Illusion Engine 08 - Input

Introduction

The input module of a game engine deals with most input from users, such as the keyboard, mouse, buttons, and so on. It builds a bridge between external input and the engine’s internal functionality.

It usually figures out all the important information about an input signal. For key input, we need to determine whether it is pressed or released, and how many times it is repeatedly pressed. For mouse input, we need to figure out the button code and the position of the cursor. Additionally, the Input class must be a static class so that its methods can be called outside of the class.

Implementation

Based on the information above, we can create a file called Input.h inside the Illusion/src/Engine/Core/Input/… folder and enter:

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#pragma once

#include "Engine/Core/Core.h"

 //--------------------namespace: Illusion starts--------------------
namespace Illusion
{

	class Input
	{

	public:

		// Static methods that could be used outside of this class
		// Call the virtual function that would be implemented in the inhirated class
		static bool IsKeyPressed(int keycode);

		static bool IsMouseButtonPressed(int button);
		static std::pair<float, float> GetMousePosition();
		static float GetMouseX();
		static float GetMouseY();

	};
	//--------------------namespace: Illusion ends--------------------
}

 //----------------------- Key Codes -----------------------

 /* Printable keys */
#define ILLUSION_KEY_SPACE              32
#define ILLUSION_KEY_APOSTROPHE         39  /* ' */
#define ILLUSION_KEY_COMMA              44  /* , */
#define ILLUSION_KEY_MINUS              45  /* - */
#define ILLUSION_KEY_PERIOD             46  /* . */
#define ILLUSION_KEY_SLASH              47  /* / */
#define ILLUSION_KEY_0                  48
#define ILLUSION_KEY_1                  49
#define ILLUSION_KEY_2                  50
#define ILLUSION_KEY_3                  51
#define ILLUSION_KEY_4                  52
#define ILLUSION_KEY_5                  53
#define ILLUSION_KEY_6                  54
#define ILLUSION_KEY_7                  55
#define ILLUSION_KEY_8                  56
#define ILLUSION_KEY_9                  57
#define ILLUSION_KEY_SEMICOLON          59  /* ; */
#define ILLUSION_KEY_EQUAL              61  /* = */
#define ILLUSION_KEY_A                  65
#define ILLUSION_KEY_B                  66
#define ILLUSION_KEY_C                  67
#define ILLUSION_KEY_D                  68
#define ILLUSION_KEY_E                  69
#define ILLUSION_KEY_F                  70
#define ILLUSION_KEY_G                  71
#define ILLUSION_KEY_H                  72
#define ILLUSION_KEY_I                  73
#define ILLUSION_KEY_J                  74
#define ILLUSION_KEY_K                  75
#define ILLUSION_KEY_L                  76
#define ILLUSION_KEY_M                  77
#define ILLUSION_KEY_N                  78
#define ILLUSION_KEY_O                  79
#define ILLUSION_KEY_P                  80
#define ILLUSION_KEY_Q                  81
#define ILLUSION_KEY_R                  82
#define ILLUSION_KEY_S                  83
#define ILLUSION_KEY_T                  84
#define ILLUSION_KEY_U                  85
#define ILLUSION_KEY_V                  86
#define ILLUSION_KEY_W                  87
#define ILLUSION_KEY_X                  88
#define ILLUSION_KEY_Y                  89
#define ILLUSION_KEY_Z                  90
#define ILLUSION_KEY_LEFT_BRACKET       91  /* [ */
#define ILLUSION_KEY_BACKSLASH          92  /* \ */
#define ILLUSION_KEY_RIGHT_BRACKET      93  /* ] */
#define ILLUSION_KEY_GRAVE_ACCENT       96  /* ` */
#define ILLUSION_KEY_WORLD_1            161 /* non-US #1 */
#define ILLUSION_KEY_WORLD_2            162 /* non-US #2 */

