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Old 25-03-2011, 04:36 PM   #1
The Fifth Horseman
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Default Distunguishing regular and keypad Enter keys in C# forms?

I'm working on a C# application that allows a user to configure a control profile for an emulator. Part of that involves binding keyboard keys to controller buttons, and is done through a clickable "on-screen keyboard" dialog. Today, I decided to add keyboard recognition to the dialog window, so that the user can simply press a key on his keyboard to map it.

It's working, apart from the fact that I don't seem to have any way of telling apart the numpad enter key with the regular enter. This is something I need to fix, but can't find any info on how this could be done.

The current code kludge handling the keyboard input in this part of my application is below:
Code:
        [DllImport("user32.dll")]
        static extern short GetAsyncKeyState(System.Windows.Forms.Keys vKey);

        private bool IsKeyPressed(Keys key)
        {
            if (Convert.ToInt32(GetAsyncKeyState(key).ToString()) == -32767)
                return true;
            else
                return false;
        }
        protected override bool ProcessDialogKey(Keys keyData)
        {
            if (IsKeyPressed(Keys.LShiftKey)) button55.PerformClick();
            else if (IsKeyPressed(Keys.RShiftKey)) button28.PerformClick();
            else if (IsKeyPressed(Keys.LMenu)) button69.PerformClick();
            else if (IsKeyPressed(Keys.LControlKey))
            {
                if (IsKeyPressed(Keys.RMenu)) button70.PerformClick();
                else button67.PerformClick();
            }
            else if (IsKeyPressed(Keys.RControlKey)) button68.PerformClick();
            else if (IsKeyPressed(Keys.RMenu)) button70.PerformClick();
            else switch (keyData)
                {
                    case Keys.Escape: button1.PerformClick(); break;
                    // there's 90-something lines of the same thing repeated, differentiated only between different Keys enums and buttons.
                    case Keys.Right: button81.PerformClick(); break;

                    default:
                        break;
                }
            
            return true;
            
        }
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Old 25-03-2011, 11:38 PM   #2
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I see you have immediately resorted to importing a native Windows API function, probably that's familiar territory for you. :P I suppose by "C# forms" you mean Windows Forms (System.Windows.Forms namespace). I haven't had more luck than you using the .NET types in that namespace, both keys can't be told apart with them AFAIK, any more than with your Windows API call--probably the Windows version of the .NET Framework calls that same WinAPI function you're importing yourself, or a similar one.

I don't really know the answer, but I think that if you want that kind of low-level information about keyboard input, you may have to use a Stream (or derived) object (System.IO namespace) and inspect the bytes yourself or something. That's the good news, the bad news is that I have no experience in keyboard IO (if it were about files I have a little bit) and I have no clue how to create an instance of Stream that's connected to the keyboard. But if you dedicate a little time to research it you'll probably find the answer.

Also you could use a different library for IO, like SDL (the one DOSBox uses, but its documentation is not stellar), you already know how to invoke native DLLs from .NET in C#.
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Old 26-03-2011, 10:35 AM   #3
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Distinguishing, my love. (Feel free to hard-delete this annoying message. ^^)
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Old 26-03-2011, 11:53 AM   #4
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Typo.
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Old 26-03-2011, 12:01 PM   #5
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I knoe
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Old 27-03-2011, 11:29 AM   #6
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Well, I think that going into SDL or any other external library just for this keyboard mapping functionality would be a kind of overkill.

IMHO it isn't possible to distinguish the RETURN (main keyboard) and ENTER (numpad) keys with GetAsyncKeyState(), precisely because both are mapped to the VK_RETURN virtual key. Same thing with other "duplicated" keys (such as +,-,*, etc.) IIRC.

I suggest that you handle the WM_KEYDOWN event message through WinAPI. With this approach you'll get both the virtual key code (stored in wParam), which is the same as what you're getting already through calling GetAsyncKeyState(), and the so called "keydata" (stored in lParam).
The 24th bit of the keydata parameter enables you to distinguish between the two ENTER keys (value 0 for RETURN, 1 for numpad ENTER).

More info: http://msdn.microsoft.com/en-us/libr...=vs.85%29.aspx

If you intend to use this approach I think you'd be better of with axing the GetAsyncKeyState() calls and just listen for the WM_KEYDOWN events.

I trust that you already know how to handle Windows messages inside a .NET application

Last edited by Kanalia; 27-03-2011 at 11:33 AM.
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Old 28-03-2011, 08:48 PM   #7
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Thank you, that helped.
It seems I'm going to have to keep GetAsyncKeyState for one special case, namely the right ALT button. It returns the Left CTRL scancode when pressed, and I can only determine it's that button by checking GetAsyncKeyState.
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Old 30-03-2011, 07:21 PM   #8
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Just for the record, today I remembered this thread and I thought that XNA (MS's .NET library for games programming) would have better types for input than Windows Forms. (Too bad Windows Forms and both WinAPI functions decide not to tell some equivalent keys apart, otherwise they could do the job.) I haven't tried XNA yet but here are some links on the topic, in case you want to explore:

http://msdn.microsoft.com/en-us/library/bb203899.aspx

http://msdn.microsoft.com/en-us/library/bb203902.aspx

http://msdn.microsoft.com/en-us/libr...ork.input.aspx

Also it occurred to me that keyboard input may not be so simple as I was thinking initially, in a multi-tasking OS like Windows. Applications don't get input directly, it's the OS that decides to send it in a message to the one application that has focus. Also searching the MSDN forums I found a lot of threads about installing global hooks with the WinAPI to monitor input, but I wonder when such a crude bypass is recommended or actually used.
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Last edited by Japo; 30-03-2011 at 07:26 PM.
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Old 01-04-2011, 06:13 PM   #9
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Quote:
Originally Posted by The Fifth Horseman View Post
Thank you, that helped.
It seems I'm going to have to keep GetAsyncKeyState for one special case, namely the right ALT button. It returns the Left CTRL scancode when pressed, and I can only determine it's that button by checking GetAsyncKeyState.
You're welcome.

As to the "special case", you don't need to keep GetAsyncKeyState just for that. The left and right ALT keys have their own keycodes defined, known respectively as VK_LMENU and VK_RMENU. Have you tried those?

Also, IIRC, the RALT = LCTRL problem occurs usually when a non-US (or maybe non-English?) keyboard layout is set in the OS. Just for kicks, try out how your program works with US keyboard layout set (instead of Polish, which I presume is the case with you ).

Also, if the above doesn't work, using the same way you already listen for WM_KEYDOWN messages, you could just add the special case for the WM_SYSKEYUP message. Details are available here: http://msdn.microsoft.com/en-us/libr...8VS.85%29.aspx
It's easy to understand so I won't explain.

Japo:
Ah yes, it's not that easy. WinAPI is a pretty complicated API and there's usually more ways than one (or even two) to accomplish something, even if it seems to be something trivial

Quote:
Originally Posted by Japo
and both WinAPI functions decide not to tell some equivalent keys apart, otherwise they could do the job.)
Well if that were really the case then we wouldn't have any good solution, right?

Utilizing XNA for a purely desktop windowed app makes about the same sense as using SDL in this case.

Last edited by Kanalia; 01-04-2011 at 06:21 PM.
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Old 02-04-2011, 12:11 PM   #10
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Yes, the issue with the right Alt was a result of the non-US layout. But then, I do have to take all the possibilities into account including that the user will be running a layout like that. :/
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