Keyboard

This is a helper for simplified keyboard state tracking modeled after the XNA Game Studio 4 (Microsoft.Xna.Framework.Input) Keyboard class.

Microsoft Wireless Keyboard 800

Related tutorial: Mouse and keyboard input

Header

#include <Keyboard.h>

Initialization

Keyboard is a singleton.

std::unique_ptr<Keyboard> keyboard;
keyboard = std::make_unique<Keyboard>();

For exception safety, it is recommended you make use of the C++ RAII pattern and use a std::unique_ptr.

Integration

Windows desktop

For Windows desktop applications, the application needs to make the appropriate calls during the main WndProc message processing:

#include <windows.h>
#include "Keyboard.h"

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_ACTIVATEAPP:
        Keyboard::ProcessMessage(message, wParam, lParam);
        break;

    case WM_KEYDOWN:
    case WM_SYSKEYDOWN:
    case WM_KEYUP:
    case WM_SYSKEYUP:
        Keyboard::ProcessMessage(message, wParam, lParam);
        break;
    }

    return DefWindowProc(hWnd, message, wParam, lParam);
}

Universal Windows Platform (UWP) apps

For Universal Windows Platform apps, you need to call SetWindow in the appropriate place.

C++/CX (/ZW)

void ViewProvider::SetWindow(CoreWindow^ window)
{
    keyboard->SetWindow(window);
}

C++/WinRT

void ViewProvider::SetWindow(winrt::Windows::UI::Core::CoreWindow window window)
{
    keyboard->SetWindow(window);
}

You only get the C++/WinRT SetWindow helper function if you have included winrt/Windows.UI.Core.h before you include Keyboard.h. Alternatively, you can always just do what the helper does for you:

keyboard->SetWindow(reinterpret_cast<ABI::Windows::UI::Core::ICoreWindow*>(winrt::get_abi(window)));

Xbox

For Microsoft GDKX when targeting Gaming.Xbox.*.x64, no additional integration is required.

For the Xbox One XDK, you follow the pattern above for Universal Windows Platform (UWP) apps.

Basic use

GetState queries the current state of the keyboard.

auto kb = keyboard->GetState();

if (kb.Back)
    // Backspace key is down

if (kb.W)
    // W key is down

if (kb.A)
    // A key is down

if (kb.S)
    // S key is down

if (kb.D)
    // D key is down

if (kb.LeftShift)
    // Left shift key is down

if (kb.RightShift)
    // Right shift key is down

if ( kb.IsKeyDown( VK_RETURN ) )
    // Return key is down

Since Keyboard is a singleton, you can make use of the static method Get if desired: auto kb = Keyboard::Get().GetState()

Key state

The Keys enumeration and State structure is a mapping of the physical 'scan codes', so the number 0 from the keyboard top-row and the 10-key keypad are distinct, as are the left shift vs. right shift, etc.

Due to limitations of C identifiers, the keyboard's top-row digits are D0 through D9. The number keypad digits are NumPad0 through NumPad9.

Keyboard state tracker

A common pattern is to trigger an action when a key is pressed or released, but you don't want to trigger the action every single frame if the key is held down for more than a single frame. This helper class simplifies this.

Keyboard::KeyboardStateTracker tracker;

...

auto state = keyboard->GetState();
tracker.Update( state );

if ( tracker.pressed.Space )
    // Space was just pressed down

if ( tracker.IsKeyReleased( VK_F1 ) )
    // F1 key was just released

The pressed member of the state tracker indicates each key that was just pushed down since the previous Update. The helper IsKeyPressed can be used to check this state.

The released member of the state tracker indicates each key that was just went up since the previous Update. The helper IsKeyReleased can be used to check this state.

You can determine which keys are 'down' vs. 'up' by looking at the original Keyboard::GetState to get the equivalent of the Mouse/GamePad HELD vs. UP tracker states.

When resuming from a pause or suspend, be sure to call Reset on the tracker object to clear the state history.

Threading model

The Keyboard class should be thread-safe with the exception of the ProcessMessage which should only be called in your windows message loop.

Remarks

This helper is intended for game controls tied to the keyboard. For chat input and editable text, you should use the platform-specific methods for text input.

Due to some quirks of the platform, If you press both Left & Right Shift keys at the same time, they will both appear down until both are released.

The IsConnected method can be used to test if a keyboard device is present on the system.

Note that on some systems, support for a virtual keyboard is reported as 'true' even without a physical keyboard.

International layouts

Keep in mind when designing the keyboard controls for your game the different layouts of standard keyboards. In particularly, note the red keys which are in different locations for international keyboards than the traditional English QWERTY keyboard.

International Keyboard Layout