Armature: convert the length Python property of bones to a RNA property.

This allows accessing it from drivers and using it in UI, as
demonstrated by adding it to the transform panel of 3D View.

As an aside, properly mark transform-related properties of Bone
read-only, as they can only be changed correctly in edit mode.

4 files changed, 52 insertions, 8 deletions

diff --git a/source/blender/depsgraph/intern/builder/deg_builder_rna.cc b/source/blender/depsgraph/intern/builder/deg_builder_rna.cc
index d3ae3da9b56..e53ac40f196 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_rna.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_rna.cc
@@ -211,7 +211,7 @@ RNANodeIdentifier RNANodeQuery::construct_node_identifier(const PointerRNA *ptr,
         }
         /* Final transform properties go to the Done node for the exit. */
         else if (STREQ(prop_name, "head") || STREQ(prop_name, "tail") ||
-                 STRPREFIX(prop_name, "matrix")) {
+                 STREQ(prop_name, "length") || STRPREFIX(prop_name, "matrix")) {
           if (source == RNAPointerSource::EXIT) {
             node_identifier.operation_code = OperationCode::BONE_DONE;
           }
diff --git a/source/blender/editors/space_view3d/view3d_buttons.c b/source/blender/editors/space_view3d/view3d_buttons.c
index 1ace1198795..9ab56dba72d 100644
--- a/source/blender/editors/space_view3d/view3d_buttons.c
+++ b/source/blender/editors/space_view3d/view3d_buttons.c
@@ -1466,6 +1466,7 @@ static void v3d_editarmature_buts(uiLayout *layout, Object *ob)
   uiItemR(col, &eboneptr, "tail_radius", 0, IFACE_("Radius"), ICON_NONE);
 
   uiItemR(col, &eboneptr, "roll", 0, NULL, ICON_NONE);
+  uiItemR(col, &eboneptr, "length", 0, NULL, ICON_NONE);
   uiItemR(col, &eboneptr, "envelope_distance", 0, IFACE_("Envelope"), ICON_NONE);
 }
 
diff --git a/source/blender/makesrna/intern/rna_armature.c b/source/blender/makesrna/intern/rna_armature.c
index cfcc37adf6c..4dc383a2460 100644
--- a/source/blender/makesrna/intern/rna_armature.c
+++ b/source/blender/makesrna/intern/rna_armature.c
@@ -36,6 +36,8 @@
 
 #ifdef RNA_RUNTIME
 
+#  include "BLI_math_vector.h"
+
 #  include "BKE_action.h"
 #  include "BKE_context.h"
 #  include "BKE_global.h"
@@ -483,6 +485,22 @@ static void rna_EditBone_matrix_set(PointerRNA *ptr, const float *values)
   ED_armature_ebone_from_mat4(ebone, (float(*)[4])values);
 }
 
+static float rna_EditBone_length_get(PointerRNA *ptr)
+{
+  EditBone *ebone = (EditBone *)(ptr->data);
+  return len_v3v3(ebone->head, ebone->tail);
+}
+
+static void rna_EditBone_length_set(PointerRNA *ptr, float length)
+{
+  EditBone *ebone = (EditBone *)(ptr->data);
+  float delta[3];
+
+  sub_v3_v3v3(delta, ebone->tail, ebone->head);
+  normalize_v3(delta);
+  madd_v3_v3v3fl(ebone->tail, ebone->head, delta, length);
+}
+
 static void rna_Bone_bbone_handle_update(Main *bmain, Scene *scene, PointerRNA *ptr)
 {
   bArmature *arm = (bArmature *)ptr->owner_id;
@@ -1141,27 +1159,28 @@ static void rna_def_bone(BlenderRNA *brna)
   prop = RNA_def_property(srna, "matrix", PROP_FLOAT, PROP_MATRIX);
   RNA_def_property_float_sdna(prop, NULL, "bone_mat");
   RNA_def_property_multi_array(prop, 2, rna_matrix_dimsize_3x3);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(prop, "Bone Matrix", "3x3 bone matrix");
 
   prop = RNA_def_property(srna, "matrix_local", PROP_FLOAT, PROP_MATRIX);
   RNA_def_property_float_sdna(prop, NULL, "arm_mat");
   RNA_def_property_multi_array(prop, 2, rna_matrix_dimsize_4x4);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(
       prop, "Bone Armature-Relative Matrix", "4x4 bone matrix relative to armature");
 
