Introduce hooks for _cairo_xlib_close_display()

This patch adds a simple hook data type for a notifier style callback
and introduces two functions to manipulate a list of callbacks for
cleaning up on display closure.

src/cairo-xlib-private.h

@@ -37,6 +37,14 @@
 #include "cairo-xlib.h"
 
 typedef struct _cairo_xlib_screen_info cairo_xlib_screen_info_t;
+typedef struct _cairo_xlib_hook cairo_xlib_hook_t;
+
+struct _cairo_xlib_hook {
+    cairo_xlib_hook_t *next;
+    void (*func) (Display *display, void *data);
+    void *data;
+    void *key;
+};
 
 struct _cairo_xlib_screen_info {
     cairo_xlib_screen_info_t *next;
@@ -46,11 +54,18 @@ struct _cairo_xlib_screen_info {
     cairo_bool_t has_render;
 
     cairo_font_options_t font_options;
+
+    cairo_xlib_hook_t *close_display_hooks;
 };
 
 cairo_private cairo_xlib_screen_info_t *
 _cairo_xlib_screen_info_get (Display *display, Screen *screen);
 
+cairo_private cairo_bool_t
+_cairo_xlib_add_close_display_hook (Display *display, void (*func) (Display *, void *), void *data, void *key);
+cairo_private void
+_cairo_xlib_remove_close_display_hook (Display *display, void *key);
+
 #if CAIRO_HAS_XLIB_XRENDER_SURFACE
 
 #include "cairo-xlib-xrender.h"

src/cairo-xlib-screen.c

@@ -247,31 +247,36 @@ CAIRO_MUTEX_DECLARE(_xlib_screen_mutex);
 
 static cairo_xlib_screen_info_t *_cairo_xlib_screen_list = NULL;
 
-/* XXX: From this function we should also run through and cleanup
- * anything else that still has a pointer to this Display*. For
- * example, we should clean up any Xlib-specific glyph caches. */
 static int
 _cairo_xlib_close_display (Display *dpy, XExtCodes *codes)
 {
-    cairo_xlib_screen_info_t *info, *prev;
+    cairo_xlib_screen_info_t *info, **prev, *next;
 
     /*
      * Unhook from the global list
      */
     CAIRO_MUTEX_LOCK (_xlib_screen_mutex);
 
-    prev = NULL;
-    for (info = _cairo_xlib_screen_list; info; info = info->next) {
+    prev = &_cairo_xlib_screen_list;
+    for (info = _cairo_xlib_screen_list; info; info = next) {
+	next = info->next;
 	if (info->display == dpy) {
-	    if (prev)
-		prev->next = info->next;
-	    else
-		_cairo_xlib_screen_list = info->next;
+	    *prev = next;
+	    /* call all registered shutdown routines */
+	    while (info->close_display_hooks) {
+		cairo_xlib_hook_t *hook = info->close_display_hooks;
+		info->close_display_hooks = hook->next;
+
+		hook->func (dpy, hook->data);
+
+		free (hook);
+	    }
 	    free (info);
-	    break;
+	} else {
+	    prev = &info->next;
 	}
-	prev = info;
     }
+    *prev = NULL;
     CAIRO_MUTEX_UNLOCK (_xlib_screen_mutex);
 
     /* Return value in accordance with requirements of
@@ -291,6 +296,11 @@ _cairo_xlib_screen_info_reset (void)
 
     for (info = _cairo_xlib_screen_list; info; info = next) {
 	next = info->next;
+	while (info->close_display_hooks) {
+	    cairo_xlib_hook_t *hook = info->close_display_hooks;
+	    info->close_display_hooks = hook->next;
+	    free (hook);
+	}
 	free (info);
     }
 
@@ -300,8 +310,8 @@ _cairo_xlib_screen_info_reset (void)
 
 }
 
-cairo_xlib_screen_info_t *
-_cairo_xlib_screen_info_get (Display *dpy, Screen *screen)
+static cairo_xlib_screen_info_t *
+_cairo_xlib_screen_info_get_unlocked (Display *dpy, Screen *screen)
 {
     cairo_xlib_screen_info_t *info;
     cairo_xlib_screen_info_t **prev;
@@ -309,26 +319,15 @@ _cairo_xlib_screen_info_get (Display *dpy, Screen *screen)
     XExtCodes *codes;
     cairo_bool_t seen_display = FALSE;
 
