Fix click-drag regression in fix for T86116

1638af109e46522a1a24645289016922bb9ca977 &
bfc70a6a958b9c35bde765ea8a02e8b1fd36db8b
caused a regression with click-drag (not tweak which has it's own logic).

Restore some changes from these commits with added comments.

Minor changes from previous functionality from
39919e35326c732141bfd2d740b19000b6bc1d51.

- `prevval` & `prevtype` are now set for all kinds of new events
  in the queue previously this was not done for some kinds of events
  (mouse wheel, ndof - for example).

- Set `prevval` & `prevtype` for other windows for mouse buttons.

2 files changed, 28 insertions, 4 deletions

diff --git a/source/blender/windowmanager/intern/wm_event_query.c b/source/blender/windowmanager/intern/wm_event_query.c
index 2f5332e9672..9b9be6bb497 100644
--- a/source/blender/windowmanager/intern/wm_event_query.c
+++ b/source/blender/windowmanager/intern/wm_event_query.c
@@ -280,8 +280,11 @@ int WM_event_drag_threshold(const struct wmEvent *event)
   if (WM_event_is_tablet(event)) {
     drag_threshold = U.drag_threshold_tablet;
   }
-  else if (ISMOUSE(event->type)) {
-    /* Mouse button or mouse motion. */
+  else if (ISMOUSE(event->prevtype)) {
+    BLI_assert(event->prevtype != MOUSEMOVE);
+    /* Using the previous type is important is we want to check the last pressed/released button,
+     * The `event->type` would include #MOUSEMOVE which is always the case when dragging
+     * and does not help us know which threshold to use. */
     drag_threshold = U.drag_threshold_mouse;
   }
   else {
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index a1a9c24d178..411ecb1cac8 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -4458,6 +4458,19 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, void
   event = *evt;
   event.is_repeat = false;
 
+  /**
+   * Always support accessing the last key press/release. This is set from `win->eventstate`,
+   * so it will always be a valid event type to store in the previous state.
+   *
+   * Note that these values are intentionally _not_ set in the `win->eventstate`,
+   * as copying these values only makes sense when `win->eventstate->{val/type}` would be
+   * written to (which only happens for some kinds of events).
+   * If this was done it could leave `win->eventstate` previous and current value
+   * set to the same key press/release state which doesn't make sense.
+   */
+  event.prevtype = event.type;
+  event.prevval = event.val;
+
   /* Ensure the event state is correct, any deviation from this may cause bugs. */
 #ifndef NDEBUG
   if ((evt->type || evt->val) && /* Ignore cleared event state. */
@@ -4498,6 +4511,10 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, void
 
         oevent = *oevt;
 
+        /* See comment for this operation on `event` for details. */
+        oevent.prevtype = oevent.type;
+        oevent.prevval = oevent.val;
+
         copy_v2_v2_int(&oevent.x, &event.x);
         oevent.type = MOUSEMOVE;
         {
@@ -4593,8 +4610,12 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, void
       if (owin) {
         wmEvent oevent = *(owin->eventstate);
 
-        oevent.x = event.x;
-        oevent.y = event.y;
+        /* See comment for this operation on `event` for details. */
+        oevent.prevtype = oevent.type;
+        oevent.prevval = oevent.val;
+
+        copy_v2_v2_int(&oevent.x, &event.x);
+
         oevent.type = event.type;
         oevent.val = event.val;
         oevent.tablet = event.tablet;