UI: Grease Pencil Modifier Drag and Drop, Layout Changes

This patch implements the list panel system D7490 for grease pencil
modifiers. It also moves their drawing to a callback in
GpencilModifierTypeInfo in line with the extensible architecture
refactoring goal T75724.

This also adds the "set_error" function for grease pencil modifiers,
which hadn't been copied from mesh modifiers yet.

The implementation is basically exactly the same as for the modifier
patch (9b099c86123fc82).

Thanks to Matias Mendiola (mendio) for providing mockups for many
of the layout changes.

Differential Revision: https://developer.blender.org/D7978

7 files changed, 137 insertions, 129 deletions

diff --git a/source/blender/editors/include/ED_object.h b/source/blender/editors/include/ED_object.h
index ebd7321a46d..0cc926987b2 100644
--- a/source/blender/editors/include/ED_object.h
+++ b/source/blender/editors/include/ED_object.h
@@ -421,6 +421,10 @@ int ED_object_gpencil_modifier_move_down(struct ReportList *reports,
 int ED_object_gpencil_modifier_move_up(struct ReportList *reports,
                                        struct Object *ob,
                                        struct GpencilModifierData *md);
+bool ED_object_gpencil_modifier_move_to_index(struct ReportList *reports,
+                                              struct Object *ob,
+                                              struct GpencilModifierData *md,
+                                              const int index);
 int ED_object_gpencil_modifier_apply(struct Main *bmain,
                                      struct ReportList *reports,
                                      struct Depsgraph *depsgraph,
diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index d89e590122c..8e9591c1963 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -2004,6 +2004,7 @@ void uiTemplatePathBuilder(uiLayout *layout,
                            struct PointerRNA *root_ptr,
                            const char *text);
 void uiTemplateModifiers(uiLayout *layout, struct bContext *C);
+void uiTemplateGpencilModifiers(uiLayout *layout, struct bContext *C);
 void uiTemplateConstraints(uiLayout *layout, struct bContext *C, bool use_bone_constraints);
 
 uiLayout *uiTemplateGpencilModifier(uiLayout *layout, struct bContext *C, struct PointerRNA *ptr);
diff --git a/source/blender/editors/interface/interface_templates.c b/source/blender/editors/interface/interface_templates.c
index 189441a1f10..56a71970f90 100644
--- a/source/blender/editors/interface/interface_templates.c
+++ b/source/blender/editors/interface/interface_templates.c
@@ -2040,147 +2040,55 @@ void uiTemplateConstraints(uiLayout *UNUSED(layout), bContext *C, bool use_bone_
 /** \name Grease Pencil Modifier Template
  * \{ */
 
