In this section, we create a basic template that we use continuously in the SDL3 programs with the C Programming Language. New code lines will be added to this template at each new step.
The program creates a rectangle with dimensions of 160 x 120 pixels, exactly in the middle of the main window it creates.
The template we will create will contain the codes that will perform the operations shown below:
main.c file content will be as follows:
#include <SDL3/SDL.h>
// Window width and height
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
// Global variables
int is_running = false; // Variable that controls the execution of the main loop of the program
SDL_Window *window = NULL; // Main window variable
SDL_Renderer *renderer = NULL; // Renderer variable
// Function prototypes
int init_window(void); // Create window and renderer
void init_vals(void); // Initialize values
void process_event(void); // Process events
void update_screen(); // Update values
void draw_screen(void); // Draw screen
void destroy_window(void); // Destroy window
int main(int argc, char* argv[])
{
// Create window and renderer
is_running = init_window();
// Initialize values
init_vals();
// Main loop
while (is_running) {
process_event(); // Processing SDL events (Here keyboard inputs).
update_screen(); // Updating variables
draw_screen(); // Drawing objects on the window (Rendering)
}
// Destroy renderer and SDL window
destroy_window();
return 0;
}
// Create window and renderer
int init_window(void)
{
// Initialize the SDL library.
if(SDL_Init(SDL_INIT_VIDEO) == false) {
SDL_Log("SDL init error: %s\n", SDL_GetError());
return false;
}
// Create a window with the specified dimensions and flags.
window = SDL_CreateWindow("SDL3 window", 640, 480, SDL_WINDOW_OPENGL);
// Check window
if(window == NULL) {
SDL_Log("Window creation error: %s\n", SDL_GetError());
return false;
}
// Create a 2D rendering context for the window.
renderer = SDL_CreateRenderer(window, NULL);
// Check renderer
if(renderer == NULL) {
SDL_Log("Renderer creation error: %s\n", SDL_GetError());
return false;
}
return true;
}
// Initialization function that runs only once at the beginning of the program
void init_vals(void)
{
}
// Function to control SDL events and process keyboard inputs
void process_event(void)
{
SDL_Event event;
// Creating a loop to process user inputs
while (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_EVENT_QUIT: // Logout action by the user (x button at the top right of the window)
is_running = false; // Terminates the execution of the program main loop.
break;
case SDL_EVENT_KEY_DOWN: // Indicate that a key was pressed.
if(event.key.key == SDLK_ESCAPE) { // Indicates that the pressed key is the Esc key.
is_running = false; // Terminates the execution of the program main loop.
}
break;
}
}
}
// Updates objects in the main window
void update_screen(void)
{
}
// Render function used to draw game objects in the main window
void draw_screen(void)
{
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); // Set the color used for drawing operations.
SDL_RenderClear(renderer); // Clear the current rendering target with the drawing color.
// Setting rectangle dimensions
SDL_FRect frect = { (WINDOW_WIDTH-160)/2, (WINDOW_HEIGHT-120)/2, 160, 120 };
SDL_SetRenderDrawColor(renderer, 255, 0, 255, 255); // Set the color to fill rectangle.
SDL_RenderFillRect(renderer, &frect); // Fill a rectangle on the current rendering target with the drawing color at subpixel precision.
// Loading all objects drawn one by one to the back buffer to the front buffer at once and loading them onto the screen
// This process prevents each drawn object from being displayed on the screen one by one.
SDL_RenderPresent(renderer); // Update on screen all operations performed since the previous call
}
// Destroy Renderer and SDL window, exit from SDL3
void destroy_window(void)
{
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
}