Fix #130688: Grease Pencil: Multiframe Editing not applying falloff curve

Mutliframe editing wasn't using the falloff.

The fix adds a new field `Vector<float> grease_pencil_falloffs` to
`struct CurvesTransformData`. References it's values with `TransData.extra`.

Pull Request: https://projects.blender.org/blender/blender/pulls/131147

source/blender/editors/transform/transform_convert.hh

@@ -99,6 +99,12 @@ struct CurvesTransformData {
    */
   blender::Vector<int> layer_offsets;
 
+  /**
+   * Grease pencil multi-frame editing falloff. One value for each drawing in a
+   * `TransDataContainer`.
+   */
+  blender::Vector<float> grease_pencil_falloffs;
+
   /**
    * Copy of all positions being transformed.
    */
@@ -184,7 +190,8 @@ void curve_populate_trans_data_structs(
     const blender::Span<blender::IndexMask> points_to_transform_indices,
     const blender::IndexMask &affected_curves,
     bool use_connected_only,
-    const blender::IndexMask &bezier_curves);
+    const blender::IndexMask &bezier_curves,
+    void *extra = nullptr);
 
 CurvesTransformData *create_curves_transform_custom_data(TransCustomData &custom_data);
 

source/blender/editors/transform/transform_convert_curves.cc

@@ -447,7 +447,8 @@ void curve_populate_trans_data_structs(
     const blender::Span<blender::IndexMask> points_to_transform_per_attr,
     const blender::IndexMask &affected_curves,
     bool use_connected_only,
-    const blender::IndexMask &bezier_curves)
+    const blender::IndexMask &bezier_curves,
+    void *extra)
 {
   using namespace blender;
   const std::array<Span<float3>, 3> src_positions_per_selection_attr = {
@@ -503,6 +504,8 @@ void curve_populate_trans_data_structs(
           td.flag = TD_SELECTED;
         }
 
+        td.extra = extra;
+
         if (value_attribute) {
           float *value = &((*value_attribute)[point_in_domain_i]);
           td.val = value;

source/blender/editors/transform/transform_convert_grease_pencil.cc

@@ -48,7 +48,7 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
     GreasePencil &grease_pencil = *static_cast<GreasePencil *>(tc.obedit->data);
 
     Vector<ed::greasepencil::MutableDrawingInfo> drawings =
-        ed::greasepencil::retrieve_editable_drawings(*scene, grease_pencil);
+        ed::greasepencil::retrieve_editable_drawings_with_falloff(*scene, grease_pencil);
 
     if (blender::animrig::is_autokey_on(scene)) {
       for (const int info_i : drawings.index_range()) {
@@ -61,7 +61,7 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
               target_layer, *target_layer.start_frame_at(current_frame), current_frame, false);
         }
       }
-      drawings = ed::greasepencil::retrieve_editable_drawings(*scene, grease_pencil);
+      drawings = ed::greasepencil::retrieve_editable_drawings_with_falloff(*scene, grease_pencil);
     }
 
     all_drawings.append(drawings);
@@ -80,6 +80,7 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
     tc.data_len = 0;
 
     const Vector<ed::greasepencil::MutableDrawingInfo> drawings = all_drawings[i];
+    curves_transform_data->grease_pencil_falloffs.reinitialize(drawings.size());
     for (ed::greasepencil::MutableDrawingInfo info : drawings) {
       const bke::CurvesGeometry &curves = info.drawing.strokes();
       Span<StringRef> selection_attribute_names = ed::curves::get_curves_selection_attribute_names(
@@ -186,7 +187,8 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
     Span<const bke::greasepencil::Layer *> layers = grease_pencil.layers();
 
     const Vector<ed::greasepencil::MutableDrawingInfo> drawings = all_drawings[i];
-    for (ed::greasepencil::MutableDrawingInfo info : drawings) {
+    for (const int drawing : drawings.index_range()) {
+      ed::greasepencil::MutableDrawingInfo info = drawings[drawing];
       const bke::greasepencil::Layer &layer = *layers[info.layer_index];
       const float4x4 layer_space_to_world_space = layer.to_world_space(*object_eval);
       bke::CurvesGeometry &curves = info.drawing.strokes_for_write();
@@ -205,6 +207,11 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
                                              ed::greasepencil::retrieve_editable_strokes(
                                                  *object, info.drawing, info.layer_index, memory) :
                                              IndexMask();
+
+      CurvesTransformData &curves_transform_data = *static_cast<CurvesTransformData *>(
+          tc.custom.type.data);
+      curves_transform_data.grease_pencil_falloffs[drawing] = info.multi_frame_falloff;
+      float &drawing_falloff = curves_transform_data.grease_pencil_falloffs[drawing];
       curve_populate_trans_data_structs(tc,
                                         curves,
                                         layer_space_to_world_space,
@@ -212,7 +219,8 @@ static void createTransGreasePencilVerts(bContext *C, TransInfo *t)
                                         points_to_transform_per_attribute[layer_offset],
                                         affected_strokes,
                                         use_connected_only,
-                                        bezier_curves[layer_offset]);
+                                        bezier_curves[layer_offset],
+                                        &drawing_falloff);
       layer_offset++;
     }
   }

source/blender/editors/transform/transform_mode_bend.cc

@@ -110,9 +110,9 @@ static void transdata_elem_bend(const TransInfo *t,
 
   if (t->options & CTX_GPENCIL_STROKES) {
     /* Grease pencil multi-frame falloff. */
-    bGPDstroke *gps = (bGPDstroke *)td->extra;
-    if (gps != nullptr) {
-      fac_scaled = fac * td->factor * gps->runtime.multi_frame_falloff;
+    float *gp_falloff = static_cast<float *>(td->extra);
+    if (gp_falloff != nullptr) {
+      fac_scaled = fac * td->factor * *gp_falloff;
     }
     else {
       fac_scaled = fac * td->factor;

source/blender/editors/transform/transform_mode_shear.cc

@@ -70,9 +70,9 @@ static void transdata_elem_shear(const TransInfo *t,
 
   if (t->options & CTX_GPENCIL_STROKES) {
     /* Grease pencil multi-frame falloff. */
-    bGPDstroke *gps = (bGPDstroke *)td->extra;
-    if (gps != nullptr) {
-      mul_v3_fl(vec, td->factor * gps->runtime.multi_frame_falloff);
+    float *gp_falloff = static_cast<float *>(td->extra);
+    if (gp_falloff != nullptr) {
+      mul_v3_fl(vec, td->factor * *gp_falloff);
     }
     else {
       mul_v3_fl(vec, td->factor);

source/blender/editors/transform/transform_mode_translate.cc

@@ -141,9 +141,9 @@ static void transdata_elem_translate(const TransInfo *t,
 
   if (t->options & CTX_GPENCIL_STROKES) {
     /* Grease pencil multi-frame falloff. */
-    bGPDstroke *gps = (bGPDstroke *)td->extra;
-    if (gps != nullptr) {
-      mul_v3_fl(tvec, td->factor * gps->runtime.multi_frame_falloff);
+    float *gp_falloff = static_cast<float *>(td->extra);
+    if (gp_falloff != nullptr) {
+      mul_v3_fl(tvec, td->factor * *gp_falloff);
     }
     else {
       mul_v3_fl(tvec, td->factor);