demos: Add "Paint" demo

This is a GtkGesture done to deal with stylus events from drawing tablets.
Those have a special number of characteristics that extend a regular
pointer, so it makes sense to wrap that.

demos/gtk-demo/demo.gresource.xml

@@ -180,6 +180,7 @@
     <file>modelbutton.c</file>
     <file>overlay.c</file>
     <file>overlay2.c</file>
+    <file>paint.c</file>
     <file>pagesetup.c</file>
     <file>panes.c</file>
     <file>pickers.c</file>

demos/gtk-demo/meson.build

@@ -45,6 +45,7 @@ demos = files([
   'modelbutton.c',
   'overlay.c',
   'overlay2.c',
+  'paint.c',
   'panes.c',
   'pickers.c',
   'pixbufs.c',

demos/gtk-demo/paint.c

@@ -0,0 +1,273 @@
+/* Paint
+ *
+ * Demonstrates practical handling of drawing tablets in a real world
+ * usecase.
+ */
+#include <gtk/gtk.h>
+
+typedef struct
+{
+  GtkWidget parent_instance;
+  cairo_surface_t *surface;
+  cairo_t *cr;
+  GdkRGBA draw_color;
+
+  GtkGesture *stylus_gesture;
+} DrawingArea;
+
+typedef struct
+{
+  GtkWidgetClass parent_class;
+} DrawingAreaClass;
+
+G_DEFINE_TYPE (DrawingArea, drawing_area, GTK_TYPE_WIDGET)
+
+static void
+drawing_area_ensure_surface (DrawingArea *area,
+                             gint         width,
+                             gint         height)
+{
+  if (!area->surface ||
+      cairo_image_surface_get_width (area->surface) != width ||
+      cairo_image_surface_get_height (area->surface) != height)
+    {
+      cairo_surface_t *surface;
+
+      surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
+                                            width, height);
+      if (area->surface)
+        {
+          cairo_t *cr;
+
+          cr = cairo_create (surface);
+          cairo_set_source_surface (cr, area->surface, 0, 0);
+          cairo_paint (cr);
+
+          cairo_surface_destroy (area->surface);
+          cairo_destroy (area->cr);
+          cairo_destroy (cr);
+        }
+
+      area->surface = surface;
+      area->cr = cairo_create (surface);
+    }
+}
+
+static void
+drawing_area_size_allocate (GtkWidget           *widget,
+                            const GtkAllocation *allocation,
+                            int                  baseline,
+                            GtkAllocation       *out_clip)
+{
+  DrawingArea *area = (DrawingArea *) widget;
+
+  drawing_area_ensure_surface (area, allocation->width, allocation->height);
+
+  GTK_WIDGET_CLASS (drawing_area_parent_class)->size_allocate (widget, allocation, baseline, out_clip);
+}
+
+static void
+drawing_area_map (GtkWidget *widget)
+{
+  GtkAllocation allocation;
+
+  GTK_WIDGET_CLASS (drawing_area_parent_class)->map (widget);
+
+  gtk_widget_get_allocation (widget, &allocation);
+  drawing_area_ensure_surface ((DrawingArea *) widget,
+                               allocation.width, allocation.height);
+}
+
+static void
+drawing_area_unmap (GtkWidget *widget)
+{
+  DrawingArea *area = (DrawingArea *) widget;
+
+  g_clear_pointer (&area->cr, cairo_destroy);
+  g_clear_pointer (&area->surface, cairo_surface_destroy);
+
+  GTK_WIDGET_CLASS (drawing_area_parent_class)->unmap (widget);
+}
+
+static gboolean
+drawing_area_draw (GtkWidget *widget,
+                   cairo_t   *cr)
+{
+  DrawingArea *area = (DrawingArea *) widget;
+  GtkAllocation allocation;
+
+  gtk_widget_get_allocation (widget, &allocation);
+  cairo_set_source_rgb (cr, 1, 1, 1);
+  cairo_paint (cr);
+
+  cairo_set_source_surface (cr, area->surface, 0, 0);
+  cairo_paint (cr);
+
+  cairo_set_source_rgb (cr, 0.6, 0.6, 0.6);
+  cairo_rectangle (cr, 0, 0, allocation.width, allocation.height);
+  cairo_stroke (cr);
+
+  return FALSE;
+}
+
+static void
+drawing_area_class_init (DrawingAreaClass *klass)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  widget_class->size_allocate = drawing_area_size_allocate;
+  widget_class->draw = drawing_area_draw;
+  widget_class->map = drawing_area_map;
+  widget_class->unmap = drawing_area_unmap;
+}
+
+static void
+drawing_area_apply_stroke (DrawingArea   *area,
+                           GdkDeviceTool *tool,
+                           gdouble        x,
+                           gdouble        y,
