WM: Utilities for select operators to work with click-dragging items

Based on work by Bastien and Brecht in the Node Editor, this adds more
generalized support for selecting items so that click+drag actions on
items (nodes, makers, dopesheet keys, etc.) works as wanted.
Note that this only adds the barebones to support this in other editors,
it's not used yet (will be done in followup commits).

The behavior is supposed to work as follows:
* Clicking an unselected item immediately selects it, and deselects
  other items (doesn't wait for release events).
* Click+drag on an unselected item immediately selects it, deselects
  others and drags it in one go (don't require selecting it first!).
* Click+drag on a selected item won't change the selection state (and
  won't send an undo push) and start dragging all selected items as soon
  as the drag event is recognized.
* Clicking on a selected item will still deselect others, but that will
  only happen on mouse release, when we know the intention is not to drag
  the item.

Included in: https://developer.blender.org/D5979

Reviewed by: Brecht van Lommel, William Reynish

1 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/windowmanager/intern/wm_operator_props.c b/source/blender/windowmanager/intern/wm_operator_props.c
index a8feb22cbf8..395de89c0da 100644
--- a/source/blender/windowmanager/intern/wm_operator_props.c
+++ b/source/blender/windowmanager/intern/wm_operator_props.c
@@ -396,6 +396,16 @@ void WM_operator_properties_select_operation_simple(wmOperatorType *ot)
   RNA_def_property_flag(prop, PROP_SKIP_SAVE);
 }
 
+void WM_operator_properties_generic_select(wmOperatorType *ot)
+{
+  PropertyRNA *prop = RNA_def_boolean(
+      ot->srna, "wait_to_deselect_others", true, "Wait to Deselect Others", "");
+  RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);
+
+  RNA_def_int(ot->srna, "mouse_x", 0, INT_MIN, INT_MAX, "Mouse X", "", INT_MIN, INT_MAX);
+  RNA_def_int(ot->srna, "mouse_y", 0, INT_MIN, INT_MAX, "Mouse Y", "", INT_MIN, INT_MAX);
+}
+
 void WM_operator_properties_gesture_box_zoom(wmOperatorType *ot)
 {
   WM_operator_properties_border(ot);