[gimp] app: fix drag'n drop of fg/bg colors under Wayland.

[Jehan <jehanp src gnome org>]

commit d4733e5b21e9d949ccc8af69bdac9a4a7513a9e9
Author: Jehan <jehan girinstud io>
Date:   Sun Sep 26 18:54:39 2021 +0200

    app: fix drag'n drop of fg/bg colors under Wayland.
    
    Commit 086ae77929 had broken dnd of colors from toolbox's color area on
    Wayland. Clearly Wayland did not like we changed focus on a click,
    breaking the drag.
    
    To fix this, do not propagate button press and release events from the
    GimpFgBgEditor editor anymore. Yet, since changing colors is usually to
    be used (often immediately) on the canvas, giving back the focus to
    canvas still makes sense. Therefore, instead of using press/release
    events, add semantic signals to GimpFgBgEditor: color-dropped,
    colors-swapped and colors-default (additionally to already existing
    color-clicked). Then connect to these new signals to grab focus for
    canvas when relevant.
    
    Thanks to Massimo for raising the broken color dnd feature.

 app/widgets/gimpfgbgeditor.c         | 46 ++++++++++++++++++++++++++++++++----
 app/widgets/gimpfgbgeditor.h         | 16 ++++++++-----
 app/widgets/gimptoolbox-color-area.c | 21 ++++++++++++++++
 3 files changed, 73 insertions(+), 10 deletions(-)
---
diff --git a/app/widgets/gimpfgbgeditor.c b/app/widgets/gimpfgbgeditor.c
index 8e3a586550..c7f319292a 100644
--- a/app/widgets/gimpfgbgeditor.c
+++ b/app/widgets/gimpfgbgeditor.c
@@ -57,6 +57,9 @@ enum
 enum
 {
   COLOR_CLICKED,
+  COLOR_DROPPED,
+  COLORS_SWAPPED,
+  COLORS_DEFAULT,
   TOOLTIP,
   LAST_SIGNAL
 };
@@ -145,6 +148,31 @@ gimp_fg_bg_editor_class_init (GimpFgBgEditorClass *klass)
                   G_TYPE_NONE, 1,
                   GIMP_TYPE_ACTIVE_COLOR);
 
+  editor_signals[COLOR_DROPPED] =
+    g_signal_new ("color-dropped",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GimpFgBgEditorClass, color_dropped),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 1,
+                  GIMP_TYPE_ACTIVE_COLOR);
+
+  editor_signals[COLORS_SWAPPED] =
+    g_signal_new ("colors-swapped",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GimpFgBgEditorClass, colors_swapped),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
+  editor_signals[COLORS_DEFAULT] =
+    g_signal_new ("colors-default",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GimpFgBgEditorClass, colors_default),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
   editor_signals[TOOLTIP] =
     g_signal_new ("tooltip",
                   G_TYPE_FROM_CLASS (klass),
@@ -512,12 +540,18 @@ gimp_fg_bg_editor_button_press (GtkWidget      *widget,
 
         case GIMP_FG_BG_TARGET_SWAP:
           if (editor->context)
-            gimp_context_swap_colors (editor->context);
+            {
+              gimp_context_swap_colors (editor->context);
+              g_signal_emit (editor, editor_signals[COLORS_SWAPPED], 0);
+            }
           break;
 
         case GIMP_FG_BG_TARGET_DEFAULT:
           if (editor->context)
-            gimp_context_set_default_colors (editor->context);
+            {
+              gimp_context_set_default_colors (editor->context);
+              g_signal_emit (editor, editor_signals[COLORS_DEFAULT], 0);
+            }
           break;
 
         default:
@@ -525,7 +559,7 @@ gimp_fg_bg_editor_button_press (GtkWidget      *widget,
         }
     }
 
-  return FALSE;
+  return GDK_EVENT_STOP;
 }
 
 static gboolean
@@ -561,7 +595,7 @@ gimp_fg_bg_editor_button_release (GtkWidget      *widget,
       editor->click_target = GIMP_FG_BG_TARGET_INVALID;
     }
 
