Phase F: restore the doc-19 bounce (footprint chooser dead-app) + regression spec

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Td4ujboGuAw26jvbDQzehj

wasm/bindings/eeschema_embind.cpp

@@ -60,6 +60,7 @@
 #include <pcbjam_remote_lock.h>
 #include "collab_common.h"
 #include "open_gate.h"
+#include "main_stack_runner.h"
 #include "collab_presence_core.h"
 #include "collab_presence_style.h"
 #include "pcbjam_theme.h"

wasm/bindings/gerbview_embind.cpp

@@ -25,6 +25,7 @@
 #include <wx/app.h>
 #include <wx/string.h>
 #include "open_gate.h"
+#include "main_stack_runner.h"
 
 using namespace emscripten;
 using json = nlohmann::json;

wasm/bindings/kicad_editor_embind.cpp

@@ -42,6 +42,7 @@
 
 #include "pcbjam_libs_reload.h"
 #include "open_gate.h"
+#include "main_stack_runner.h"
 #include "timer_park.h"
 #include "fiber_park.h"
 

wasm/bindings/main_stack_runner.h

@@ -0,0 +1,86 @@
+/*
+ * Main-stack runner: the KiCad half of wx's nested-loop bounce
+ * (pcbjam docs/features/async/19, 20 D3).
+ *
+ * A quasi-modal's nested event loop parks its whole stack for the dialog's
+ * lifetime. When that stack is a TOOL coroutine's, the park suspends the
+ * fiber's body where the fiber layer cannot see it: the stale-fiber guard
+ * quarantines the fiber, then REFUSES its own resume, and the dialog stops
+ * responding to clicks (only the titlebar x still works, because that path is
+ * ungated). That is the Symbol Properties hang.
+ *
+ * wx detects "this nested loop is about to park on a non-main stack" — it can,
+ * cheaply and exactly, by comparing a frame address against
+ * emscripten_stack_get_base()/end() — but it must not know what a coroutine
+ * is. So it calls this runner, and KiCad's TOOL_MANAGER moves the loop onto
+ * the main stack via its own RunMainStack mechanism, which suspends the
+ * coroutine the legitimate way: a fiber swap the layer records
+ * (swap_suspended = true), so no quarantine, no refused resume.
+ *
+ * This lives in pcbjam's binding layer rather than in KiCad or wx precisely
+ * because it is the only place that may know about both.
+ */
+#pragma once
+
+#include <wx/app.h>
+
+#include <eda_base_frame.h>
+#include <tool/tool_manager.h>
+
+#include <wx/wasm/private/mainstack.h>
+
+namespace pcbjam_main_stack
+{
+
+/**
+ * Run aFunc on the main stack if a tool coroutine is currently active.
+ *
+ * Returns 1 when the body has been run (bounced, or run inline because there
+ * was no coroutine to bounce off), 0 when there was nothing to run it with —
+ * no frame or no tool manager — in which case wx parks in place exactly as it
+ * did before this hook existed.
+ */
+inline int run_on_main_stack( void ( *aFunc )( void* ), void* aArg )
+{
+    if( !wxTheApp )
+        return 0;
+
+    auto* frame = dynamic_cast<EDA_BASE_FRAME*>( wxTheApp->GetTopWindow() );
+
+    if( !frame )
+        return 0;
+
+    TOOL_MANAGER* toolMgr = frame->GetToolManager();
+
+    if( !toolMgr )
+        return 0;
+
+    // RunOnMainStackIfActiveTool runs the body inline when no coroutine is
+    // running. Either way the body HAS run, so report it as handled — letting
+    // wx fall through would run the nested loop a second time.
+    bool ran = false;
+
+    toolMgr->RunOnMainStackIfActiveTool(
+            [aFunc, aArg, &ran]()
+            {
+                ran = true;
+                aFunc( aArg );
+            } );
+
+    return ran ? 1 : 0;
+}
+
+/**
+ * Installs at static-init time. Only stores a function pointer, so it is safe
+ * before wx exists; every lookup above happens lazily per call, since frames
+ * come and go. Included by more than one binding TU — setting the same pointer
+ * twice is idempotent.
+ */
+struct INSTALLER
+{
+    INSTALLER() { wxWasmSetMainStackRunner( &run_on_main_stack ); }
+};
+
+inline INSTALLER g_installer;
+
+} // namespace pcbjam_main_stack

wasm/bindings/pcbnew_embind.cpp

@@ -53,6 +53,7 @@
 #include "collab_common.h"
 #include "collab_presence_core.h"
 #include "open_gate.h"
+#include "main_stack_runner.h"
 #include "timer_park.h"
 #include "fiber_park.h"
 #include "collab_presence_style.h"

wasm/bindings/pl_editor_embind.cpp

@@ -18,6 +18,7 @@
 #include <wx/window.h>
 #include <nlohmann/json.hpp>
 #include "open_gate.h"
+#include "main_stack_runner.h"
 #include <eda_draw_frame.h>
 #include <kiid.h>
 #include <pcbjam_read_only.h>