WIP: Anim: implement "Copy Driver to Selected" operator

No functional change.

@@ -1567,0 +1587,4 @@
+ * otherwise.  Returns true in poll mode if a copy could be successfully made,
+ * and false otherwise.
+ */
+static bool copy_driver_to_selected_button(bContext *C, bool poll)

@@ -1567,0 +1621,4 @@
+   * side data. */
+  std::optional<std::string> path;
+  bool use_path_from_id;
+  blender::Vector<PointerRNA> lb;

@@ -1567,0 +1628,4 @@
+
+  /* Copy the driver to the list of target properties. */
+  int copy_count = 0;
+  for (PointerRNA &link : lb) {

@@ -1567,0 +1695,4 @@
+
+static bool copy_driver_to_selected_button_poll(bContext *C)
+{
+  return copy_driver_to_selected_button(C, true);

@@ -1567,0 +1700,4 @@
+
+static int copy_driver_to_selected_button_exec(bContext *C, wmOperator * /* op */)
+{
+  if (copy_driver_to_selected_button(C, false)) {

@@ -1567,0 +1703,4 @@
+  if (copy_driver_to_selected_button(C, false)) {
+    DEG_relations_tag_update(CTX_data_main(C));
+
+    /* TODO: ask someone in-the-know whether this call is needed or not.

@@ -1567,0 +1723,4 @@
+
+static void UI_OT_copy_driver_to_selected_button(wmOperatorType *ot)
+{
+  /* identifiers */

@@ -1567,0 +1727,4 @@
+  ot->name = "Copy Driver to Selected";
+  ot->idname = "UI_OT_copy_driver_to_selected_button";
+  ot->description =
+      "Copy the property's driver from the active item to the same property of all selected items "

@@ -761,3 +776,4 @@
                 ICON_DRIVER,
                 "ANIM_OT_driver_button_edit");
       }
+      else {

@@ -1567,0 +1572,4 @@
+ * \{ */
+
+/**
+ * Gets the driver(s) of the given property.

@@ -1567,0 +1598,4 @@
+
+  const bool is_array_prop = RNA_property_array_check(prop);
+  if (r_is_array_prop != nullptr) {
+    *r_is_array_prop = is_array_prop;

@@ -1567,0 +1613,4 @@
+
+  blender::Vector<FCurve *> drivers = {};
+  if (!is_array_prop) {
+    drivers.append(BKE_fcurve_find(&adt->drivers, path->c_str(), index));

@@ -1567,0 +1617,4 @@
+  }
+  else {
+    /* For array properties, we always allocate space for all elements of an
+     * array property, and the unused ones just remain null. */

@@ -1567,0 +1626,4 @@
+    }
+  }
+
+  /* If we didn't get any drivers to copy, early-out. */

@@ -1567,0 +1647,4 @@
+ *
+ * Note: intended to be used in conjunction with `get_property_drivers()` above.
+ *
+ * \param src_drivers The array of drivers to paste.  If `is_array_prop`

@@ -1567,0 +1653,4 @@
+ * \param is_array_prop Whether `src_drivers` are drivers for the elements
+ * of an array property.
+ * \param dst_ptr The RNA pointer for the destination property.
+ * \param dist_prop The destination property RNA.

@@ -1567,0 +1669,4 @@
+  /* Get the RNA path and relevant animdata for the property we're copying to. */
+  const std::optional<std::string> dst_path = RNA_path_from_ID_to_property(dst_ptr, dst_prop);
+  if (!dst_path.has_value()) {
+    return 0;

@@ -1567,0 +1684,4 @@
+    }
+    const int dst_index = is_array_prop ? i : -1;
+
+    /* If it's already animated by something other than a driver, skip. */

@@ -1567,0 +1701,4 @@
+     * drivers to find one that matches.  We should be able to make this more
+     * efficient with a little cleverness .*/
+    {
+      FCurve *old_driver = BKE_fcurve_find(&dst_adt->drivers, dst_path->c_str(), dst_index);

@@ -1567,0 +1709,4 @@
+    }
+
+    /* Create the new driver. */
+    FCurve *new_driver = BKE_fcurve_copy(src_drivers[i]);

@@ -1567,0 +1732,4 @@
+ * bool to switch between exec and poll behavior.  This isn't great, but seems
+ * like the lesser evil under the circumstances.
+ *
+ * \param all If true, copies drivers of all elements of an array property.

@@ -1567,0 +1806,4 @@
+
+    const int paste_count = paste_property_drivers(
+        src_drivers.as_span(), is_array_prop, &dst_ptr, dst_prop);
+    if (paste_count > 0) {

@@ -1567,0 +1842,4 @@
+  ot->description =
+      "Copy the property's driver from the active item to the same property of all selected "
+      "items, "
+      "if the same property exists";