Add hashes to images

Upon successfull reading an image file, this computes a SHA1 hash of the
image and saves it with the picture tag in the log file. When a file is
not successfully loaded (for example because the log was created on a
different computer) we look up the hash in a dictionary that maps hashes
to local file names.

That dictionary (actually two for both directions), is loaded on startup
and saved upon destruction of the main window.

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/mainwindow.cpp

@@ -37,6 +37,8 @@
 #endif
 #include <QNetworkProxy>
 #include <QUndoStack>
+#include <qthelper.h>
+#include <QtConcurrentRun>
 
 MainWindow *MainWindow::m_Instance = NULL;
 
@@ -50,6 +52,7 @@ MainWindow::MainWindow() : QMainWindow(),
 	Q_ASSERT_X(m_Instance == NULL, "MainWindow", "MainWindow recreated!");
 	m_Instance = this;
 	ui.setupUi(this);
+	read_hashes();
 	// Define the States of the Application Here, Currently the states are situations where the different
 	// widgets will change on the mainwindow.
 
@@ -201,6 +204,7 @@ MainWindow::MainWindow() : QMainWindow(),
 
 MainWindow::~MainWindow()
 {
+	write_hashes();
 	m_Instance = NULL;
 }