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

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• Hash : b88ca1b4
  Author :
  Date : 2015-02-10T16:28:56
  

  the last parameter of XChangeProperty is the number of elements.. and when the element format is 32.. the element is "long" so we have 5 long elements here. Yes this seems confusing as on mac+linux Long is either 32 or 64bits depending on the architecture, but this is how the X11 protocol is defined. Thus 5 is the correct value for the nelts here. Not 5 or 10 depending on the architecture. More info on the confusion https://bugs.freedesktop.org/show_bug.cgi?id=16802

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• 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;
  }
  

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