Terminal: Rewrite rendering

The rendering has been rewritten to use cached GlyphRuns instead
of text layouts. The VTerm specific code was moved into
TerminalSurface.

Change-Id: I10caa3db4ee932414987c9ddae2dcb777dc1f6e7
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/terminal/celliterator.cpp

@@ -0,0 +1,89 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0+ OR GPL-3.0 WITH Qt-GPL-exception-1.0
+
+#include "celliterator.h"
+
+#include "terminalsurface.h"
+
+#include <stdexcept>
+
+namespace Terminal::Internal {
+
+CellIterator::CellIterator(const TerminalSurface *surface, QPoint pos)
+    : m_state(State::INSIDE)
+    , m_surface(surface)
+{
+    m_pos = (pos.x()) + (pos.y() * surface->liveSize().width());
+    m_maxpos = surface->fullSize().width() * (surface->fullSize().height()) - 1;
+    updateChar();
+}
+
+CellIterator::CellIterator(const TerminalSurface *surface, int pos)
+    : m_state(State::INSIDE)
+    , m_surface(surface)
+{
+    m_pos = pos;
+    m_maxpos = surface->fullSize().width() * (surface->fullSize().height()) - 1;
+    updateChar();
+}
+
+CellIterator::CellIterator(const TerminalSurface *surface, State state)
+    : m_state(state)
+    , m_surface(surface)
+    , m_pos()
+{
+    m_maxpos = surface->fullSize().width() * (surface->fullSize().height()) - 1;
+    if (state == State::END) {
+        m_pos = m_maxpos + 1;
+    }
+}
+
+QPoint CellIterator::gridPos() const
+{
+    return m_surface->posToGrid(m_pos);
+}
+
+void CellIterator::updateChar()
+{
+    QPoint cell = m_surface->posToGrid(m_pos);
+    m_char = m_surface->fetchCharAt(cell.x(), cell.y());
+    if (m_char == 0)
+        m_char = U' ';
+}
+
+CellIterator &CellIterator::operator-=(int n)
+{
+    if (n == 0)
+        return *this;
+
+    if (m_pos - n < 0)
+        throw new std::runtime_error("-= n too big!");
+
+    m_pos -= n;
+    updateChar();
+
+    m_state = State::INSIDE;
+
+    if (m_pos == 0) {
+        m_state = State::BEGIN;
+    }
+
+    return *this;
+}
+
+CellIterator &CellIterator::operator+=(int n)
+{
+    if (n == 0)
+        return *this;
+
+    if (m_pos + n < m_maxpos) {
+        m_state = State::INSIDE;
+        m_pos += n;
+        updateChar();
+    } else {
+        *this = m_surface->end();
+    }
+    return *this;
+}
+
+} // namespace Terminal::Internal