LibVT: Make selection follow terminal history scrollback :^)

The buffer positions referred to by a VT::Position now include history
scrollback, meaning that a VT::Position with row=0 is at the start of
the history.

The active terminal buffer keeps moving in VT::Position coordinates
whenever we scroll. This allows selection to follow history. It also
allows us to click hyperlinks in history.

Fixes #957.

Libraries/LibVT/Terminal.cpp

@@ -107,7 +107,7 @@ bool Terminal::Line::has_only_one_background_color() const
 void Terminal::clear()
 {
     for (size_t i = 0; i < rows(); ++i)
-        line(i).clear(m_current_attribute);
+        m_lines[i].clear(m_current_attribute);
     set_cursor(0, 0);
 }
 
@@ -587,7 +587,7 @@ void Terminal::escape$P(const ParamVector& params)
     if (num == 0)
         num = 1;
 
-    auto& line = this->line(m_cursor_row);
+    auto& line = m_lines[m_cursor_row];
 
     // Move n characters of line to the left
     for (int i = m_cursor_column; i < line.m_length - num; i++)
@@ -827,7 +827,7 @@ void Terminal::put_character_at(unsigned row, unsigned column, u8 ch)
 {
     ASSERT(row < rows());
     ASSERT(column < columns());
-    auto& line = this->line(row);
+    auto& line = m_lines[row];
     line.characters[column] = ch;
     line.attributes[column] = m_current_attribute;
     line.attributes[column].flags |= Attribute::Touched;
@@ -1087,7 +1087,7 @@ void Terminal::set_size(u16 columns, u16 rows)
 
 void Terminal::invalidate_cursor()
 {
-    line(m_cursor_row).dirty = true;
+    m_lines[m_cursor_row].dirty = true;
 }
 
 void Terminal::execute_hashtag(u8 hashtag)
@@ -1110,7 +1110,7 @@ Attribute Terminal::attribute_at(const Position& position) const
 {
     if (!position.is_valid())
         return {};
-    if (position.row() >= static_cast<int>(m_lines.size()))
+    if (position.row() >= static_cast<int>(line_count()))
         return {};
     auto& line = this->line(position.row());
     if (position.column() >= line.m_length)

Libraries/LibVT/Terminal.h

@@ -37,7 +37,7 @@ namespace VT {
 
 class TerminalClient {
 public:
-    virtual ~TerminalClient() { }
+    virtual ~TerminalClient() {}
 
     virtual void beep() = 0;
     virtual void set_window_title(const StringView&) = 0;
@@ -126,15 +126,22 @@ public:
         u16 m_length { 0 };
     };
 
+    size_t line_count() const
+    {
+        return m_history.size() + m_lines.size();
+    }
+
     Line& line(size_t index)
     {
-        ASSERT(index < m_rows);
-        return m_lines[index];
+        if (index < m_history.size())
+            return m_history[index];
+        return m_lines[index - m_history.size()];
     }
     const Line& line(size_t index) const
     {
-        ASSERT(index < m_rows);
-        return m_lines[index];
+        if (index < m_history.size())
+            return m_history[index];
+        return m_lines[index - m_history.size()];
     }
 
     size_t max_history_size() const { return 500; }

Libraries/LibVT/TerminalWidget.cpp

@@ -327,7 +327,7 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
     invalidate_cursor();
 
     int rows_from_history = 0;
-    int first_row_from_history = 0;
+    int first_row_from_history = m_terminal.history().size();
     int row_with_cursor = m_terminal.cursor_row();
     if (m_scrollbar->value() != m_scrollbar->max()) {
         rows_from_history = min((int)m_terminal.rows(), m_scrollbar->max() - m_scrollbar->value());
@@ -335,17 +335,11 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
         row_with_cursor = m_terminal.cursor_row() + rows_from_history;
     }
 
-    auto line_for_visual_row = [&](u16 row) -> const VT::Terminal::Line& {
-        if (row < rows_from_history)
-            return m_terminal.history().at(first_row_from_history + row);
-        return m_terminal.line(row - rows_from_history);
-    };
-
-    for (u16 row = 0; row < m_terminal.rows(); ++row) {
-        auto row_rect = this->row_rect(row);
+    for (u16 visual_row = 0; visual_row < m_terminal.rows(); ++visual_row) {
+        auto row_rect = this->row_rect(visual_row);
         if (!event.rect().contains(row_rect))
             continue;
-        auto& line = line_for_visual_row(row);
+        auto& line = m_terminal.line(first_row_from_history + visual_row);
         bool has_only_one_background_color = line.has_only_one_background_color();
         if (m_visual_beep_timer->is_active())
             painter.clear_rect(row_rect, Color::Red);
@@ -380,12 +374,12 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
             for (u16 column = this_char_column; column < next_char_column; ++column) {
                 should_reverse_fill_for_cursor_or_selection |= m_cursor_blink_state
                     && m_has_logical_focus
-                    && row == row_with_cursor
+                    && visual_row == row_with_cursor
                     && column == m_terminal.cursor_column();
-                should_reverse_fill_for_cursor_or_selection |= selection_contains({ row, column });
+                should_reverse_fill_for_cursor_or_selection |= selection_contains({ first_row_from_history + visual_row, column });
                 attribute = line.attributes[column];
                 text_color = color_from_rgb(should_reverse_fill_for_cursor_or_selection ? attribute.background_color : attribute.foreground_color);
-                auto character_rect = glyph_rect(row, column);
+                auto character_rect = glyph_rect(visual_row, column);
                 auto cell_rect = character_rect.inflated(0, m_line_spacing);
                 if (!has_only_one_background_color || should_reverse_fill_for_cursor_or_selection) {
                     painter.clear_rect(cell_rect, color_from_rgb(should_reverse_fill_for_cursor_or_selection ? attribute.foreground_color : attribute.background_color).with_alpha(m_opacity));
@@ -429,7 +423,7 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
             if (codepoint == ' ')
                 continue;
 
-            auto character_rect = glyph_rect(row, this_char_column);
+            auto character_rect = glyph_rect(visual_row, this_char_column);
             auto num_columns = next_char_column - this_char_column;
             character_rect.move_by((num_columns - 1) * font().glyph_width('x') / 2, 0);
             painter.draw_glyph_or_emoji(
@@ -441,7 +435,7 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
     }
 
     if (!m_has_logical_focus && row_with_cursor < m_terminal.rows()) {
-        auto& cursor_line = line_for_visual_row(row_with_cursor);
+        auto& cursor_line = m_terminal.line(first_row_from_history + row_with_cursor);
         if (m_terminal.cursor_row() < (m_terminal.rows() - rows_from_history)) {
             auto cell_rect = glyph_rect(row_with_cursor, m_terminal.cursor_column()).inflated(0, m_line_spacing);
             painter.draw_rect(cell_rect, color_from_rgb(cursor_line.attributes[m_terminal.cursor_column()].foreground_color));
@@ -586,6 +580,7 @@ VT::Position TerminalWidget::buffer_position_at(const Gfx::Point& position) cons
         row = m_terminal.rows() - 1;
     if (column >= m_terminal.columns())
         column = m_terminal.columns() - 1;
+    row += m_scrollbar->value();
     return { row, column };
 }