   prop = RNA_def_property(srna, "tail", PROP_FLOAT, PROP_TRANSLATION);
   RNA_def_property_float_sdna(prop, NULL, "tail");
   RNA_def_property_array(prop, 3);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
-  RNA_def_property_ui_text(prop, "Tail", "Location of tail end of the bone");
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(
+      prop, "Tail", "Location of tail end of the bone relative to its parent");
   RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
 
   prop = RNA_def_property(srna, "tail_local", PROP_FLOAT, PROP_TRANSLATION);
   RNA_def_property_float_sdna(prop, NULL, "arm_tail");
   RNA_def_property_array(prop, 3);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(
       prop, "Armature-Relative Tail", "Location of tail end of the bone relative to armature");
   RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
@@ -1169,7 +1188,7 @@ static void rna_def_bone(BlenderRNA *brna)
   prop = RNA_def_property(srna, "head", PROP_FLOAT, PROP_TRANSLATION);
   RNA_def_property_float_sdna(prop, NULL, "head");
   RNA_def_property_array(prop, 3);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(
       prop, "Head", "Location of head end of the bone relative to its parent");
   RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
@@ -1177,11 +1196,16 @@ static void rna_def_bone(BlenderRNA *brna)
   prop = RNA_def_property(srna, "head_local", PROP_FLOAT, PROP_TRANSLATION);
   RNA_def_property_float_sdna(prop, NULL, "arm_head");
   RNA_def_property_array(prop, 3);
-  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(
       prop, "Armature-Relative Head", "Location of head end of the bone relative to armature");
   RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
 
+  prop = RNA_def_property(srna, "length", PROP_FLOAT, PROP_DISTANCE);
+  RNA_def_property_float_sdna(prop, NULL, "length");
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(prop, "Length", "Length of the bone");
+
   RNA_api_bone(srna);
 }
 
@@ -1227,6 +1251,14 @@ static void rna_def_edit_bone(BlenderRNA *brna)
   RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
   RNA_def_property_update(prop, 0, "rna_Armature_editbone_transform_update");
 
+  prop = RNA_def_property(srna, "length", PROP_FLOAT, PROP_DISTANCE);
+  RNA_def_property_float_funcs(prop, "rna_EditBone_length_get", "rna_EditBone_length_set", NULL);
+  RNA_def_property_range(prop, 0, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
+  RNA_def_property_ui_text(prop, "Length", "Length of the bone. Changing moves the tail end");
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_update(prop, 0, "rna_Armature_editbone_transform_update");
+
   rna_def_bone_common(srna, 1);
   rna_def_bone_curved_common(srna, false, true);
 
diff --git a/source/blender/makesrna/intern/rna_pose.c b/source/blender/makesrna/intern/rna_pose.c
index 2f460e79ec9..e514fd82aca 100644
--- a/source/blender/makesrna/intern/rna_pose.c
+++ b/source/blender/makesrna/intern/rna_pose.c
@@ -274,6 +274,12 @@ static void rna_PoseChannel_rotation_mode_set(PointerRNA *ptr, int value)
   pchan->rotmode = value;
 }
 
+static float rna_PoseChannel_length_get(PointerRNA *ptr)
+{
+  bPoseChannel *pchan = ptr->data;
+  return len_v3v3(pchan->pose_head, pchan->pose_tail);
+}
+
 static void rna_PoseChannel_name_set(PointerRNA *ptr, const char *value)
 {
   Object *ob = (Object *)ptr->owner_id;
@@ -1135,6 +1141,11 @@ static void rna_def_pose_channel(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Pose Tail Position", "Location of tail of the channel's bone");
   RNA_def_property_ui_range(prop, -FLT_MAX, FLT_MAX, 1, RNA_TRANSLATION_PREC_DEFAULT);
 
+  prop = RNA_def_property(srna, "length", PROP_FLOAT, PROP_DISTANCE);
+  RNA_def_property_float_funcs(prop, "rna_PoseChannel_length_get", NULL, NULL);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(prop, "Length", "Length of the bone");
+
   /* IK Settings */
   prop = RNA_def_property(srna, "is_in_ik_chain", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_funcs(prop, "rna_PoseChannel_has_ik_get", NULL);