Question

I have noticied that when using the PorgressBar. If I set the value to x, the value displayed is not immediately updated, it takes a small amount of time to draw it as the bar is animated from its current value to the new value.

This is easy to see in the following code:

Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Label1.Text = ""
    Dim progressHandler = New Progress(Of Integer)(Sub(value) ProgressBar1.Value = value)
    Dim progress = CType(progressHandler, IProgress(Of Integer))
    Await Task.Run(Sub()
                       For i = 1 To 100
                           progress.Report(i)
                           Thread.Sleep(10)
                       Next
                   End Sub)
    Label1.Text = "Value Now at 100%"
    Await Task.Delay(650) 'it takes this long for the bar to be rendered
    Label1.Text += " - Finished drawing"
End Sub

You will notice running this code that the Value Now at 100% appears a long time before the bar has actually reached 100%.

Is there any way that I can detect when the bar has finished rendering?

Answer 1

I just tried this out and can see exactly what you mean. Unfortunately after spending a little while seeing if the DrawToBitmap functions on the progress bar might help, I’ve come up short.

The next step would be to create a custom progress bar that exposes events for when rendering has completed.

For a reasonable example on how to create a custom progress bar, try here:
http://msdn.microsoft.com/en-us/library/system.windows.forms.progressbarrenderer(v=VS.100).aspx

A quick scan over the code looks like you should be able to plug in an ‘OnRendered’ event or similar on or around the calls to ‘DrawHorizontalChunks’ (or ‘DrawVerticalChunks’).

Probably not the answer you was after, but at least gives you the control you need if you pursue it?

Note: I haven’t tried this myself, so please don’t send me hate mail if you spend all day on this to find you get the same results…

Good Luck!

EDIT:

Wasn’t happy with my response, seemed a bit lazy… The following uses a custom progress bar as I described. It has a couple basic properties for setting Max/Min values, Performing steps, and setting the value directly. I’ve tested this by changing the sleep interval to various amounts, in all cases the form displayed the progress bar as full before closing. Note the new OnRendered event.

Imports System
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Windows.Forms.VisualStyles

Public Class Form1
    Inherits Form
    Private WithEvents bar1 As ProgressBarWithRender = New ProgressBarWithRender()


    Public Sub New()
        InitializeComponent()
        Me.Size = New Size(500, 500)
        bar1.Location = New Point(100, 100)
        bar1.Width = 300
        bar1.Height = 50
        bar1.Maximum = 30
        bar1.Step = 1
        Controls.Add(bar1)
    End Sub

    Public Sub OnRendered(ByVal valueRendered As Integer) Handles bar1.OnRendered
        If valueRendered = bar1.Maximum Then
            ' We know everything has been drawn
            Me.Close()
        End If
    End Sub


    <STAThread()> _
    Public Shared Sub Main()
        ' The call to EnableVisualStyles below does not affect
        ' whether ProgressBarRenderer.IsSupported is true; as 
        ' long as visual styles are enabled by the operating system, 
        ' IsSupported is true.
        Application.EnableVisualStyles()
        Application.Run(New Form1())

    End Sub 'Main

    Private Sub Form1_Click(sender As Object, e As System.EventArgs) Handles Me.Click
        For i = 1 To 30
            bar1.PerformStep()
            Threading.Thread.Sleep(10)
        Next
    End Sub

End Class 'Form1

Public Class ProgressBarWithRender
    Inherits Control

    Public Delegate Sub RenderedEventArgs(ByVal valueRendered As Integer)
    Public Event OnRendered As RenderedEventArgs

    Private ProgressBarRectangles() As Rectangle

    Public Property [Step] As Integer

    Public Property InnerPadding As Integer = 3

    Private _Maximum As Integer
    Public Property Maximum As Integer
        Get
            Return _Maximum
        End Get
        Set(value As Integer)
            _Maximum = value
            CalculateTickSizes()
        End Set
    End Property

    Private _Minimum As Integer
    Public Property Minimum As Integer
        Get
            Return _Minimum
        End Get
        Set(value As Integer)
            _Minimum = value
            CalculateTickSizes()
        End Set
    End Property

    Private _Value As Integer
    Public Property Value As Integer
        Get
            Return _Value
        End Get
        Set(newValue As Integer)
            If newValue < Me.Value AndAlso newValue > 0 Then
                Throw New NotImplementedException("ProgressBarWithRender does not support decrementing the value")
            End If
            Me._Value = newValue
        End Set
    End Property

    Public Sub PerformStep()
        ' Ensure step doesn't exceed boundaries
        If Value + [Step] > Maximum Then
            Value = Maximum
        ElseIf Value + [Step] < Minimum Then
            Value = Minimum
        Else
            Value += [Step]
        End If

        ' We are limited by the Renderers Chunk Width, so we possibly can't draw every step if there is a high maximum
        Dim g As Graphics = Me.CreateGraphics
        ProgressBarRenderer.DrawHorizontalChunks(g, ProgressBarRectangles(Value - Minimum))
        RaiseEvent OnRendered(Value)

    End Sub

    Protected Overrides Sub OnPaint(e As System.Windows.Forms.PaintEventArgs)
        MyBase.OnPaint(e)
        If Not ProgressBarRenderer.IsSupported Then
            Throw New NotImplementedException("Progress Bar Rendering is not supported")
        End If
        ProgressBarRenderer.DrawHorizontalBar(e.Graphics, ClientRectangle)
    End Sub

    Private Sub CalculateTickSizes()
        ' Changing the Maximum will change the tick rectangle size
        ProgressBarRectangles = New Rectangle(Maximum) {}
        Dim chunkThickness As Integer = ProgressBarRenderer.ChunkThickness + (ProgressBarRenderer.ChunkSpaceThickness * 2)
        Dim tickThickness As Double = ((ClientRectangle.Width - (InnerPadding * 2)) - (ProgressBarRenderer.ChunkSpaceThickness * 2)) / (Maximum - Minimum)
        If tickThickness < chunkThickness Then
            Debug.Print("This will go wrong because we can't draw small enough chunks...")
        End If
        For i As Integer = 0 To Maximum
            Dim filledRectangle As Integer = CInt(tickThickness * i)
            ProgressBarRectangles(i) = New Rectangle(ClientRectangle.X + InnerPadding,
                                                     ClientRectangle.Y + InnerPadding,
                                                     filledRectangle,
                                                     ClientRectangle.Height - (InnerPadding * 2))
        Next
    End Sub

End Class