Lette.Wpf.AppCommands 1.0.3

Lette.Wpf.AppCommands

MVVM-friendly attached behavior for Window, where you can bind WPF ICommands to system-defined application commands.

BIG NOTE: These are not the same as the WPF ApplicationCommands.

Motivation

I wanted my WPF app to react to the "back" button on my mouse. Creating a custom MouseBinding and reacting to XButton1 was fairly easy.

However, most mice with extra buttons can be customized through its accompanying software. Hence, the XButton1 isn't always the "back" button.

This package catches the underlying system-defined application commands, and is therefore well-suited for handling BrowserBackwards and BrowserForward messages that may be triggered from any button on the mouse. (Or on any other type of specialized hardware, for that matter!)

Usage

Add this XAML to your MainWindow (of type Window):

<l:Window.AppCommandBindings>
    <AppCommandBinding AppCommand="BrowserForward" Command="{Binding ForwardCommand}" />
    <AppCommandBinding AppCommand="BrowserBackward" Command="{Binding BackwardCommand}" />
</l:Window.AppCommandBindings>

This will invoke the ICommand in the Command property (with an optional CommandParameter value) whenever your MainWindow receives a corresponding application command.

How it works (or should work)

These bindings listen for WM_APPCOMMAND messages with an lparam containing an APPCOMMAND_* corresponding to the AppCommand value, as they come in on the MainWindow message loop (WndProc).

See the docs on WM_APPCOMMAND for more info on the available commands.

Note that these messages are usually broadcast by specialized hardware, ie. configurable extra buttons on your mouse or media keys on your keyboard.

Many mice with two extra buttons have those two buttons wired up for back and forward navigation out of the box.

Known shortcomings

Works only when your application is active.

The current version of this software will only detect these messages when your application is active.

Pressing the "back" button on your mouse while not hovering over your application will most likely activate whatever window is below the mouse cursor, hence deactivating yours.

Some messages never reach your app

Even if your app is active, some messages gets handled earlier by other software and are stopped from propagating.

Exactly why (shell hooks?) this happens, and how to deal with it, is unclear to me at the moment.

Disclaimer

Technically, all defined APPCOMMAND_* values are supported, but YMMV.