Try to get strokes and call subdiv func with C++ api

(Not working yet)

@@ -32,6 +32,8 @@
 #include "ED_grease_pencil.hh"
 #include "ED_screen.hh"
 
+#include "../../geometry/GEO_subdivide_curves.hh"

@@ -1643,0 +1768,4 @@
+                                                       wmOperator * /*op*/,
+                                                       const PropertyRNA *prop)
+{
+  /* I'm not sure how to deal with these below: */

@@ -1643,0 +1803,4 @@
+
+  /* api callbacks */
+  ot->exec = gpencil_stroke_subdivide_exec;
+  ot->poll = grease_active_layer_poll;

@@ -1643,0 +1689,4 @@
+      use_point_selection = VArray<bool>(point_selection);
+    }
+    else {
+      use_point_selection = VArray<bool>::ForSingle(true, curves.point_num);

@@ -1643,0 +1764,4 @@
+  return OPERATOR_FINISHED;
+}
+
+bool grease_active_layer_poll(bContext *C)

@@ -1643,0 +1727,4 @@
+      changed.store(true, std::memory_order_relaxed);
+
+      /* Smooth curves after being subdivided. */
+      auto do_smooth = [&](const char *attr) {

@@ -1643,0 +1671,4 @@
+    bke::CurvesGeometry &curves = info.drawing.strokes_for_write();
+
+    const OffsetIndices points_by_curve = curves.points_by_curve();
+    const VArray<bool> cyclic = curves.cyclic();

@@ -1643,0 +1676,4 @@
+
+    const VArray<bool> point_selection = *curves.attributes().lookup_or_default<bool>(
+        ".selection", bke::AttrDomain::Point, true);
+    VArray<bool> use_point_selection;

@@ -1643,0 +1687,4 @@
+    if (selection_domain == bke::AttrDomain::Curve || (!only_selected)) {
+      /* Subdivide entire selected curve, every stroke subdivides to the same cut. */
+      vcuts = VArray<int>::ForSingle(cuts, curves.points_num());
+      blender::bke::AnonymousAttributePropagationInfo pinfo;

@@ -1643,0 +1678,4 @@
+    }
+    else if (selection_domain == bke::AttrDomain::Point) {
+      /* Subdivide between selected points. Only cut between selected points. */
+      /* Make the cut array the same length as point count for specifying */

@@ -1643,0 +1680,4 @@
+      /* Subdivide between selected points. Only cut between selected points. */
+      /* Make the cut array the same length as point count for specifying */
+      /* cut/uncut for each segment. */
+      Array<int> use_cuts(curves.points_num(), 0);

@@ -1643,0 +1690,4 @@
+      /* The cut is after each point, so the last point selected wouldn't need to be registered. */
+      for (const int curves_i : curves.curves_range()) {
+        for (const int points_i : points_by_curve[curves_i]) {
+          const bool cyc = cyclic[curves_i];

@@ -1643,0 +1691,4 @@
+      for (const int curves_i : curves.curves_range()) {
+        for (const int points_i : points_by_curve[curves_i]) {
+          const bool cyc = cyclic[curves_i];
+          if (selection[points_i] && /* Point is selected. */

@@ -1643,0 +1706,4 @@
+    }
+
+    blender::bke::AnonymousAttributePropagationInfo pinfo;
+    curves = blender::geometry::subdivide_curves(curves, strokes, vcuts, pinfo);

@@ -1643,0 +1712,4 @@
+  });
+
+  if (changed) {
+    /* Notifiers. */

@@ -1643,0 +1713,4 @@
+
+  if (changed) {
+    /* Notifiers. */
+    DEG_id_tag_update(&grease_pencil.id, ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);

@@ -1643,0 +1741,4 @@
+
+  /* properties */
+  prop = RNA_def_int(ot->srna, "number_cuts", 1, 1, 10, "Number of Cuts", "", 1, 5);
+  /* avoid re-using last var because it can cause _very_ high value and annoy users */

@@ -1643,0 +1758,4 @@
+  wmOperatorType *ot;
+
+  ot = WM_operatortype_append_macro("GREASE_PENCIL_OT_stroke_subdivide_smooth",
+                                    "Subdivide And Smooth",

@@ -1643,0 +1672,4 @@
+
+    VArray<int> vcuts = {};
+
+    if (selection_domain == bke::AttrDomain::Curve || (!only_selected)) {

@@ -1643,0 +1693,4 @@
+        for (const int points_i : points_by_curve[curves_i]) {
+          const bool is_cyclic = cyclic[curves_i];
+          /* The point itself should be selected. */
+          if (!selection[points_i]){ continue; }

@@ -1643,0 +1695,4 @@
+          /* The point itself should be selected. */
+          if (!selection[points_i]){ continue; }
+          /* If the next point in the curve is selected, then cut this segment. */
+          if ((points_i < points_by_curve[curves_i].last()) && selection[points_i + 1]){

@@ -1643,0 +1690,4 @@
+      Array<int> use_cuts(curves.points_num(), 0);
+
+      /* The cut is after each point, so the last point selected wouldn't need to be registered. */
+      for (const int curves_i : curves.curves_range()) {

@@ -1643,0 +1699,4 @@
+            continue;
+          }
+          /* If the next point in the curve is selected, then cut this segment. */
+          if ((points_i < points_by_curve[curves_i].last()) && selection[points_i + 1]) {

@@ -1643,0 +1705,4 @@
+        }
+        /* Always register the last point in the curve, the subdiv call will check for cyclic
+         * curves and cut them correctly. */
+        use_cuts[points_by_curve[curves_i].last()] = cuts;

@@ -1643,0 +1707,4 @@
+         * curves and cut them correctly. */
+        use_cuts[points_by_curve[curves_i].last()] = cuts;
+      }
+      vcuts = VArray<int>::ForContainer(use_cuts);

@@ -1643,0 +1685,4 @@
+          ".selection", bke::AttrDomain::Point, true);
+
+      const OffsetIndices points_by_curve = curves.points_by_curve();
+      const VArray<bool> cyclic = curves.cyclic();

@@ -1643,0 +1700,4 @@
+            continue;
+          }
+          /* If the next point in the curve is selected, then cut this segment. */
+          if (selection[point + 1]) {