Use async CreateBrowser() + pump loop on Linux to avoid CreateBrowserSync() deadlock

CefBrowserHost::CreateBrowserSync() creates an internal nested RunLoop that
cannot drive the in-process renderer thread when --single-process is active
and Python owns the UI thread via CefDoMessageLoopWork(). The result is a
~60s timeout and a null browser return.

Fix: on Linux, call the async CefBrowserHost::CreateBrowser() instead and
pump CefDoMessageLoopWork() in a Python loop until OnAfterCreated fires and
populates g_pyBrowsers. Then retrieve the CefBrowser ref from there.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: linesight

src/cefpython.pyx

@@ -806,11 +806,36 @@ def CreateBrowserSync(windowInfo=None,
     cdef CefRefPtr[CefDictionaryValue] extra_info
 
     # CEF browser creation.
-    with nogil:
-        cefBrowser = cef_browser_static.CreateBrowserSync(
+    IF UNAME_SYSNAME == "Linux":
+        # CefBrowserHost::CreateBrowserSync() deadlocks when combined with
+        # --single-process + external pump mode (CefDoMessageLoopWork). The
+        # nested RunLoop it creates cannot drive the in-process renderer
+        # thread initialisation. Use async CreateBrowser() and keep pumping
+        # the message loop until OnAfterCreated fires and populates
+        # g_pyBrowsers, then retrieve the CefBrowser ref from there.
+        cdef set _before_browser_ids = set(g_pyBrowsers.keys())
+        cef_browser_static.CreateBrowser(
                 cefWindowInfo, <CefRefPtr[CefClient]?>clientHandler,
                 cefNavigateUrl, cefBrowserSettings, extra_info,
                 cefRequestContext)
+        cdef PyBrowser _linux_pyBrowser = None
+        cdef int _i
+        for _i in range(6000):  # up to 60 s at 0.01 s/iter
+            with nogil:
+                CefDoMessageLoopWork()
+            _new_browser_ids = set(g_pyBrowsers.keys()) - _before_browser_ids
+            if _new_browser_ids:
+                _linux_pyBrowser = GetPyBrowserById(min(_new_browser_ids))
+                if _linux_pyBrowser is not None:
+                    cefBrowser = _linux_pyBrowser.cefBrowser
+                break
+            time.sleep(0.01)
+    ELSE:
+        with nogil:
+            cefBrowser = cef_browser_static.CreateBrowserSync(
+                    cefWindowInfo, <CefRefPtr[CefClient]?>clientHandler,
+                    cefNavigateUrl, cefBrowserSettings, extra_info,
+                    cefRequestContext)
 
     if not cefBrowser or not cefBrowser.get():
         Debug("CefBrowser::CreateBrowserSync() failed")

src/extern/cef/cef_browser_static.pxd

@@ -4,6 +4,7 @@
 
 include "platform_cimports.pxi"
 
+from libcpp cimport bool as cpp_bool
 from cef_ptr cimport CefRefPtr
 # noinspection PyUnresolvedReferences
 from cef_client cimport CefClient
@@ -18,6 +19,14 @@ from cef_string cimport CefString
 # Specifying namespace allows to import a static method.
 cdef extern from "include/cef_browser.h" namespace "CefBrowserHost":
 
+    cdef cpp_bool CreateBrowser(
+        CefWindowInfo&,
+        CefRefPtr[CefClient],
+        CefString&,
+        CefBrowserSettings&,
+        CefRefPtr[CefDictionaryValue],
+        CefRefPtr[CefRequestContext]) nogil
+
     cdef CefRefPtr[CefBrowser] CreateBrowserSync(
         CefWindowInfo&,
         CefRefPtr[CefClient],