/* Function keys */
#define ILLUSION_KEY_ESCAPE             256
#define ILLUSION_KEY_ENTER              257
#define ILLUSION_KEY_TAB                258
#define ILLUSION_KEY_BACKSPACE          259
#define ILLUSION_KEY_INSERT             260
#define ILLUSION_KEY_DELETE             261
#define ILLUSION_KEY_RIGHT              262
#define ILLUSION_KEY_LEFT               263
#define ILLUSION_KEY_DOWN               264
#define ILLUSION_KEY_UP                 265
#define ILLUSION_KEY_PAGE_UP            266
#define ILLUSION_KEY_PAGE_DOWN          267
#define ILLUSION_KEY_HOME               268
#define ILLUSION_KEY_END                269
#define ILLUSION_KEY_CAPS_LOCK          280
#define ILLUSION_KEY_SCROLL_LOCK        281
#define ILLUSION_KEY_NUM_LOCK           282
#define ILLUSION_KEY_PRINT_SCREEN       283
#define ILLUSION_KEY_PAUSE              284
#define ILLUSION_KEY_F1                 290
#define ILLUSION_KEY_F2                 291
#define ILLUSION_KEY_F3                 292
#define ILLUSION_KEY_F4                 293
#define ILLUSION_KEY_F5                 294
#define ILLUSION_KEY_F6                 295
#define ILLUSION_KEY_F7                 296
#define ILLUSION_KEY_F8                 297
#define ILLUSION_KEY_F9                 298
#define ILLUSION_KEY_F10                299
#define ILLUSION_KEY_F11                300
#define ILLUSION_KEY_F12                301
#define ILLUSION_KEY_F13                302
#define ILLUSION_KEY_F14                303
#define ILLUSION_KEY_F15                304
#define ILLUSION_KEY_F16                305
#define ILLUSION_KEY_F17                306
#define ILLUSION_KEY_F18                307
#define ILLUSION_KEY_F19                308
#define ILLUSION_KEY_F20                309
#define ILLUSION_KEY_F21                310
#define ILLUSION_KEY_F22                311
#define ILLUSION_KEY_F23                312
#define ILLUSION_KEY_F24                313
#define ILLUSION_KEY_F25                314
#define ILLUSION_KEY_KP_0               320
#define ILLUSION_KEY_KP_1               321
#define ILLUSION_KEY_KP_2               322
#define ILLUSION_KEY_KP_3               323
#define ILLUSION_KEY_KP_4               324
#define ILLUSION_KEY_KP_5               325
#define ILLUSION_KEY_KP_6               326
#define ILLUSION_KEY_KP_7               327
#define ILLUSION_KEY_KP_8               328
#define ILLUSION_KEY_KP_9               329
#define ILLUSION_KEY_KP_DECIMAL         330
#define ILLUSION_KEY_KP_DIVIDE          331
#define ILLUSION_KEY_KP_MULTIPLY        332
#define ILLUSION_KEY_KP_SUBTRACT        333
#define ILLUSION_KEY_KP_ADD             334
#define ILLUSION_KEY_KP_ENTER           335
#define ILLUSION_KEY_KP_EQUAL           336
#define ILLUSION_KEY_LEFT_SHIFT         340
#define ILLUSION_KEY_LEFT_CONTROL       341
#define ILLUSION_KEY_LEFT_ALT           342
#define ILLUSION_KEY_LEFT_SUPER         343
#define ILLUSION_KEY_RIGHT_SHIFT        344
#define ILLUSION_KEY_RIGHT_CONTROL      345
#define ILLUSION_KEY_RIGHT_ALT          346
#define ILLUSION_KEY_RIGHT_SUPER        347
#define ILLUSION_KEY_MENU               348

//----------------------- Key Codes -----------------------

//------------------ Mouse Button Codes -------------------

 // Mouse Button Code
#define ILLUSION_MOUSE_BUTTON_1         0
#define ILLUSION_MOUSE_BUTTON_2         1
#define ILLUSION_MOUSE_BUTTON_3         2
#define ILLUSION_MOUSE_BUTTON_4         3
#define ILLUSION_MOUSE_BUTTON_5         4
#define ILLUSION_MOUSE_BUTTON_6         5
#define ILLUSION_MOUSE_BUTTON_7         6
#define ILLUSION_MOUSE_BUTTON_8         7
#define ILLUSION_MOUSE_BUTTON_LAST      ILLUSION_MOUSE_BUTTON_8
#define ILLUSION_MOUSE_BUTTON_LEFT      ILLUSION_MOUSE_BUTTON_1
#define ILLUSION_MOUSE_BUTTON_RIGHT     ILLUSION_MOUSE_BUTTON_2
#define ILLUSION_MOUSE_BUTTON_MIDDLE    ILLUSION_MOUSE_BUTTON_3

//------------------ Mouse Button Codes -------------------
  • All methods in the Input class are static, so they can be called using code like: Illusion::Input::FunctionName(Argument list) without declaring any instance of Input class.
  • Under the definition of the Input class, we’ve defined a list of macros that represent the keycode and mouse button codes. The values of these codes correspond to those in the GLFW library, allowing us to use these macros in our code instead of those from the GLFW library.

