[RESOLVED] Opacity increase slowly works but form is empty before it reaches max

[pourkascheff]

Hi all o7
Consider following code to achieve a sort of fade-in effect:

    Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
        Me.Invoke(Sub()
                      While Me.Opacity < 0.9
                          Me.Opacity += 0.00001 'BRIGHT UP BACKGROUND
                      End While
                  End Sub)
    End Sub

It does the matter but the form is empty (All labels and pictures are invisible apparently) until while loop completes (I guess) How do I rectify this?
- Without Me.Invoke = not even fading.
- Tried "FormLoad" event = not even fading.
- Not a Timer control fan.
- Never tried "InitializeComponent()".

[pourkascheff]

Temporary worked out with a "Timer" as follows:

    Private Sub FADEIN_Tick(sender As Object, e As EventArgs) Handles FADEIN.Tick
        If Me.Opacity < 0.9 Then
            Me.Opacity += 0.01
        Else
            'DO FINISHING THINGS OR CALL A FUNC.
            FADEIN.Enabled = False
        End If
    End Sub

I convinced that when you are pursuing graphical goals, you have to switch over on bad things. Like more control, more inefficient ways to code.

[.paul.]

It’s a matter of threading. If you’re tying up the UI thread with a while loop, it can’t be doing anything else…

[Shaggy Hiker]

InitializeComponent is a function that is generated for you. I'm not sure what you expected it to do, but you shouldn't be calling it yourself, aside from the one call in the constructor. Calling it at any other time would create some weird results.

A timer is pretty much the only option that seems likely to work for this. You are dealing with the UI, which means the UI thread. The loop you are running will cause the form to at least invalidate, but it never gets a chance to paint, because that would require the loop to pause. It's somewhat possible that you might achieve your goal with Application.DoEvents, and that might be pretty harmless in this particular case, but that's usually a bad thing to be doing. Therefore, the timer is the best option.

[.paul.]

InitializeComponent is a function that is generated for you. I'm not sure what you expected it to do, but you shouldn't be calling it yourself, aside from the one call in the constructor. Calling it at any other time would create some weird results.

A timer is pretty much the only option that seems likely to work for this. You are dealing with the UI, which means the UI thread. The loop you are running will cause the form to at least invalidate, but it never gets a chance to paint, because that would require the loop to pause. It's somewhat possible that you might achieve your goal with Application.DoEvents, and that might be pretty harmless in this particular case, but that's usually a bad thing to be doing. Therefore, the timer is the best option.

Your loquacious answer filled in the blanks in my terse reply. I was going to mention DoEvents, but I thought it was better left unsaid without a good explanation…

[Shaggy Hiker]

It's not usually a good suggestion to make, but in this case, where the form really can't be doing anything else, it just might be a good solution. I still prefer the timer, myself. Timers are quite efficient.

[dbasnett]

FWIW this worked nicely

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        Me.Visible = False
        Me.DoubleBuffered = True
        Me.Opacity = 0.0
    End Sub

    Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
        Me.Visible = True
        Dim tsk As Task = Task.Run(Sub()
                                       For x As Integer = 1 To 100
                                           Threading.Thread.Sleep(10)
                                           Me.BeginInvoke(Sub()
                                                              Me.Opacity += 0.01
                                                          End Sub)
                                       Next
                                   End Sub)
    End Sub

[pourkascheff]

Perfect, thanks.

[vbdotnut]

When it come to presentation effects with WinForms... what I have learned.... Just dont do it!

[.paul.]

Perfect, thanks.

dBasnett’s answer looks all shiny and new, but in reality, it’s not more efficient than the Timer method.
It’s a secondary thread with 100 cross thread operations, so probably not as efficient as the timer IMO…

[vbdotnut]

dBasnett’s answer looks all shiny and new, but in reality, it’s not more efficient than the Timer method.
It’s a secondary thread with 100 cross thread operations, so probably not as efficient as the timer IMO…

Even more efficient would be to not do it at all. Its just not necessary.