[mutter/wip/carlosg/device-size-through-udev: 1/2] backends: Use udev to determine absolute input devices' size

[Carlos Garnacho <carlosg src gnome org>]

commit be068f5ff86d74b3991c52fc2300e1b7a498c796
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Mar 20 23:18:30 2019 +0100

    backends: Use udev to determine absolute input devices' size
    
    Use the ID_INPUT_WIDTH_MM/ID_INPUT_HEIGHT_MM udev properties to figure out
    absolute input devices' physical size. This works across both backends, and
    requires less moving pieces to have it get the right results.
    
    Concretely, fixes size detection on X11/libinput, which makes touchscreen
    mapping go wrong.
    
    https://gitlab.gnome.org/GNOME/mutter/issues/514

 src/backends/meta-input-mapper.c | 45 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/meta-input-mapper.c b/src/backends/meta-input-mapper.c
index 1a3cb2c7b..b71e9d188 100644
--- a/src/backends/meta-input-mapper.c
+++ b/src/backends/meta-input-mapper.c
@@ -20,6 +20,10 @@
 
 #include "config.h"
 
+#ifdef HAVE_LIBGUDEV
+#include <gudev/gudev.h>
+#endif
+
 #include "meta-input-mapper-private.h"
 #include "meta-monitor-manager-private.h"
 #include "meta-logical-monitor.h"
@@ -39,6 +43,9 @@ struct _MetaInputMapper
   ClutterDeviceManager *input_device_manager;
   GHashTable *input_devices; /* ClutterInputDevice -> MetaMapperInputInfo */
   GHashTable *output_devices; /* MetaLogicalMonitor -> MetaMapperOutputInfo */
+#ifdef HAVE_LIBGUDEV
+  GUdevClient *udev_client;
+#endif
 };
 
 typedef enum
@@ -270,6 +277,33 @@ match_edid (MetaMapperInputInfo  *input,
   return TRUE;
 }
 
+static gboolean
+input_device_get_physical_size (MetaInputMapper    *mapper,
+                                ClutterInputDevice *device,
+                                double             *width,
+                                double             *height)
+{
+#ifdef HAVE_LIBGUDEV
+  g_autoptr (GUdevDevice) udev_device = NULL;
+  const char *node;
+
+  node = clutter_input_device_get_device_node (device);
+  udev_device = g_udev_client_query_by_device_file (mapper->udev_client, node);
+
+  if (udev_device &&
+      g_udev_device_has_property (udev_device, "ID_INPUT_WIDTH_MM"))
+    {
+      *width = g_udev_device_get_property_as_double (udev_device,
+                                                     "ID_INPUT_WIDTH_MM");
+      *height = g_udev_device_get_property_as_double (udev_device,
+                                                      "ID_INPUT_HEIGHT_MM");
+      return TRUE;
+    }
+#endif
+
+  return FALSE;
+}
+
 static gboolean
 find_size_match (MetaMapperInputInfo  *input,
                  GList                *monitors,
@@ -282,7 +316,8 @@ find_size_match (MetaMapperInputInfo  *input,
 
   min_w_diff = min_h_diff = MAX_SIZE_MATCH_DIFF;
 
-  if (!clutter_input_device_get_physical_size (input->device, &i_width, &i_height))
+  if (!input_device_get_physical_size (input->mapper, input->device,
+                                       &i_width, &i_height))
     return FALSE;
 
   for (l = monitors; l; l = l->next)
@@ -520,6 +555,9 @@ meta_input_mapper_finalize (GObject *object)
 
   g_hash_table_unref (mapper->input_devices);
   g_hash_table_unref (mapper->output_devices);
+#ifdef HAVE_LIBGUDEV
+  g_clear_object (&mapper->udev_client);
+#endif
 
   G_OBJECT_CLASS (meta_input_mapper_parent_class)->finalize (object);
 }
@@ -527,11 +565,16 @@ meta_input_mapper_finalize (GObject *object)
 static void
 meta_input_mapper_constructed (GObject *object)
 {
+  const char *udev_subsystems[] = { "input", NULL };
   MetaInputMapper *mapper = META_INPUT_MAPPER (object);
   MetaBackend *backend;
 
   G_OBJECT_CLASS (meta_input_mapper_parent_class)->constructed (object);
 
+#ifdef HAVE_LIBGUDEV
+  mapper->udev_client = g_udev_client_new (udev_subsystems);
+#endif
+
   mapper->input_device_manager = clutter_device_manager_get_default ();
   g_signal_connect (mapper->input_device_manager, "device-removed",
                     G_CALLBACK (input_mapper_device_removed_cb), mapper);