CODEWITHSUNDEEP
c++windows
Jack Harvin
Jack Harvin

Reputation: 6755

C++ Event Hooks

I'm trying to understand event hooks in C++. I know what an event is, I've used them a lot in Java, C# and Javascript.

What I'm having trouble with is finding the documentation, and tutorials on stuff like global hooks, dll injection, global hooks without a DLL.

Lets say that I wanted to iterate through the browser tabis in FireFox .. would I need to hope that FireFox has an API for C++? Or lets say I wanted to do something when a user opens a new tab would I need to use a hook that FireFox would provide in their API?

The above is just an example so people know what I'm trying to learn/understand. Am I thinking on the right ines?

I seen a post on a forum and for the past 2 hours I've took an interest. I always say that a tricky challange, or a new challange, makes a stronger programmer.

Any resources, or any help, would be very much appreciated.

Upvotes: 1

Views: 4919

Answers (3)

atzz
atzz

Reputation: 18010

C++ itself does not have events or hooks, but a lot of C++ libraries and frameworks implement them. For an example of generic events library, see Boost.Signals.

Some of the implementations allow their events to be seen by other applications, but the API is application-specific (e.g. for Firefox, see XPCOM).

Windows has a mechanizm of hooks that allows to monitor various events in its windowing system. However, it is an OS feature, not related to C++. As it's a system mechanizm, all Windows applications are affected even if they don't do anything for it. The documentation for Windows hooks can be found here. Also, since you mentioned "global hooks without a DLL", see SetWinEventHook, which is a higher-level API than Windows hooks linked above and can be used with hook functions both implemented in DLLs or EXEs.

Upvotes: 3

anand
anand

Reputation: 11309

I dont think firefox would be having a C++ aPI to find the open tabs.... If you want to find out open tabs or whenever a new tab is open , you can basically hook the firefox window and get all events happening on that window to your hook procedure.

If you open spy++ in VC++ and track firefox window , you can see a new MozillaContentWindowClass gets created every time whenever a new tab is opened. So you can basically iterate through window handles and get information about open tabs.

You can use SetWindowLongPtr to set the subclass procedure for that window.

Upvotes: 0

kellogs
kellogs

Reputation: 2857

Look up MSDN for SetWindowsHookEx. It should be your entrance in Windows hooks. If you ar etargetting a parituclar window for mthe system then a less intrusive option is SetWindowLongPtr. For the first API you are going to need some Dll injection - which gets automatically for you by the system. Just follow these steps:

Create a Dll that exports a HOOKPROC function (actual type dependent upon the hook tpe - read in the docs)

Load that Dll in your application and retrieve a pointer to the HOOKPROC function. LoadLibrary / GetProcAddress APIs may be used for this.

From your application, make a call to SetWindowsHookEx feeding in the appropriate parameters - this will inject the dll in the target process. So, the dll is now loaded into both your app's process and in the target process. So you will need a mechanism to IPC between the two processes probably. Lots of ways here - sockets, pipes, shared segment in DLL, filesystem, windows messages, COM servers + events, etc etc.

The former API, while less powerful, does not require DLL injection.

Choose wisely & good luck!

Upvotes: 3

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