SFML - Part 4 - Moving a sprite with the keyboard

This article is part of a tutorial dedicated to SFML. The reader may consult the other parts of the tutorial by following this link : SFML tutorial.

Introduction

This post presents how to move a sprite with the keyboard in fullscreen mode with SFML. Example presented on this page has been prepared with the following software versions:

XUbuntu 16.04 LTS
Qt Creator 3.5.1
SFML 2.3.2

The following video is a preview of the result:

Example and source code

The following program create a fullscreen mode window and display the sprite on the screen. The sprite can be moved with the arrows keys of the keyboard.

/*!
 * \file    main.cpp
 * \brief   move a sprite with the keyboard (https://www.lucidarme.me/?p=6127)
 * \author  Philippe Lucidarme
 * \version 1.0
 * \date    12/18/2016
 */

// SFML libraries
#include <SFML/Graphics.hpp>
#include <iostream>
#include <math.h>

// Sprite speed (high values = high speed)
#define         SPRITE_SPEED        5

int main()
{
    // _____________________
    // ::: Create window :::

    // Create a window with the same pixel depth as the desktop
    sf::VideoMode desktopMode = sf::VideoMode::getDesktopMode();

    sf::RenderWindow window(sf::VideoMode(  desktopMode.width,
                                            desktopMode.height,
                                            desktopMode.bitsPerPixel),
                            "SFML part 3",
                            sf::Style::Fullscreen);

    // Enable vertical sync. (vsync)
    window.setVerticalSyncEnabled (true);
    // When a key is pressed, sf::Event::KeyPressed will be true only once
    window.setKeyRepeatEnabled(false);

    // ____________________
    // ::: Load texture :::

    // Create texture from PNG file
    sf::Texture texture;
    if (!texture.loadFromFile("../../img/sfml-icon-small.png"))
    {
        std::cerr << "Error while loading texture" << std::endl;
        return -1;
    }
    // Enable the smooth filter. The texture appears smoother so that pixels are less noticeable.
    texture.setSmooth(true);

    // _______________________________________
    // ::: Create sprite and apply texture :::

    // Create the sprite and apply the texture
    sf::Sprite sprite;
    sprite.setTexture(texture);
    sf::FloatRect spriteSize=sprite.getGlobalBounds();
    sprite.setOrigin(spriteSize.width/2.,spriteSize.height/2.);

        // _________________
    // ::: Main loop :::

    // Sprite coordinates
    int x=window.getSize().x/2.;
    int y=window.getSize().y/2.;

    // Flags for key pressed
    bool upFlag=false;
    bool downFlag=false;
    bool leftFlag=false;
    bool rightFlag=false;

    sf::Clock timer;
    while (window.isOpen())
    {
        // Process events
        sf::Event event;
        while (window.pollEvent(event))
        {
            // Close the window if a key is pressed or if requested
            if (event.type == sf::Event::Closed) window.close();

            // If a key is pressed
            if (event.type == sf::Event::KeyPressed)
            {
                switch (event.key.code)
                {
                // If escape is pressed, close the application
                case  sf::Keyboard::Escape : window.close(); break;

                // Process the up, down, left and right keys
                case sf::Keyboard::Up :     upFlag=true; break;
                case sf::Keyboard::Down:    downFlag=true; break;
                case sf::Keyboard::Left:    leftFlag=true; break;
                case sf::Keyboard::Right:   rightFlag=true; break;
                default : break;
                }
            }

            // If a key is released
            if (event.type == sf::Event::KeyReleased)
            {
                switch (event.key.code)
                {
                // Process the up, down, left and right keys
                case sf::Keyboard::Up :     upFlag=false; break;
                case sf::Keyboard::Down:    downFlag=false; break;
                case sf::Keyboard::Left:    leftFlag=false; break;
                case sf::Keyboard::Right:   rightFlag=false; break;
                default : break;
                }
            }
        }

        // Update coordinates
        if (leftFlag) x-=SPRITE_SPEED;
        if (rightFlag) x+=SPRITE_SPEED;
        if (upFlag) y-=SPRITE_SPEED;
        if (downFlag) y+=SPRITE_SPEED;

        // Check screen boundaries
        if (x<0) x=0;
        if (x>(int)window.getSize().x) x=window.getSize().x;
        if (y<0) y=0;
        if (y>(int)window.getSize().y) y=window.getSize().y;

        // Clear the window and apply grey background
        window.clear( sf::Color(127,127,127));

        // Rotate and draw the sprite
        sprite.setPosition(x,y);
        sprite.setRotation( timer.getElapsedTime().asSeconds() / M_PI * 90.f );
        window.draw(sprite);

        // Update display and wait for vsync
        window.display();
    }
    return 0;
}

Download

Qt project for this example can be downloaded here:

Source code on GitLab

SFML - Part 4 - Moving a sprite with the keyboard

Introduction

Example and source code

Download

See also