Qt: Initialize QMimeDatabase in a worker thread.

As part of its initialization, QMimeDatabase parses the freedesktop.org
shared-mime-info database, which is a large-ish (2 - 4 MB) XML file.
This takes about 85 - 90 ms here.

We first access QMimeDatabase in our startup sequence when we load the
normal and capture application icons. Create a worker thread that
initializes QMimeDatabase as early as possible and load load the normal
and capture icons as late as possible.

Change-Id: I27e3d65d8ee1308a62d12d3ff7e1b95f82c2e75a
Reviewed-on: https://code.wireshark.org/review/24471
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/wireshark-qt.cpp b/wireshark-qt.cpp
index a4341e5835..c1a5f27c62 100644
--- a/wireshark-qt.cpp
+++ b/wireshark-qt.cpp
@@ -96,6 +96,8 @@
 #include "caputils/capture-pcap-util.h"
 
 #include <QMessageBox>
+#include <QMimeDatabase>
+#include <QThread>
 
 #ifdef _WIN32
 #  include "caputils/capture-wpcap.h"
@@ -138,6 +140,19 @@
 */
 #define DEBUG_STARTUP_TIME_LOGLEVEL 252
 
+// QMimeDatabase can be slow to initialize. Do so in a worker thread
+// as early as possible.
+// https://github.com/lxde/pcmanfm-qt/issues/415
+class MimeDatabaseInitThread : public QThread
+{
+private:
+    void run()
+    {
+        QMimeDatabase mime_db;
+        mime_db.mimeTypeForData(QByteArray());
+    }
+};
+
 /* update the main window */
 void main_window_update(void)
 {
@@ -380,6 +395,9 @@ int main(int argc, char *qt_argv[])
     QTextCodec::setCodecForTr(utf8codec);
 #endif
 
+    MimeDatabaseInitThread mime_db_init_thread;
+    mime_db_init_thread.start();
+
     /* Set the C-language locale to the native environment. */
     setlocale(LC_ALL, "");