contenttype - Dave's Blog

WinRT Toast from PowerShell

2016 Jun 15, 3:54

I've made a PowerShell script to show system toast notifications with WinRT and PowerShell. Along the way I learned several interesting things.

First off calling WinRT from PowerShell involves a strange syntax. If you want to use a class you write [-Class-,-Namespace-,ContentType=WindowsRuntime] first to tell PowerShell about the type. For example here I create a ToastNotification object:

[void][Windows.UI.Notifications.ToastNotification,Windows.UI.Notifications,ContentType=WindowsRuntime];
$toast = New-Object Windows.UI.Notifications.ToastNotification -ArgumentList $xml;

And here I call the static method CreateToastNotifier on the ToastNotificationManager class:

[void][Windows.UI.Notifications.ToastNotificationManager,Windows.UI.Notifications,ContentType=WindowsRuntime];
$notifier = [Windows.UI.Notifications.ToastNotificationManager]::CreateToastNotifier($AppUserModelId);

With this I can call WinRT methods and this is enough to show a toast but to handle the click requires a little more work.

To handle the user clicking on the toast I need to listen to the Activated event on the Toast object. However Register-ObjectEvent doesn't handle WinRT events. To work around this I created a .NET event wrapper class to turn the WinRT event into a .NET event that Register-ObjectEvent can handle. This is based on Keith Hill's blog post on calling WinRT async methods in PowerShell. With the event wrapper class I can run the following to subscribe to the event:

function WrapToastEvent {
    param($target, $eventName);

    Add-Type -Path (Join-Path $myPath "PoshWinRT.dll")
    $wrapper = new-object "PoshWinRT.EventWrapper[Windows.UI.Notifications.ToastNotification,System.Object]";
    $wrapper.Register($target, $eventName);
}

[void](Register-ObjectEvent -InputObject (WrapToastEvent $toast "Activated") -EventName FireEvent -Action { 
    ...
});

To handle the Activated event I want to put focus back on the PowerShell window that created the toast. To do this I need to call the Win32 function SetForegroundWindow. Doing so from PowerShell is surprisingly easy. First you must tell PowerShell about the function:

Add-Type @"
    using System;
    using System.Runtime.InteropServices;
    public class PInvoke {
        [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SetForegroundWindow(IntPtr hwnd);
    }
"@

Then to call:

[PInvoke]::SetForegroundWindow((Get-Process -id $myWindowPid).MainWindowHandle);

But figuring out the HWND to give to SetForegroundWindow isn't totally straight forward. Get-Process exposes a MainWindowHandle property but if you start a cmd.exe prompt and then run PowerShell inside of that, the PowerShell process has 0 for its MainWindowHandle property. We must follow up process parents until we find one with a MainWindowHandle:

$myWindowPid = $pid;
while ($myWindowPid -gt 0 -and (Get-Process -id $myWindowPid).MainWindowHandle -eq 0) {
    $myWindowPid = (gwmi Win32_Process -filter "processid = $($myWindowPid)" | select ParentProcessId).ParentProcessId;
}

WinRT Launcher API in PowerShell

2016 Mar 31, 10:12

You can call WinRT APIs from PowerShell. Here's a short example using the WinRT Launcher API:

[Windows.System.Launcher,Windows.System,ContentType=WindowsRuntime]
$uri = New-Object System.Uri "http://example.com/"
[Windows.System.Launcher]::LaunchUriAsync($uri)

Note that like using WinRT in .NET, you use the System.Uri .NET class instead of the Windows.Foundation.Uri WinRT class which is not projected and under the covers the system will convert the System.Uri to a Windows.Foundation.Uri.

Internet Media Types and the Web

2010 Sep 30, 2:48A surprisingly readable and delightfully accurate summary of the history of MIME in the web followed by proposed next steps. Sounds like a plan to me! "We need a realistic transition plan from the unreliable web to the more reliable one. Part of this is to encourage senders (web servers) to mean what they say, and encourage recipients (browsers) to give preference to what the senders are sending."

mime contenttype browser web ietf reference history mimetype mime-sniffing sniffing technical

RFC 4288 Media Type Specifications and Registration Procedures

2007 Sep 10, 5:08Syntax of mime-type names.

mime reference standard ietf internet mimetype contenttype rfc