[gimp/nielsdg/fix-pick-color-on-wayland] libgimpwidgets: Use Screenshot portal for picking

[Niels De Graef <nielsdg src gnome org>]

commit b6377056b845e7c96d1aa43c687b9dffe5d6858e
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Mon Dec 13 09:13:19 2021 +0100

    libgimpwidgets: Use Screenshot portal for picking
    
    Freedesktop (XDG) portals are a collection of D-Bus APIs that work
    across desktop environments, display servers and work within
    containerized applications, like Flatpak. The internal implementation
    can then choose to implement these in such a way that takes into account
    security considerations, as well as making sure the user consents to
    certain actions.
    
    One such portal is the `Screenshot` portal, which contains a
    `Screenshot()` method as well as `PickColor()`. We already use the
    former for taking a screenshot, and this commit makes sure our color
    picker also makes use of the latter.
    
    By doing this, color picking is now possible on the major Wayland
    compositors.
    
    (Honestly, we should remove DE-specific backends like that of KWin, to
    have less variation on the possible results of a color picking
    operation).

 libgimpwidgets/Makefile.am          |   4 +-
 libgimpwidgets/gimppickbutton-xdg.c | 175 ++++++++++++++++++++++++++++++++++++
 libgimpwidgets/gimppickbutton-xdg.h |  25 ++++++
 libgimpwidgets/gimppickbutton.c     |   5 +-
 libgimpwidgets/meson.build          |   1 +
 5 files changed, 208 insertions(+), 2 deletions(-)
---
diff --git a/libgimpwidgets/Makefile.am b/libgimpwidgets/Makefile.am
index 2e99f00721..0a354093bf 100644
--- a/libgimpwidgets/Makefile.am
+++ b/libgimpwidgets/Makefile.am
@@ -155,7 +155,9 @@ libgimpwidgets_sources += \
        gimppickbutton-default.c        \
        gimppickbutton-default.h        \
        gimppickbutton-kwin.c           \
-       gimppickbutton-kwin.h
+       gimppickbutton-kwin.h           \
+       gimppickbutton-xdg.c            \
+       gimppickbutton-xdg.h
 endif
 
