wayland: Store and retrieve implicit grab information for tablet tools

Window moving and resizing depends on the `meta_wayland_seat_get_grab_info`
function succeeding. At the moment, tablet tools do not generate implicit
grabs like the pointer and touch. This commit adds the necessary elements
to track implicit grabs and retrieve their information.

https://bugzilla.gnome.org/show_bug.cgi?id=777333

src/wayland/meta-wayland-seat.c

@@ -411,36 +411,58 @@ meta_wayland_seat_get_grab_info (MetaWaylandSeat    *seat,
                                  gfloat             *x,
                                  gfloat             *y)
 {
-  ClutterEventSequence *sequence = NULL;
-  gboolean can_grab_surface = FALSE;
+  MetaWaylandCompositor *compositor;
+  MetaWaylandTabletSeat *tablet_seat;
+  GList *tools, *l;
+
+  compositor = meta_wayland_compositor_get_default ();
+  tablet_seat = meta_wayland_tablet_manager_ensure_seat (compositor->tablet_manager, seat);
+  tools = g_hash_table_get_values (tablet_seat->tools);
 
   if (meta_wayland_seat_has_touch (seat))
+    {
+      ClutterEventSequence *sequence;
       sequence = meta_wayland_touch_find_grab_sequence (seat->touch,
                                                         surface,
                                                         serial);
-
       if (sequence)
         {
           meta_wayland_touch_get_press_coords (seat->touch, sequence, x, y);
+          return TRUE;
+        }
     }
-  else
-    {
-      if (meta_wayland_seat_has_pointer (seat) &&
-          (!require_pressed || seat->pointer->button_count > 0))
-        can_grab_surface = meta_wayland_pointer_can_grab_surface (seat->pointer,
-                                                                  surface,
-                                                                  serial);
 
-      if (can_grab_surface)
+  if (meta_wayland_seat_has_pointer (seat))
+    {
+      if ((!require_pressed || seat->pointer->button_count > 0) &&
+          meta_wayland_pointer_can_grab_surface (seat->pointer, surface, serial))
         {
           if (x)
             *x = seat->pointer->grab_x;
           if (y)
             *y = seat->pointer->grab_y;
+
+          return TRUE;
         }
     }
 
-  return sequence || can_grab_surface;
+  for (l = tools; l; l = l->next)
+    {
+      MetaWaylandTabletTool *tool = l->data;
+
+      if ((!require_pressed || tool->button_count > 0) &&
+          meta_wayland_tablet_tool_can_grab_surface (tool, surface, serial))
+        {
+          if (x)
+            *x = tool->grab_x;
+          if (y)
+            *y = tool->grab_y;
+
+          return TRUE;
+        }
+    }
+
+  return FALSE;
 }
 
 gboolean

src/wayland/meta-wayland-seat.h

@@ -31,6 +31,7 @@
 #include "meta-wayland-keyboard.h"
 #include "meta-wayland-touch.h"
 #include "meta-wayland-data-device.h"
+#include "meta-wayland-tablet-tool.h"
 
 struct _MetaWaylandSeat
 {

src/wayland/meta-wayland-tablet-tool.c

@@ -572,9 +572,15 @@ meta_wayland_tablet_tool_account_button (MetaWaylandTabletTool *tool,
                                          const ClutterEvent    *event)
 {
   if (event->type == CLUTTER_BUTTON_PRESS)
+    {
       tool->pressed_buttons |= 1 << (event->button.button - 1);
+      tool->button_count++;
+    }
   else if (event->type == CLUTTER_BUTTON_RELEASE)
+    {
       tool->pressed_buttons &= ~(1 << (event->button.button - 1));
+      tool->button_count--;
+    }
 }
 
 static void
@@ -840,6 +846,9 @@ handle_button_event (MetaWaylandTabletTool *tool,
   if (!tool->focus_surface)
     return;
 
+  if (event->type == CLUTTER_BUTTON_PRESS && tool->button_count == 1)
+    clutter_event_get_coords (event, &tool->grab_x, &tool->grab_y);
+
   if (event->type == CLUTTER_BUTTON_PRESS && event->button.button == 1)
     broadcast_down (tool, event);
   else if (event->type == CLUTTER_BUTTON_RELEASE && event->button.button == 1)
@@ -918,3 +927,32 @@ meta_wayland_tablet_tool_set_cursor_position (MetaWaylandTabletTool *tool,
   if (tool->cursor_renderer)
     meta_cursor_renderer_set_position (tool->cursor_renderer, new_x, new_y);
 }
+
+static gboolean
+tablet_tool_can_grab_surface (MetaWaylandTabletTool *tool,
+                              MetaWaylandSurface    *surface)
+{
+  GList *l;
+
+  if (tool->focus_surface == surface)
+    return TRUE;
+
+  for (l = surface->subsurfaces; l; l = l->next)
+    {
+      MetaWaylandSurface *subsurface = l->data;
+
+      if (tablet_tool_can_grab_surface (tool, subsurface))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
+gboolean
+meta_wayland_tablet_tool_can_grab_surface (MetaWaylandTabletTool *tool,
+                                           MetaWaylandSurface    *surface,
+                                           uint32_t               serial)
+{
+  return ((tool->down_serial == serial || tool->button_serial == serial) &&
+          tablet_tool_can_grab_surface (tool, surface));
+}

src/wayland/meta-wayland-tablet-tool.h

@@ -48,11 +48,14 @@ struct _MetaWaylandTabletTool
 
   MetaWaylandSurface *current;
   guint32 pressed_buttons;
+  guint32 button_count;
 
   guint32 proximity_serial;
   guint32 down_serial;
   guint32 button_serial;
 
+  float grab_x, grab_y;
+
   MetaWaylandTablet *current_tablet;
 };
 
@@ -79,5 +82,8 @@ void     meta_wayland_tablet_tool_set_cursor_position (MetaWaylandTabletTool  *t
                                                        int                     new_x,
                                                        int                     new_y);
 
+gboolean meta_wayland_tablet_tool_can_grab_surface (MetaWaylandTabletTool *tool,
+                                                    MetaWaylandSurface    *surface,
+                                                    uint32_t               serial);
 
 #endif /* META_WAYLAND_TABLET_TOOL_H */