1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <xcb/xcb.h>
   4 
   5 xcb_connection_t *conn;
   6 xcb_screen_t *screen;
   7 xcb_window_t win;
   8 xcb_gcontext_t gc;
   9 
  10 int main(void)
  11 {
  12     int screen_num, i;
  13     xcb_screen_iterator_t iter;
  14     uint32_t mask, values[10];
  15 
  16     conn = xcb_connect(NULL, &screen_num);
  17 
  18     /* get screen information */
  19     iter = xcb_setup_roots_iterator(xcb_get_setup(conn));
  20     for (i = 0; i < screen_num; ++i)
  21         xcb_screen_next(&iter);
  22     screen = iter.data;
  23     puts("screen information:");
  24     printf("%dx%d, root = %x\n", screen->width_in_pixels,
  25         screen->height_in_pixels, screen->root);
  26 
  27     /* create gc */
  28     gc = xcb_generate_id(conn);
  29     mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
  30     values[0] = screen->black_pixel;
  31     values[1] = 0;
  32     xcb_create_gc(conn, gc, screen->root, mask, values);
  33 
  34     /* create window */
  35     win = xcb_generate_id(conn);
  36     mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
  37     values[0] = screen->white_pixel;
  38     values[1] = XCB_EVENT_MASK_EXPOSURE;
  39     xcb_create_window(conn, XCB_COPY_FROM_PARENT,
  40         win, screen->root, 0, 0, 200, 100, 1,
  41         XCB_WINDOW_CLASS_INPUT_OUTPUT,
  42         screen->root_visual, mask, values);
  43 
  44     /* show window */
  45     xcb_map_window(conn, win);
  46     xcb_flush(conn);
  47 
  48     xcb_generic_event_t *event;
  49     while (event = xcb_wait_for_event(conn)) {
  50         /* この~0x80は何なのだろう */
  51         switch (event->response_type & ~0x80) {
  52         case XCB_EXPOSE:
  53             xcb_poly_rectangle(conn, win, gc, 1,
  54                 &(xcb_rectangle_t){ 10, 10, 100, 50 }); /* C99の複合リテラル */
  55             /* どうやらXCBでもリクエストはバッファリングされるらしい
  56                この場合特にバッファをフラッシュする要因が無いようなので、
  57                明示的にxcb_flushしないとリクエストがサーバに送られない = 描画されない */
  58             xcb_flush(conn);
  59             break;
  60         default:
  61             break;
  62         }
  63         free(event);
  64     }
  65     xcb_disconnect(conn);
  66     return 0;
  67 }