Ah, the text input - I have very recent experience with this.
Problem
Usually, Keyboard.GetKeyboardState() sucks at getting text input, and that is for many reasons, some of them being:
- You have to code a HUGE switch to detect what key had been pressed
- You have to manually detect whether to capitalize letters (Shift or CapsLock)
- You have to decipher those
OemPeriod-like keys (as in test) to see where they actually are, and map them to specific values.
- There is no way to detect/use keyboard layout or keyboard language
- You have to implement own mechanism for timing repetition in case of key being held down
Second part of the problem is detecting which of your TextBoxes (or UI controls in general) is currently receiving this input, since you don't want all of your boxes to receive text as you type.
Third, you need to draw the TextBox in specified bounds, and you could also want to draw the caret (the blinking vertical position indicator), the current selection (if you want to go so far to implement it), the texture that represents the box, and the textures for highlighted (with mouse) or selected (has focus) state.
Fourth, you have to manually implement copy-paste features.
Quick note
You probably don't need all these features, as I didn't need them. You'd just want simple input, and detection for keys such as enter or tab, as well as mouse click. Maybe also paste.
Solution
The thing is (at least when we talk about Windows, not X-Box or WP7), the operating system already has the mechanisms necessary to implement everything you need from your keyboard:
- Gives characters based on current keyboard layout and language
- Automatically handles repeating input (in case of key being held down)
- Automatically capitalizes and provides special characters
Solution I use for getting keyboard input, I've copied off this Gamedev.net forum post. It is the code below, and you just need to copy-paste it into a .cs file which you'll never have to open again.
It is used for receiving localized input from your keyboard, and all you need to do is initialize it in your Game.Initialize() override method (by using Game.Window), and hook up to the events to receive input anywhere you'd like.
You need to add PresentationCore (PresentationCore.dll) to your references in order to use this code (needed for System.Windows.Input namespace). This works for .NET 4.0 and for .NET 4.0 Client Profile.
EventInput
using System;
using System.Runtime.InteropServices;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;
using System.Text;
using System.Windows.Input;
namespace EventInput
{
public class KeyboardLayout
{
const uint KLF_ACTIVATE = 1; //activate the layout
const int KL_NAMELENGTH = 9; // length of the keyboard buffer
const string LANG_EN_US = "00000409";
const string LANG_HE_IL = "0001101A";
[DllImport("user32.dll")]
private static extern long LoadKeyboardLayout(
string pwszKLID, // input locale identifier
uint Flags // input locale identifier options
);
[DllImport("user32.dll")]
private static extern long GetKeyboardLayoutName(
System.Text.StringBuilder pwszKLID //[out] string that receives the name of the locale identifier
);
public static string getName()
{
System.Text.StringBuilder name = new System.Text.StringBuilder(KL_NAMELENGTH);
GetKeyboardLayoutName(name);
return name.ToString();
}
}
public class CharacterEventArgs : EventArgs
{
private readonly char character;
private readonly int lParam;
public CharacterEventArgs(char character, int lParam)
{
this.character = character;
this.lParam = lParam;
}
public char Character
{
get { return character; }
}
public int Param
{
get { return lParam; }
}
public int RepeatCount
{
get { return lParam & 0xffff; }
}
public bool ExtendedKey
{
get { return (lParam & (1 << 24)) > 0; }
}
public bool AltPressed
{
get { return (lParam & (1 << 29)) > 0; }
}
public bool PreviousState
{
get { return (lParam & (1 << 30)) > 0; }
}
public bool TransitionState
{
get { return (lParam & (1 << 31)) > 0; }
}
}
public class KeyEventArgs : EventArgs
{
private Keys keyCode;
public KeyEventArgs(Keys keyCode)
{
this.keyCode = keyCode;
}
public Keys KeyCode
{
get { return keyCode; }
}
}
public delegate void CharEnteredHandler(object sender, CharacterEventArgs e);
public delegate void KeyEventHandler(object sender, KeyEventArgs e);
public static class EventInput
{
/// <summary>
/// Event raised when a character has been entered.
/// </summary>
public static event CharEnteredHandler CharEntered;
/// <summary>
/// Event raised when a key has been pressed down. May fire multiple times due to keyboard repeat.
/// </summary>
public static event KeyEventHandler KeyDown;
/// <summary>
/// Event raised when a key has been released.
