Start reworking UI after learning more about Qt

The sliderules tab will now use two "models" that contains encoding
and decoding data. Custom Qt widgets and the Qt signal/slot mechanism
will be used for all data/filter updates.

For example, a signal that is emitted when the encoding table's ISA
family is changed is connected only to a slot in the encoding model. The
model would then emit its own signal that is connected to any UI slot
that needs to display the changed data. This flow of `User Interaction ->
Model Update -> UI Update` will ensure there are no recursive loops in the
signal/slot connection tree.

src/sliderulesmodels.cpp

@@ -0,0 +1,32 @@
+#include "sliderulesmodels.h"
+
+#include "processorhandler.h"
+
+namespace Ripes {
+
+ISAEncodingTableModel::ISAEncodingTableModel(QObject *parent)
+    : QAbstractTableModel(parent) {
+  const auto isaInfo = ProcessorHandler::currentISA();
+  setFamily(isaInfo->isaFamily());
+}
+
+void ISAEncodingTableModel::setFamily(ISAFamily family) {
+  if (!m_isaInfo || m_isaInfo->isaFamily() != family) {
+    m_isaInfo = ISAInfoRegistry::getISA(*ISAFamilySets.at(family).begin(),
+                                        QStringList());
+    emit familyChanged(family);
+  }
+}
+
+int ISAEncodingTableModel::rowCount(const QModelIndex &) const { return 1; }
+
+int ISAEncodingTableModel::columnCount(const QModelIndex &) const { return 1; }
+
+QVariant ISAEncodingTableModel::data(const QModelIndex &index, int role) const {
+  if (role == Qt::DisplayRole) {
+    return QVariant::fromValue(m_isaInfo->isaFamily());
+  }
+  return QVariant();
+}
+
+} // namespace Ripes

src/sliderulesmodels.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "isainfo.h"
+
+#include <QTableView>
+
+namespace Ripes {
+
+class ISAEncodingTableModel : public QAbstractTableModel {
+  Q_OBJECT
+public:
+  ISAEncodingTableModel(QObject *parent = nullptr);
+
+  // TODO(raccog): This could be a variable that is controlable in the UI.
+  constexpr static size_t BIT_COLUMNS = 32;
+
+  enum Column {
+    EXTENSION = 0,
+    TYPE,
+    DESCRIPTION,
+    OPCODE,
+    // TODO(raccog): The field columns should be variable based on the maximum
+    // number of fields
+    FIELD0,
+    FIELD1,
+    FIELD2,
+    BIT_START,
+    BIT_END = BIT_START + BIT_COLUMNS
+  };
+
+  virtual int rowCount(const QModelIndex &) const override;
+  virtual int columnCount(const QModelIndex &) const override;
+  virtual QVariant data(const QModelIndex &index,
+                        int role = Qt::DisplayRole) const override;
+  //  virtual QVariant headerData(int section, Qt::Orientation orientation,
+  //                              int role = Qt::DisplayRole) const override;
+
+public slots:
+  /// Updates the Model and emits `familyChanged()` signal if the model's ISA
+  /// family has changed.
+  ///
+  /// This should only be `connect()`ed to UI signals whose function names end
+  /// in `Activated`. Can also be `connect()`ed to
+  /// `ProcessorHandler::processorChanged()`.
+  void setFamily(ISAFamily family);
+
+signals:
+  /// Called when the ISA family of the model changes. Use this to update UI.
+  void familyChanged(ISAFamily family);
+
+protected:
+  std::shared_ptr<const ISAInfoBase> m_isaInfo = nullptr;
+};
+
+} // namespace Ripes