Add keyboard handling

[Lakritzator]

With Windows 7 new events were introduced to the shell notify icon, as documented here.

Short form: before mouse events were created, even when no mouse was used, now there are special events for this.

This was found while improving the readability in #10 and we decided to make an issue for the keyboard event handling on it's own to prevent mixing stuff. All the details are in there!

[Lakritzator]

In fact there are a couple of steps to do:

• Change the events going through the system from being mouse only, to something which also works when the keyboard is used. Currently if for instance a popup is show, the mouse location is used. This doesn't make sense when it's activated via the keyboard
• Implement the 3 missing messages, marked by TODO, in the WindowMessageSink

[sanslash332]

Hello! please review this!

For the blind users that relies major of the time with the keyboard, is anoying to point mouse to the system tray icon to popup the context menu, or open the application.

Currently if you do this:

press windows+b to focus the system tray.
Search with the arrows your application icon
press enter to perform the same action that the left click (open your application window in regular cases) nothin appens.

Same case if you press application key (context menu key) to perform the right click action. nothin append.

In my case I had to create special global key hooks to manually open the context menu, or open the application window because the icon doesnt work for these cases.

I talk about blind people because im a blind coder and various people that is using my program is blind too.

Thanks for all

[Lakritzator]

Thanks for your feedback! We really welcome help from someone with good experience on the topic. I know how hard it is to support inaccessibility from Greenshot.

There is already a pull-request (#57) for implementing better keyboard support so I guess that will bring us into the right direction. He talks about an issue with the enter key, as this causes a double event, but I will need to talk to the developer of the PR about what he really means.

[sanslash332]

@Lakritzator
Hello! any updates on this issue?