Nivot Ink

Friday, May 23, 2008

UPDATE May 26th: You must run PowerShell v2.0 CTP in STA mode for this to work. Start the shell, then run "powershell -sta" from the command line to start a new version of the shell in "single thread apartment" mode (STA). This is required for WPF to work correctly.

That is a bit of a mouthful of a title for this post but it's the best I could come up with. This post takes some of James' scripty bits and Jaykul's scripty bits and shows you how to create a countdown timer written in PowerShell script that runs in the background without blocking input. Just like Jaykul's original clock, you can drag it around and right-clicking it will close it. His version was the current time and it also showed some system resources. I changed it into a countdown and removed the other nested graphs. When it hits 00:00:00 it turns red. Here's what it looks like:

Here's the source of invoke-background.ps1:

param([string]$scriptName)
# original script James Brundage (blogs.msdn.com/powershell)
$rs = [Management.Automation.Runspaces.RunspaceFactory]::CreateRunspace()
$rs.ApartmentState, $rs.ThreadOptions = “STA”, “ReuseThread”
$rs.Open()
# Reference the WPF assemblies
$psCmd = {Add-Type}.GetPowerShell()
$psCmd.SetRunspace($rs)
$psCmd.AddParameter("AssemblyName", "PresentationCore").Invoke()
$psCmd.Command.Clear()
$psCmd = $psCmd.AddCommand("Add-Type")
$psCmd.AddParameter("AssemblyName", "PresentationFramework").Invoke()
$psCmd.Command.Clear()
$psCmd = $psCmd.AddCommand("Add-Type")
$psCmd.AddParameter("AssemblyName", "WindowsBase").Invoke()
$sb = $executionContext.InvokeCommand.NewScriptBlock(
(Join-Path $pwd $scriptname)
)
$psCmd = $sb.GetPowerShell()
$psCmd.SetRunspace($rs)
$null = $psCmd.BeginInvoke()

Next, here's the modified clock script:

param (
[timespan]$period = (New-Object system.TimeSpan(0,5,0)),
$clockxaml="<path to xaml file>\clock.xaml"
)
### Import the WPF assemblies
Add-Type -Assembly PresentationFramework
Add-Type -Assembly PresentationCore
$clock = [Windows.Markup.XamlReader]::Load(
(New-Object System.Xml.XmlNodeReader (
[Xml](Get-Content $clockxaml) ) ) )
$then = [datetime]::Now
$red = [System.Windows.Media.Color]::FromRgb(255,0,0)
$redbrush = new-object system.windows.media.solidcolorbrush $red
$label = $clock.FindName("ClockLabel")
$done = $false
# Create a script block which will update the UI
$updateBlock = {
if (!$done) {
# update the clock
$elapsed = ([datetime]::Now - $then)
$remaining = $null;
if ($elapsed -lt $period) {
$remaining = ($period - $elapsed).ToString().substring(0,8)
} else {
$label.Foreground = $redbrush
$remaining = "00:00:00"
$done = $true
}
$clock.Resources["Time"] = $remaining
}
}
## Hook up some event handlers
$clock.Add_SourceInitialized( {
## Before the window's even displayed ...
## We'll create a timer
$timer = new-object System.Windows.Threading.DispatcherTimer
## Which will fire 2 times every second
$timer.Interval = [TimeSpan]"0:0:0.50"
## And will invoke the $updateBlock
$timer.Add_Tick( $updateBlock )
## Now start the timer running
$timer.Start()
if(! $timer.IsEnabled ) {
$clock.Close()
}
} )
$clock.Add_MouseLeftButtonDown( {
$_.Handled = $true
$clock.DragMove() # WPF Magic!
} )
$clock.Add_MouseRightButtonDown( {
$_.Handled = $true
$timer.Stop() # we'd like to stop that timer now, thanks.
$clock.Close() # and close the windows
} )
## Lets go ahead and invoke that update block
&$updateBlock
## And then show the window
$clock.ShowDialog()

...and finally the modified clock.xaml file:

<Window xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:system="clr-namespace:System;assembly=mscorlib"
WindowStyle='None' AllowsTransparency='True'
Topmost='True' Background="Transparent" ShowInTaskbar='False'
SizeToContent='WidthAndHeight' WindowStartupLocation='CenterOwner' >
<Window.Resources>
<system:String x:Key="Time">12:34.56</system:String>
</Window.Resources>
<Grid Height="2.2in">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Label Name="ClockLabel" Grid.Column="2" Opacity="0.7" Content="{DynamicResource Time}" FontFamily="Impact, Arial" FontWeight="800" FontSize="2in" >
<Label.Foreground>
<LinearGradientBrush>
<GradientStop Color="#CC064A82" Offset="1"/>
<GradientStop Color="#FF6797BF" Offset="0.8"/>
<GradientStop Color="#FF6797BF" Offset="0.4"/>
<GradientStop Color="#FFD4DBE1" Offset="0"/>
</LinearGradientBrush>
</Label.Foreground>
</Label>
</Grid>
</Window>