-#define ERROR_LIBDATA_MESSAGE TIP_("Can't edit external library data")
-
-static uiLayout *gpencil_draw_modifier(uiLayout *layout, Object *ob, GpencilModifierData *md)
+/**
+ * Function with void * argument for #uiListPanelIDFromDataFunc.
+ */
+static void gpencil_modifier_panel_id(void *md_link, char *r_name)
 {
-  const GpencilModifierTypeInfo *mti = BKE_gpencil_modifier_get_info(md->type);
-  PointerRNA ptr;
-  uiBlock *block;
-  uiLayout *box, *column, *row, *sub;
-  uiLayout *result = NULL;
-
-  /* create RNA pointer */
-  RNA_pointer_create(&ob->id, &RNA_GpencilModifier, md, &ptr);
-
-  column = uiLayoutColumn(layout, true);
-  uiLayoutSetContextPointer(column, "modifier", &ptr);
-
-  /* rounded header ------------------------------------------------------------------- */
-  box = uiLayoutBox(column);
-
-  row = uiLayoutRow(box, false);
-  block = uiLayoutGetBlock(row);
-
-  UI_block_emboss_set(block, UI_EMBOSS_NONE);
-  /* Open/Close .................................  */
-  uiItemR(row, &ptr, "show_expanded", 0, "", ICON_NONE);
-
-  /* modifier-type icon */
-  uiItemL(row, "", RNA_struct_ui_icon(ptr.type));
-  UI_block_emboss_set(block, UI_EMBOSS);
-
-  /* modifier name */
-  if (mti->isDisabled && mti->isDisabled(md, 0)) {
-    uiLayoutSetRedAlert(row, true);
-  }
-  uiItemR(row, &ptr, "name", 0, "", ICON_NONE);
-  uiLayoutSetRedAlert(row, false);
-
-  /* mode enabling buttons */
-  UI_block_align_begin(block);
-  uiItemR(row, &ptr, "show_render", 0, "", ICON_NONE);
-  uiItemR(row, &ptr, "show_viewport", 0, "", ICON_NONE);
-
-  if (mti->flags & eGpencilModifierTypeFlag_SupportsEditmode) {
-    sub = uiLayoutRow(row, true);
-    uiLayoutSetActive(sub, false);
-    uiItemR(sub, &ptr, "show_in_editmode", 0, "", ICON_NONE);
-  }
-
-  UI_block_align_end(block);
-
-  /* Up/Down + Delete ........................... */
-  UI_block_align_begin(block);
-  uiItemO(row, "", ICON_TRIA_UP, "OBJECT_OT_gpencil_modifier_move_up");
-  uiItemO(row, "", ICON_TRIA_DOWN, "OBJECT_OT_gpencil_modifier_move_down");
-  UI_block_align_end(block);
-
-  UI_block_emboss_set(block, UI_EMBOSS_NONE);
-  uiItemO(row, "", ICON_X, "OBJECT_OT_gpencil_modifier_remove");
-  UI_block_emboss_set(block, UI_EMBOSS);
-
-  /* modifier settings (under the header) --------------------------------------------------- */
-  if (md->mode & eGpencilModifierMode_Expanded) {
-    /* apply/convert/copy */
-    box = uiLayoutBox(column);
-    row = uiLayoutRow(box, false);
-
-    /* only here obdata, the rest of modifiers is ob level */
-    UI_block_lock_set(block, BKE_object_obdata_is_libdata(ob), ERROR_LIBDATA_MESSAGE);
-
-    uiLayoutSetOperatorContext(row, WM_OP_INVOKE_DEFAULT);
-
-    sub = uiLayoutRow(row, false);
-    if (mti->flags & eGpencilModifierTypeFlag_NoApply) {
-      uiLayoutSetEnabled(sub, false);
-    }
-    uiItemEnumO(sub,
-                "OBJECT_OT_gpencil_modifier_apply",
-                CTX_IFACE_(BLT_I18NCONTEXT_OPERATOR_DEFAULT, "Apply"),
-                0,
-                "apply_as",
-                MODIFIER_APPLY_DATA);
-
-    UI_block_lock_clear(block);
-    UI_block_lock_set(block, ob && ID_IS_LINKED(ob), ERROR_LIBDATA_MESSAGE);
-
-    uiItemO(row,
-            CTX_IFACE_(BLT_I18NCONTEXT_OPERATOR_DEFAULT, "Copy"),
-            ICON_NONE,
-            "OBJECT_OT_gpencil_modifier_copy");
-
-    /* result is the layout block inside the box,
-     * that we return so that modifier settings can be drawn */
-    result = uiLayoutColumn(box, false);
-    block = uiLayoutAbsoluteBlock(box);
-  }
-
-  /* error messages */
-  if (md->error) {
-    box = uiLayoutBox(column);
-    row = uiLayoutRow(box, false);
-    uiItemL(row, md->error, ICON_ERROR);
-  }
-
-  return result;
+  ModifierData *md = (ModifierData *)md_link;
+  BKE_gpencil_modifierType_panel_id(md->type, r_name);
 }
 
-uiLayout *uiTemplateGpencilModifier(uiLayout *layout, bContext *UNUSED(C), PointerRNA *ptr)
+void uiTemplateGpencilModifiers(uiLayout *UNUSED(layout), bContext *C)
 {
-  Object *ob;
-  GpencilModifierData *md, *vmd;
-  int i;
+  ScrArea *sa = CTX_wm_area(C);
+  ARegion *region = CTX_wm_region(C);
+  Object *ob = get_context_object(C);
+  ListBase *modifiers = &ob->greasepencil_modifiers;
 
-  /* verify we have valid data */
-  if (!RNA_struct_is_a(ptr->type, &RNA_GpencilModifier)) {
-    RNA_warning("Expected modifier on object");
-    return NULL;
-  }
+  bool panels_match = UI_panel_list_matches_data(region, modifiers, gpencil_modifier_panel_id);
 
