[gimp] libgimp: fix legacy plug-ins, which I broke with the big ID removal

[Michael Natterer <mitch src gnome org>]

commit 37897b13fea42fa713f1b2b0bcf59ccc30abd7f4
Author: Michael Natterer <mitch gimp org>
Date:   Thu Aug 29 18:36:59 2019 +0200

    libgimp: fix legacy plug-ins, which I broke with the big ID removal
    
    - hand out and leak proxy object objects to legacy API like candy,
      bypassing the factory in GimpPlugIn, because there is no plug-in
      singleton.
    
    - gimpgpcompat.c: image, item etc. are now objects, simply forgot this
      file.

 libgimp/gimpdisplay.c  | 14 +++++++++++---
 libgimp/gimpgpcompat.c | 52 +++++++++++++++++++++++++++++++++++---------------
 libgimp/gimpimage.c    | 14 +++++++++++---
 libgimp/gimpitem.c     | 43 +++++++++++++++++++++++++++++++++++++----
 4 files changed, 98 insertions(+), 25 deletions(-)
---
diff --git a/libgimp/gimpdisplay.c b/libgimp/gimpdisplay.c
index f796231b40..b66067c783 100644
--- a/libgimp/gimpdisplay.c
+++ b/libgimp/gimpdisplay.c
@@ -160,10 +160,18 @@ gimp_display_get_by_id (gint32 display_id)
 {
   if (display_id > 0)
     {
-      GimpPlugIn    *plug_in   = gimp_get_plug_in ();
-      GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
+      GimpPlugIn *plug_in = gimp_get_plug_in ();
 
-      return _gimp_procedure_get_display (procedure, display_id);
+      if (plug_in)
+        {
+          GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
+
+          return _gimp_procedure_get_display (procedure, display_id);
+        }
+
+      return g_object_new (GIMP_TYPE_DISPLAY,
+                           "id", display_id,
+                           NULL);
     }
 
   return NULL;
diff --git a/libgimp/gimpgpcompat.c b/libgimp/gimpgpcompat.c
index 895849abd3..cf2c9dc36a 100644
--- a/libgimp/gimpgpcompat.c
+++ b/libgimp/gimpgpcompat.c
@@ -457,31 +457,38 @@ _gimp_params_to_value_array (const GimpParam  *params,
           break;
 
         case GIMP_PDB_ITEM:
-          g_value_set_int (&value, params[i].data.d_item);
+          g_value_set_object (&value,
+                              gimp_item_get_by_id (params[i].data.d_item));
           break;
 
         case GIMP_PDB_DISPLAY:
-          g_value_set_int (&value, params[i].data.d_display);
+          g_value_set_object (&value,
+                              gimp_display_get_by_id (params[i].data.d_display));
           break;
 
         case GIMP_PDB_IMAGE:
-          g_value_set_int (&value, params[i].data.d_image);
+          g_value_set_object (&value,
+                              gimp_image_get_by_id (params[i].data.d_image));
           break;
 
         case GIMP_PDB_LAYER:
-          g_value_set_int (&value, params[i].data.d_layer);
+          g_value_set_object (&value,
+                              gimp_item_get_by_id (params[i].data.d_layer));
           break;
 
         case GIMP_PDB_CHANNEL:
-          g_value_set_int (&value, params[i].data.d_channel);
+          g_value_set_object (&value,
+                              gimp_item_get_by_id (params[i].data.d_channel));
           break;
 
         case GIMP_PDB_DRAWABLE:
-          g_value_set_int (&value, params[i].data.d_drawable);
+          g_value_set_object (&value,
+                              gimp_item_get_by_id (params[i].data.d_drawable));
           break;
 
         case GIMP_PDB_SELECTION:
-          g_value_set_int (&value, params[i].data.d_selection);
+          g_value_set_object (&value,
+                              gimp_item_get_by_id (params[i].data.d_selection));
           break;
 
         case GIMP_PDB_COLORARRAY:
@@ -538,7 +545,8 @@ _gimp_value_array_to_params (GimpValueArray *args,
 
   for (i = 0; i < length; i++)
     {
-      GValue *value = gimp_value_array_index (args, i);
+      GValue  *value = gimp_value_array_index (args, i);
+      GObject *object;
 
       params[i].type = _gimp_pdb_gtype_to_arg_type (G_VALUE_TYPE (value));
 
