From b44b461a76effad6016a643e83654748303c9423 Mon Sep 17 00:00:00 2001
From: Sam <16504129+sagudev@users.noreply.github.com>
Date: Fri, 29 Aug 2025 17:09:19 +0200
Subject: [PATCH] script: do not update `Document` rendering when waiting on
 asynchronous canvas image updates (#39022)

This is fixup for #37776. We forget to skip documents with
waiting_on_canvas_image_updates flag.

Testing: Existing WPT tests and manual testing
Fixes: #39021

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
---
 components/script/dom/document.rs  | 4 ++++
 components/script/script_thread.rs | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index eac3429cc33..5eecfdb03c0 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -2743,6 +2743,10 @@ impl Document {
         self.waiting_on_canvas_image_updates.set(false);
     }
 
+    pub(crate) fn waiting_on_canvas_image_updates(&self) -> bool {
+        self.waiting_on_canvas_image_updates.get()
+    }
+
     /// From <https://drafts.csswg.org/css-font-loading/#fontfaceset-pending-on-the-environment>:
     ///
     /// > A FontFaceSet is pending on the environment if any of the following are true:
diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index 2ab84a8d621..6972163bc5e 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -1158,6 +1158,10 @@ impl ScriptThread {
                 continue;
             }
 
+            if document.waiting_on_canvas_image_updates() {
+                continue;
+            }
+
             // TODO(#31581): The steps in the "Revealing the document" section need to be implemented
             // `process_pending_input_events` handles the focusing steps as well as other events
             // from the compositor.