From b74b1f936abc1321024ff3699ae58d977d333785 Mon Sep 17 00:00:00 2001
From: Intubun <41478036+Intubun@users.noreply.github.com>
Date: Mon, 4 May 2026 13:29:49 +0200
Subject: [PATCH] Save and restore GrDisplayStatus across long operations
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CIFGenSubcells() and extSubtree() set GrDisplayStatus =
DISPLAY_IN_PROGRESS while they run a 5-second progress timer, then
unconditionally restore DISPLAY_IDLE on exit. In native builds the
initial state is always IDLE, so this is harmless. In WASM/headless
builds the null display driver sets DISPLAY_SUSPEND at startup, and
forcing IDLE at the end of these long operations destroys the
SUSPEND guard that protects WindUpdate() from running display
callbacks against a non-existent screen.

Save the previous status before overwriting and restore it on exit.
This is also reentrant-safe: nested DISPLAY_IN_PROGRESS scopes (e.g.
extract followed by gds write) now keep the outer state intact.

* cif/CIFhier.c — CIFGenSubcells
* extract/ExtSubtree.c — extSubtree
---
 cif/CIFhier.c        | 6 ++++--
 extract/ExtSubtree.c | 4 +++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/cif/CIFhier.c b/cif/CIFhier.c
index 828bf289..d9b36025 100644
--- a/cif/CIFhier.c
+++ b/cif/CIFhier.c
@@ -735,8 +735,10 @@ CIFGenSubcells(
 
     /* This routine can take a long time, so use the display
      * timer to force a 5-second progress check (like is done
-     * with extract)
+     * with extract).  Save and restore GrDisplayStatus so that
+     * a headless (DISPLAY_SUSPEND) build isn't left in DISPLAY_IDLE.
      */
+    unsigned char savedDisplayStatus = GrDisplayStatus;
     GrDisplayStatus = DISPLAY_IN_PROGRESS;
     SigSetTimer(5);			/* Print at 5-second intervals */
     cuts = 0;
@@ -861,7 +863,7 @@ CIFGenSubcells(
 
     CIFHierTileOps += CIFTileOps - oldTileOps;
 
-    GrDisplayStatus = DISPLAY_IDLE;
+    GrDisplayStatus = savedDisplayStatus;
     SigRemoveTimer();
 
     UndoEnable();
diff --git a/extract/ExtSubtree.c b/extract/ExtSubtree.c
index 7b68b1fd..733baddf 100644
--- a/extract/ExtSubtree.c
+++ b/extract/ExtSubtree.c
@@ -174,8 +174,10 @@ extSubtree(parentUse, reg, f)
     int cuts, totcuts;
     float pdone, plast;
     SearchContext scx;
+    int savedDisplayStatus;
 
     /* Use the display timer to force a 5-second progress check */
+    savedDisplayStatus = GrDisplayStatus;
     GrDisplayStatus = DISPLAY_IN_PROGRESS;
     SigSetTimer(5);		    /* Print at 5-second intervals */
 
@@ -348,7 +350,7 @@ done:
     /* Output connections and node adjustments */
     extOutputConns(&ha.ha_connHash, f);
     HashKill(&ha.ha_connHash);
-    GrDisplayStatus = DISPLAY_IDLE;
+    GrDisplayStatus = savedDisplayStatus;
     SigRemoveTimer();
 
     /* Clear the CU_SUB_EXTRACTED flag from all children instances */