-    /* There is an apparent deadlock between this mutex and the
-     * mutex for the display, but it's actually safe. For the
-     * app to call XCloseDisplay() while any other thread is
-     * inside this function would be an error in the logic
-     * app, and the CloseDisplay hook is the only other place we
-     * acquire this mutex.
-     */
-    CAIRO_MUTEX_LOCK (_xlib_screen_mutex);
-
     for (prev = &_cairo_xlib_screen_list; (info = *prev); prev = &(*prev)->next)
     {
 	if (info->display == dpy) {
 	    seen_display = TRUE;
-	    if (info->screen == screen)
-	    {
+	    if (info->screen == screen || screen == NULL) {
 		/*
 		 * MRU the list
 		 */
-		if (prev != &_cairo_xlib_screen_list)
-		{
+		if (prev != &_cairo_xlib_screen_list) {
 		    *prev = info->next;
 		    info->next = _cairo_xlib_screen_list;
 		    _cairo_xlib_screen_list = info;
@@ -339,18 +338,17 @@ _cairo_xlib_screen_info_get (Display *dpy, Screen *screen)
     }
 
     if (info)
-	goto out;
+	return info;
 
     info = malloc (sizeof (cairo_xlib_screen_info_t));
     if (!info)
-	goto out;
+	return NULL;
 
     if (!seen_display) {
 	codes = XAddExtension (dpy);
 	if (!codes) {
 	    free (info);
-	    info = NULL;
-	    goto out;
+	    return NULL;
 	}
 
 	XESetCloseDisplay (dpy, codes->extension, _cairo_xlib_close_display);
@@ -361,17 +359,108 @@ _cairo_xlib_screen_info_get (Display *dpy, Screen *screen)
     info->has_render = (XRenderQueryExtension (dpy, &event_base, &error_base) &&
 			(XRenderFindVisualFormat (dpy, DefaultVisual (dpy, DefaultScreen (dpy))) != 0));
 
+    info->close_display_hooks = NULL;
+
     _cairo_xlib_init_screen_font_options (info);
 
     info->next = _cairo_xlib_screen_list;
     _cairo_xlib_screen_list = info;
 
- out:
+    return info;
+}
+cairo_xlib_screen_info_t *
+_cairo_xlib_screen_info_get (Display *dpy, Screen *screen)
+{
+    cairo_xlib_screen_info_t *info;
+
+    /* There is an apparent deadlock between this mutex and the
+     * mutex for the display, but it's actually safe. For the
+     * app to call XCloseDisplay() while any other thread is
+     * inside this function would be an error in the logic
+     * app, and the CloseDisplay hook is the only other place we
+     * acquire this mutex.
+     */
+    CAIRO_MUTEX_LOCK (_xlib_screen_mutex);
+
+    info = _cairo_xlib_screen_info_get_unlocked (dpy, screen);
+
     CAIRO_MUTEX_UNLOCK (_xlib_screen_mutex);
 
     return info;
 }
 
+cairo_bool_t
+_cairo_xlib_add_close_display_hook (Display *dpy, void (*func) (Display *, void *), void *data, void *key)
+{
+    cairo_xlib_screen_info_t *info;
+    cairo_xlib_hook_t *hook;
+    cairo_xlib_hook_t **prev;
+    cairo_bool_t success = FALSE;
+
+    CAIRO_MUTEX_LOCK (_xlib_screen_mutex);
+
+    info = _cairo_xlib_screen_info_get_unlocked (dpy,  NULL);
+    if (!info)
+	goto unlock;
+
+    for (prev = &info->close_display_hooks; (hook = *prev); prev = &hook->next)
+    {
+	if (hook->key == key) {
+	    /*
+	     * MRU the list
+	     */
+	    if (prev != &info->close_display_hooks) {
+		*prev = hook->next;
+		hook->next = info->close_display_hooks;
+		info->close_display_hooks = hook;
+	    }
+	    break;
+	}
+    }
+
+    if (!hook) {
+	hook = malloc (sizeof (cairo_xlib_hook_t));
+	if (!hook)
+	    goto unlock;
+	hook->func = func;
+	hook->data = data;
+	hook->key = key;
+	hook->next = info->close_display_hooks;
+	info->close_display_hooks = hook;
+    }
+
+    success = TRUE;
+ unlock:
+    CAIRO_MUTEX_UNLOCK (_xlib_screen_mutex);
+    return success;
+}
+
+void
+_cairo_xlib_remove_close_display_hook (Display *dpy, void *key)
+{
+    cairo_xlib_screen_info_t *info;
+    cairo_xlib_hook_t *hook;
+    cairo_xlib_hook_t **prev;
+
+    CAIRO_MUTEX_LOCK (_xlib_screen_mutex);
+
+    info = _cairo_xlib_screen_info_get_unlocked (dpy, NULL);
+    if (!info)
+	goto unlock;
+
+    for (prev = &info->close_display_hooks; (hook = *prev); prev = &hook->next)
+    {
+	if (hook->key == key) {
+	    *prev = hook->next;
+	    free (hook);
+	    break;
+	}
+    }
+
+unlock:
+    CAIRO_MUTEX_UNLOCK (_xlib_screen_mutex);
+}
+
 void
 _cairo_xlib_screen_reset_static_data (void)
 {