/*

 *	touch.c

 *	written by Holmes Futrell

 *	use however you want

 */

#include "SDL.h"

#include "math.h"

#include "common.h"

#define BRUSH_SIZE 32           /* width and height of the brush */

#define PIXELS_PER_ITERATION 5  /* number of pixels between brush blots when forming a line */

static SDL_Texture *brush = 0;       /* texture for the brush */

/*

	draws a line from (startx, starty) to (startx + dx, starty + dy)

	this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart

*/

void

drawLine(SDL_Renderer *renderer, float startx, float starty, float dx, float dy)

{

    float distance = sqrt(dx * dx + dy * dy);   /* length of line segment (pythagoras) */

    int iterations = distance / PIXELS_PER_ITERATION + 1;       /* number of brush sprites to draw for the line */

    float dx_prime = dx / iterations;   /* x-shift per iteration */

    float dy_prime = dy / iterations;   /* y-shift per iteration */

    SDL_Rect dstRect;           /* rect to draw brush sprite into */

    dstRect.w = BRUSH_SIZE;

    dstRect.h = BRUSH_SIZE;

    /* setup x and y for the location of the first sprite */

    float x = startx - BRUSH_SIZE / 2.0f;

    float y = starty - BRUSH_SIZE / 2.0f;

    int i;

    /* draw a series of blots to form the line */

    for (i = 0; i < iterations; i++) {

        dstRect.x = x;

        dstRect.y = y;

        /* shift x and y for next sprite location */

        x += dx_prime;

        y += dy_prime;

        /* draw brush blot */

        SDL_RenderCopy(renderer, brush, NULL, &dstRect);

    }

}

/*

	loads the brush texture

*/

void

initializeTexture(SDL_Renderer *renderer)

{

    SDL_Surface *bmp_surface;

    bmp_surface = SDL_LoadBMP("stroke.bmp");

    if (bmp_surface == NULL) {

        fatalError("could not load stroke.bmp");

    }

    brush =

        SDL_CreateTextureFromSurface(renderer, bmp_surface);

    SDL_FreeSurface(bmp_surface);

    if (brush == 0) {

        fatalError("could not create brush texture");

    }

    /* additive blending -- laying strokes on top of eachother makes them brighter */

    SDL_SetTextureBlendMode(brush, SDL_BLENDMODE_ADD);

    /* set brush color (red) */

    SDL_SetTextureColorMod(brush, 255, 100, 100);

}

int

main(int argc, char *argv[])

{

    int x, y, dx, dy;           /* mouse location          */

    Uint8 state;                /* mouse (touch) state */

    SDL_Event event;

    SDL_Window *window;         /* main window */

	SDL_Renderer *renderer;

    int done;                   /* does user want to quit? */

    /* initialize SDL */

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {

        fatalError("Could not initialize SDL");

    }

    /* create main window and renderer */

    window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,

                                SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN |

                                SDL_WINDOW_BORDERLESS);

    renderer = SDL_CreateRenderer(window, 0, 0);

    /*load brush texture */

    initializeTexture(renderer);

    /* fill canvass initially with all black */

    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);

    SDL_RenderPresent(renderer);

    done = 0;

    while (!done && SDL_WaitEvent(&event)) {

        switch (event.type) {

        case SDL_QUIT:

            done = 1;

            break;

        case SDL_MOUSEMOTION:

            state = SDL_GetMouseState(&x, &y);  /* get its location */

            SDL_GetRelativeMouseState(&dx, &dy);        /* find how much the mouse moved */

            if (state & SDL_BUTTON_LMASK) {     /* is the mouse (touch) down? */

                drawLine(renderer, x - dx, y - dy, dx, dy);       /* draw line segment */

                SDL_RenderPresent(renderer);

            }

            break;

        }

    }

    /* cleanup */

    SDL_DestroyTexture(brush);

    SDL_Quit();

    return 0;

}