Xcode-iPhoneOS/Demos/src/touch.c
author Sam Lantinga <slouken@libsdl.org>
Sun, 13 Mar 2011 11:17:11 -0700
changeset 5483 ccec742c9b7d
parent 5285 ee03772989eb
permissions -rw-r--r--
Removed unreferenced variable
     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 
    30     dstRect.w = BRUSH_SIZE;
    31     dstRect.h = BRUSH_SIZE;
    32 
    33     /* setup x and y for the location of the first sprite */
    34     float x = startx - BRUSH_SIZE / 2.0f;
    35     float y = starty - BRUSH_SIZE / 2.0f;
    36 
    37     int i;
    38     /* draw a series of blots to form the line */
    39     for (i = 0; i < iterations; i++) {
    40         dstRect.x = x;
    41         dstRect.y = y;
    42         /* shift x and y for next sprite location */
    43         x += dx_prime;
    44         y += dy_prime;
    45         /* draw brush blot */
    46         SDL_RenderCopy(renderer, brush, NULL, &dstRect);
    47     }
    48 }
    49 
    50 /*
    51 	loads the brush texture
    52 */
    53 void
    54 initializeTexture(SDL_Renderer *renderer)
    55 {
    56     SDL_Surface *bmp_surface;
    57     bmp_surface = SDL_LoadBMP("stroke.bmp");
    58     if (bmp_surface == NULL) {
    59         fatalError("could not load stroke.bmp");
    60     }
    61     brush =
    62         SDL_CreateTextureFromSurface(renderer, bmp_surface);
    63     SDL_FreeSurface(bmp_surface);
    64     if (brush == 0) {
    65         fatalError("could not create brush texture");
    66     }
    67     /* additive blending -- laying strokes on top of eachother makes them brighter */
    68     SDL_SetTextureBlendMode(brush, SDL_BLENDMODE_ADD);
    69     /* set brush color (red) */
    70     SDL_SetTextureColorMod(brush, 255, 100, 100);
    71 }
    72 
    73 int
    74 main(int argc, char *argv[])
    75 {
    76 
    77     int x, y, dx, dy;           /* mouse location          */
    78     Uint8 state;                /* mouse (touch) state */
    79     SDL_Event event;
    80     SDL_Window *window;         /* main window */
    81 	SDL_Renderer *renderer;
    82     int done;                   /* does user want to quit? */
    83 
    84     /* initialize SDL */
    85     if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    86         fatalError("Could not initialize SDL");
    87     }
    88 
    89     /* create main window and renderer */
    90     window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,
    91                                 SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN |
    92                                 SDL_WINDOW_BORDERLESS);
    93     renderer = SDL_CreateRenderer(window, 0, 0);
    94 
    95     /*load brush texture */
    96     initializeTexture(renderer);
    97 
    98     /* fill canvass initially with all black */
    99     SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
   100     SDL_RenderClear(renderer);
   101     SDL_RenderPresent(renderer);
   102 
   103     done = 0;
   104     while (!done && SDL_WaitEvent(&event)) {
   105         switch (event.type) {
   106         case SDL_QUIT:
   107             done = 1;
   108             break;
   109         case SDL_MOUSEMOTION:
   110             state = SDL_GetMouseState(&x, &y);  /* get its location */
   111             SDL_GetRelativeMouseState(&dx, &dy);        /* find how much the mouse moved */
   112             if (state & SDL_BUTTON_LMASK) {     /* is the mouse (touch) down? */
   113                 drawLine(renderer, x - dx, y - dy, dx, dy);       /* draw line segment */
   114                 SDL_RenderPresent(renderer);
   115             }
   116             break;
   117         }
   118     }
   119 
   120     /* cleanup */
   121     SDL_DestroyTexture(brush);
   122     SDL_Quit();
   123 
   124     return 0;
   125 }