From d751093a87021e99ec655d0e29dd46d1801229d9 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Sat, 23 Aug 2025 10:47:52 -0400
Subject: [PATCH] xo-imgui: ex2: animate GC copy step

---
 include/xo/alloc/GC.hpp         | 12 +++++++++---
 include/xo/alloc/generation.hpp | 10 ++++++++++
 src/alloc/GC.cpp                | 13 +++++++++----
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/xo/alloc/GC.hpp b/include/xo/alloc/GC.hpp
index 7c4f42c6..8ddb3e23 100644
--- a/include/xo/alloc/GC.hpp
+++ b/include/xo/alloc/GC.hpp
@@ -154,6 +154,8 @@ namespace xo {
 
             /** true iff GC permitted in current state **/
             bool is_gc_enabled() const { return gc_enabled_ == 0; }
+            /** true iff GC has been requested **/
+            bool is_gc_pending() const { return incr_gc_pending_ || full_gc_pending_; }
             /** true during (and only during) a GC cycle **/
             bool gc_in_progress() const { return runstate_.in_progress(); }
             /** @return reserved size of Nursery to-space **/
@@ -223,10 +225,14 @@ namespace xo {
              *
              *  GC is enabled when number of calls to @ref enable_gc is at least as large
              *  as number of calls to @ref disable_gc.
+             *
+             *  @return true iff GC performed
              **/
-            void enable_gc();
-            /** same as @c this->enable_gc() followed by @c this->disable_gc() **/
-            void enable_gc_once();
+            bool enable_gc();
+            /** same as @c this->enable_gc() followed by @c this->disable_gc()
+             *  @return true iff GC performed
+             **/
+            bool enable_gc_once();
 
             // inherited from IAlloc..
 
diff --git a/include/xo/alloc/generation.hpp b/include/xo/alloc/generation.hpp
index 2ed89276..0acd943a 100644
--- a/include/xo/alloc/generation.hpp
+++ b/include/xo/alloc/generation.hpp
@@ -7,6 +7,7 @@
 
 #include <ostream>
 #include <cstdint>
+#include <cassert>
 
 namespace xo {
     namespace gc {
@@ -31,6 +32,15 @@ namespace xo {
             not_found
         };
 
+        inline generation valid_genresult2gen(generation_result x) {
+            assert(x != generation_result::not_found);
+
+            if (x == generation_result::nursery)
+                return generation::nursery;
+            else
+                return generation::tenured;
+        }
+
     } /*namespace gc*/
 } /*namespace xo*/
 
diff --git a/src/alloc/GC.cpp b/src/alloc/GC.cpp
index e6fb188f..200ac218 100644
--- a/src/alloc/GC.cpp
+++ b/src/alloc/GC.cpp
@@ -1233,21 +1233,26 @@ namespace xo {
             --gc_enabled_;
         }
 
-        void
+        bool
         GC::enable_gc() {
             ++gc_enabled_;
 
             if (gc_enabled_ == 0) {
                 /* unblock gc */
-                if (incr_gc_pending_)
+                if (incr_gc_pending_) {
                     this->request_gc(full_gc_pending_ ? generation::tenured : generation::nursery);
+                    return true;
+                }
             }
+
+            return false;
         }
 
-        void
+        bool
         GC::enable_gc_once() {
-            this->enable_gc();
+            bool retval = this->enable_gc();
             this->disable_gc();
+            return retval;
         }
 
     } /*namespace gc*/