Add optional log handler to fl_test_gtk_logs

Author: gspencergoog

shell/platform/linux/testing/fl_test_gtk_logs.cc

@@ -11,25 +11,35 @@ namespace testing {
 namespace {
 
 bool gtk_initialized = false;
+GLogWriterFunc log_writer_cb = nullptr;
 GLogLevelFlags fl_received_log_levels = (GLogLevelFlags)0x0;
 
 GLogWriterOutput log_writer(GLogLevelFlags log_level,
                             const GLogField* fields,
                             gsize n_fields,
                             gpointer user_data) {
   fl_received_log_levels = (GLogLevelFlags)(log_level | fl_received_log_levels);
-  return g_log_writer_default(log_level, fields, n_fields, user_data);
+  if (log_writer_cb == nullptr) {
+    return g_log_writer_default(log_level, fields, n_fields, user_data);
+  }
+  GLogWriterOutput result =
+      log_writer_cb(log_level, fields, n_fields, user_data);
+  if (result != G_LOG_WRITER_HANDLED) {
+    return g_log_writer_default(log_level, fields, n_fields, user_data);
+  }
+  return result;
 }
 
 }  // namespace
 
-void fl_ensure_gtk_init() {
+void fl_ensure_gtk_init(GLogWriterFunc writer) {
   if (!gtk_initialized) {
     gtk_init(0, nullptr);
     g_log_set_writer_func(log_writer, nullptr, nullptr);
     gtk_initialized = true;
   }
   fl_reset_received_gtk_log_levels();
+  log_writer_cb = writer;
 }
 
 void fl_reset_received_gtk_log_levels() {

shell/platform/linux/testing/fl_test_gtk_logs.h

@@ -19,9 +19,12 @@ namespace testing {
  * To retrieve the bitfield of recorded log levels, use
  * `fl_get_received_gtk_log_levels()`.
  *
+ * @param[in] writer The custom log writer function to use. If `nullptr`, the
+ *               default log writer function will be used.
+ *
  * @brief Ensures that GTK has been initialized and starts monitoring logs.
  */
-void fl_ensure_gtk_init();
+void fl_ensure_gtk_init(GLogWriterFunc writer = nullptr);
 
 /**
  * Resets the recorded GTK log levels to zero.