From 482cefea6abc66d1488c7071aff1f656b318a592 Mon Sep 17 00:00:00 2001
From: Dana Jansens <danakj@orodu.net>
Date: Sun, 2 Mar 2008 22:58:45 -0500
Subject: [PATCH] take the selecton for the screens that we will be managing,
 and skip the ones where a CM is already running

---
 Makefile   |   4 +--
 dcompmgr.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 101 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 12968a4..0409160 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,8 @@
 sources = $(wildcard *.c)
 objs = $(sources:.c=.o)
 
-CFLAGS=$(shell pkg-config --cflags xcb-composite)
-LIBS=$(shell pkg-config --libs xcb-composite)
+CFLAGS=$(shell pkg-config --cflags xcb-composite glib-2.0) -ggdb
+LIBS=$(shell pkg-config --libs xcb-composite glib-2.0)
 
 dcompmgr: $(objs)
 	$(CC) -o $@ $^ $(LIBS) $(LDFLAGS)
diff --git a/dcompmgr.c b/dcompmgr.c
index 679284e..84d6a78 100644
--- a/dcompmgr.c
+++ b/dcompmgr.c
@@ -1,3 +1,101 @@
-int main(int argc, char **argv)
+#include <glib.h>
+#include <stdio.h>
+#include <string.h>
+#include <xcb/xcb.h>
+
+#define _(a) (a)
+
+/* inherits from xcb_screen_t */
+typedef struct {
+    xcb_screen_t super;
+    int          num;
+    xcb_window_t selwin; /* for the selection */
+} d_screen_t;
+
+static xcb_connection_t  *conn;
+static const xcb_setup_t *setup;
+static d_screen_t        *screens = NULL;
+
+static gboolean
+register_screen (d_screen_t *sc)
 {
+    char *name;
+    int len, s;
+    xcb_window_t w;
+    xcb_intern_atom_cookie_t ack;
+    xcb_intern_atom_reply_t *arep;
+    xcb_get_selection_owner_cookie_t sck;
+    xcb_get_selection_owner_reply_t *srep;
+    gboolean taken;
+
+    w = xcb_generate_id(conn);
+    xcb_create_window(conn, XCB_COPY_FROM_PARENT, w, sc->super.root,
+                      0, 0, 1, 1, 0, XCB_WINDOW_CLASS_INPUT_ONLY,
+                      sc->super.root_visual, 0, NULL);
+
+    name = g_strdup_printf("_NET_WM_CM_S%d", sc->num);
+    ack = xcb_intern_atom(conn, FALSE, strlen(name), name);
+    arep = xcb_intern_atom_reply(conn, ack, NULL);
+    g_free(name);
+
+    sck = xcb_get_selection_owner(conn, arep->atom);
+    srep = xcb_get_selection_owner_reply(conn, sck, NULL);
+    taken = !!srep->owner;
+    free(srep);
+    if (taken) {
+        printf(_("screen %d already has a composite manager, skipping\n"),
+               sc->num);
+        return FALSE;
+    }
+
+    xcb_set_selection_owner(conn, w, arep->atom, XCB_CURRENT_TIME);
+    sck = xcb_get_selection_owner(conn, arep->atom);
+    srep = xcb_get_selection_owner_reply(conn, sck, NULL);
+    taken = srep->owner == w;
+    if (taken) {
+        sc->selwin = w;
+        return TRUE;
+    }
+    else {
+        xcb_destroy_window(conn, w);
+        return FALSE;
+    }
+}
+
+static gint
+all_screens()
+{
+    xcb_screen_iterator_t it;
+    int count, i;
+    d_screen_t sc;
+
+    count = i = 0;
+    for (it = xcb_setup_roots_iterator(setup); it.rem; xcb_screen_next(&it)) {
+        sc.super = *it.data;
+        sc.num = i++;
+        if (register_screen(&sc)) {
+            ++count;
+            screens = g_renew(d_screen_t, screens, count);
+            screens[count-1] = sc;
+            printf(_("managing screen %d\n"), sc.num);
+        }
+    }
+    return count;
+}
+
+int
+main(int argc, char **argv)
+{
+    conn = xcb_connect(NULL, NULL);
+    if (!conn) {
+        printf(_("Unable to connect to display\n"));
+        return 1;
+    }
+    setup = xcb_get_setup(conn);
+
+    all_screens();
+    
+
+    xcb_disconnect(conn);
+    return 0;
 }
-- 
1.9.1