GPencil: Fix wrong python API for Point weights

The old property never worked as expected because it was impossible expose the data as props.

Now, there are two methods to handle this: weight_get and weight_set

Example use:
```import bpy
ob = bpy.context.active_object
gpd = ob.data
gps = gpd.layers[0].frames[0].strokes[0]
i = 0
print("Weights\n================================")
for pt in gps.points:
    gps.points.weight_set(vertex_group_index=0, point_index=i, weight=0.5)
    i +=1

i = 0
for pt in gps.points:
    weight = gps.points.weight_get(vertex_group_index=0, point_index=i)
    print(weight)
    i +=1
```

Reviewed By: brecht

Maniphest Tasks: T84967

Differential Revision: https://developer.blender.org/D10177
b3f989

1 files changed, 102 insertions, 30 deletions

diff --git a/source/blender/makesrna/intern/rna_gpencil.c b/source/blender/makesrna/intern/rna_gpencil.c
index 4d9c53df013..5437c93ef61 100644
--- a/source/blender/makesrna/intern/rna_gpencil.c
+++ b/source/blender/makesrna/intern/rna_gpencil.c
@@ -168,6 +168,7 @@ static const EnumPropertyItem rna_enum_gpencil_caps_modes_items[] = {
 
 #  include "BKE_action.h"
 #  include "BKE_animsys.h"
+#  include "BKE_deform.h"
 #  include "BKE_gpencil.h"
 #  include "BKE_gpencil_curve.h"
 #  include "BKE_gpencil_geom.h"
@@ -831,6 +832,59 @@ static void rna_GPencil_stroke_point_update(ID *id, bGPDstroke *stroke)
   }
 }
 
+static float rna_GPencilStrokePoints_weight_get(bGPDstroke *stroke,
+                                                ReportList *reports,
+                                                int vertex_group_index,
+                                                int point_index)
+{
+  MDeformVert *dvert = stroke->dvert;
+  if (dvert == NULL) {
+    BKE_report(reports, RPT_ERROR, "Groups: No groups for this stroke");
+    return -1.0f;
+  }
+
+  if (dvert->totweight <= vertex_group_index || vertex_group_index < 0) {
+    BKE_report(reports, RPT_ERROR, "Groups: index out of range");
+    return -1.0f;
+  }
+
+  if (stroke->totpoints <= point_index || point_index < 0) {
+    BKE_report(reports, RPT_ERROR, "GPencilStrokePoints: index out of range");
+    return -1.0f;
+  }
+
+  MDeformVert *pt_dvert = stroke->dvert + point_index;
+  MDeformWeight *dw = BKE_defvert_find_index(pt_dvert, vertex_group_index);
+  if (dw) {
+    return dw->weight;
+  }
+
+  return -1.0f;
+}
+
+static void rna_GPencilStrokePoints_weight_set(
+    bGPDstroke *stroke, ReportList *reports, int vertex_group_index, int point_index, float weight)
+{
+  BKE_gpencil_dvert_ensure(stroke);
+
+  MDeformVert *dvert = stroke->dvert;
+  if (dvert == NULL) {
+    BKE_report(reports, RPT_ERROR, "Groups: No groups for this stroke");
+    return;
+  }
+
+  if (stroke->totpoints <= point_index || point_index < 0) {
+    BKE_report(reports, RPT_ERROR, "GPencilStrokePoints: index out of range");
+    return;
+  }
+
+  MDeformVert *pt_dvert = stroke->dvert + point_index;
+  MDeformWeight *dw = BKE_defvert_ensure_index(pt_dvert, vertex_group_index);
+  if (dw) {
+    dw->weight = weight;
+  }
+}
+
 static bGPDstroke *rna_GPencil_stroke_new(bGPDframe *frame)
 {
   bGPDstroke *stroke = BKE_gpencil_stroke_new(0, 0, 1.0f);
@@ -1069,21 +1123,6 @@ static void rna_GPencil_clear(bGPdata *gpd)
   WM_main_add_notifier(NC_GPENCIL | ND_DATA | NA_EDITED, NULL);
 }
 
