Add basic WM calls and move to dedicated file

Makefile

@@ -20,8 +20,8 @@ V =	0.0
 XCB_INCS =	-I/usr/X11R6/include
 XCB_LIBS =	-L/usr/X11R6/lib -lxcb
 
-HDR =		err.h
-OBJ =		err.o main.o
+HDR =		err.h wm.h
+OBJ =		err.o main.o wm.o
 SRC =		${OBJ:.o=.c}
 DIST_FILES =	COPYING Makefile THANKS ${HDR} ${SRC}
 

main.c

@@ -13,30 +13,13 @@
  * <http://creativecommons.org/publicdomain/zero/1.0/>.
  */
 
+#include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <xcb/xcb.h>
 
 #include "err.h"
-
-static struct {
-	xcb_connection_t *conn;
-} wm;
-
-static void
-wm_setup(void)
-{
-}
-
-static void
-wm_print_info(void)
-{
-}
-
-static void
-wm_teardown(void)
-{
-}
+#include "wm.h"
 
 static void
 usage(void)
@@ -48,12 +31,14 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
+	struct wm wm;
+
 	if (argc != 1)
 		usage();
 
-	wm_setup();
-	wm_print_info();
-	wm_teardown();
+	wm_setup(&wm);
+	wm_print_screen_info(stderr, &wm);
+	wm_teardown(&wm);
 
 	return 0;
 }

wm.c

@@ -0,0 +1,63 @@
+/*
+ * orcawm - XCB window manager
+ *
+ * Written in 2020 by Lucas
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to the
+ * public domain worldwide. This software is distributed without any
+ * warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication
+ * along with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include <inttypes.h>
+#include <stdio.h>
+
+#include "err.h"
+#include "wm.h"
+
+static int
+detect_other_window_manager(const struct wm *wm)
+{
+	return 0;
+}
+
+void
+wm_setup(struct wm *wm)
+{
+	wm->conn = xcb_connect(NULL, &wm->screen);
+	if (xcb_connection_has_error(wm->conn))
+		errx(1, "Error connecting to X server");
+	if (detect_other_window_manager(wm))
+		errx(1, "Another window manager is already running");
+}
+
+void
+wm_print_screen_info(FILE *fp, const struct wm *wm)
+{
+	const xcb_setup_t *setup;
+	xcb_screen_t *screen;
+	xcb_screen_iterator_t iter;
+	int i;
+
+	setup = xcb_get_setup(wm->conn);
+	iter = xcb_setup_roots_iterator(setup);
+	for (i = 0; i < wm->screen; i++)
+		xcb_screen_next(&iter);
+
+	if ((screen = iter.data) != NULL)
+		fprintf(fp, "[%d] %08" PRIx32 " %" PRIu16 "x%" PRIu16 "\n",
+		    wm->screen, screen->root, screen->width_in_pixels,
+		    screen->height_in_pixels);
+	else
+		fprintf(fp, "[%d] NO_DATA\n", wm->screen);
+}
+
+void
+wm_teardown(struct wm *wm)
+{
+	xcb_disconnect(wm->conn);
+}

wm.h

@@ -0,0 +1,25 @@
+/*
+ * orcawm - XCB window manager
+ *
+ * Written in 2020 by Lucas
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to the
+ * public domain worldwide. This software is distributed without any
+ * warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication
+ * along with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include <xcb/xcb.h>
+
+struct wm {
+	xcb_connection_t *conn;
+	int screen;
+};
+
+void wm_setup(struct wm *);
+void wm_print_screen_info(FILE *, const struct wm *);
+void wm_teardown(struct wm *);