Huddled Masses

Posts Tagged ‘Win32’

There are so many fun things you can do in Windows when your scripting language allows you to make PInvoke calls to Win32 APIs … but I have to say it’s amazing how many things have been added to Windows recently and still left out of the .Net framework …

Anyway, on to the Aero Peek stuff. If you haven’t seen it, Aero Peek is a feature of Windows 7, which lets you get a peek at your desktop, or at a single window for a moment. Basically, you can press Win+Space (the Windows logo key and the space bar) and all of your open windows instantly turn transparent, revealing … whatever was on your desktop: wallpaper, icons, and gadgets. You can also use it by hovering your mouse on the right corner of the taskbar, or you can peek at a single window by hovering over it’s taskbar button and then over it’s thumbnail.

In any case, I have a couple of windows which I would like to have stay visible on the desktop when I hit the aero peek hotkey: Rainlendar and Miranda. It turns out there’s a simple API call for this: DwmSetWindowAttribute which lets you set the DWMWA_EXCLUDED_FROM_PEEK attribute to ENABLED … causing a window to no longer hide when you press that hotkey. Of course, that API call should be made by those apps, in response to a user setting (so I’ve told their authors about it), but it doesn’t have to be (so I wrote a script to do it myself).

In the old days, I would have written a little systray app which would give you a popup list of all windows, or perhaps added a menu item to a window’s right-click menu … and I would have had to deal with creating some way to persist which apps you wanted to apply this to, and then I could have applied the setting to them whenever you opened them.

But now, I have PowerShell. I don’t need to give you menus and store settings, because I can just let you edit a little script instead.

So here’s a script which will let you turn off Aero Peek transparency for windows by window title and/or process name … Once you have this function available, you can keep Rainlendar’s calendar, tasks, and event windows all visible by just running Remove-AeroPeek -Process Rainlendar2 or you can keep your Miranda contact list visible by running Remove-AeroPeek "Miranda IM" (although you should not that depends on the window title matching just that one window — and Miranda lets you change what your title is, so you may have to adjust it).

Of course, that script really deserves explanation, because it’s showing off quite a few advanced things…

The first thing is that I’m using a Try/Catch block in the BEGIN block to make sure I only execute that code once. You can’t call Add-Type with the same code multiple times in a single PowerShell session, because the type will already exist when you call it the second time. So the code in the try block will throw an exception if the type doesn’t already exist, and in the catch handler, we’ll create the type, and define the other function we need.

Add-Type is a super-powerful cmdlet which compiles code on the fly (or imports types from pre-compiled assemblies). In this case we’re using it to import a little class called Dwm which I started writing myself from PInvoke.net and the MSDN documentation, but then eventually copied most of from a NeoWin forum thread… All this class really does is define the API function and the flags we need to pass to it, and then provides a wrapper for the DwmSetWindowAttribute call. We could have written that call in PowerShell, but at the end of the day, once you start compiling C# code in PowerShell, it’s hard to know when to stop

The Select-Window function is (yet another customized version of) a function I wrote awhile back on PoshCode as part of my (still in progress) rewrite of WASP to use the UIAutomationClient … I’ve just modified it to add only the three properties of the window that I’m interested in: Title and ProcessId (for identifying the correct windows) and Handle (for passing to the DwmSetWindowAttribute call). It uses the RootElement property of System.Windows.Automation.AutomationElement to do a search, and then a series of GetCurrentPropertyValue calls to determine the Name, ProcessId, and NativeWindowHandle of the windows it finds.

That’s pretty much all there is to it, other than filtering out the window(s) that we want and actually calling the API. I think I’m going to have to play a little bit more with this to see what else we can do — I’ve already realized that this means we can make little widgets with PowerBoots and set them to stick around just like regular desktop gadgets …

There are many desirable behaviors for Windows applications that are just much harder to do than they should be with the tools that Microsoft has provided in the .Net Framework. In WPF, many of these behaviors are even harder to create than in Windows Forms because the necessary hooks take a bit more work to write (thanks to the fact that there’s no window handles, so dropping down to “Native” code is harder. Luckily, WPF Attached Properties give us a whole new way to reuse these behaviors once they’re written.

I’ve started working on a few classes I’m calling NativeBehaviors, because they rely on intercepting the native Window Message processing, and I’ve put together a simple framework to let me write them, which I thought I would share. The first one I wrote is a SnapToBehavior, which implements a feature that people seem to be constantly re-implementing in apps. Basically, it makes a window snap to the screen edge when it gets close (and prevents them from being moved off-screen). I’ve also written a Global HotkeysBehavior which lets you register Hotkeys that work whenever your app is running (even if another app is active) so you can create a Hotkey to hide your app and show it, or whatever.