-  return FALSE;
+  return GDK_EVENT_STOP;
 }
 
 static gboolean
@@ -729,10 +763,14 @@ gimp_fg_bg_editor_drop_color (GtkWidget     *widget,
         {
         case GIMP_FG_BG_TARGET_FOREGROUND:
           gimp_context_set_foreground (editor->context, color);
+          g_signal_emit (editor, editor_signals[COLOR_DROPPED], 0,
+                         GIMP_ACTIVE_COLOR_FOREGROUND);
           break;
 
         case GIMP_FG_BG_TARGET_BACKGROUND:
           gimp_context_set_background (editor->context, color);
+          g_signal_emit (editor, editor_signals[COLOR_DROPPED], 0,
+                         GIMP_ACTIVE_COLOR_BACKGROUND);
           break;
 
         default:
diff --git a/app/widgets/gimpfgbgeditor.h b/app/widgets/gimpfgbgeditor.h
index 43113d50ca..c06af6930c 100644
--- a/app/widgets/gimpfgbgeditor.h
+++ b/app/widgets/gimpfgbgeditor.h
@@ -68,12 +68,16 @@ struct _GimpFgBgEditorClass
 
   /*  signals  */
 
-  void (* color_clicked) (GimpFgBgEditor  *editor,
-                          GimpActiveColor  color);
-
-  void (* tooltip)       (GimpFgBgEditor *editor,
-                          GimpFgBgTarget  target,
-                          GtkTooltip      tooltip);
+  void (* color_clicked)  (GimpFgBgEditor  *editor,
+                           GimpActiveColor  color);
+  void (* color_dropped)  (GimpFgBgEditor  *editor,
+                           GimpActiveColor  color);
+  void (* colors_swapped) (GimpFgBgEditor  *editor);
+  void (* colors_default) (GimpFgBgEditor  *editor);
+
+  void (* tooltip)        (GimpFgBgEditor *editor,
+                           GimpFgBgTarget  target,
+                           GtkTooltip      tooltip);
 };
 
 
diff --git a/app/widgets/gimptoolbox-color-area.c b/app/widgets/gimptoolbox-color-area.c
index 56f7c8197d..b8e0c0d72b 100644
--- a/app/widgets/gimptoolbox-color-area.c
+++ b/app/widgets/gimptoolbox-color-area.c
@@ -28,6 +28,7 @@
 
 #include "core/gimp.h"
 #include "core/gimpcontext.h"
+#include "core/gimpdisplay.h"
 
 #include "gimpaction.h"
 #include "gimpcolordialog.h"
@@ -59,6 +60,7 @@ static void   color_area_dialog_update      (GimpColorDialog      *dialog,
 static void   color_area_color_clicked      (GimpFgBgEditor       *editor,
                                              GimpActiveColor       active_color,
                                              GimpContext          *context);
+static void   color_area_color_changed      (GimpContext          *context);
 static void   color_area_tooltip            (GimpFgBgEditor       *editor,
                                              GimpFgBgTarget        target,
                                              GtkTooltip           *tooltip,
@@ -98,6 +100,15 @@ gimp_toolbox_color_area_create (GimpToolbox *toolbox,
   g_signal_connect (color_area, "color-clicked",
                     G_CALLBACK (color_area_color_clicked),
                     context);
+  g_signal_connect_swapped (color_area, "colors-swapped",
+                            G_CALLBACK (color_area_color_changed),
+                            context);
+  g_signal_connect_swapped (color_area, "colors-default",
+                            G_CALLBACK (color_area_color_changed),
+                            context);
+  g_signal_connect_swapped (color_area, "color-dropped",
+                            G_CALLBACK (color_area_color_changed),
+                            context);
 
   g_signal_connect (color_area, "tooltip",
                     G_CALLBACK (color_area_tooltip),
@@ -198,6 +209,9 @@ color_area_dialog_update (GimpColorDialog      *dialog,
       gimp_context_set_background (context, &revert_bg);
       break;
     }
+
+  if (gimp_context_get_display (context))
+    gimp_display_grab_focus (gimp_context_get_display (context));
 }
 
 static void
@@ -263,6 +277,13 @@ color_area_color_clicked (GimpFgBgEditor  *editor,
   color_dialog_active = TRUE;
 }
 
+static void
+color_area_color_changed (GimpContext *context)
+{
+  if (gimp_context_get_display (context))
+    gimp_display_grab_focus (gimp_context_get_display (context));
+}
+
 static gboolean
 accel_find_func (GtkAccelKey *key,
                  GClosure    *closure,