[gnome-flashback] monitor-spec: add hash function

[Alberts Muktupāvels <muktupavels src gnome org>]

commit ca854a80b60df04ce84b3dde7a5d481faad2beb1
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Sep 12 23:23:27 2021 +0300

    monitor-spec: add hash function
    
    Based on mutter commit:
    https://gitlab.gnome.org/GNOME/mutter/-/commit/4615da2122d9

 backends/gf-monitor-spec-private.h |  2 ++
 backends/gf-monitor-spec.c         | 11 +++++++++++
 2 files changed, 13 insertions(+)
---
diff --git a/backends/gf-monitor-spec-private.h b/backends/gf-monitor-spec-private.h
index 7dd1dd4..2c3bd70 100644
--- a/backends/gf-monitor-spec-private.h
+++ b/backends/gf-monitor-spec-private.h
@@ -36,6 +36,8 @@ struct _GfMonitorSpec
 
 GfMonitorSpec *gf_monitor_spec_clone   (GfMonitorSpec  *spec);
 
+guint          gf_monitor_spec_hash    (gconstpointer   key);
+
 gboolean       gf_monitor_spec_equals  (GfMonitorSpec  *spec,
                                         GfMonitorSpec  *other_spec);
 
diff --git a/backends/gf-monitor-spec.c b/backends/gf-monitor-spec.c
index 41e3f51..67e8d1d 100644
--- a/backends/gf-monitor-spec.c
+++ b/backends/gf-monitor-spec.c
@@ -41,6 +41,17 @@ gf_monitor_spec_clone (GfMonitorSpec *spec)
   return new_spec;
 }
 
+guint
+gf_monitor_spec_hash (gconstpointer key)
+{
+  const GfMonitorSpec *monitor_spec = key;
+
+  return (g_str_hash (monitor_spec->connector) +
+          g_str_hash (monitor_spec->vendor) +
+          g_str_hash (monitor_spec->product) +
+          g_str_hash (monitor_spec->serial));
+}
+
 gboolean
 gf_monitor_spec_equals (GfMonitorSpec *spec,
                         GfMonitorSpec *other_spec)