In the rest of this article I’ll show you how to achieve this in WPF using my base NativeBehavior class, and how to use it on a Window. Since some of you won’t really care how it works, let’s start with:

How to make your WPF Windows snap to screen edges in 3 easy steps:

Step 1. Add a reference to the Huddled.Wpf.Interop library.
Step 2. Add my Xml namespace to your root Window element
Step 3. Paste three lines from below….

I should point out the “SnapDistance” property of the SnapToBehavior is actually a WPF “Thickness” which lets you specify the distance from the screen edge as a single number to use on all sides, or as a separate number for each side: Left, Top, Right, Bottom. And that’s pretty much all there is to know.

How to implement a NativeBehavior.

The implementation of the SnapToBehavior is actually ridiculously simple, given the NativeBehavior framework. I simply created a SnapToBehavior class which derives from NativeBehavior, and implemented the single mandatory method:

When my new behavior is added to the Behaviors collection, my handler will be registered, and whenever the WM_WINDOWPOSCHANGING message arrives, it will be called. Now I defined a DependencyProperty for the SnapDistance, so that you could set that in XAML. It’s extremely simple, and VisualStudio has a built-in snippet for dependency properties, but here’s the code:

Once I have that, the last piece of the puzzle is to actually handle the window position changing message (think of it as an event, if you’re not used to Win32 message-based programming).

The basics of handling WM_WINDOWPOSCHANGING is that you get a structure passed in which has the proposed position of the Window, (including it’s z-index related to other apps) and you can basically tweak that however you like. Obviously there are lots of possibilities for this single message: always-on-bottom windows, undraggable windows, etc., but in our case we’re just concerned about how close we are to the edge.

We use the SystemParameters class to get the VirtualScreenLeft, VirtualScreenTop, and VirtualScreenWidth and VirtualScreenHeight which define the rectangle we’ll use for snapping. In the case of non-rectangular arrangements of multiple monitors this isn’t quite sufficient, but for our example anything more would be a distraction. Then we just check to see if the proposed position is within the “SnapDistance” of any of the edges, and if so, we change the position to be against the edge. That’s really all there is to it.

If you look at the code example below you’ll see I have to “Marshal” the WindowPosition structure in and out of an IntPtr which is passed in the WindowMessage … that’s the downside of intercepting window messages that the framework doesn’t already translate for us, but in this particular case, it’s actually fairly trivial.

Download it, or get the source code

If you’d like, you can download the current Huddled Interop for WPF library right now, or you can check out the source from CodePlex SVN or just download the most recent commit (You are only interested in the “Huddled” project which is in the “trunk”, not the “trunk-3.5”). The source is licensed freely under the BSD or GPL v2 (and a few other licenses, see the top of the source code files).

Either way you’ll get not just the SnapToBehavior but also the global HotkeysBehavior, and the Native Behaviors framework which I’ll write more about later, but for now, in case you want to try to use it, here’s an example using both the SnapTo and HotkeysBehavior (you can find this in the GlobalHotkeys demo project, which includes some sample code for handling hotkey conflicts). Enjoy.

I have a problem with my laptop where I connect to my home network and my work network, and my school network … and I have to use different proxy settings for Windows internet connection settings (which are used by virtually all .Net apps, including PowerShell) by default…

Of course, there are a lot of different apps that can manage those settings (and more) automatically using Windows NLA to trigger. However, I have an extra special requirement: when I plug in at work or at home, I want to run Synergy on the laptop as a client … but the name and ip of the host is different, of course — so I need to stop synergy and restart it with a different server name … something I can easily accomplish from a script or batch file … but changing proxies is a bit trickier.

I thought it would a simple call to a .Net library method, but after much searching, the only way of setting or retrieving Internet options seems to be through the old WinInet API, using InternetSetOptions (or InternetQueryOption to read them). Of course, to use these, you have to map the INTERNET_PER_CONN_OPTION_LIST and INTERNET_PER_CONN_OPTION structures to C#, and do whole lot of marshalling and manual memory management.

I did find some C# mappings for the Option structure on PInvoke.net but not for the others. I actually started writing them all by hand and then found a “recipe” in the (see the examples link) C# 3.0 Cookbook for retrieving Internet settings which had versions of all the structures I needed, as well as definitions for the flags I wanted. So… without further ado, let me share the code with you … Read the rest of this entry »