-  ob = (Object *)ptr->owner_id;
-  md = ptr->data;
+  if (!panels_match) {
+    UI_panels_free_instanced(C, region);
+    GpencilModifierData *md = modifiers->first;
+    for (int i = 0; md; i++, md = md->next) {
+      const GpencilModifierTypeInfo *mti = BKE_gpencil_modifier_get_info(md->type);
+      if (mti->panelRegister) {
+        char panel_idname[MAX_NAME];
+        gpencil_modifier_panel_id(md, panel_idname);
 
-  if (!ob || !(GS(ob->id.name) == ID_OB)) {
-    RNA_warning("Expected modifier on object");
-    return NULL;
+        Panel *new_panel = UI_panel_add_instanced(sa, region, &region->panels, panel_idname, i);
+        if (new_panel != NULL) {
+          UI_panel_set_expand_from_list_data(C, new_panel);
+        }
+      }
+    }
   }
-
-  UI_block_lock_set(uiLayoutGetBlock(layout), (ob && ID_IS_LINKED(ob)), ERROR_LIBDATA_MESSAGE);
-
-  /* find modifier and draw it */
-  vmd = ob->greasepencil_modifiers.first;
-  for (i = 0; vmd; i++, vmd = vmd->next) {
-    if (md == vmd) {
-      return gpencil_draw_modifier(layout, ob, md);
+  else {
+    /* The expansion might have been changed elsewhere, so we still need to set it. */
+    LISTBASE_FOREACH (Panel *, panel, &region->panels) {
+      if ((panel->type != NULL) && (panel->type->flag & PNL_INSTANCED))
+        UI_panel_set_expand_from_list_data(C, panel);
     }
   }
-
-  return NULL;
 }
 
 /** \} */
 
+/** \} */
+
+#define ERROR_LIBDATA_MESSAGE TIP_("Can't edit external library data")
+
 /* -------------------------------------------------------------------- */
 /** \name Grease Pencil Shader FX Template
  * \{ */
diff --git a/source/blender/editors/object/object_gpencil_modifier.c b/source/blender/editors/object/object_gpencil_modifier.c
index 6d0f53cfa1e..99215686280 100644
--- a/source/blender/editors/object/object_gpencil_modifier.c
+++ b/source/blender/editors/object/object_gpencil_modifier.c
@@ -211,6 +211,40 @@ int ED_object_gpencil_modifier_move_down(ReportList *UNUSED(reports),
   return 1;
 }
 
+bool ED_object_gpencil_modifier_move_to_index(ReportList *reports,
+                                              Object *ob,
+                                              GpencilModifierData *md,
+                                              const int index)
+{
+  BLI_assert(md != NULL);
+  BLI_assert(index >= 0);
+  if (index >= BLI_listbase_count(&ob->greasepencil_modifiers)) {
+    BKE_report(reports, RPT_WARNING, "Cannot move modifier beyond the end of the stack");
+    return false;
+  }
+
+  int md_index = BLI_findindex(&ob->greasepencil_modifiers, md);
+  BLI_assert(md_index != -1);
+  if (md_index < index) {
+    /* Move modifier down in list. */
+    for (; md_index < index; md_index++) {
+      if (!ED_object_gpencil_modifier_move_down(reports, ob, md)) {
+        break;
+      }
+    }
+  }
+  else {
+    /* Move modifier up in list. */
+    for (; md_index > index; md_index--) {
+      if (!ED_object_gpencil_modifier_move_up(reports, ob, md)) {
+        break;
+      }
+    }
+  }
+
+  return true;
+}
+
 static int gpencil_modifier_apply_obdata(
     ReportList *reports, Main *bmain, Depsgraph *depsgraph, Object *ob, GpencilModifierData *md)
 {
@@ -596,6 +630,60 @@ void OBJECT_OT_gpencil_modifier_move_down(wmOperatorType *ot)
   gpencil_edit_modifier_properties(ot);
 }
 