To implement these methods, we need to use the interfaces provided by the GLFW library. Inside the same folder, create a file called Input.cpp and enter:

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#include "pch.h"
#include "Input.h"

#include "Engine/Core/Application/Application.h"

#include <GLFW/glfw3.h>

 //--------------------namespace: Illusion starts--------------------

namespace Illusion
{

	bool Input::IsKeyPressed(int keycode)
	{
		auto window = Application::Get().GetWindow().GetNativeWindow();
		auto state = glfwGetKey(window, keycode);
		return state == GLFW_PRESS || state == GLFW_REPEAT;
	}

	bool Input::IsMouseButtonPressed(int button)
	{
		auto window = Application::Get().GetWindow().GetNativeWindow();
		auto state = glfwGetMouseButton(window, button);
		return state == GLFW_PRESS;
	}

	std::pair<float, float> Input::GetMousePosition()
	{
		auto window = Application::Get().GetWindow().GetNativeWindow();
		double xpos, ypos;
		glfwGetCursorPos(window, &xpos, &ypos);
		return { (float)xpos, (float)ypos };

	}

	float Input::GetMouseX()
	{
		auto [x, y] = GetMousePosition();
		return x;
	}

	float Input::GetMouseY()
	{
		auto [x, y] = GetMousePosition();
		return y;
	}
	//--------------------namespace: Illusion ends--------------------
}
  • We use Application::Get() to obtain the application instance, then .GetWindow() to get the previously defined window wrapper, and finally .GetNativeWindow() to get the GLFW window instance.

Utilization

To integrate the input module into the engine, we need to include the header file inside Engine.h.

There are two ways to use the Input module in the code:

  1. Use the code defined with Event dispatcher.
  2. Simply use the functions provided in the module.

For case 1, you can revise the TestLayer like this:

TestLayer.h

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#pragma once

#include <Engine.h>
class TestLayer : public Illusion::Layer
{
public:
	TestLayer();
	virtual ~TestLayer() = default;

	virtual void OnAttach() override;
	virtual void OnDetach() override;

	void OnUpdate() override;
	void OnEvent(Illusion::Event& event) override;

private:
	void OnKeyPressed(Illusion::KeyPressedEvent&);
};

TestLayer.cpp

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#include "TestLayer.h"
TestLayer::TestLayer()
	:Layer("TestLayer"), m_CameraController(2560.0f / 1440.0f, true)
{}
void TestLayer::OnAttach() {}
void TestLayer::OnDetach() {}
void TestLayer::OnUpdate(Illusion::Timestep timestep)
{
	// Render
	// Set the clear color
	// Clear the color buffer with the clear color
    glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}
void TestLayer::OnEvent(Illusion::Event& event) 
{
	Illusion::EventDispatcher dispatcher(e);
	dispatcher.Dispatch<Illusion::KeyPressedEvent>(ENGINE_BIND_EVENT_FN(TestLayer::OnKeyPressed));
}

bool TestLayer::OnKeyPressed(Illusion::KeyPressedEvent& e)
{
	ENGINE_CORE_TRACE(e.GetKeyCode());
	return false;
}
  • The code above implements a function that will print whatever you press on the keyboard.

For case 2, you can revise the TestLayer like this:

TestLayer.cpp

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#include "TestLayer.h"
TestLayer::TestLayer()
	:Layer("TestLayer"), m_CameraController(2560.0f / 1440.0f, true)
{}
void TestLayer::OnAttach() {}
void TestLayer::OnDetach() {}
void TestLayer::OnUpdate(Illusion::Timestep timestep)
{
	// Render
	// Set the clear color
	// Clear the color buffer with the clear color
    glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	
	if(Illusion::Input::IsMouseButtonPressed(Illusion::ILLUSION_MOUSE_BUTTON_LEFT))
	{
		ENGINE_CORE_TARCE(Illusion::Input::GetMouseX());
		ENGINE_CORE_TARCE(Illusion::Input::GetMouseY());
	}
}
void TestLayer::OnEvent(Illusion::Event& event) {}
  • The code above will output the cursor’s position whenever you press the left mouse button.
Game Engine
#Original #C++ #Game Development #Computer Graphics
Illusion Engine 08 - Input
https://rigel.github.io/Input/
Author
Rigel
Posted on
August 30, 2022
Licensed under