Code refactoring

This commit refactors vast parts of the sqlitetypes.h interface. Its
main goals are: less code, easier code, a more modern interface, reduced
likelihood for strange errors and more flexibility for future
extensions.

The main reason why the sqlitetypes.h functions were working so well in
DB4S was not because they were that stable but because they were
extremely interlinked with the rest of the code. This is fine because we
do not plan to ship them as a separate library. But it makes it hard to
find the obvious spot to fix an issue or to put a new function. It can
always be done in the sqlitetypes function or in the rest of the DB4S
code because it is just not clear what the interface between the two
should look like. This is supposed to be improved by this commit. One
main thing here is to make ownership of objects a bit clearer.

In theory the new code should be faster too but that difference will be
neglectable from a user POV.

This commit also fixes a hidden bug which caused all table constraints
to be removed in the Edit Table dialog when a single field was removed
from the table.

This is all still WIP and more work is needed to be done here.

src/MainWindow.cpp

@@ -51,11 +51,34 @@
 #include <QShortcut>
 #include <QTextCodec>
 #include <QUrlQuery>
+#include <QDataStream>      // This include seems to only be necessary for the Windows build
 
 #ifdef Q_OS_MACX //Needed only on macOS
     #include <QOpenGLWidget>
 #endif
 
+// These are needed for reading and writing object files
+QDataStream& operator<<(QDataStream& ds, const sqlb::ObjectIdentifier& objid)
+{
+    ds << objid.toVariant();
+    return ds;
+}
+QDataStream& operator>>(QDataStream& ds, sqlb::ObjectIdentifier& objid)
+{
+    // Read in the item
+    QVariant v;
+    ds >> v;
+
+    // If it is a string list, we can treat it as an object identifier. If it isn't, we assume it's just a
+    // single string and use interpret it as the table name in the main schema. This is done for backwards
+    // compatability with old project file formats.
+    if(v.toStringList().isEmpty())
+        objid = sqlb::ObjectIdentifier("main", v.toString());
+    else
+        objid = sqlb::ObjectIdentifier(v);
+    return ds;
+}
+
 MainWindow::MainWindow(QWidget* parent)
     : QMainWindow(parent),
       ui(new Ui::MainWindow),
@@ -587,7 +610,7 @@ void MainWindow::populateTable()
         QVector<QString> v;
         bool only_defaults = true;
         const sqlb::FieldInfoList& tablefields = db.getObjectByName(tablename)->fieldInformation();
-        for(int i=0; i<tablefields.size(); ++i)
+        for(size_t i=0; i<tablefields.size(); ++i)
         {
             QString format = storedData.displayFormats[i+1];
             if(format.size())
@@ -616,7 +639,7 @@ void MainWindow::populateTable()
     if(db.getObjectByName(currentlyBrowsedTableName())->type() == sqlb::Object::Table)
     {
         // Table
-        sqlb::TablePtr table = db.getObjectByName(currentlyBrowsedTableName()).dynamicCast<sqlb::Table>();
+        sqlb::TablePtr table = db.getObjectByName<sqlb::Table>(currentlyBrowsedTableName());
         ui->actionUnlockViewEditing->setVisible(false);
         ui->actionShowRowidColumn->setVisible(!table->isWithoutRowidTable());
     } else {
@@ -2819,17 +2842,17 @@ void MainWindow::copyCurrentCreateStatement()
 void MainWindow::jumpToRow(const sqlb::ObjectIdentifier& table, QString column, const QByteArray& value)
 {
     // First check if table exists
-    sqlb::TablePtr obj = db.getObjectByName(table).dynamicCast<sqlb::Table>();
+    sqlb::TablePtr obj = db.getObjectByName<sqlb::Table>(table);
     if(!obj)
         return;
 
     // If no column name is set, assume the primary key is meant
     if(!column.size())
-        column = obj->fields().at(obj->findPk())->name();
+        column = obj->findPk()->name();
 
     // If column doesn't exist don't do anything
-    int column_index = obj->findField(column);
-    if(column_index == -1)
+    auto column_index = sqlb::findField(obj, column);
+    if(column_index == obj->fields.end())
         return;
 
     // Jump to table
@@ -2837,7 +2860,7 @@ void MainWindow::jumpToRow(const sqlb::ObjectIdentifier& table, QString column,
     populateTable();
 
     // Set filter
-    ui->dataTable->filterHeader()->setFilter(column_index+1, "=" + value);
+    ui->dataTable->filterHeader()->setFilter(column_index-obj->fields.begin()+1, "=" + value);
 }
 
 void MainWindow::showDataColumnPopupMenu(const QPoint& pos)
@@ -2909,9 +2932,9 @@ void MainWindow::editDataColumnDisplayFormat()
     int field_number = sender()->property("clicked_column").toInt();
     QString field_name;
     if (db.getObjectByName(current_table)->type() == sqlb::Object::Table)
-      field_name = db.getObjectByName(current_table).dynamicCast<sqlb::Table>()->fields().at(field_number-1)->name();
+      field_name = db.getObjectByName<sqlb::Table>(current_table)->fields.at(field_number-1).name();
     else
-      field_name = db.getObjectByName(current_table).dynamicCast<sqlb::View>()->fieldNames().at(field_number-1);
+      field_name = db.getObjectByName<sqlb::View>(current_table)->fieldNames().at(field_number-1);
     // Get the current display format of the field
     QString current_displayformat = browseTableSettings[current_table].displayFormats[field_number];
 
@@ -3044,7 +3067,7 @@ void MainWindow::unlockViewEditing(bool unlock, QString pk)
     if(unlock != settings.unlockViewPk.isEmpty() && settings.unlockViewPk == pk)
         return;
 
-    sqlb::ViewPtr obj = db.getObjectByName(currentTable).dynamicCast<sqlb::View>();
+    sqlb::ViewPtr obj = db.getObjectByName<sqlb::View>(currentTable);
 
     // If the view gets unlocked for editing and we don't have a 'primary key' for this view yet, then ask for one
     if(unlock && pk.isEmpty())