User Input - ClanLib SDK

User Input

Input in ClanLib is accessed via a clan::InputContext object, which is usually acquired from a clan::DisplayWindow object. The input context interface is a container holding one or more clan::InputDevice objects, each acting as either a keyboard, mouse, joystick or tablet source. The input device interface provides access to various polling functions or signal callbacks, which are invoked when ClanLib receives these input messages.

The following example shows how to get the input devices for the first keyboard, mouse and joystick:

clan::DisplayWindow window(640, 480, "Hello Input");
clan::InputContext ic = window.get_ic();
clan::InputDevice keyboard = ic.get_keyboard();
clan::InputDevice mouse = ic.get_mouse();
clan::InputDevice joystick = ic.get_joystick();
clan::DisplayWindow
Top-level window class.
Definition display_window.h:101
clan::InputDevice
InputDevice.
Definition input_device.h:47

Polling a device is fairly simple and straight forward (just call the appropriate functions), but the actual state of an input device does not always update immediately - in some cases they are updated based on input messages received from the underlying windowing system, which means that they will not update until you have made a call to clan::KeepAlive::process(). The following code correctly polls for hitting escape to quit the loop:

clan::DisplayWindow window(640, 480, "Hello Input");
clan::InputContext ic = window.get_ic();
clan::InputDevice keyboard = ic.get_keyboard();
while (true)
{
bool escape_down = keyboard.get_keycode(clan::KEY_ESCAPE);
if (escape_down)
break;
clan::KeepAlive::process();
window.get_gc().clear(clan::Color::white);
window.flip();
clan::System::sleep(10);
}
clan::Color::white
static Color white
Definition color.h:700
clan::InputDevice::get_keycode
bool get_keycode(int keycode) const
Returns true if the passed key code is down for this device. See keys.h for list of key codes.
clan::System::sleep
static void sleep(int millis)
Sleep for 'millis' milliseconds.

An alternative to polling input devices is to set up callback functions that get invoked whenever an input event occurs. To do this, simply connect a slot function to the signal you want to listen in on:

bool quit = false;
void my_callback(const clan::InputEvent &event, const clan::InputState &state)
{
if (event.id == clan::KEY_ESCAPE)
quit = true;
}
int main(int, char**)
{
try
{
clan::SetupCore setup_core;
clan::SetupDisplay setup_display;
clan::SetupGL setup_gl;
clan::DisplayWindow window(640, 480, "Hello Input");
clan::InputContext ic = window.get_ic();
clan::InputDevice keyboard = ic.get_keyboard();
clan::Slot slot = keyboard.sig_key_up().connect(&my_callback);
while (!quit)
{
clan::KeepAlive::process();
window.get_gc().clear(clan::Color::white);
window.flip();
clan::System::sleep(10);
}
}
catch(clan::Exception &exception)
{
// Create a console window for text-output if not available
clan::ConsoleWindow console("Console", 80, 160);
clan::Console::write_line("Exception caught: " + exception.get_message_and_stack_trace());
console.display_close_message();
return -1;
}
return 0;
}
clan::ConsoleWindow
Text console window.
Definition console_window.h:42
clan::Console::write_line
static void write_line(const std::string &text)
Writes text to the console window and then advances to a new line.
Definition console.h:185
clan::Exception
Top-level exception class.
Definition exception.h:42
clan::Exception::get_message_and_stack_trace
std::string get_message_and_stack_trace() const
Returns the message and call stack present when the exception object was created, formatted using new...
clan::InputDevice::sig_key_up
Signal< void(const InputEvent &)> & sig_key_up()
Signal emitted when key is released.
clan::InputEvent
Input event class.
Definition input_event.h:43
clan::InputEvent::id
InputCode id
The exact input.
Definition input_event.h:62
clan::Slot
Definition signal.h:44