[Bf-blender-cvs] [3ff7d0796d0] blender-v3.4-release: GHOST/Wayland: limit the size of the events_pending vector

[Campbell Barton]

Commit: 3ff7d0796d09883f6d64d80cf3722d43bf8eb33c
Author: Campbell Barton
Date:   Tue Nov 15 16:33:45 2022 +1100
Branches: blender-v3.4-release
https://developer.blender.org/rB3ff7d0796d09883f6d64d80cf3722d43bf8eb33c

GHOST/Wayland: limit the size of the events_pending vector

Avoid keeping allocated overly large events_pending vector in case of
long delays between processing events.

While in practice this isn't likely to cause problems, it's better to
avoid keeping unnecessarily large allocations.

Also remove invalid comment.

===================================================================

M	intern/ghost/intern/GHOST_SystemWayland.cpp

===================================================================

diff --git a/intern/ghost/intern/GHOST_SystemWayland.cpp b/intern/ghost/intern/GHOST_SystemWayland.cpp
index 4f04900c457..f8f0302c282 100644
--- a/intern/ghost/intern/GHOST_SystemWayland.cpp
+++ b/intern/ghost/intern/GHOST_SystemWayland.cpp
@@ -92,8 +92,6 @@ static bool has_libdecor = true;
 
 /* -------------------------------------------------------------------- */
 /** \name Forward Declarations
- *
- * Control local functionality, compositors specific workarounds.
  * \{ */
 
 static void keyboard_handle_key_repeat_cancel(struct GWL_Seat *seat);
@@ -120,6 +118,10 @@ static void gwl_display_event_thread_destroy(GWL_Display *display);
 
 static void ghost_wl_display_lock_without_input(struct wl_display *wl_display,
                                                 std::mutex *server_mutex);
+
+/** Default size for pending event vector. */
+constexpr size_t events_pending_default_size = 4096 / sizeof(void *);
+
 #endif /* USE_EVENT_BACKGROUND_THREAD */
 
 /** In nearly all cases use `pushEvent_maybe_pending`
@@ -5255,6 +5257,7 @@ static void *gwl_display_event_thread_fn(void *display_voidp)
 static void gwl_display_event_thread_create(GWL_Display *display)
 {
   GHOST_ASSERT(display->events_pthread == 0, "Only call once");
+  display->events_pending.reserve(events_pending_default_size);
   display->events_pthread_is_active = true;
   pthread_create(&display->events_pthread, nullptr, gwl_display_event_thread_fn, display);
   pthread_detach(display->events_pthread);
@@ -5433,6 +5436,13 @@ bool GHOST_SystemWayland::processEvents(bool waitForEvent)
       pushEvent(event);
     }
     display_->events_pending.clear();
+
+    if (UNLIKELY(display_->events_pending.capacity() > events_pending_default_size)) {
+      /* Avoid over allocation in the case of occasional delay between processing events
+       * causing many events to be collected and making this into a large array. */
+      display_->events_pending.shrink_to_fit();
+      display_->events_pending.reserve(events_pending_default_size);
+    }
   }
 #endif /* USE_EVENT_BACKGROUND_THREAD */