From 35098e927cd9c8b92d4eaea7d3f73958cc211f82 Mon Sep 17 00:00:00 2001
From: Vittorio Romeo <[EMAIL REDACTED]>
Date: Wed, 6 May 2026 01:25:30 +0200
Subject: [PATCH] emscripten: don't dispatch user input to hidden windows
---
src/video/emscripten/SDL_emscriptenevents.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/src/video/emscripten/SDL_emscriptenevents.c b/src/video/emscripten/SDL_emscriptenevents.c
index 6326d6967e9c2..d4bd854a9e41a 100644
--- a/src/video/emscripten/SDL_emscriptenevents.c
+++ b/src/video/emscripten/SDL_emscriptenevents.c
@@ -713,6 +713,15 @@ static void Emscripten_UpdateMouseFromEvent(SDL_WindowData *window_data, const E
{
SDL_assert(event->pointer_type == PTRTYPE_MOUSE);
+ // Hidden windows (e.g. a shared GL-context window) may share the DOM canvas with the
+ // visible window. Their pointer-event listeners would otherwise fire alongside the
+ // visible window's, fighting over `mouse->focus` and producing events tagged with the
+ // hidden window's ID -- causing downstream consumers that key by window ID to silently
+ // drop them. Hidden windows shouldn't take part in user-input dispatch.
+ if (window_data->window->flags & SDL_WINDOW_HIDDEN) {
+ return;
+ }
+
// rescale (in case canvas is being scaled)
double client_w, client_h;
emscripten_get_element_css_size(window_data->canvas_id, &client_w, &client_h);
@@ -838,6 +847,11 @@ static void Emscripten_HandleMouseFocus(SDL_WindowData *window_data, const Emscr
{
SDL_assert(event->pointer_type == PTRTYPE_MOUSE);
+ // Hidden windows shouldn't ever become the mouse-focus target.
+ if (window_data->window->flags & SDL_WINDOW_HIDDEN) {
+ return;
+ }
+
const bool isPointerLocked = window_data->has_pointer_lock;
if (!isPointerLocked) {