Add LogFilterByMessage GTK log filter

This will allow suppressing GTK log messages with the specified
fixed contents.

include/wx/gtk/private/log.h

@@ -45,6 +45,9 @@ protected:
                         const GLogField* fields,
                         gsize n_fields) const = 0;
 
+    // Typically called from the derived class dtor to stop using this filter.
+    void Uninstall();
+
 private:
     // The function used as glib log writer.
     static GLogWriterOutput
@@ -92,6 +95,32 @@ private:
     wxDECLARE_NO_COPY_CLASS(LogFilterByLevel);
 };
 
+// LogFilterByMessage filters out all the messages with the specified content.
+class LogFilterByMessage : public LogFilter
+{
+public:
+    // Objects of this class are supposed to be created with literal strings as
+    // argument, so don't bother copying the string but just use the pointer.
+    explicit LogFilterByMessage(const char* message)
+        : m_message(message)
+    {
+        Install();
+    }
+
+    // Remove this filter when the object goes out of scope.
+    ~LogFilterByMessage();
+
+protected:
+    bool Filter(GLogLevelFlags WXUNUSED(log_level),
+                const GLogField* fields,
+                gsize n_fields) const wxOVERRIDE;
+
+private:
+    const char* const m_message;
+
+    wxDECLARE_NO_COPY_CLASS(LogFilterByMessage);
+};
+
 #endif // wxHAS_GLIB_LOG_WRITER
 
 } // namespace wxGTKImpl

src/gtk/app.cpp

@@ -222,6 +222,45 @@ void LogFilter::Install()
     ms_first = this;
 }
 
+void LogFilter::Uninstall()
+{
+    if ( !ms_installed )
+    {
+        // We don't do anything at all in this case.
+        return;
+    }
+
+    // We should be uninstalling only the currently installed filter.
+    wxASSERT( ms_first == this );
+
+    ms_first = m_next;
+}
+
+bool LogFilterByMessage::Filter(GLogLevelFlags WXUNUSED(log_level),
+                                const GLogField* fields,
+                                gsize n_fields) const
+{
+    for ( gsize n = 0; n < n_fields; ++n )
+    {
+        const GLogField& f = fields[n];
+        if ( strcmp(f.key, "MESSAGE") == 0 )
+        {
+            if ( strcmp(static_cast<const char*>(f.value), m_message) == 0 )
+            {
+                // This is the message we want to filter.
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+LogFilterByMessage::~LogFilterByMessage()
+{
+    Uninstall();
+}
+
 } // namespace wxGTKImpl
 
 /* static */