Building counter GUI using powershell

I have remaining Time of 20 sec. How can I create a PowerShell GUI that shows a countdown timer with an OK button? The timer should show the remaining time in decreasing order (e.g., 20, 19, 18) and should close automatically when the remaining time is complete. If the user clicks the OK button before the remaining time is complete, it should close the timer.

#Remaing time in seconds
$delay = 10

#Add assembly for windows forms
Add-Type -AssemblyName System.Windows.Forms

$Counter_Form = New-Object System.Windows.Forms.Form
$Counter_Form.Text = "Countdown Timer!"
$Counter_Form.Width = 450
$Counter_Form.Height = 200

$Counter_Label = New-Object System.Windows.Forms.Label
$Counter_Label.Width = 300
$Counter_Label.Height = 30
$Counter_Label.ForeColor = "Green"

$normalfont = New-Object System.Drawing.Font("Times New Roman", 14)
$Counter_Label.Font = $normalfont
$Counter_Label.Left = 20
$Counter_Label.Top = 20

$Counter_Form.Controls.Add($Counter_Label)


#Adding button so that that exist without waiting for counter to complete
$OK_Button = New-Object System.Windows.Forms.Button
$OK_Button.Text = "OK"
$OK_Button.Width = 100
$OK_Button.Height = 30
$OK_Button.Left = 20
$OK_Button.Top = 70
$OK_Button.Add_Click({
    #here closing the form but we can shut down the system also
    $Counter_Form.Close()
})
$Counter_Form.Controls.Add($OK_Button)



while ($delay -ge 0)
{
     
    $Counter_Form.Visible = $true
    $Counter_Label.Text = "Seconds Remaining: $($delay)"
    
    if ($delay -lt 5)
    { 
        $Counter_Label.ForeColor = "Red"
        $fontsize = 20 - $delay
        
        $warningfont = New-Object System.Drawing.Font("Times New Roman", $fontsize, ([System.Drawing.FontStyle]::Bold -bor [System.Drawing.FontStyle]::Underline))
        $Counter_Label.Font = $warningfont
    } 

    Start-Sleep 1
    $delay -= 1
}

$Counter_Form.Visible = $false

$Counter_Form.ShowDialog()

In above code I have added OK button but it's not working .

You can use a Timer instance as Jimi recommended in comments and in its Tick event you can define the logic for each tick which is pretty much the same that what you have in your while loop.

Add-Type -AssemblyName System.Windows.Forms

# We need to use a reference type here (a hashtable in this case)
# so that the Timer event can update it from that scope
$delay = @{ Counter = 10 }

$Counter_Form = [System.Windows.Forms.Form]@{
    Text   = 'Countdown Timer!'
    Width  = 450
    Height = 200
}

$Counter_Label = [System.Windows.Forms.Label]@{
    Width     = 300
    Height    = 30
    ForeColor = 'Green'
    Font      = New-Object System.Drawing.Font('Times New Roman', 14)
    Left      = 20
    Top       = 20
    Text      = 'Hello world!'
}
$Counter_Form.Controls.Add($Counter_Label)

$OK_Button = [System.Windows.Forms.Button]@{
    Text   = 'OK'
    Width  = 100
    Height = 30
    Left   = 20
    Top    = 70
}

$OK_Button.Add_Click({
    # If we click OK, stop the timer!
    $timer.Stop()
    # And update the label
    $Counter_Label.Text = 'Everything good!'
    $Counter_Label.ForeColor = 'Green'
    $Counter_Label.Font = [System.Drawing.Font]::new('Times New Roman', 14)
})
$Counter_Form.Controls.Add($OK_Button)

# Create a Timer instance
$timer = [System.Windows.Forms.Timer]::new()
# With 1 second interval ticks
$timer.Interval = [timespan]::FromSeconds(1).TotalMilliseconds
$timer.Add_Tick({
    $text = 'Seconds remaining: {0}' -f $delay.Counter--
    # You can always troubleshoot using `Out-Host` here, remove it when done
    $text | Out-Host
    $Counter_Label.Text = $text

    if ($delay.Counter -eq -1) {
        # Send a Cancel Dialog, this will trigger the disposal of all resources
        $Counter_Form.DialogResult = 'Cancel'
    }

    if ($delay.Counter -lt 5) {
        $Counter_Label.ForeColor = 'Red'
        $Counter_Label.Font = [System.Drawing.Font]::new(
            'Times New Roman',
            20 - $delay.Counter,
            [System.Drawing.FontStyle]::Bold -bor [System.Drawing.FontStyle]::Underline)
    }
})

