Added SDL2 Experiment 2
Learning how to take input from the keyboard.
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// SDL Experiment 02, Barra Ó Catháin.
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// ===================================
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#include <SDL2/SDL.h>
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#include <SDL2/SDL_image.h>
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#include <SDL2/SDL_timer.h>
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#include <stdbool.h>
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#include <stdint.h>
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void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32_t radius)
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{
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const int32_t diameter = (radius * 2);
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int32_t x = (radius - 1);
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int32_t y = 0;
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int32_t tx = 1;
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int32_t ty = 1;
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int32_t error = (tx - diameter);
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while (x >= y)
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{
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// Each of the following renders an octant of the circle
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SDL_RenderDrawPoint(renderer, centreX + x, centreY - y);
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SDL_RenderDrawPoint(renderer, centreX + x, centreY + y);
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SDL_RenderDrawPoint(renderer, centreX - x, centreY - y);
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SDL_RenderDrawPoint(renderer, centreX - x, centreY + y);
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SDL_RenderDrawPoint(renderer, centreX + y, centreY - x);
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SDL_RenderDrawPoint(renderer, centreX + y, centreY + x);
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SDL_RenderDrawPoint(renderer, centreX - y, centreY - x);
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SDL_RenderDrawPoint(renderer, centreX - y, centreY + x);
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if (error <= 0)
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{
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++y;
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error += ty;
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ty += 2;
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}
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if (error > 0)
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{
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--x;
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tx += 2;
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error += (tx - diameter);
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}
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}
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}
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// Get the largest radius for a circle that can fit in the width and height of a rectangle:
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static inline int getRadius(int width, int height)
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{
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return (width/2 < height/2) ? width/2 : height/2;
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}
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int main(int argc, char ** argv)
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{
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SDL_Event event;
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bool quit = false;
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int width = 0, height = 0, positionX = 0, positionY = 0, velocityX = 0, velocityY = 0;
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uint32_t rendererFlags = SDL_RENDERER_ACCELERATED;
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// Initialize the SDL library, video, sound, and input:
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if (SDL_Init(SDL_INIT_EVERYTHING) != 0)
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{
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printf("SDL Initialization Error: %s\n", SDL_GetError());
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}
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if (SDL_Init(SDL_INIT_EVERYTHING) != 0)
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{
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printf("SDL Initialization Error: %s\n", SDL_GetError());
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}
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IMG_Init(IMG_INIT_PNG);
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// Create an SDL window and rendering context in that window:
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SDL_Window * window = SDL_CreateWindow("SDL_TEST", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 640, 0);
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SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags);
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SDL_Texture * targetTexture;
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targetTexture = IMG_LoadTexture(renderer, "./02-TGT.png");
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SDL_Rect targetText;
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targetText.w = 16;
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targetText.h = 8;
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// Enable resizing the window:
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SDL_SetWindowResizable(window, SDL_TRUE);
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while (!quit)
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{
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// Check if the user wants to quit:
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while (SDL_PollEvent(&event))
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{
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switch (event.type)
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{
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case SDL_QUIT:
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{
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quit = true;
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break;
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}
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case SDL_KEYDOWN:
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{
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switch (event.key.keysym.sym)
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{
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case SDLK_LEFT:
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{
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velocityX += -1;
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break;
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}
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case SDLK_RIGHT:
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{
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velocityX += 1;
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break;
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}
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case SDLK_UP:
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{
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velocityY += -1;
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break;
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}
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case SDLK_DOWN:
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{
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velocityY += 1;
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break;
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}
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default:
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{
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break;
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}
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}
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break;
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}
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default:
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{
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break;
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}
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}
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}
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// Move the position:
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positionX += velocityX;
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positionY += velocityY;
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// Store the window's current width and height:
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SDL_GetWindowSize(window, &width, &height);
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// Set the colour to black:
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SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
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// Clear the screen, filling it with black:
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SDL_RenderClear(renderer);
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// Set the colour to yellow:
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SDL_SetRenderDrawColor(renderer, 255, 255, 0, 255);
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// Draw a line from the center of the window to the position pointer:
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SDL_RenderDrawLine(renderer, width/2, height/2, positionX, positionY);
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// Draw a circle around the position pointer:
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DrawCircle(renderer, positionX, positionY, 15);
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// Set the rect at the correct position to put the TGT down:
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targetText.x = positionX + 20;
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targetText.y = positionY - 4;
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if(positionX < width/2)
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{
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targetText.x = positionX - 36;
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}
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SDL_RenderCopy(renderer, targetTexture, NULL, &targetText);
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// Present the rendered graphics:
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SDL_RenderPresent(renderer);
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// Delay enough so that we run at 144 frames:
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SDL_Delay(1000 / 144);
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}
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return 0;
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}
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// ===========================================================================================
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// Local Variables:
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// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-02.c -lSDL2_image -lm"
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// End:
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