[vte] terminal: Skip commit signal emission when there are no handlers

[Christian Persch <chpe src gnome org>]

commit bc680aaa835daed9ed8cc0e4b9f2e1dfa4848afb
Author: Christian Persch <chpe src gnome org>
Date:   Thu Nov 21 20:01:30 2019 +0100

    terminal: Skip commit signal emission when there are no handlers

 src/vte.cc    | 3 +++
 src/widget.cc | 9 +++++++++
 src/widget.hh | 2 ++
 3 files changed, 14 insertions(+)
---
diff --git a/src/vte.cc b/src/vte.cc
index d43bc314..b4527155 100644
--- a/src/vte.cc
+++ b/src/vte.cc
@@ -736,6 +736,9 @@ Terminal::emit_commit(std::string_view const& str)
         if (str.size() == 0)
                 return;
 
+        if (!widget() || !widget()->should_emit_signal(SIGNAL_COMMIT))
+                return;
+
        _vte_debug_print(VTE_DEBUG_SIGNALS,
                          "Emitting `commit' of %" G_GSSIZE_FORMAT" bytes.\n", str.size());
 
diff --git a/src/widget.cc b/src/widget.cc
index c93b3a2e..ed2cc4df 100644
--- a/src/widget.cc
+++ b/src/widget.cc
@@ -428,6 +428,15 @@ Widget::size_allocate(GtkAllocation* allocation) noexcept
                                        allocation->height);
 }
 
+bool
+Widget::should_emit_signal(int id) noexcept
+{
+        return g_signal_has_handler_pending(object(),
+                                            signals[id],
+                                            0 /* detail */,
+                                            false /* not interested in blocked handlers */) != FALSE;
+}
+
 void
 Widget::unmap() noexcept
 {
diff --git a/src/widget.hh b/src/widget.hh
index d442b3fe..d904fe33 100644
--- a/src/widget.hh
+++ b/src/widget.hh
@@ -136,6 +136,8 @@ public:
         void feed_child(std::string_view const& str) { terminal()->feed_child(str); }
         void feed_child_binary(std::string_view const& str) { terminal()->feed_child_binary(str); }
 
+        bool should_emit_signal(int id) noexcept;
+
 protected:
 
         enum class CursorType {