From 53c173d01ee97f2b33dc81b1ca77a1a16ad976e6 Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Sat, 30 Aug 2025 21:49:27 +0200
Subject: [PATCH] [consider merging] avoid a warning on writing cells/files in
 'under_construction' mode when there is nothing to update

---
 src/db/db/dbLayout.cc              | 10 ++++++++--
 src/db/db/dbLayout.h               |  8 ++++++++
 src/db/db/dbWriter.cc              |  2 +-
 src/db/db/gsiDeclDbLayout.cc       |  7 +++++++
 src/db/unit_tests/dbLayoutTests.cc |  4 ++++
 5 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/db/db/dbLayout.cc b/src/db/db/dbLayout.cc
index 1cc992459..bf2a84e0e 100644
--- a/src/db/db/dbLayout.cc
+++ b/src/db/db/dbLayout.cc
@@ -1780,7 +1780,7 @@ Layout::force_update ()
   //  NOTE: the assumption is that either one thread is writing or
   //  multiple threads are reading. Hence, we do not need to lock hier_dirty() or bboxes_dirty().
   //  We still do double checking as another thread might do the update as well.
-  if (! hier_dirty () && ! bboxes_dirty ()) {
+  if (! update_needed ()) {
     return;
   }
 
@@ -1829,10 +1829,16 @@ Layout::update () const
   }
 }
 
+bool
+Layout::update_needed () const
+{
+  return hier_dirty () || bboxes_dirty ();
+}
+
 void 
 Layout::do_update ()
 {
-  if (! hier_dirty () && ! bboxes_dirty ()) {
+  if (! update_needed ()) {
     return;
   }
 
diff --git a/src/db/db/dbLayout.h b/src/db/db/dbLayout.h
index 02b98a593..4c0d0078a 100644
--- a/src/db/db/dbLayout.h
+++ b/src/db/db/dbLayout.h
@@ -1619,6 +1619,14 @@ public:
    */
   top_down_const_iterator end_top_cells () const;
   
+  /**
+   *  @brief Gets a value indicating whether an update is needed
+   *
+   *  If this value is false, update or force_update will not
+   *  do anything.
+   */
+  bool update_needed () const;
+
   /**
    *  @brief Provide a const version of the update method
    *
diff --git a/src/db/db/dbWriter.cc b/src/db/db/dbWriter.cc
index bab0f58dd..9cf4cfb9a 100644
--- a/src/db/db/dbWriter.cc
+++ b/src/db/db/dbWriter.cc
@@ -58,7 +58,7 @@ Writer::write (db::Layout &layout, tl::OutputStream &stream)
 {
   tl::SelfTimer timer (tl::verbosity () >= 21, tl::to_string (tr ("Writing file: ")) + stream.path ());
 
-  if (layout.under_construction ()) {
+  if (layout.under_construction () && layout.update_needed ()) {
     tl::warn << tl::to_string (tr ("Cannot properly write a layout that is under construction - forcing update."));
     layout.force_update ();
   }
diff --git a/src/db/db/gsiDeclDbLayout.cc b/src/db/db/gsiDeclDbLayout.cc
index 647dbd921..c222a74ac 100644
--- a/src/db/db/gsiDeclDbLayout.cc
+++ b/src/db/db/gsiDeclDbLayout.cc
@@ -1758,6 +1758,13 @@ Class<db::Layout> decl_Layout ("db", "Layout",
     "is ongoing or the layout is brought into invalid state by\n"
     "\"start_changes\".\n"
   ) +
+  gsi::method ("update_needed", &db::Layout::update_needed,
+    "@brief Gets a value indicating whether the Layout object needs an update\n"
+    "If this method returns false, \\update will not do anything. This is useful to force an update at "
+    "specific times during 'under_construction' conditions.\n"
+    "\n"
+    "This method has been introduced in version 0.30.4."
+  ) +
   gsi::method ("update", (void (db::Layout::*) ()) &db::Layout::force_update,
     "@brief Updates the internals of the layout\n"
     "This method updates the internal state of the layout. Usually this is done automatically\n"
diff --git a/src/db/unit_tests/dbLayoutTests.cc b/src/db/unit_tests/dbLayoutTests.cc
index e96cb5c28..00fbb2056 100644
--- a/src/db/unit_tests/dbLayoutTests.cc
+++ b/src/db/unit_tests/dbLayoutTests.cc
@@ -294,7 +294,9 @@ TEST(2)
   EXPECT_EQ (g.hier_generation_id (), size_t (3));
 
   g.clear ();
+  EXPECT_EQ (g.update_needed (), true);
   g.update ();
+  EXPECT_EQ (g.update_needed (), false);
   el.reset ();
   EXPECT_EQ (g.hier_generation_id (), size_t (4));
 
@@ -387,7 +389,9 @@ TEST(3)
   EXPECT_EQ (el.hier_dirty, true);
 
   el.reset ();
+  EXPECT_EQ (g.update_needed (), true);
   g.update ();
+  EXPECT_EQ (g.update_needed (), false);
 
   top->shapes (0).insert (db::Box (0, 0, 10, 20));
   top->shapes (1).insert (db::Box (0, 0, 10, 20));