+                           gdouble        pressure)
+{
+  if (gdk_device_tool_get_tool_type (tool) == GDK_DEVICE_TOOL_TYPE_ERASER)
+    {
+      cairo_set_line_width (area->cr, 10 * pressure);
+      cairo_set_operator (area->cr, CAIRO_OPERATOR_DEST_OUT);
+    }
+  else
+    {
+      cairo_set_line_width (area->cr, 4 * pressure);
+      cairo_set_operator (area->cr, CAIRO_OPERATOR_SATURATE);
+    }
+
+  cairo_set_source_rgba (area->cr, area->draw_color.red,
+                         area->draw_color.green, area->draw_color.blue,
+                         area->draw_color.alpha * pressure);
+
+  //cairo_set_source_rgba (area->cr, 0, 0, 0, pressure);
+
+  cairo_line_to (area->cr, x, y);
+  cairo_stroke (area->cr);
+  cairo_move_to (area->cr, x, y);
+}
+
+static void
+stylus_gesture_down (GtkGestureStylus *gesture,
+                     gdouble           x,
+                     gdouble           y,
+                     DrawingArea      *area)
+{
+  cairo_new_path (area->cr);
+}
+
+static void
+stylus_gesture_motion (GtkGestureStylus *gesture,
+                       gdouble           x,
+                       gdouble           y,
+                       DrawingArea      *area)
+{
+  GdkTimeCoord *backlog;
+  GdkDeviceTool *tool;
+  gdouble pressure;
+  guint n_items;
+
+  tool = gtk_gesture_stylus_get_device_tool (gesture);
+
+  if (gtk_gesture_stylus_get_backlog (gesture, &backlog, &n_items))
+    {
+      guint i;
+
+      for (i = 0; i < n_items; i++)
+        {
+          drawing_area_apply_stroke (area, tool,
+                                     backlog[i].axes[GDK_AXIS_X],
+                                     backlog[i].axes[GDK_AXIS_Y],
+                                     backlog[i].axes[GDK_AXIS_PRESSURE]);
+        }
+    }
+  else
+    {
+      if (!gtk_gesture_stylus_get_axis (gesture, GDK_AXIS_PRESSURE, &pressure))
+        pressure = 1;
+
+      drawing_area_apply_stroke (area, tool, x, y, pressure);
+    }
+
+  gtk_widget_queue_draw (GTK_WIDGET (area));
+}
+
+static void
+drawing_area_init (DrawingArea *area)
+{
+  gtk_widget_set_has_window (GTK_WIDGET (area), FALSE);
+
+  area->stylus_gesture = gtk_gesture_stylus_new (GTK_WIDGET (area));
+  g_signal_connect (area->stylus_gesture, "down",
+                    G_CALLBACK (stylus_gesture_down), area);
+  g_signal_connect (area->stylus_gesture, "motion",
+                    G_CALLBACK (stylus_gesture_motion), area);
+
+  area->draw_color = (GdkRGBA) { 0, 0, 0, 1 };
+}
+
+GtkWidget *
+drawing_area_new (void)
+{
+  return g_object_new (drawing_area_get_type (), NULL);
+}
+
+void
+drawing_area_set_color (DrawingArea *area,
+                        GdkRGBA     *color)
+{
+  area->draw_color = *color;
+}
+
+static void
+color_button_color_set (GtkColorButton *button,
+                        DrawingArea    *draw_area)
+{
+  GdkRGBA color;
+
+  gtk_color_chooser_get_rgba (GTK_COLOR_CHOOSER (button), &color);
+  drawing_area_set_color (draw_area, &color);
+}
+
+GtkWidget *
+do_paint (GtkWidget *toplevel)
+{
+  static GtkWidget *window = NULL;
+
+  if (!window)
+    {
+      GtkWidget *draw_area, *headerbar, *colorbutton;
+
+      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+
+      draw_area = drawing_area_new ();
+      gtk_container_add (GTK_CONTAINER (window), draw_area);
+
+      headerbar = gtk_header_bar_new ();
+      gtk_header_bar_set_title (GTK_HEADER_BAR (headerbar), "Paint");
+      gtk_header_bar_set_show_title_buttons (GTK_HEADER_BAR (headerbar), TRUE);
+
+      colorbutton = gtk_color_button_new ();
+      g_signal_connect (colorbutton, "color-set",
+                        G_CALLBACK (color_button_color_set), draw_area);
+      gtk_color_chooser_set_rgba (GTK_COLOR_CHOOSER (colorbutton),
+                                  &(GdkRGBA) { 0, 0, 0, 1 });
+
+      gtk_header_bar_pack_end (GTK_HEADER_BAR (headerbar), colorbutton);
+      gtk_window_set_titlebar (GTK_WINDOW (window), headerbar);
+
+      g_signal_connect (window, "destroy",
+                        G_CALLBACK (gtk_widget_destroyed), &window);
+
+    }
+
+  if (!gtk_widget_get_visible (window))
+    gtk_widget_show (window);
+  else
+    gtk_widget_destroy (window);
+
+  return window;
+}

