Anyone have a C# example showing an owner drawn tabcontrol with hot-tracking effects?

Question

Anyone have a C# example showing an owner drawn tabcontrol with hot-tracking effects?

I've implemented a nice owner drawn tabcontrol using C# and .NET 2.0 but i'm stumped when it comes to implementing hot-tracking effects.

Any Ideas?

Answer 1

Here's one way to do it, using MouseEnter, MouseMove, and MouseLeave to trigger the necessary redraws. I made it a little more complicated than the most basic implementation, to avoid flicker. It's up to you how to indicate the current hot-track tab; in the example I just changed the background color of the tab.

In my case the tab was a member of a Form and I handled the various events in the form, but it could easily be adapted to use virtual overrides in a custom-derived TabControl class.

// the index of the current hot-tracking tab
private int hotTrackTab = -1;

// returns the index of the tab under the cursor, or -1 if no tab is under
private int GetTabUnderCursor()
{
    Point cursor = this.tabs.PointToClient( Cursor.Position );
    for( int i = 0; i < this.tabs.TabPages.Count; i++ )
    {
        if( this.tabs.GetTabRect( i ).Contains( cursor ) )
            return i;
    }
    return -1;
}

// updates hot tracking based on the current cursor position
private void UpdateHotTrack()
{
    int hot = GetTabUnderCursor();
    if( hot != this.hotTrackTab )
    {
        // invalidate the old hot-track item to remove hot-track effects
        if( this.hotTrackTab != -1 )
            this.tabs.Invalidate( this.tabs.GetTabRect( this.hotTrackTab ) );

        this.hotTrackTab = hot;

        // invalidate the new hot-track item to add hot-track effects
        if( this.hotTrackTab != -1 )
            this.tabs.Invalidate( this.tabs.GetTabRect( this.hotTrackTab ) );

        // force the tab to redraw invalidated regions
        this.tabs.Update();
    }
}

private void tabs_DrawItem( object sender, DrawItemEventArgs e )
{
    // draw the background based on hot tracking
    if( e.Index == this.hotTrackTab )
    {
        using( Brush b = new SolidBrush( Color.Yellow ) )
            e.Graphics.FillRectangle( b, e.Bounds );
    }
    else
    {
        e.DrawBackground();
    }

    // draw the text label for the item, other effects, etc
}


private void tabs_MouseEnter( object sender, EventArgs e )
{
    UpdateHotTrack();
}

private void tabs_MouseLeave( object sender, EventArgs e )
{
    UpdateHotTrack();
}

private void tabs_MouseMove( object sender, MouseEventArgs e )
{
    UpdateHotTrack();
}