color.Empty;
itemCurrent.ForeColor = Color.Empty;
itemCurrent.Font = null;
}

if (itemNew != null)
{
// set hot background color of an item newly hovered
itemNew.BackColor = Color.GreenYellow;
itemNew.ForeColor = Color.DarkRed;
itemNew.Font = this.fontHot;
}

listView.EndUpdate();
}
}
[/csharp]

Visual Basic

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Private Sub ListViewHitTestChanged(sender As Object, eventArgs As BetterListViewHitTestChangedEventArgs)
Dim listView As BetterListView = TryCast(sender, BetterListView)
Dim itemCurrent As BetterListViewItem = eventArgs.HitTestInfoCurrent.ItemDisplay
Dim itemNew As BetterListViewItem = eventArgs.HitTestInfoNew.ItemDisplay

If Not ReferenceEquals(itemCurrent, itemNew) Then
listView.BeginUpdate()

If itemCurrent IsNot Nothing Then
‘ reset colors and font to default
itemCurrent.BackColor = Color.Empty
itemCurrent.ForeColor = Color.Empty
itemCurrent.Font = Nothing
End If

If itemNew IsNot Nothing Then
‘ set hot background color of an item newly hovered
itemNew.BackColor = Color.GreenYellow
itemNew.ForeColor = Color.DarkRed
itemNew.Font = Me.fontHot
End If

listView.EndUpdate()
End If
End Sub
[/vb]

This method is called whenever an element over which mouse cursors hovers changes. For example, when one moves the mouse cursor between two item’s expand button element and text element or between two items. We detect just the latter case and set item properties accordingly.

Thats’ it!

Of course, you can change any of the properties during hot tracking or make use of rich Owner Drawing capabilities.

Making items invisible

The above image shows two groups of items. The first groups uses hiding of items with the Visible property, while the second group simply turns off drawing of ceratin items.

The first approach is useful when you need to hide item as if it is removed, but keep it actually within Items collection.

The second approach need to create new control inheriting from BetterListView, overrride the OnDrawItem method and set properties like BetterListViewDrawItemEventArgs.DrawImage to false or simply not call the base implementation of OnDrawItem.

The second (owner drawing) approach is useful when you need just to switch off display of item without changing the item layout.