From b20b00923a588dfa3d89ba44a0370b333199740f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kristian=20H=C3=B8gsberg?= <krh@bitplanet.net>
Date: Thu, 15 Aug 2013 11:54:03 -0700
Subject: [PATCH] window: Add API to check for subcompositor, use in subsurface
 example

This way we can fail with a nice error message.
---
 clients/subsurfaces.c |  6 ++++++
 clients/window.c      | 11 +++++++++++
 clients/window.h      |  3 +++
 3 files changed, 20 insertions(+)

diff --git a/clients/subsurfaces.c b/clients/subsurfaces.c
index f93057e7..51b07a2f 100644
--- a/clients/subsurfaces.c
+++ b/clients/subsurfaces.c
@@ -781,6 +781,12 @@ main(int argc, char *argv[])
 		return -1;
 	}
 
+	if (!display_has_subcompositor(display)) {
+		fprintf(stderr, "compositor does not support "
+			"the subcompositor extension\n");
+		return -1;
+	}
+
 	app = demoapp_create(display);
 
 	display_run(display);
diff --git a/clients/window.c b/clients/window.c
index 3410354c..7223e377 100644
--- a/clients/window.c
+++ b/clients/window.c
@@ -5367,6 +5367,17 @@ display_get_display(struct display *display)
 	return display->display;
 }
 
+int
+display_has_subcompositor(struct display *display)
+{
+	if (display->subcompositor)
+		return 1;
+
+	wl_display_roundtrip(display->display);
+
+	return display->subcompositor != NULL;
+}
+
 cairo_device_t *
 display_get_cairo_device(struct display *display)
 {
diff --git a/clients/window.h b/clients/window.h
index a8177341..1646d5a8 100644
--- a/clients/window.h
+++ b/clients/window.h
@@ -78,6 +78,9 @@ display_get_user_data(struct display *display);
 struct wl_display *
 display_get_display(struct display *display);
 
+int
+display_has_subcompositor(struct display *display);
+
 cairo_device_t *
 display_get_cairo_device(struct display *display);