sdl

FORK: Simple Directmedia Layer
git clone https://git.neptards.moe/neptards/sdl.git
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touch.c (3892B)

      1 /*
      2  *  touch.c
      3  *  written by Holmes Futrell
      4  *  use however you want
      5  */
      6 
      7 #include "SDL.h"
      8 #include <math.h>
      9 #include "common.h"
     10 
     11 #define BRUSH_SIZE 32           /* width and height of the brush */
     12 #define PIXELS_PER_ITERATION 5  /* number of pixels between brush blots when forming a line */
     13 
     14 static SDL_Texture *brush = 0;       /* texture for the brush */
     15 
     16 /*
     17     draws a line from (startx, starty) to (startx + dx, starty + dy)
     18     this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart
     19 */
     20 void
     21 drawLine(SDL_Renderer *renderer, float startx, float starty, float dx, float dy)
     22 {
     23 
     24     float distance = sqrt(dx * dx + dy * dy);   /* length of line segment (pythagoras) */
     25     int iterations = distance / PIXELS_PER_ITERATION + 1;       /* number of brush sprites to draw for the line */
     26     float dx_prime = dx / iterations;   /* x-shift per iteration */
     27     float dy_prime = dy / iterations;   /* y-shift per iteration */
     28     SDL_Rect dstRect;           /* rect to draw brush sprite into */
     29     float x;
     30     float y;
     31     int i;
     32 
     33     dstRect.w = BRUSH_SIZE;
     34     dstRect.h = BRUSH_SIZE;
     35 
     36     /* setup x and y for the location of the first sprite */
     37     x = startx - BRUSH_SIZE / 2.0f;
     38     y = starty - BRUSH_SIZE / 2.0f;
     39 
     40     /* draw a series of blots to form the line */
     41     for (i = 0; i < iterations; i++) {
     42         dstRect.x = x;
     43         dstRect.y = y;
     44         /* shift x and y for next sprite location */
     45         x += dx_prime;
     46         y += dy_prime;
     47         /* draw brush blot */
     48         SDL_RenderCopy(renderer, brush, NULL, &dstRect);
     49     }
     50 }
     51 
     52 /*
     53     loads the brush texture
     54 */
     55 void
     56 initializeTexture(SDL_Renderer *renderer)
     57 {
     58     SDL_Surface *bmp_surface;
     59     bmp_surface = SDL_LoadBMP("stroke.bmp");
     60     if (bmp_surface == NULL) {
     61         fatalError("could not load stroke.bmp");
     62     }
     63     brush =
     64         SDL_CreateTextureFromSurface(renderer, bmp_surface);
     65     SDL_FreeSurface(bmp_surface);
     66     if (brush == 0) {
     67         fatalError("could not create brush texture");
     68     }
     69     /* additive blending -- laying strokes on top of eachother makes them brighter */
     70     SDL_SetTextureBlendMode(brush, SDL_BLENDMODE_ADD);
     71     /* set brush color (red) */
     72     SDL_SetTextureColorMod(brush, 255, 100, 100);
     73 }
     74 
     75 int
     76 main(int argc, char *argv[])
     77 {
     78 
     79     int x, y, dx, dy;           /* mouse location          */
     80     Uint8 state;                /* mouse (touch) state */
     81     SDL_Event event;
     82     SDL_Window *window;         /* main window */
     83     SDL_Renderer *renderer;
     84     int done;                   /* does user want to quit? */
     85     int w, h;
     86 
     87     /* initialize SDL */
     88     if (SDL_Init(SDL_INIT_VIDEO) < 0) {
     89         fatalError("Could not initialize SDL");
     90     }
     91 
     92     /* create main window and renderer */
     93     window = SDL_CreateWindow(NULL, 0, 0, 320, 480, SDL_WINDOW_BORDERLESS | SDL_WINDOW_ALLOW_HIGHDPI);
     94     renderer = SDL_CreateRenderer(window, 0, 0);
     95 
     96     SDL_GetWindowSize(window, &w, &h);
     97     SDL_RenderSetLogicalSize(renderer, w, h);
     98 
     99     /* load brush texture */
    100     initializeTexture(renderer);
    101 
    102     /* fill canvass initially with all black */
    103     SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
    104     SDL_RenderClear(renderer);
    105     SDL_RenderPresent(renderer);
    106 
    107     done = 0;
    108     while (!done && SDL_WaitEvent(&event)) {
    109         switch (event.type) {
    110         case SDL_QUIT:
    111             done = 1;
    112             break;
    113         case SDL_MOUSEMOTION:
    114             state = SDL_GetMouseState(&x, &y);  /* get its location */
    115             SDL_GetRelativeMouseState(&dx, &dy);        /* find how much the mouse moved */
    116             if (state & SDL_BUTTON_LMASK) {     /* is the mouse (touch) down? */
    117                 drawLine(renderer, x - dx, y - dy, dx, dy);       /* draw line segment */
    118                 SDL_RenderPresent(renderer);
    119             }
    120             break;
    121         }
    122     }
    123 
    124     /* cleanup */
    125     SDL_DestroyTexture(brush);
    126     SDL_Quit();
    127 
    128     return 0;
    129 }