-static void rna_GpencilVertex_groups_begin(CollectionPropertyIterator *iter, PointerRNA *ptr)
-{
-  bGPDstroke *gps = ptr->data;
-
-  if (gps->dvert) {
-    MDeformVert *dvert = gps->dvert;
-
-    rna_iterator_array_begin(
-        iter, (void *)dvert->dw, sizeof(MDeformWeight), dvert->totweight, 0, NULL);
-  }
-  else {
-    rna_iterator_array_begin(iter, NULL, 0, 0, 0, NULL);
-  }
-}
-
 static char *rna_GreasePencilGrid_path(PointerRNA *UNUSED(ptr))
 {
   return BLI_strdup("grid");
@@ -1293,6 +1332,54 @@ static void rna_def_gpencil_stroke_points_api(BlenderRNA *brna, PropertyRNA *cpr
   func = RNA_def_function(srna, "update", "rna_GPencil_stroke_point_update");
   RNA_def_function_ui_description(func, "Recalculate internal triangulation data");
   RNA_def_function_flag(func, FUNC_USE_SELF_ID);
+
+  func = RNA_def_function(srna, "weight_get", "rna_GPencilStrokePoints_weight_get");
+  RNA_def_function_ui_description(func, "Get vertex group point weight");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  RNA_def_int(func,
+              "vertex_group_index",
+              0,
+              0,
+              INT_MAX,
+              "Vertex Group Index",
+              "Index of Vertex Group in the array of groups",
+              0,
+              INT_MAX);
+  RNA_def_int(func,
+              "point_index",
+              0,
+              0,
+              INT_MAX,
+              "Point Index",
+              "Index of the Point in the array",
+              0,
+              INT_MAX);
+  parm = RNA_def_float(
+      func, "weight", 0, -FLT_MAX, FLT_MAX, "Weight", "Point Weight", -FLT_MAX, FLT_MAX);
+  RNA_def_function_return(func, parm);
+
+  func = RNA_def_function(srna, "weight_set", "rna_GPencilStrokePoints_weight_set");
+  RNA_def_function_ui_description(func, "Set vertex group point weight");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  RNA_def_int(func,
+              "vertex_group_index",
+              0,
+              0,
+              INT_MAX,
+              "Vertex Group Index",
+              "Index of Vertex Group in the array of groups",
+              0,
+              INT_MAX);
+  RNA_def_int(func,
+              "point_index",
+              0,
+              0,
+              INT_MAX,
+              "Point Index",
+              "Index of the Point in the array",
+              0,
+              INT_MAX);
+  RNA_def_float(func, "weight", 0, -FLT_MAX, FLT_MAX, "Weight", "Point Weight", -FLT_MAX, FLT_MAX);
 }
 
 /* This information is read only and it can be used by add-ons */
@@ -1520,21 +1607,6 @@ static void rna_def_gpencil_stroke(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Stroke Points", "Stroke data points");
   rna_def_gpencil_stroke_points_api(brna, prop);
 
-  /* vertex groups */
-  prop = RNA_def_property(srna, "groups", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_collection_funcs(prop,
-                                    "rna_GpencilVertex_groups_begin",
-                                    "rna_iterator_array_next",
-                                    "rna_iterator_array_end",
-                                    "rna_iterator_array_get",
-                                    NULL,
-                                    NULL,
-                                    NULL,
-                                    NULL);
-  RNA_def_property_struct_type(prop, "GpencilVertexGroupElement");
-  RNA_def_property_ui_text(
-      prop, "Groups", "Weights for the vertex groups this vertex is member of");
-
   /* Triangles */
   prop = RNA_def_property(srna, "triangles", PROP_COLLECTION, PROP_NONE);
   RNA_def_property_collection_sdna(prop, NULL, "triangles", "tot_triangles");