Cleanup: Reduce `void *` reliance of new sequencer C++ Outliner elements

Plan is to remove things like `TreeElement.directdata` and to instead
expose specific queries in the new type specific tree-element classes.
e.g. like here: `TreeElementSequence.getSequence()`

For now uses `tree_element_cast<>()` to get the new type specific
tree-element, later these should replace `TreeElement` all together.

source/blender/editors/space_outliner/outliner_intern.hh

@@ -107,7 +107,7 @@ typedef struct TreeElement {
   short idcode;              /* From TreeStore id. */
   short xend;                /* Width of item display, for select. */
   const char *name;
-  void *directdata;  /* Armature Bones, Base, Sequence, Strip... */
+  void *directdata;  /* Armature Bones, Base, ... */
   PointerRNA rnaptr; /* RNA Pointer. */
 } TreeElement;
 

source/blender/editors/space_outliner/outliner_select.cc

@@ -80,6 +80,9 @@
 #include "RNA_define.h"
 
 #include "outliner_intern.hh"
+#include "tree/tree_element_seq.hh"
+
+using namespace blender::ed::outliner;
 
 /**
  * \note changes to selection are by convention and not essential.
@@ -676,7 +679,8 @@ static void tree_element_sequence_activate(bContext *C,
                                            TreeElement *te,
                                            const eOLSetState set)
 {
-  Sequence *seq = (Sequence *)te->directdata;
+  const TreeElementSequence *te_seq = tree_element_cast<TreeElementSequence>(te);
+  Sequence *seq = &te_seq->getSequence();
   Editing *ed = SEQ_editing_get(scene);
 
   if (BLI_findindex(ed->seqbasep, seq) != -1) {
@@ -954,7 +958,8 @@ static eOLDrawState tree_element_posegroup_state_get(const ViewLayer *view_layer
 
 static eOLDrawState tree_element_sequence_state_get(const Scene *scene, const TreeElement *te)
 {
-  const Sequence *seq = (const Sequence *)te->directdata;
+  const TreeElementSequence *te_seq = tree_element_cast<TreeElementSequence>(te);
+  const Sequence *seq = &te_seq->getSequence();
   const Editing *ed = scene->ed;
 
   if (ed && ed->act_seq == seq && seq->flag & SELECT) {
@@ -965,7 +970,9 @@ static eOLDrawState tree_element_sequence_state_get(const Scene *scene, const Tr
 
 static eOLDrawState tree_element_sequence_dup_state_get(const TreeElement *te)
 {
-  const Sequence *seq = (const Sequence *)te->directdata;
+  const TreeElementSequenceStripDuplicate *te_dup =
+      tree_element_cast<TreeElementSequenceStripDuplicate>(te);
+  const Sequence *seq = &te_dup->getSequence();
   if (seq->flag & SELECT) {
     return OL_DRAWSEL_NORMAL;
   }

source/blender/editors/space_outliner/outliner_tools.cc

@@ -96,9 +96,12 @@
 #include "SEQ_sequencer.h"
 
 #include "outliner_intern.hh"
+#include "tree/tree_element_seq.hh"
 
 static CLG_LogRef LOG = {"ed.outliner.tools"};
 
+using namespace blender::ed::outliner;
+
 /* -------------------------------------------------------------------- */
 /** \name ID/Library/Data Set/Un-link Utilities
  * \{ */
@@ -1285,7 +1288,8 @@ static void ebone_fn(int event, TreeElement *te, TreeStoreElem *UNUSED(tselem),
 
 static void sequence_fn(int event, TreeElement *te, TreeStoreElem *UNUSED(tselem), void *scene_ptr)
 {
-  Sequence *seq = (Sequence *)te->directdata;
+  TreeElementSequence *te_seq = tree_element_cast<TreeElementSequence>(te);
+  Sequence *seq = &te_seq->getSequence();
   Scene *scene = (Scene *)scene_ptr;
   Editing *ed = SEQ_editing_get(scene);
   if (BLI_findindex(ed->seqbasep, seq) != -1) {

source/blender/editors/space_outliner/tree/tree_element_seq.cc

@@ -41,7 +41,6 @@ TreeElementSequence::TreeElementSequence(TreeElement &legacy_te, Sequence &seque
    * so this is "safe".
    */
   legacy_te.idcode = sequence_.type;
-  legacy_te.directdata = &sequence_;
   legacy_te.name = sequence_.name + 2;
 }
 
@@ -70,6 +69,11 @@ void TreeElementSequence::expand(SpaceOutliner &space_outliner) const
   }
 }
 
+Sequence &TreeElementSequence::getSequence() const
+{
+  return sequence_;
+}
+
 /* -------------------------------------------------------------------- */
 /* Strip */
 
@@ -84,7 +88,6 @@ TreeElementSequenceStrip::TreeElementSequenceStrip(TreeElement &legacy_te, Strip
   else {
     legacy_te_.name = IFACE_("Strip None");
   }
-  legacy_te_.directdata = &strip;
 }
 
 /* -------------------------------------------------------------------- */
@@ -92,13 +95,17 @@ TreeElementSequenceStrip::TreeElementSequenceStrip(TreeElement &legacy_te, Strip
 
 TreeElementSequenceStripDuplicate::TreeElementSequenceStripDuplicate(TreeElement &legacy_te,
                                                                      Sequence &sequence)
-    : AbstractTreeElement(legacy_te)
+    : AbstractTreeElement(legacy_te), sequence_(sequence)
 {
   BLI_assert(legacy_te.store_elem->type == TSE_SEQUENCE_DUP);
 
   legacy_te_.idcode = sequence.type;
-  legacy_te_.directdata = &sequence;
   legacy_te_.name = sequence.strip->stripdata->name;
 }
 
+Sequence &TreeElementSequenceStripDuplicate::getSequence() const
+{
+  return sequence_;
+}
+
 }  // namespace blender::ed::outliner

source/blender/editors/space_outliner/tree/tree_element_seq.hh

@@ -35,6 +35,8 @@ class TreeElementSequence : public AbstractTreeElement {
 
   bool expandPoll(const SpaceOutliner &) const override;
   void expand(SpaceOutliner &) const override;
+
+  Sequence &getSequence() const;
 };
 
 /* -------------------------------------------------------------------- */
@@ -47,8 +49,12 @@ class TreeElementSequenceStrip : public AbstractTreeElement {
 /* -------------------------------------------------------------------- */
 
 class TreeElementSequenceStripDuplicate : public AbstractTreeElement {
+  Sequence &sequence_;
+
  public:
   TreeElementSequenceStripDuplicate(TreeElement &legacy_te, Sequence &sequence);
+
+  Sequence &getSequence() const;
 };
 
 }  // namespace blender::ed::outliner