@@ -620,31 +628,45 @@ _gimp_value_array_to_params (GimpValueArray *args,
           break;
 
         case GIMP_PDB_ITEM:
-          params[i].data.d_item = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_item =
+            object ? gimp_item_get_id (GIMP_ITEM (object)) : -1;
           break;
 
         case GIMP_PDB_DISPLAY:
-          params[i].data.d_display = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_display =
+            object ? gimp_display_get_id (GIMP_DISPLAY (object)) : -1;
           break;
 
         case GIMP_PDB_IMAGE:
-          params[i].data.d_image = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_image =
+            object ? gimp_image_get_id (GIMP_IMAGE (object)) : -1;
           break;
 
         case GIMP_PDB_LAYER:
-          params[i].data.d_layer = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_layer =
+            object ? gimp_item_get_id (GIMP_ITEM (object)) : -1;
           break;
 
         case GIMP_PDB_CHANNEL:
-          params[i].data.d_channel = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_channel =
+            object ? gimp_item_get_id (GIMP_ITEM (object)) : -1;
           break;
 
         case GIMP_PDB_DRAWABLE:
-          params[i].data.d_drawable = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_drawable =
+            object ? gimp_item_get_id (GIMP_ITEM (object)) : -1;
           break;
 
         case GIMP_PDB_SELECTION:
-          params[i].data.d_selection = g_value_get_int (value);
+          object = g_value_get_object (value);
+          params[i].data.d_selection =
+            object ? gimp_item_get_id (GIMP_ITEM (object)) : -1;
           break;
 
         case GIMP_PDB_COLORARRAY:
diff --git a/libgimp/gimpimage.c b/libgimp/gimpimage.c
index c5020d5aea..5d26e57f0d 100644
--- a/libgimp/gimpimage.c
+++ b/libgimp/gimpimage.c
@@ -158,10 +158,18 @@ gimp_image_get_by_id (gint32 image_id)
 {
   if (image_id > 0)
     {
-      GimpPlugIn    *plug_in   = gimp_get_plug_in ();
-      GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
+      GimpPlugIn *plug_in = gimp_get_plug_in ();
 
-      return _gimp_procedure_get_image (procedure, image_id);
+      if (plug_in)
+        {
+          GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
+
+          return _gimp_procedure_get_image (procedure, image_id);
+        }
+
+      return g_object_new (GIMP_TYPE_IMAGE,
+                           "id", image_id,
+                           NULL);
     }
 
   return NULL;
diff --git a/libgimp/gimpitem.c b/libgimp/gimpitem.c
index 5500bab53a..acdc8cb2ca 100644
--- a/libgimp/gimpitem.c
+++ b/libgimp/gimpitem.c
@@ -163,10 +163,45 @@ gimp_item_get_by_id (gint32 item_id)
 {
   if (item_id > 0)
     {
-      GimpPlugIn    *plug_in   = gimp_get_plug_in ();
-      GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
-
-      return _gimp_procedure_get_item (procedure, item_id);
+      GimpPlugIn *plug_in = gimp_get_plug_in ();
+
+      if (plug_in)
+        {
+          GimpProcedure *procedure = _gimp_plug_in_get_procedure (plug_in);
+
+          return _gimp_procedure_get_item (procedure, item_id);
+        }
+
+      if (gimp_item_id_is_layer (item_id))
+        {
+          return g_object_new (GIMP_TYPE_LAYER,
+                               "id", item_id,
+                               NULL);
+        }
+      else if (gimp_item_id_is_layer_mask (item_id))
+        {
+          return g_object_new (GIMP_TYPE_LAYER_MASK,
+                               "id", item_id,
+                               NULL);
+        }
+      else if (gimp_item_id_is_selection (item_id))
+        {
+          return g_object_new (GIMP_TYPE_SELECTION,
+                               "id", item_id,
+                               NULL);
+        }
+      else if (gimp_item_id_is_channel (item_id))
+        {
+          return g_object_new (GIMP_TYPE_CHANNEL,
+                               "id", item_id,
+                               NULL);
+        }
+      else if (gimp_item_id_is_vectors (item_id))
+        {
+          return g_object_new (GIMP_TYPE_VECTORS,
+                               "id", item_id,
+                               NULL);
+        }
     }
 
   return NULL;