/// </summary>
public static event KeyEventHandler KeyUp;
delegate IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
static bool initialized;
static IntPtr prevWndProc;
static WndProc hookProcDelegate;
static IntPtr hIMC;
//various Win32 constants that we need
const int GWL_WNDPROC = -4;
const int WM_KEYDOWN = 0x100;
const int WM_KEYUP = 0x101;
const int WM_CHAR = 0x102;
const int WM_IME_SETCONTEXT = 0x0281;
const int WM_INPUTLANGCHANGE = 0x51;
const int WM_GETDLGCODE = 0x87;
const int WM_IME_COMPOSITION = 0x10f;
const int DLGC_WANTALLKEYS = 4;
//Win32 functions that we're using
[DllImport("Imm32.dll", CharSet = CharSet.Unicode)]
static extern IntPtr ImmGetContext(IntPtr hWnd);
[DllImport("Imm32.dll", CharSet = CharSet.Unicode)]
static extern IntPtr ImmAssociateContext(IntPtr hWnd, IntPtr hIMC);
[DllImport("user32.dll", CharSet = CharSet.Unicode)]
static extern IntPtr CallWindowProc(IntPtr lpPrevWndFunc, IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
[DllImport("user32.dll", CharSet = CharSet.Unicode)]
static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
/// <summary>
/// Initialize the TextInput with the given GameWindow.
/// </summary>
/// <param name="window">The XNA window to which text input should be linked.</param>
public static void Initialize(GameWindow window)
{
if (initialized)
throw new InvalidOperationException("TextInput.Initialize can only be called once!");
hookProcDelegate = new WndProc(HookProc);
prevWndProc = (IntPtr)SetWindowLong(window.Handle, GWL_WNDPROC,
(int)Marshal.GetFunctionPointerForDelegate(hookProcDelegate));
hIMC = ImmGetContext(window.Handle);
initialized = true;
}
static IntPtr HookProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
{
IntPtr returnCode = CallWindowProc(prevWndProc, hWnd, msg, wParam, lParam);
switch (msg)
{
case WM_GETDLGCODE:
returnCode = (IntPtr)(returnCode.ToInt32() | DLGC_WANTALLKEYS);
break;
case WM_KEYDOWN:
if (KeyDown != null)
KeyDown(null, new KeyEventArgs((Keys)wParam));
break;
case WM_KEYUP:
if (KeyUp != null)
KeyUp(null, new KeyEventArgs((Keys)wParam));
break;
case WM_CHAR:
if (CharEntered != null)
CharEntered(null, new CharacterEventArgs((char)wParam, lParam.ToInt32()));
break;
case WM_IME_SETCONTEXT:
if (wParam.ToInt32() == 1)
ImmAssociateContext(hWnd, hIMC);
break;
case WM_INPUTLANGCHANGE:
ImmAssociateContext(hWnd, hIMC);
returnCode = (IntPtr)1;
break;
}
return returnCode;
}
}
}
Now you could already use this as it is (by subscribing to EventInput.CharEntered event), and use logic to detect where to send your input.
KeyboardDispatcher, IKeyboardSubscriber
What I did was create a class KeyboardDispatcher, which handles the dispatching of keyboard input by way of having a property of type IKeyboardSubscriber to which it sends received input. The idea is that you set this property to that UI control that you want to receive input.
Definitions are as follows:
public interface IKeyboardSubscriber
{
void RecieveTextInput(char inputChar);
void RecieveTextInput(string text);
void RecieveCommandInput(char command);
void RecieveSpecialInput(Keys key);
bool Selected { get; set; } //or Focused
}
public class KeyboardDispatcher
{
public KeyboardDispatcher(GameWindow window)
{
EventInput.EventInput.Initialize(window);
EventInput.EventInput.CharEntered += new EventInput.CharEnteredHandler(EventInput_CharEntered);
EventInput.EventInput.KeyDown += new EventInput.KeyEventHandler(EventInput_KeyDown);
}
void EventInput_KeyDown(object sender, EventInput.KeyEventArgs e)
{
if (_subscriber == null)
return;
_subscriber.RecieveSpecialInput(e.KeyCode);
}
void EventInput_CharEntered(object sender, EventInput.CharacterEventArgs e)
{
if (_subscriber == null)
return;
if (char.IsControl(e.Character))
{
//ctrl-v
if (e.Character == 0x16)
{
//XNA runs in Multiple Thread Apartment state, which cannot recieve clipboard
Thread thread = new Thread(PasteThread);
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
thread.Join();
_subscriber.RecieveTextInput(_pasteResult);
}
else
{
_subscriber.RecieveCommandInput(e.Character);
}
}
else
{
_subscriber.RecieveTextInput(e.Character);
}
}
IKeyboardSubscriber _subscriber;
public IKeyboardSubscriber Subscriber
{
get { return _subscriber; }
