Fix #127293: GPv3: Show regular keyframes Dope Sheet for GP object data

In the Dope Sheet, show regular keyframes for GreasePencil object data.
The GPv3 transition missed a few cases in the animation
channel/filtering code to add the channels from regular Actions on
GreasePencil data blocks.

Pull Request: https://projects.blender.org/blender/blender/pulls/129807

source/blender/editors/animation/anim_channels_defines.cc

@@ -3576,7 +3576,7 @@ static void acf_gpd_color(bAnimContext * /*ac*/, bAnimListElem * /*ale*/, float
 /* TODO: just get this from RNA? */
 static int acf_gpd_icon(bAnimListElem * /*ale*/)
 {
-  return ICON_OUTLINER_OB_GREASEPENCIL;
+  return ICON_OUTLINER_DATA_GREASEPENCIL;
 }
 
 /* check if some setting exists for this channel */

source/blender/editors/animation/anim_filter.cc

@@ -2206,29 +2206,38 @@ static size_t animdata_filter_grease_pencil_data(bAnimContext *ac,
 
   size_t items = 0;
 
+  /* The Grease Pencil mode is not supposed to show channels for regular F-Curves from regular
+   * Actions. At some point this might be desirable, but it would also require changing the
+   * filtering flags for pretty much all operators running there.  */
+  const bool show_animdata = grease_pencil->adt && (ac->datatype != ANIMCONT_GPENCIL);
+
   /* When asked from "AnimData" blocks (i.e. the top-level containers for normal animation),
    * for convenience, this will return grease pencil data-blocks instead.
    * This may cause issues down the track, but for now, this will do.
    */
   if (filter_mode & ANIMFILTER_ANIMDATA) {
-    /* Just add data block container. */
-    if (grease_pencil->adt != nullptr) {
-      ANIMCHANNEL_NEW_CHANNEL(
-          ac->bmain, grease_pencil, ANIMTYPE_GREASE_PENCIL_DATABLOCK, grease_pencil, nullptr);
+    if (show_animdata) {
+      items += animfilter_block_data(ac, anim_data, (ID *)grease_pencil, filter_mode);
     }
+    ANIMCHANNEL_NEW_CHANNEL(
+        ac->bmain, grease_pencil, ANIMTYPE_GREASE_PENCIL_DATABLOCK, grease_pencil, nullptr);
   }
   else {
     ListBase tmp_data = {nullptr, nullptr};
     size_t tmp_items = 0;
 
-    if (!(filter_mode & ANIMFILTER_FCURVESONLY)) {
-      /* Add grease pencil layer channels. */
-      BEGIN_ANIMFILTER_SUBCHANNELS (grease_pencil->flag &GREASE_PENCIL_ANIM_CHANNEL_EXPANDED) {
+    /* Add grease pencil layer channels. */
+    BEGIN_ANIMFILTER_SUBCHANNELS (grease_pencil->flag &GREASE_PENCIL_ANIM_CHANNEL_EXPANDED) {
+      if (show_animdata) {
+        tmp_items += animfilter_block_data(ac, &tmp_data, (ID *)grease_pencil, filter_mode);
+      }
+
+      if (!(filter_mode & ANIMFILTER_FCURVESONLY)) {
         tmp_items += animdata_filter_grease_pencil_layers_data(
             ac, &tmp_data, grease_pencil, filter_mode);
       }
-      END_ANIMFILTER_SUBCHANNELS;
     }
+    END_ANIMFILTER_SUBCHANNELS;
 
     if (tmp_items == 0) {
       /* If no sub-channels, return early. */

source/blender/editors/animation/keyframes_draw.cc

@@ -30,6 +30,7 @@
 #include "UI_resources.hh"
 #include "UI_view2d.hh"
 
+#include "ED_anim_api.hh"
 #include "ED_keyframes_draw.hh"
 #include "ED_keyframes_keylist.hh"
 
@@ -479,6 +480,9 @@ static void build_channel_keylist(ChannelListElement *elem, blender::float2 rang
       break;
     }
     case ChannelType::GREASE_PENCIL_DATA: {
+      if (elem->ac->datatype != ANIMCONT_GPENCIL && elem->adt) {
+        action_to_keylist(elem->adt, elem->adt->action, elem->keylist, elem->saction_flag, range);
+      }
       grease_pencil_data_block_to_keylist(
           elem->adt, elem->grease_pencil, elem->keylist, elem->saction_flag, false);
       break;
@@ -789,7 +793,8 @@ void ED_add_action_channel(ChannelDrawList *channel_list,
 }
 
 void ED_add_grease_pencil_datablock_channel(ChannelDrawList *channel_list,
-                                            bDopeSheet * /*ads*/,
+                                            bAnimContext *ac,
+                                            AnimData *adt,
                                             const GreasePencil *grease_pencil,
                                             const float ypos,
                                             const float yscale_fac,
@@ -800,7 +805,12 @@ void ED_add_grease_pencil_datablock_channel(ChannelDrawList *channel_list,
                                                            ypos,
                                                            yscale_fac,
                                                            eSAction_Flag(saction_flag));
+  /* GreasePencil properties can be animated via an Action, so the GP-related
+   * animation data is not limited to GP drawings. */
+  draw_elem->adt = adt;
+  draw_elem->act = adt ? adt->action : nullptr;
   draw_elem->grease_pencil = grease_pencil;
+  draw_elem->ac = ac;
 }
 
 void ED_add_grease_pencil_cels_channel(ChannelDrawList *channel_list,

source/blender/editors/include/ED_keyframes_draw.hh

@@ -130,7 +130,8 @@ void ED_add_grease_pencil_layer_group_channel(ChannelDrawList *draw_list,
 
 /* Grease Pencil data channels */
 void ED_add_grease_pencil_datablock_channel(ChannelDrawList *draw_list,
-                                            bDopeSheet *ads,
+                                            bAnimContext *ac,
+                                            AnimData *adt,
                                             const GreasePencil *grease_pencil,
                                             const float ypos,
                                             const float yscale_fac,

source/blender/editors/space_action/action_draw.cc

@@ -432,7 +432,8 @@ static void draw_keyframes(bAnimContext *ac,
         break;
       case ALE_GREASE_PENCIL_DATA:
         ED_add_grease_pencil_datablock_channel(draw_list,
-                                               ads,
+                                               ac,
+                                               ale->adt,
                                                static_cast<const GreasePencil *>(ale->data),
                                                ycenter,
                                                scale_factor,