gtk/gtk.h

@@ -116,6 +116,7 @@
 #include <gtk/gtkgesturepan.h>
 #include <gtk/gtkgesturerotate.h>
 #include <gtk/gtkgesturesingle.h>
+#include <gtk/gtkgesturestylus.h>
 #include <gtk/gtkgestureswipe.h>
 #include <gtk/gtkgesturezoom.h>
 #include <gtk/gtkglarea.h>

gtk/gtkgesturestylus.c

@@ -0,0 +1,330 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2017-2018, Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author(s): Carlos Garnacho <carlosg@gnome.org>
+ */
+
+/**
+ * SECTION:gtkgesturestylus
+ * @Short_description: Gesture for stylus input
+ * @Title: GtkGestureStylus
+ * @See_also: #GtkGesture, #GtkGestureSingle
+ *
+ * #GtkGestureStylus is a #GtkGesture implementation specific to stylus
+ * input. The provided signals just provide the basic information
+ */
+
+#include "config.h"
+#include "gtkgesturestylus.h"
+#include "gtkgesturestylusprivate.h"
+#include "gtkprivate.h"
+#include "gtkintl.h"
+
+G_DEFINE_TYPE (GtkGestureStylus, gtk_gesture_stylus, GTK_TYPE_GESTURE_SINGLE)
+
+enum {
+  PROXIMITY,
+  DOWN,
+  MOTION,
+  UP,
+  N_SIGNALS
+};
+
+static guint signals[N_SIGNALS] = { 0, };
+
+static gboolean
+gtk_gesture_stylus_handle_event (GtkEventController *controller,
+                                 const GdkEvent     *event)
+{
+  GdkModifierType modifiers;
+  guint n_signal;
+  gdouble x, y;
+
+  GTK_EVENT_CONTROLLER_CLASS (gtk_gesture_stylus_parent_class)->handle_event (controller, event);
+
+  if (!gdk_event_get_device_tool (event))
+    return FALSE;
+  if (!gdk_event_get_coords (event, &x, &y))
+    return FALSE;
+
+  switch ((guint) gdk_event_get_event_type (event))
+    {
+    case GDK_BUTTON_PRESS:
+      n_signal = DOWN;
+      break;
+    case GDK_BUTTON_RELEASE:
+      n_signal = UP;
+      break;
+    case GDK_MOTION_NOTIFY:
+      gdk_event_get_state (event, &modifiers);
+
+      if (modifiers & GDK_BUTTON1_MASK)
+        n_signal = MOTION;
+      else
+        n_signal = PROXIMITY;
+      break;
+    default:
+      return FALSE;
+    }
+
+  g_signal_emit (controller, signals[n_signal], 0, x, y);
+
+  return TRUE;
+}
+
+static void
+gtk_gesture_stylus_class_init (GtkGestureStylusClass *klass)
+{
+  GObjectClass *object_class;
+  GtkEventControllerClass *event_controller_class;
+
+  object_class = G_OBJECT_CLASS (klass);
+  event_controller_class = GTK_EVENT_CONTROLLER_CLASS (klass);
+
+  event_controller_class->handle_event = gtk_gesture_stylus_handle_event;
+
+  signals[PROXIMITY] =
+    g_signal_new (I_("proximity"),
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GtkGestureStylusClass, proximity),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 2, G_TYPE_DOUBLE, G_TYPE_DOUBLE);
+  signals[DOWN] =
+    g_signal_new (I_("down"),
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GtkGestureStylusClass, down),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 2, G_TYPE_DOUBLE, G_TYPE_DOUBLE);
+  signals[MOTION] =
+    g_signal_new (I_("motion"),