+/* ************************* Move to Index Gpencil Modifier Operator ************************* */
+
+static bool gpencil_modifier_move_to_index_poll(bContext *C)
+{
+  return gpencil_edit_modifier_poll(C);
+}
+
+static int gpencil_modifier_move_to_index_exec(bContext *C, wmOperator *op)
+{
+  Object *ob = ED_object_active_context(C);
+  GpencilModifierData *md = gpencil_edit_modifier_property_get(op, ob, 0);
+  int index = RNA_int_get(op->ptr, "index");
+
+  if (!ED_object_gpencil_modifier_move_to_index(op->reports, ob, md, index)) {
+    return OPERATOR_CANCELLED;
+  }
+
+  DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
+  WM_event_add_notifier(C, NC_OBJECT | ND_MODIFIER, ob);
+
+  return OPERATOR_FINISHED;
+}
+
+static int gpencil_modifier_move_to_index_invoke(bContext *C,
+                                                 wmOperator *op,
+                                                 const wmEvent *UNUSED(event))
+{
+  if (gpencil_edit_modifier_invoke_properties(C, op)) {
+    return gpencil_modifier_move_to_index_exec(C, op);
+  }
+  else {
+    return OPERATOR_CANCELLED;
+  }
+}
+
+void OBJECT_OT_gpencil_modifier_move_to_index(wmOperatorType *ot)
+{
+  ot->name = "Move Active Modifier to Index";
+  ot->idname = "OBJECT_OT_gpencil_modifier_move_to_index";
+  ot->description =
+      "Change the modifier's position in the list so it evaluates after the set number of "
+      "others";
+
+  ot->invoke = gpencil_modifier_move_to_index_invoke;
+  ot->exec = gpencil_modifier_move_to_index_exec;
+  ot->poll = gpencil_modifier_move_to_index_poll;
+
+  /* flags */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO | OPTYPE_INTERNAL;
+  edit_modifier_properties(ot);
+  RNA_def_int(
+      ot->srna, "index", 0, 0, INT_MAX, "Index", "The index to move the modifier to", 0, INT_MAX);
+}
+
 /************************ apply modifier operator *********************/
 
 static int gpencil_modifier_apply_exec(bContext *C, wmOperator *op)
diff --git a/source/blender/editors/object/object_intern.h b/source/blender/editors/object/object_intern.h
index 1cd91f7c1f3..8feeb3b6067 100644
--- a/source/blender/editors/object/object_intern.h
+++ b/source/blender/editors/object/object_intern.h
@@ -190,6 +190,7 @@ void OBJECT_OT_gpencil_modifier_add(struct wmOperatorType *ot);
 void OBJECT_OT_gpencil_modifier_remove(struct wmOperatorType *ot);
 void OBJECT_OT_gpencil_modifier_move_up(struct wmOperatorType *ot);
 void OBJECT_OT_gpencil_modifier_move_down(struct wmOperatorType *ot);
+void OBJECT_OT_gpencil_modifier_move_to_index(struct wmOperatorType *ot);
 void OBJECT_OT_gpencil_modifier_apply(struct wmOperatorType *ot);
 void OBJECT_OT_gpencil_modifier_copy(struct wmOperatorType *ot);
 
diff --git a/source/blender/editors/object/object_ops.c b/source/blender/editors/object/object_ops.c
index 84bc10f8064..1060a808cfe 100644
--- a/source/blender/editors/object/object_ops.c
+++ b/source/blender/editors/object/object_ops.c
@@ -152,6 +152,7 @@ void ED_operatortypes_object(void)
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_remove);
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_move_up);
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_move_down);
+  WM_operatortype_append(OBJECT_OT_gpencil_modifier_move_to_index);
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_apply);
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_copy);
 
diff --git a/source/blender/editors/space_buttons/space_buttons.c b/source/blender/editors/space_buttons/space_buttons.c
index 187334a5c34..2cc9679dd3f 100644
--- a/source/blender/editors/space_buttons/space_buttons.c
+++ b/source/blender/editors/space_buttons/space_buttons.c
@@ -30,11 +30,10 @@
 #include "BLI_utildefines.h"
 
 #include "BKE_context.h"
+#include "BKE_gpencil_modifier.h" /* Types for registering panels. */
 #include "BKE_modifier.h"
 #include "BKE_screen.h"
 
-#include "DNA_modifier_types.h"
-
 #include "ED_screen.h"
 #include "ED_space_api.h"
 #include "ED_view3d.h" /* To draw toolbar UI. */
@@ -643,6 +642,12 @@ void ED_spacetype_buttons(void)
       mti->panelRegister(art);
     }
   }
+  for (int i = 0; i < NUM_GREASEPENCIL_MODIFIER_TYPES; i++) {
+    const GpencilModifierTypeInfo *mti = BKE_gpencil_modifier_get_info(i);
+    if (mti != NULL && mti->panelRegister != NULL) {
+      mti->panelRegister(art);
+    }
+  }
 
   /* regions: header */
   art = MEM_callocN(sizeof(ARegionType), "spacetype buttons region");