 
diff --git a/libgimpwidgets/gimppickbutton-xdg.c b/libgimpwidgets/gimppickbutton-xdg.c
new file mode 100644
index 0000000000..f9fc189350
--- /dev/null
+++ b/libgimpwidgets/gimppickbutton-xdg.c
@@ -0,0 +1,175 @@
+/* LIBGIMP - The GIMP Library
+ * Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
+ *
+ * gimppickbutton-xdg.c
+ * Copyright (C) 2021 Niels De Graef <nielsdegraef gmail com>
+ *
+ * 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
+ * Library 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
+ * <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl.h>
+#include <gtk/gtk.h>
+
+#ifdef GDK_WINDOWING_X11
+#include <gdk/gdkx.h>
+#endif
+
+#include "libgimpcolor/gimpcolor.h"
+
+#include "gimpwidgetstypes.h"
+#include "gimppickbutton.h"
+#include "gimppickbutton-default.h"
+#include "gimppickbutton-xdg.h"
+
+#include "libgimp/libgimp-intl.h"
+#include "libgimp/gimpui.h"
+
+gboolean
+_gimp_pick_button_xdg_available (void)
+{
+  GDBusProxy *proxy = NULL;
+
+  proxy = g_dbus_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
+                                         G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
+                                         NULL,
+                                         "org.freedesktop.portal.Desktop",
+                                         "/org/freedesktop/portal/desktop",
+                                         "org.freedesktop.portal.Screenshot",
+                                         NULL, NULL);
+
+  if (proxy)
+    {
+      GError *error = NULL;
+
+      g_dbus_proxy_call_sync (proxy, "org.freedesktop.DBus.Peer.Ping",
+                              NULL,
+                              G_DBUS_CALL_FLAGS_NONE,
+                              -1, NULL, &error);
+      if (! error)
+        return TRUE;
+
+      g_clear_error (&error);
+
+      g_object_unref (proxy);
+      proxy = NULL;
+    }
+
+  return FALSE;
+}
+
+static void
+pick_color_xdg_dbus_signal (GDBusProxy      *proxy,
+                            gchar           *sender_name,
+                            gchar           *signal_name,
+                            GVariant        *parameters,
+                            GimpPickButton  *button)
+{
+  if (g_strcmp0 (signal_name, "Response") == 0)
+    {
+      GVariant *results;
+      guint32   response;
+
+      g_variant_get (parameters, "(u@a{sv})",
+                     &response,
+                     &results);
+
+      /* Possible values:
+       * 0: Success, the request is carried out
+       * 1: The user cancelled the interaction
+       * 2: The user interaction was ended in some other way
+       * Cf. 
https://github.com/flatpak/xdg-desktop-portal/blob/master/data/org.freedesktop.portal.Request.xml
+       */
+      if (response == 0)
+        {
+          GimpRGB color;
+
+          if (g_variant_lookup (results, "color", "(ddd)", &color.r, &color.g, &color.b))
+            {
+              g_signal_emit_by_name (button, "color-picked", &color);
+            }
+        }
+
+      g_variant_unref (results);
+      /* Quit anyway. */
+      gtk_main_quit ();
+    }
+}
+
+/* entry point to this file, called from gimppickbutton.c */
+void
+_gimp_pick_button_xdg_pick (GimpPickButton *button)
+{
+  GDBusProxy *proxy = NULL;
+  GVariant *retval;
+  gchar    *opath         = NULL;
+  gchar    *parent_window = NULL;
+
+#ifdef GDK_WINDOWING_X11
+  if (GDK_IS_X11_DISPLAY (gdk_display_get_default ()))
+    {
+      GdkWindow *window;
+
+      window = gtk_widget_get_window (GTK_WIDGET (button));
+      if (window)
+        {
+          gint id;
+
+          id = GDK_WINDOW_XID (window);
+          parent_window = g_strdup_printf ("x11:0x%x", id);
+        }
+    }
+#endif
+
+  proxy = g_dbus_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
+                                         G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
+                                         NULL,
+                                         "org.freedesktop.portal.Desktop",
+                                         "/org/freedesktop/portal/desktop",
+                                         "org.freedesktop.portal.Screenshot",
+                                         NULL, NULL);
+  if (!proxy)
+    {
+      return;
+    }
+
+  retval = g_dbus_proxy_call_sync (proxy, "PickColor",
+                                   g_variant_new ("(sa{sv})", parent_window ? parent_window : "", NULL),
+                                   G_DBUS_CALL_FLAGS_NONE,
+                                   -1, NULL, NULL);
+  g_free (parent_window);
+  g_clear_object (&proxy);
+  if (retval)
+    {
+      g_variant_get (retval, "(o)", &opath);
+      g_variant_unref (retval);
+    }
+
+  if (opath)
+    {
+      GDBusProxy *proxy2 = NULL;
+
+      proxy2 = g_dbus_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
+                                              G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
+                                              NULL,
+                                              "org.freedesktop.portal.Desktop",
+                                              opath,
+                                              "org.freedesktop.portal.Request",
+                                              NULL, NULL);
+      g_signal_connect (proxy2, "g-signal",
+                        G_CALLBACK (pick_color_xdg_dbus_signal),
+                        button);
+
+      gtk_main ();
+      g_object_unref (proxy2);
+      g_free (opath);
+    }
+}
diff --git a/libgimpwidgets/gimppickbutton-xdg.h b/libgimpwidgets/gimppickbutton-xdg.h
new file mode 100644
index 0000000000..394665e3bb
--- /dev/null
+++ b/libgimpwidgets/gimppickbutton-xdg.h
@@ -0,0 +1,25 @@
+/* LIBGIMP - The GIMP Library
+ * Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
+ *
+ * gimppickbutton-xdg.h
+ * Copyright (C) 2021 Niels De Graef <nielsdegraef gmail com>
+ *
+ * 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
+ * Library 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
+ * <https://www.gnu.org/licenses/>.
+ */
+
+/* Private header file which is not meant to be exported. */
+#ifndef __GIMP_PICK_BUTTON_XDG_H__
+#define __GIMP_PICK_BUTTON_XDG_H__
+
+gboolean _gimp_pick_button_xdg_available (void);
+void     _gimp_pick_button_xdg_pick      (GimpPickButton *button);
+
+#endif /* __GIMP_PICK_BUTTON_XDG_H__ */
+
diff --git a/libgimpwidgets/gimppickbutton.c b/libgimpwidgets/gimppickbutton.c
index 43ab6ae9ad..0a21eaa1fe 100644
--- a/libgimpwidgets/gimppickbutton.c
+++ b/libgimpwidgets/gimppickbutton.c
@@ -32,6 +32,7 @@
 #include "gimppickbutton.h"
 #include "gimppickbutton-default.h"
 #include "gimppickbutton-kwin.h"
+#include "gimppickbutton-xdg.h"
 #include "gimppickbutton-private.h"
 
 #ifdef GDK_WINDOWING_QUARTZ
@@ -143,7 +144,9 @@ gimp_pick_button_clicked (GtkButton *button)
 #ifdef GDK_WINDOWING_QUARTZ
   _gimp_pick_button_quartz_pick (GIMP_PICK_BUTTON (button));
 #else
-  if (_gimp_pick_button_kwin_available ())
+  if (_gimp_pick_button_xdg_available ())
+    _gimp_pick_button_xdg_pick (GIMP_PICK_BUTTON (button));
+  else if (_gimp_pick_button_kwin_available ())
     _gimp_pick_button_kwin_pick (GIMP_PICK_BUTTON (button));
   else
     _gimp_pick_button_default_pick (GIMP_PICK_BUTTON (button));
diff --git a/libgimpwidgets/meson.build b/libgimpwidgets/meson.build
index 488ce7ad5f..0627789a98 100644
--- a/libgimpwidgets/meson.build
+++ b/libgimpwidgets/meson.build
@@ -180,6 +180,7 @@ else
   libgimpwidgets_sources += [
     'gimppickbutton-default.c',
     'gimppickbutton-kwin.c',
+    'gimppickbutton-xdg.c',
   ]
 endif