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GtkGestureStylusClass, motion),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 2, G_TYPE_DOUBLE, G_TYPE_DOUBLE);
+  signals[UP] =
+    g_signal_new (I_("up"),
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GtkGestureStylusClass, up),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 2, G_TYPE_DOUBLE, G_TYPE_DOUBLE);
+}
+
+static void
+gtk_gesture_stylus_init (GtkGestureStylus *gesture)
+{
+}
+
+/**
+ * gtk_gesture_stylus_new:
+ * @widget: a #GtkWidget
+ *
+ * Creates a new #GtkGestureStylus.
+ *
+ * Returns: a newly created stylus gesture
+ *
+ * Since: 3.94
+ **/
+GtkGesture *
+gtk_gesture_stylus_new (GtkWidget *widget)
+{
+  return g_object_new (GTK_TYPE_GESTURE_STYLUS,
+                       "widget", widget,
+                       NULL);
+}
+
+static const GdkEvent *
+gesture_get_current_event (GtkGestureStylus *gesture)
+{
+  GdkEventSequence *sequence;
+
+  sequence = gtk_gesture_single_get_current_sequence (GTK_GESTURE_SINGLE (gesture));
+
+  return gtk_gesture_get_last_event (GTK_GESTURE (gesture), sequence);
+}
+
+/**
+ * gtk_gesture_stylus_get_axis:
+ * @gesture: a #GtkGestureStylus
+ * @axis: requested device axis
+ * @value: (out): return location for the axis value
+ *
+ * Returns the current value for the requested @axis. This function
+ * must be called from either the #GtkGestureStylus:down,
+ * #GtkGestureStylus:motion, #GtkGestureStylus:up or #GtkGestureStylus:proximity
+ * signals.
+ *
+ * Returns: #TRUE if there is a current value for the axis
+ *
+ * Since: 3.94
+ **/
+gboolean
+gtk_gesture_stylus_get_axis (GtkGestureStylus *gesture,
+			     GdkAxisUse        axis,
+			     gdouble          *value)
+{
+  const GdkEvent *event;
+
+  g_return_val_if_fail (GTK_IS_GESTURE_STYLUS (gesture), FALSE);
+  g_return_val_if_fail (axis < GDK_AXIS_LAST, FALSE);
+  g_return_val_if_fail (value != NULL, FALSE);
+
+  event = gesture_get_current_event (gesture);
+  if (!event)
+    return FALSE;
+
+  return gdk_event_get_axis (event, axis, value);
+}
+
+/**
+ * gtk_gesture_stylus_get_axes:
+ * @gesture: a GtkGestureStylus
+ * @axes: array of requested axes, terminated with #GDK_AXIS_IGNORE
+ * @values: (out): return location for the axis values
+ *
+ * Returns the current values for the requested @axes. This function
+ * must be called from either the #GtkGestureStylus:down,
+ * #GtkGestureStylus:motion, #GtkGestureStylus:up or #GtkGestureStylus:proximity
+ * signals.
+ *
+ * Returns: #TRUE if there is a current value for the axes
+ **/
+gboolean
+gtk_gesture_stylus_get_axes (GtkGestureStylus  *gesture,
+			     GdkAxisUse         axes[],
+			     gdouble          **values)
+{
+  const GdkEvent *event;
+  GArray *array;
+  gint i;
+
+  g_return_val_if_fail (GTK_IS_GESTURE_STYLUS (gesture), FALSE);
+  g_return_val_if_fail (values != NULL, FALSE);
+
+  event = gesture_get_current_event (gesture);
+  if (!event)
+    return FALSE;
+
+  while (axes[i] != GDK_AXIS_IGNORE)
+    {
+      gdouble value;
+
+      if (axes[i] >= GDK_AXIS_LAST)
+        {
