kc3-lang/SDL/Xcode-iOS/Demos/src/touch.c

Branch : - branch - v2.28 - tag -

• Show log

  Commit

• Author : Philipp Wiesemann
  Date : 2015-06-21 17:33:46
  Hash : 0e45984f
  Message : Fixed crash if initialization of EGL failed but was tried again later. The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly uninitialized data structure if loading the library first failed. A later try to use EGL then skipped initialization and assumed it was previously successful because the data structure now already existed. This led to at least one crash in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was dereferenced to make a call to eglBindAPI().

• Xcode-iOS/Demos/src/touch.c

• /*
   *  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_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_RenderClear(renderer);
      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;
  }