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

1 files changed, 39 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/gpencil_modifier.c b/source/blender/blenkernel/intern/gpencil_modifier.c
index 2f8500bd1df..6496b219be1 100644
--- a/source/blender/blenkernel/intern/gpencil_modifier.c
+++ b/source/blender/blenkernel/intern/gpencil_modifier.c
@@ -53,6 +53,9 @@
 
 #include "MOD_gpencil_modifiertypes.h"
 
+#include "CLG_log.h"
+
+static CLG_LogRef LOG = {"bke.gpencil_modifier"};
 static GpencilModifierTypeInfo *modifier_gpencil_types[NUM_GREASEPENCIL_MODIFIER_TYPES] = {NULL};
 
 /* *************************************************** */
@@ -428,9 +431,9 @@ GpencilModifierData *BKE_gpencil_modifier_new(int type)
   BLI_strncpy(md->name, DATA_(mti->name), sizeof(md->name));
 
   md->type = type;
-  md->mode = eGpencilModifierMode_Realtime | eGpencilModifierMode_Render |
-             eGpencilModifierMode_Expanded;
+  md->mode = eGpencilModifierMode_Realtime | eGpencilModifierMode_Render;
   md->flag = eGpencilModifierFlag_OverrideLibrary_Local;
+  md->ui_expand_flag = 1; /* Only expand the parent panel at first. */
 
   if (mti->flags & eGpencilModifierTypeFlag_EnableInEditmode) {
     md->mode |= eGpencilModifierMode_Editmode;
@@ -508,7 +511,8 @@ bool BKE_gpencil_modifier_depends_ontime(GpencilModifierData *md)
 const GpencilModifierTypeInfo *BKE_gpencil_modifier_get_info(GpencilModifierType type)
 {
   /* type unsigned, no need to check < 0 */
-  if (type < NUM_GREASEPENCIL_MODIFIER_TYPES && modifier_gpencil_types[type]->name[0] != '\0') {
+  if (type < NUM_GREASEPENCIL_MODIFIER_TYPES && type > 0 &&
+      modifier_gpencil_types[type]->name[0] != '\0') {
     return modifier_gpencil_types[type];
   }
   else {
@@ -516,6 +520,17 @@ const GpencilModifierTypeInfo *BKE_gpencil_modifier_get_info(GpencilModifierType
   }
 }
 
+/**
+ * Get the idname of the modifier type's panel, which was defined in the #panelRegister callback.
+ */
+void BKE_gpencil_modifierType_panel_id(GpencilModifierType type, char *r_idname)
+{
+  const GpencilModifierTypeInfo *mti = BKE_gpencil_modifier_get_info(type);
+
+  strcpy(r_idname, GPENCIL_MODIFIER_TYPE_PANEL_PREFIX);
+  strcat(r_idname, mti->name);
+}
+
 void BKE_gpencil_modifier_copydata_generic(const GpencilModifierData *md_src,
                                            GpencilModifierData *md_dst)
 {
@@ -553,6 +568,7 @@ void BKE_gpencil_modifier_copydata_ex(GpencilModifierData *md,
 
   target->mode = md->mode;
   target->flag = md->flag;
+  target->ui_expand_flag = md->ui_expand_flag; /* Expand the parent panel by default. */
 
   if (mti->copyData) {
     mti->copyData(md, target);
@@ -587,6 +603,26 @@ GpencilModifierData *BKE_gpencil_modifiers_findby_type(Object *ob, GpencilModifi
   return md;
 }
 
+void BKE_gpencil_modifier_set_error(GpencilModifierData *md, const char *_format, ...)
+{
+  char buffer[512];
+  va_list ap;
+  const char *format = TIP_(_format);
+
+  va_start(ap, _format);
+  vsnprintf(buffer, sizeof(buffer), format, ap);
+  va_end(ap);
+  buffer[sizeof(buffer) - 1] = '\0';
+
+  if (md->error) {
+    MEM_freeN(md->error);
+  }
+
+  md->error = BLI_strdup(buffer);
+
+  CLOG_STR_ERROR(&LOG, md->error);
+}
+
 void BKE_gpencil_modifiers_foreach_ID_link(Object *ob, GreasePencilIDWalkFunc walk, void *userData)
 {
   GpencilModifierData *md = ob->greasepencil_modifiers.first;