+          g_warning ("Requesting unknown axis %d, did you "
+                     "forget to add a last GDK_AXIS_IGNORE axis?",
+                     axes[i]);
+          g_array_free (array, TRUE);
+          return FALSE;
+        }
+
+      gdk_event_get_axis (event, axes[i], &value);
+      g_array_append_val (array, value);
+      i++;
+    }
+
+  *values = g_array_free (array, FALSE);
+  return TRUE;
+}
+
+/**
+ * gtk_gesture_stylus_get_backlog:
+ * @gesture: a #GtkGestureStylus
+ * @backlog: (out): coordinates and times for the backlog events
+ * @n_elems: (out): return location for the number of elements
+ *
+ * By default, GTK+ will limit rate of input events. On stylus input where
+ * accuracy of strokes is paramount, this function returns the accumulated
+ * coordinate/timing state before the emission of the current
+ * #GtkGestureStylus:motion signal.
+ *
+ * This function may only be called within a #GtkGestureStylus::motion
+ * signal handler, the state given in this signal and obtainable through
+ * gtk_gesture_stylus_get_axis() call express the latest (most up-to-date)
+ * state in motion history.
+ *
+ * @backlog is provided in chronological order.
+ *
+ * Returns: #TRUE if there is a backlog to unfold in the current state.
+ **/
+gboolean
+gtk_gesture_stylus_get_backlog (GtkGestureStylus  *gesture,
+				GdkTimeCoord     **backlog,
+				guint             *n_elems)
+{
+  GdkEvent *event;
+  GArray *backlog_array;
+  GList *history, *l;
+  gint i;
+
+  g_return_val_if_fail (GTK_IS_GESTURE_STYLUS (gesture), FALSE);
+  g_return_val_if_fail (backlog != NULL && n_elems != NULL, FALSE);
+
+  event = gesture_get_current_event (gesture);
+
+  if (event)
+    history = gdk_event_get_history (event);
+  if (!history)
+    return FALSE;
+
+  backlog_array = g_array_new (FALSE, FALSE, sizeof (GdkTimeCoord));
+  for (l = history; l; l = l->next)
+    {
+      GdkTimeCoord time_coord;
+      GdkEvent *ev = l->data;
+
+      time_coord.time = gdk_event_get_time (ev);
+
+      for (i = 0; i < GDK_AXIS_LAST; i++)
+        gdk_event_get_axis (event, i, &time_coord.axes[i]);
+
+      g_array_append_val (backlog_array, time_coord);
+    }
+
+  *n_elems = backlog_array->len;
+  *backlog = g_array_free (backlog_array, FALSE);
+  g_list_free (history);
+
+  return TRUE;
+}
+
+/**
+ * gdk_gesture_stylus_get_device_tool:
+ * @gesture: a #GtkGestureStylus
+ *
+ * Returns the #GdkDeviceTool currently driving input through this gesture.
+ * This function must be called from either the #GtkGestureStylus:down,
+ * #GtkGestureStylus:motion, #GtkGestureStylus:up or #GtkGestureStylus:proximity
+ * signals.
+ *
+ * Returns: (transfer none): The current stylus tool
+ **/
+GdkDeviceTool *
+gtk_gesture_stylus_get_device_tool (GtkGestureStylus *gesture)
+{
+  const GdkEvent *event;
+
+  g_return_val_if_fail (GTK_IS_GESTURE_STYLUS (gesture), FALSE);
+
+  event = gesture_get_current_event (gesture);
+  if (!event)
+    return NULL;
+
+  return gdk_event_get_device_tool (event);
+}

