The Awesomeness of user32.dll

I think that the user32.dll is actually quite awesome and powerfull since you can make your application use user functions and some more things like manipulating windows with your application. It can be used especially if something would be easier and more efficient by quickly making the application doing it instead of the user (for example the password manager KeePass can enter the login data for you, which is definitely faster if you also use KeePass to generate passwords and don't know these generated passwords yourself).

What is the user32.dll?

Sounds awesome right? So what exactly is the user32.dll? Well, it is a dll in the Windows OS which has many different methods which let the application perform and capture user actions and manipulation of other windows.

User actions which can be made with the user32.dll are for example pressing certain keyboard keys, holding the keyboard keys for a certain amount of time, moving the mouse, pressing mouse buttons and more. Additionally to performing user inputs there is also a posibillity to create hooks in the windows system to perform actions when the user performs a certain action. Like for example you could make an application which could save additional files or texts in the cache by implementing a hook which is checking if the user presses CTRL + C and a number key. And to paste it again another hook for CTRL + V and the same number key.

The window actions are also pretty awesome because you can get a window by it's name and use the window handle to perform manipulation of windows. Manipulation includes closing of windows, resizing of windows (sometimes even possible when the window is not resizable by the user), even putting a window into your own window and more.

What have I used the user32.dll for and how was the experience

For a few different things which interested me I used the user32.dll already. One of my private projects is a dll which uses the user32.dll and provides methods in C# to easier make and capture inputs with it. Another private project uses it to check if a window is focused and counts how long the user plays a game. Since it is possible that the user opens like a browser for example for a walkthrough or closes the laptop and therefore is not actively playing the game the time outside of the game is not counted since the game window isn't focused.

All in all I really like the things you can do with the user32.dll. If there is one thing I didn't really like about using it in C# however, is that since it is an external assembly you have to import the dll function and create all structs yourself which leads to tons of duplicate code across projects which use the user32.dll for the same purpose. So using it is a bit complex and was also confusing at first especially since the user32.dll (winuser.h) documentation of Microsoft does not really describe the data types of the parameters of the imported method. However the Website pinvoke was a huge help.

Technically the user32.dll could also be missused for keylogging and other input logging since you can run a method everytime a user performs for example a key press and get the key which has been pressed. But overall I think it definitely has more positives than negatives and it's great that we can use it in windows applications.

Usefull links for more Information

Pinvoke

Microsoft winuser.h documenation