How to install SDL on Linux

The libsdl direct media library is open source and cross-platform. It helps that it’s also part of Linux already. You can see this if you open a terminal and do a

apt-cache search libsdl2 | grep dev

This will show you what libraries are available

david@david-VM-PC9:~$ apt-cache search libsdl2 | grep dev
libsdl2-dev - Simple DirectMedia Layer development files
libsdl2-gfx-dev - development files for SDL2_gfx
libsdl2-image-dev - Image loading library for Simple DirectMedia Layer 2, development files
libsdl2-mixer-dev - Mixer library for Simple DirectMedia Layer 2, development files
libsdl2-net-dev - Network library for Simple DirectMedia Layer 2, development files
libsdl2-ttf-dev - TrueType Font library for Simple DirectMedia Layer 2, development files

Although SDL is available, the dev files aren’t installed by default and we want all the headers for C/C++ programs to use them.

We need to install the devs for the libraries we’ll need which are libsdl2-dev, libsdl2-image-dev (you do want to display graphics don’t you?), libsdl2-mixer-dev (for sounds) and if you want text you’ll need libsdl2-ttf-dev.

So install all those with

sudo apt install libsdl2-dev

sudo apt install libsdl2-image-dev

sudo apt install libsdl2-mixer-dev

sudo apt install libsdl2-ttf-dev

Where do the headers get installed?

A quick search for sdl.h found it and associated header files in /usr/include/SDL2,¬† a total of 76 header files though we’ll rarely use more than half a dozen.

Note. When I first wrote this, Ubuntu was on 18.04 LTS and clang was 6. When I updated this on 20.04 LTS, clang was version 10.0 and I got a weird include error.

The source code hasn’t changed but the VS Code JSON files have been altered slightly.

This is tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "type": "shell",
            "label": "clang-10.0 build active file",
            "command": "/usr/bin/clang-10",
            "args": [
                "-g",
                "${file}","${workspaceFolder}/hr_time.c",
                "-o",
                "${fileDirname}/demo",  
                "-I/usr/include/SDL2",              
                "-lSDL2"
            ],
            "options": {
                "cwd": "/usr/bin"
            },
            "group": {
                "kind": "build",
                "isDefault": true
            }
        }
    ]
}

The two changes between this and earlier versions are the command line to compile which is now /usr/bin/clang-10 though I think clang without the -10 will also do.

The second change luine is the addition of "-I/usr/include/SDL2", ¬†which tells the compiler the include path. Without it the compiler complains it can’t find the include file “begin_code.h” which is part of SDL2.

This is a listing of the demo program.

// sdldemo.c Author D. Bolton 7th March 2020
#include "hr_time.h"
#include <time.h>
#include<linux/time.h>
#define __timespec_defined 1
#define __timeval_defined 1
#define __itimerspec_defined 1
#include <SDL2/SDL.h>   /* All SDL App's need this */
#include <stdio.h>
#include <stdlib.h>

#define QUITKEY SDLK_ESCAPE
#define WIDTH 1024
#define HEIGHT 768

SDL_Window* screen = NULL;
SDL_Renderer *renderer;
SDL_Event event;
SDL_Rect source, destination, dst;

int errorCount = 0;
int keypressed;
int rectCount = 0;
stopWatch s;

/* returns a number between 1 and max */
int Random(int max) {
	return (rand() % max) + 1;
}

void LogError(char * msg) {
	//FILE * err;
	//int error;
	//error = fopen_s(&err,"errorlog.txt", "a");
	printf("%s\n", msg);
	//fclose(err);
	errorCount++;
}

/* Sets Window caption according to state - eg in debug mode or showing fps */
void SetCaption(char * msg) {
		SDL_SetWindowTitle(screen, msg);
}

/* Initialize all setup, set screen mode, load images etc */
void InitSetup() {
	srand((unsigned int)time(NULL));
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_CreateWindowAndRenderer(WIDTH, HEIGHT, SDL_WINDOW_SHOWN, &screen, &renderer);
	if (!screen) {
		LogError("InitSetup failed to create window");
	}
	SetCaption("Example One");
}

/* Cleans up after game over */
void FinishOff() {
	SDL_DestroyRenderer(renderer);
	SDL_DestroyWindow(screen);
	//Quit SDL
	SDL_Quit();
	exit(0);
}

/* read a character */
char getaChar() {
	int result = -1;

	while (SDL_PollEvent(&event)) {
		if (event.type == SDL_KEYDOWN)
		{
			result = event.key.keysym.sym;
			break;
		}
	}
	return result;
}

void DrawRandomRectangle() {
	char buff[20];
	SDL_Rect rect;
	SDL_SetRenderDrawColor(renderer, Random(256) - 1, Random(256) - 1, Random(256) - 1,255);
	rect.h = 200;// Random(100) + 20;
	rect.w = 200;// Random(100) + 20;
	rect.y = Random(HEIGHT - rect.h - 1);
	rect.x = Random(WIDTH - rect.w - 1);
	SDL_RenderFillRect(renderer,&rect);

	rectCount++;
	if (rectCount % 10000 == 0) {
		SDL_RenderPresent(renderer);
		stopTimer(&s);
		snprintf(buff,sizeof(buff),"%10.6f", diff(&s));
		SetCaption(buff);
		startTimer(&s);
	}
}

/* main game loop. Handles demo mode, high score and game play */
void GameLoop() {
	int gameRunning = 1;
	startTimer(&s);
	while (gameRunning)
	{
		DrawRandomRectangle();
		while (SDL_PollEvent(&event)) {
			switch (event.type) {
				case SDL_KEYDOWN:
					keypressed = event.key.keysym.sym;
					if (keypressed == QUITKEY)
					{
						gameRunning = 0;
						break;
					}

					break;
				case SDL_QUIT: /* if mouse click to close window */
				{
					gameRunning = 0;
					break;
				}
				case SDL_KEYUP: {
					break;
				}
			} /* switch */

		} /* while SDL_PollEvent */
	}
}

int main(int argc,char * args[])
{
	InitSetup();
	GameLoop();
	FinishOff();
    return 0;
}

When you run this you’ll get a Window with random sized coloured rectangles like this and the time to draw 10,000 in the Window caption bar. Timing is done in the hr_time.h and .c files. These can be found in the file sdldemo.zip along with the VS code JSON files on GitHub.

SDl Demo program

 

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