gtk/gtkgesturestylus.h

@@ -0,0 +1,63 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2017-2018, Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author(s): Carlos Garnacho <carlosg@gnome.org>
+ */
+#ifndef __GTK_GESTURE_STYLUS_H__
+#define __GTK_GESTURE_STYLUS_H__
+
+#include <gtk/gtkgesture.h>
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_GESTURE_STYLUS         (gtk_gesture_stylus_get_type ())
+#define GTK_GESTURE_STYLUS(o)           (G_TYPE_CHECK_INSTANCE_CAST ((o), GTK_TYPE_GESTURE_STYLUS, GtkGestureStylus))
+#define GTK_GESTURE_STYLUS_CLASS(k)     (G_TYPE_CHECK_CLASS_CAST ((k), GTK_TYPE_GESTURE_STYLUS, GtkGestureStylusClass))
+#define GTK_IS_GESTURE_STYLUS(o)        (G_TYPE_CHECK_INSTANCE_TYPE ((o), GTK_TYPE_GESTURE_STYLUS))
+#define GTK_IS_GESTURE_STYLUS_CLASS(k)  (G_TYPE_CHECK_CLASS_TYPE ((k), GTK_TYPE_GESTURE_STYLUS))
+#define GTK_GESTURE_STYLUS_GET_CLASS(o) (G_TYPE_INSTANCE_GET_CLASS ((o), GTK_TYPE_GESTURE_STYLUS, GtkGestureStylusClass))
+
+typedef struct _GtkGestureStylus GtkGestureStylus;
+typedef struct _GtkGestureStylusClass GtkGestureStylusClass;
+
+GDK_AVAILABLE_IN_3_94
+GType             gtk_gesture_stylus_get_type (void) G_GNUC_CONST;
+
+GDK_AVAILABLE_IN_3_94
+GtkGesture *      gtk_gesture_stylus_new      (GtkWidget *widget);
+
+GDK_AVAILABLE_IN_3_94
+gboolean          gtk_gesture_stylus_get_axis (GtkGestureStylus *gesture,
+					       GdkAxisUse        axis,
+					       gdouble          *value);
+GDK_AVAILABLE_IN_3_94
+gboolean          gtk_gesture_stylus_get_axes (GtkGestureStylus  *gesture,
+					       GdkAxisUse         axis[],
+					       gdouble          **axes);
+GDK_AVAILABLE_IN_3_94
+gboolean          gtk_gesture_stylus_get_backlog (GtkGestureStylus  *gesture,
+						  GdkTimeCoord     **backlog,
+						  guint             *n_elems);
+GDK_AVAILABLE_IN_3_94
+GdkDeviceTool *   gtk_gesture_stylus_get_device_tool (GtkGestureStylus *gesture);
+
+G_END_DECLS
+
+#endif /* __GTK_GESTURE_STYLUS_H__ */

gtk/gtkgesturestylusprivate.h

@@ -0,0 +1,51 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2017-2018, Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author(s): Carlos Garnacho <carlosg@gnome.org>
+ */
+#ifndef __GTK_GESTURE_STYLUS_PRIVATE_H__
+#define __GTK_GESTURE_STYLUS_PRIVATE_H__
+
+#include "gtkgesturesingleprivate.h"
+#include "gtkgesturestylus.h"
+
+struct _GtkGestureStylus
+{
+  GtkGestureSingle parent_instance;
+};
+
+struct _GtkGestureStylusClass
+{
+  GtkGestureSingleClass parent_class;
+
+  void (*proximity) (GtkGestureStylus *gesture,
+                     gdouble           x,
+                     gdouble           y);
+  void (*down)      (GtkGestureStylus *gesture,
+                     gdouble           x,
+                     gdouble           y);
+  void (*motion)    (GtkGestureStylus *gesture,
+                     gdouble           x,
+                     gdouble           y);
+  void (*up)        (GtkGestureStylus *gesture,
+                     gdouble           x,
+                     gdouble           y);
+
+  /*< private >*/
+  gpointer padding[10];
+};
+
+#endif /* __GTK_GESTURE_STYLUS_PRIVATE_H__ */

gtk/meson.build

@@ -181,6 +181,7 @@ gtk_public_sources = files([
   'gtkgesturepan.c',
   'gtkgesturerotate.c',
   'gtkgesturesingle.c',
+  'gtkgesturestylus.c',
   'gtkgestureswipe.c',
   'gtkgesturezoom.c',
   'gtkgizmo.c',
@@ -463,6 +464,7 @@ gtk_public_headers = files([
   'gtkgesturepan.h',
   'gtkgesturerotate.h',
   'gtkgesturesingle.h',
+  'gtkgesturestylus.h',
   'gtkgestureswipe.h',
   'gtkgesturezoom.h',
   'gtkglarea.h',