Rewriting in XCB

blit.c

@@ -1,6 +1,6 @@
+#include <X11/Xcms.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
-#include <X11/Xcms.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

blit2.c

@@ -0,0 +1,153 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <xcb/xcb.h>
+
+/*
+ * Here is the definition of xcb_cw_t
+    typedef enum {
+        XCB_CW_BACK_PIXMAP       = 1L<<0,
+        XCB_CW_BACK_PIXEL        = 1L<<1,
+        XCB_CW_BORDER_PIXMAP     = 1L<<2,
+        XCB_CW_BORDER_PIXEL      = 1L<<3,
+        XCB_CW_BIT_GRAVITY       = 1L<<4,
+        XCB_CW_WIN_GRAVITY       = 1L<<5,
+        XCB_CW_BACKING_STORE     = 1L<<6,
+        XCB_CW_BACKING_PLANES    = 1L<<7,
+        XCB_CW_BACKING_PIXEL     = 1L<<8,
+        XCB_CW_OVERRIDE_REDIRECT = 1L<<9,
+        XCB_CW_SAVE_UNDER        = 1L<<10,
+        XCB_CW_EVENT_MASK        = 1L<<11,
+        XCB_CW_DONT_PROPAGATE    = 1L<<12,
+        XCB_CW_COLORMAP          = 1L<<13,
+        XCB_CW_CURSOR            = 1L<<14
+    } xcb_cw_t;
+  * Why does this matter?
+  * This lets us define what events we want to handle
+  * See here https://xcb.freedesktop.org/tutorial/events/
+  */
+
+xcb_connection_t*
+getDisplay() {
+  /* Get a display to use */
+  /* Currently just uses the default display */
+
+  xcb_connection_t *display = xcb_connect (NULL, NULL);
+
+  if (display == NULL) {
+    fprintf(stderr, "Could not open the display! :(\n");
+    exit(1);
+  }
+
+  return display;
+}
+
+xcb_screen_t*
+getScreen(xcb_connection_t *display) {
+  const xcb_setup_t *setup = xcb_get_setup(display);
+  xcb_screen_iterator_t iter = xcb_setup_roots_iterator(setup);
+  xcb_screen_t *screen = iter.data;
+
+  return screen;
+}
+
+xcb_window_t
+getWindow(xcb_connection_t *display,
+          xcb_screen_t *screen) {
+  /* Create the window */
+  xcb_window_t window = xcb_generate_id(display);
+
+  xcb_cw_t mask = XCB_CW_EVENT_MASK;
+
+  /* Define all the events we want to handle with xcb */
+  /* XCB_EVENT_MASK_EXPOSURE is the "exposure" event */
+  /* I.e. it fires when our window shows up on the screen */
+
+  uint32_t valwin[1] = { XCB_EVENT_MASK_EXPOSURE };
+
+  xcb_create_window(display, /* Connection */
+                    XCB_COPY_FROM_PARENT,  /* depth (same as root) */
+                    window, /* window Id */
+                    screen->root, /* parent window */
+                    0, /* x */
+                    0, /* y */
+                    150,
+                    150,/* width, height */
+                    10, /* border_width  */
+                    XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */
+                    screen->root_visual, /* visual */
+                    mask, /* value mask, used for events */
+                    valwin); /* masks, used for events */
+
+  return window;
+}
+
+int
+main(void) {
+
+  xcb_connection_t *display = getDisplay();
+
+  xcb_screen_t *screen = getScreen(display);
+
+  xcb_window_t window = getWindow(display, screen);
+
+  xcb_map_window(display, window);
+
+  xcb_flush(display);
+
+  struct timespec req;
+  struct timespec rem;
+
+  req.tv_sec = 0;
+  req.tv_nsec = 20000000;
+
+  /* Our event! */
+  xcb_generic_event_t *event;
+  xcb_expose_event_t *expose;
+
+  while (1) {
+    event = xcb_poll_for_event(display);
+
+    if (event != NULL) {
+      printf("Got an event\n");
+
+      /* The ~0x80 is needed to get the lower 7 bits
+       * Per the docs:
+       * A structure is used to pass events received from the X server.
+       * XCB supports exactly the events specified in the protocol (33 events).
+       * This structure contains the type of event received (including a bit for whether it came from the server or another client),
+       * as well as the data associated with the event
+       * (e.g. position on the screen where the event was generated,
+       * mouse button associated with the event,
+       * region of the screen associated with a "redraw" event, etc).
+       * The way to read the event's data depends on the event type.
+       */
+      switch (event->response_type & ~0x80) {
+        case XCB_EXPOSE: {
+          expose = (xcb_expose_event_t *)event;
+          printf("Window %u exposed. Region to be redrawn at location (%u,%u), with dimension (%u,%u)\n",
+                 expose->window, expose->x,
+                 expose->y,
+                 expose->width,
+                 expose->height);
+          break;
+        }
+
+        default: {
+          /* Unknown event type, ignore it */
+          printf ("Unknown event: %PRIu8\n", event->response_type);
+          break;
+        }
+
+        /* Events have to be explicitly free'd */
+        free(event);
+      }
+    }
+
+    nanosleep(&req, &rem);
+  }
+
+  xcb_disconnect(display);
+  return 0;
+}

build.sh

@@ -1,6 +1,7 @@
 #! /usr/bin/env bash
 
 
-xlib=$(pkg-config --cflags --libs x11)
+args=$(pkg-config --cflags --libs xcb x11)
 
-gcc $xlib blit.c
+#gcc $args blit.c
+gcc $args blit2.c