$Counter_Form.Add_Shown({
    $Counter_Form.Activate()
    $timer.Start()
})

# when exiting the form
if ($Counter_Form.ShowDialog()) {
    $timer.Dispose()

    $Counter_Form.Controls | ForEach-Object {
        $_.Dispose()
    }

    $Counter_Form.Dispose()
}

<!-- language-all: sh -->

In order to keep a WinForms form responsive to user input, you need one of two approaches:

• Either: Call .ShowDialog() to display a form modally, i.e. to block execution until the form is closed.

  • Short of using jobs, the only PowerShell code that can execute while the form is being displayed is in script blocks serving as event handlers for the form's controls, if any.

  • Santiago Squarzon's helpful answer contains a .ShowDialog() solution that uses a timer control for periodically updating the countdown display.

• Or: If you want PowerShell code to remain in control of the foreground thread, as in your attempt, the simplest approach is to call .Show() (or set .Visible = $true), which displays the form non-modally and returns control the caller right away, followed by [System.Windows.Forms.Application]::DoEvents() calls in a loop, interspersed with short periods of sleep.

  • If you sleep too long - or perform tasks in the loop that take too long to execute - your form will become unresponsive or respond only with a delay.

  • While [System.Windows.Forms.Application]::DoEvents() is generally discouraged, it works as intended in simple, one-form scenarios such as this one and avoids the complexities of job-based parallelism, by allowing for performing (short-running) operations while the form is being shown.

Therefore, to fix your own approach you need to:

• Call [System.Windows.Forms.Application]::DoEvents() in your countdown loop.

• Sleep for less than 1 second between loop iterations, so that pressing the OK button or moving the window responds more quickly; 100 milliseconds works well.

The following is a streamlined, corrected version of your code:

• Given that the loop iterations are now invoked every 100+ milliseconds, a timestamp-based approach is used to calculate the remaining number of seconds.

• using namespace statements and hashtable-based object initializations simplify the code.

using namespace System.Windows.Forms
using namespace System.Drawing
Add-Type -AssemblyName System.Windows.Forms
$Counter_Form = [Form] @{
Text = 'Countdown Timer'
Width = 350; Height = 160
FormBorderStyle = 'FixedDialog' # Prevent resizing
ControlBox = $false  # Hide buttons in title bar.
StartPosition = 'CenterScreen'
TopMost = $true
}
$Counter_Form.Controls.AddRange(@(
($Counter_Label = [Label] @{
Left = 20; Top = 20; Width = 300; Height = 30
ForeColor = 'Green'
Font = [Font]::new('Times New Roman', 14)
})
($OK_Button = [Button] @{
Text = 'OK'
Left = 20; Top = 70; Width = 100; Height = 30
})  
))
# Add handler for the button-click event: close the form.
$OK_Button.add_Click({
$Counter_Form.Close()
})
# Countdown period in seconds
$delay = 10
# Calculate the point in time when the delay has elapsed.
$closeAt = [datetime]::UtcNow.AddSeconds($delay)
$Counter_Form.Visible = $true
while ($Counter_Form.Visible -and ($secsRemaining = [int] ($closeAt - [datetime]::UtcNow).TotalSeconds) -ge 0) {     
$newLabelText = "Seconds Remaining: $secsRemaining"
if ($newLabelText -ne $Counter_Label.Text) {    
if ($secsRemaining -lt 5) { 
$Counter_Label.ForeColor = 'Red'
$fontsize = 20 - $secsRemaining        
$warningfont = [Font]::new('Times New Roman', $fontSize, [FontStyle] 'Bold, Underline')
$Counter_Label.Font = $warningfont
} 
$Counter_Label.Text = $newLabelText
}
# Process form events.
[System.Windows.Forms.Application]::DoEvents()
# Sleep only *a little*, so as to keep the form responsive.
[Threading.Thread]::Sleep(100)
}
$Counter_Form.Visible = $false