backends: Add support for tablet tool pressure ranges

Introduced in libinput 1.26 this feature allows restricting the
tablet tool pressure range to a subset of its physical range. The
use-case is either to require some higher-than-usual minimum pressure
before the pen reacts, or lower-than-usual pressure to reach the maximum
logical pressure.

libinput takes a [0.0, 1.0] normalized range which we expose as percent
in the gsettings. The wacom driver doesn't have an exact equivalent but
it has a Threshold setting (range [1, 2048]) that defines when a button
is generated for tip down.

See gsettings-desktop-schemas!84

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3794>

meson.build

@@ -49,7 +49,7 @@ wayland_server_req = '>= 1.23'
 wayland_protocols_req = '>= 1.36'
 
 # native backend version requirements
-libinput_req = '>= 1.19.0'
+libinput_req = '>= 1.26.0'
 gbm_req = '>= 21.3'
 libdrm_req = '>= 2.4.118'
 

src/backends/meta-input-settings-dummy.c

@@ -188,7 +188,8 @@ static void
 meta_input_settings_dummy_set_stylus_pressure (MetaInputSettings      *settings,
                                                ClutterInputDevice     *device,
                                                ClutterInputDeviceTool *tool,
-                                               const gint32            curve[4])
+                                               const gint32            curve[4],
+                                               const gdouble           range[2])
 {
 }
 

src/backends/meta-input-settings-private.h

@@ -139,7 +139,8 @@ struct _MetaInputSettingsClass
   void (* set_stylus_pressure) (MetaInputSettings            *settings,
                                 ClutterInputDevice           *device,
                                 ClutterInputDeviceTool       *tool,
-                                const gint32                  curve[4]);
+                                const gint32                  curve[4],
+                                const gdouble                 range[2]);
   void (* set_stylus_button_map) (MetaInputSettings          *settings,
                                   ClutterInputDevice         *device,
                                   ClutterInputDeviceTool     *tool,

src/backends/meta-input-settings.c

@@ -1562,6 +1562,8 @@ update_stylus_pressure (MetaInputSettings      *input_settings,
   MetaInputSettingsClass *input_settings_class;
   GSettings *tool_settings;
   const gint32 *curve;
+  const guint32 *percent;
+  gdouble range[2];
   GVariant *variant;
   gsize n_elems;
 
@@ -1584,8 +1586,24 @@ update_stylus_pressure (MetaInputSettings      *input_settings,
   if (n_elems != 4)
     return;
 
+  if (clutter_input_device_tool_get_tool_type (tool) ==
+      CLUTTER_INPUT_DEVICE_TOOL_ERASER)
+    variant = g_settings_get_value (tool_settings, "eraser-pressure-range");
+  else
+    variant = g_settings_get_value (tool_settings, "pressure-range");
+
+  percent = g_variant_get_fixed_array (variant, &n_elems, sizeof (guint32));
+  if (n_elems != 2)
+    return;
+
+  range[0] = CLAMP (percent[0] / 100.0, 0.0, 1.0);
+  range[1] = CLAMP (percent[1] / 100.0, 0.0, 1.0);
+
+  if (range[0] >= range[1])
+    return;
+
   input_settings_class = META_INPUT_SETTINGS_GET_CLASS (input_settings);
-  input_settings_class->set_stylus_pressure (input_settings, device, tool, curve);
+  input_settings_class->set_stylus_pressure (input_settings, device, tool, curve, range);
 }
 
 static void

src/backends/native/meta-input-device-tool-native.c

@@ -117,7 +117,8 @@ meta_input_device_tool_native_new (struct libinput_tablet_tool *tool,
 
 void
 meta_input_device_tool_native_set_pressure_curve_in_impl (ClutterInputDeviceTool *tool,
-                                                          double                  curve[4])
+                                                          double                  curve[4],
+                                                          double                  range[2])
 {
   MetaInputDeviceToolNative *evdev_tool;
   graphene_point_t p1, p2;
@@ -141,6 +142,8 @@ meta_input_device_tool_native_set_pressure_curve_in_impl (ClutterInputDeviceTool
       evdev_tool->pressure_curve[1] = p2;
       init_pressurecurve (evdev_tool);
     }
+
+  libinput_tablet_tool_config_pressure_range_set (evdev_tool->tool, range[0], range[1]);
 }
 
 void

src/backends/native/meta-input-device-tool-native.h

@@ -53,7 +53,8 @@ GDesktopStylusButtonAction meta_input_device_tool_native_get_button_code_in_impl
                                                                                   uint32_t                button);
 
 void                     meta_input_device_tool_native_set_pressure_curve_in_impl (ClutterInputDeviceTool *tool,
-                                                                                   double                  curve[4]);
+                                                                                   double                  curve[4],
+                                                                                   double                  range[2]);
 void                     meta_input_device_tool_native_set_button_code_in_impl (ClutterInputDeviceTool     *tool,
                                                                                 uint32_t                    button,
                                                                                 GDesktopStylusButtonAction  evcode);

src/backends/native/meta-input-settings-native.c

@@ -696,16 +696,21 @@ static void
 meta_input_settings_native_set_stylus_pressure (MetaInputSettings      *settings,
                                                 ClutterInputDevice     *device,
                                                 ClutterInputDeviceTool *tool,
-                                                const gint              curve[4])
+                                                const gint              curve[4],
+                                                const gdouble           range[2])
 {
   gdouble pressure_curve[4];
+  gdouble pressure_range[2];
 
   pressure_curve[0] = (gdouble) curve[0] / 100;
   pressure_curve[1] = (gdouble) curve[1] / 100;
   pressure_curve[2] = (gdouble) curve[2] / 100;
   pressure_curve[3] = (gdouble) curve[3] / 100;
 
-  meta_input_device_tool_native_set_pressure_curve_in_impl (tool, pressure_curve);
+  pressure_range[0] = (gdouble) range[0];
+  pressure_range[1] = (gdouble) range[1];
+
+  meta_input_device_tool_native_set_pressure_curve_in_impl (tool, pressure_curve, pressure_range);
 }
 
 static void

src/backends/x11/meta-input-settings-x11.c

@@ -892,12 +892,19 @@ static void
 meta_input_settings_x11_set_stylus_pressure (MetaInputSettings      *settings,
                                              ClutterInputDevice     *device,
                                              ClutterInputDeviceTool *tool,
-                                             const gint32            pressure[4])
+                                             const gint32            pressure[4],
+                                             const gdouble           range[2])
 {
   guint32 values[4] = { pressure[0], pressure[1], pressure[2], pressure[3] };
+  guint32 threshold = (guint32) MAX (2048 * range[0], 1.0);
 
   change_property (settings, device, "Wacom Pressurecurve", XA_INTEGER, 32,
                    &values, G_N_ELEMENTS (values));
+
+  /* The wacom driver doesn't have a full equivalent to the pressure range.
+   * Threshold only applies to the tip down event but that's better than nothing */
+  change_property (settings, device, "Wacom Pressure Threshold", XA_INTEGER, 32,
+                   &threshold, 1);
 }
 
 static void