In this section, we will examine the program that allows the texture color to be changed with color modulation when the mouse is hovered over a texture created from a .png image file and loaded into the main window, the texture color to be changed with color modulation, the texture to be moved with the mouse, whether the mouse is inside the texture and the position of the left button.
When the program runs, the following operations are performed in addition to the basic operations:
main.c file content will be as follows:
#include <stdio.h>
#include <SDL3/SDL.h>
#include <SDL3_image/SDL_image.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_Texture *texture = NULL; // Texture variable
SDL_Renderer *renderer = NULL; // Renderer variable
float x, y; // Mouse coordinates
bool mouse_in; // Mouse in texture control variable
bool lb_down; // Mouse left button state variable
SDL_Rect rect_texture; // Texture rectangle variable
// Function prototypes
int init_window(void); // Create window and renderer
void init_vars(void); // Initialize variables
void load_img(void); // Load image to texture
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 variables
init_vars();
// Load .png file to texture
load_img();
// 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 and a 2D rendering context for the window.
if(!SDL_CreateWindowAndRenderer("SDL3 window", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
return false;
}
return true;
}
// Initialization function that runs only once at the beginning of the program
void init_vars(void)
{
mouse_in = false;
lb_down = false;
rect_texture.x = (WINDOW_WIDTH-300)/2;
rect_texture.y = (WINDOW_HEIGHT-240)/2;
rect_texture.w = 300;
rect_texture.h = 240;
}
// Load image to texture
void load_img(void)
{
// Loading image to texture
texture = IMG_LoadTexture(renderer, "duck.png");
if(texture == NULL) {
SDL_Log("IMG_LoadTexture error: %s\n", SDL_GetError());
}
}
// Function to control SDL events and process keyboard inputs
void process_event(void)
{
SDL_Event event;
SDL_Point coor_drag_start;
// Creating a loop to process user inputs
while (SDL_PollEvent(&event)) {
switch (event.type) {
// Fare işlemi
case SDL_EVENT_MOUSE_MOTION:
case SDL_EVENT_MOUSE_BUTTON_DOWN:
case SDL_EVENT_MOUSE_BUTTON_UP:
{
SDL_GetMouseState(&x, &y);
SDL_Point mouse_pos = { event.motion.x, event.motion.y };
// Checking whether the mouse is inside the texture.
if(SDL_PointInRect(&mouse_pos, &rect_texture)) {
mouse_in = true;
SDL_SetCursor(SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_POINTER));
switch(event.type) {
case SDL_EVENT_MOUSE_MOTION:
if(lb_down) {
if((mouse_pos.x-coor_drag_start.x)>=0 && (mouse_pos.x-coor_drag_start.x)<=(WINDOW_WIDTH-300) &&
(mouse_pos.y-coor_drag_start.y)>=0 && (mouse_pos.y-coor_drag_start.y)<=(WINDOW_HEIGHT-240)) {
rect_texture.x = mouse_pos.x - coor_drag_start.x;
rect_texture.y = mouse_pos.y - coor_drag_start.y;
}
}
break;
case SDL_EVENT_MOUSE_BUTTON_DOWN:
if(!lb_down && event.button.button==SDL_BUTTON_LEFT) {
lb_down = true;
coor_drag_start.x = mouse_pos.x - rect_texture.x;
coor_drag_start.y = mouse_pos.y - rect_texture.y;
}
break;
case SDL_EVENT_MOUSE_BUTTON_UP:
if(lb_down && event.button.button==SDL_BUTTON_LEFT) {
lb_down = false;
}
break;
}
}
else {
mouse_in = false;
SDL_SetCursor(SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_DEFAULT));
}
}
break;
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: // Key pressed.
if(event.key.key==SDLK_ESCAPE) {
is_running = false;
}
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.
SDL_FRect frect_dst = { (float) rect_texture.x, (float) rect_texture.y, 300, 240 };
if(mouse_in) {
SDL_SetTextureColorMod(texture, 240, 170, 0);
}
else {
SDL_SetTextureColorMod(texture, 255, 255, 255);
}
SDL_RenderTexture(renderer, texture, NULL, &frect_dst);
// 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
char cdizi[100];
sprintf(cdizi, "SDL3 window - Mouse: x: %.2f y: %.2f %s Left button: %s",
x, y, mouse_in ? "in" : "out", lb_down ? "Down" : "Up");
SDL_SetWindowTitle(window, cdizi);
}
// Destroy Renderer and SDL window, exit from SDL3
void destroy_window(void)
{
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
}