LibVT+Kernel: Clean up scroll API

This commit cleans up some of the `#ifdef`-ed code smell in
`Terminal`, by extending the scroll APIs to take a range of lines as a
parameter. This makes it possible to use the same code for `IL`/`DL` as
for scrolling.

Note that the current scrolling implementation is very naive, and does
many insertions/deletions in the middle of arrays, whereas swaps should
be enough. This optimization will come in a later commit.

The `linefeed` override was removed from `VirtualConsole`. Previously,
it exhibited incorrect behavior by moving to column 0. Now that we use
the method defined in `Terminal`, code which relied on this behavior
stopped working. We go instead go through the TTY layer which handles
the various output flags. Passing the input character-by-character
seems a bit excessive, so a fix for it will come in another PR.

Kernel/TTY/TTY.h

@@ -58,7 +58,7 @@ protected:
 
     TTY(unsigned major, unsigned minor);
     void emit(u8, bool do_evaluate_block_conditions = false);
-    virtual void echo(u8) = 0;
+    void echo_with_processing(u8);
 
     bool can_do_backspace() const;
     void do_backspace();
@@ -80,7 +80,8 @@ protected:
 private:
     // ^CharacterDevice
     virtual bool is_tty() const final override { return true; }
-    inline void echo_with_processing(u8);
+
+    virtual void echo(u8) = 0;
 
     template<typename Functor>
     void process_output(u8, Functor put_char);

Kernel/TTY/VirtualConsole.cpp

@@ -48,6 +48,9 @@ void ConsoleImpl::set_size(u16 determined_columns, u16 determined_rows)
     m_columns = determined_columns;
     m_rows = determined_rows;
 
+    m_scroll_region_top = 0;
+    m_scroll_region_bottom = determined_rows - 1;
+
     m_current_state.cursor.clamp(rows() - 1, columns() - 1);
     m_normal_saved_state.cursor.clamp(rows() - 1, columns() - 1);
     m_alternate_saved_state.cursor.clamp(rows() - 1, columns() - 1);
@@ -59,52 +62,34 @@ void ConsoleImpl::set_size(u16 determined_columns, u16 determined_rows)
     m_horizontal_tabs[determined_columns - 1] = 1;
     m_client.terminal_did_resize(m_columns, m_rows);
 }
-void ConsoleImpl::scroll_up()
+void ConsoleImpl::scroll_up(u16 region_top, u16 region_bottom, size_t count)
 {
     // NOTE: We have to invalidate the cursor first.
     m_client.invalidate_cursor(cursor_row());
-    m_client.scroll_up();
+    m_client.scroll_up(region_top, region_bottom, count);
 }
-void ConsoleImpl::scroll_down()
+
+void ConsoleImpl::scroll_down(u16 region_top, u16 region_bottom, size_t count)
 {
+    m_client.invalidate_cursor(cursor_row());
+    m_client.scroll_down(region_top, region_bottom, count);
 }
-void ConsoleImpl::linefeed()
+
-{
-    u16 new_row = cursor_row();
-    u16 max_row = rows() - 1;
-    if (new_row == max_row) {
-        // NOTE: We have to invalidate the cursor first.
-        m_client.invalidate_cursor(new_row);
-        m_client.scroll_up();
-    } else {
-        ++new_row;
-    }
-    set_cursor(new_row, 0);
-}
 void ConsoleImpl::put_character_at(unsigned row, unsigned column, u32 ch)
 {
     m_client.put_character_at(row, column, ch, m_current_state.attribute);
     m_last_code_point = ch;
 }
-void ConsoleImpl::set_window_title(const String&)
+
-{
-}
 void ConsoleImpl::ICH(Parameters)
 {
     // FIXME: Implement this
 }
-void ConsoleImpl::IL(Parameters)
+
-{
-    // FIXME: Implement this
-}
 void ConsoleImpl::DCH(Parameters)
 {
     // FIXME: Implement this
 }
-void ConsoleImpl::DL(Parameters)
-{
-    // FIXME: Implement this
-}
 
 void VirtualConsole::set_graphical(bool graphical)
 {
@@ -196,8 +181,11 @@ UNMAP_AFTER_INIT VirtualConsole::VirtualConsole(const unsigned index, const Circ
     , m_console_impl(*this)
 {
     initialize();
-    for (auto& ch : log) {
+    // HACK: We have to go through the TTY layer for correct newline handling.
-        echo(ch);
+    // It would be nice to not have to make all these calls, but we can't get the underlying data pointer
+    // and head index. If we did that, we could reduce this to at most 2 calls.
+    for (auto ch : log) {
+        emit_char(ch);
     }
 }
 
@@ -305,7 +293,9 @@ void VirtualConsole::set_active(bool active)
 
 void VirtualConsole::emit_char(char ch)
 {
-    echo(ch);
+    // Since we are standards-compliant by not moving to column 1 on '\n', we have to add an extra carriage return to
+    // do newlines properly. The `TTY` layer handles adding it.
+    echo_with_processing(static_cast<u8>(ch));
 }
 
 void VirtualConsole::flush_dirty_lines()
@@ -381,10 +371,7 @@ String VirtualConsole::device_name() const
 
 void VirtualConsole::echo(u8 ch)
 {
-    if (should_echo_input()) {
+    m_console_impl.on_input(ch);
-        auto buffer = UserOrKernelBuffer::for_kernel_buffer(&ch);
-        on_tty_write(buffer, 1);
-    }
 }
 
 VirtualConsole::Cell& VirtualConsole::cell_at(size_t x, size_t y)
@@ -407,11 +394,30 @@ void VirtualConsole::clear()
     m_console_impl.set_cursor(0, 0);
 }
 
-void VirtualConsole::scroll_up()
+void VirtualConsole::scroll_up(u16 region_top, u16 region_bottom, size_t count)
 {
-    memmove(m_cells->vaddr().as_ptr(), m_cells->vaddr().offset(columns() * sizeof(Cell)).as_ptr(), ((rows() - 1) * columns() * sizeof(Cell)));
+    VERIFY(region_top <= region_bottom);
-    clear_line(rows() - 1);
+    size_t region_size = region_bottom - region_top + 1;
-    m_console_impl.m_need_full_flush = true;
+    count = min(count, region_size);
+    size_t line_bytes = (columns() * sizeof(Cell));
+    memmove(m_cells->vaddr().offset(line_bytes * region_top).as_ptr(), m_cells->vaddr().offset(line_bytes * (region_top + count)).as_ptr(), line_bytes * (region_size - count));
+    for (size_t i = 0; i < count; ++i)
+        clear_line(region_bottom - i);
+    for (u16 row = region_top; row <= region_bottom; ++row)
+        m_lines[row].dirty = true;
+}
+
+void VirtualConsole::scroll_down(u16 region_top, u16 region_bottom, size_t count)
+{
+    VERIFY(region_top <= region_bottom);
+    size_t region_size = region_bottom - region_top + 1;
+    count = min(count, region_size);
+    size_t line_bytes = (columns() * sizeof(Cell));
+    memmove(m_cells->vaddr().offset(line_bytes * (region_top + count)).as_ptr(), m_cells->vaddr().offset(line_bytes * region_top).as_ptr(), line_bytes * (region_size - count));
+    for (size_t i = 0; i < count; ++i)
+        clear_line(region_top + i);
+    for (u16 row = region_top; row <= region_bottom; ++row)
+        m_lines[row].dirty = true;
 }
 
 void VirtualConsole::clear_line(size_t y_index)

Kernel/TTY/VirtualConsole.h

@@ -37,17 +37,12 @@ private:
     virtual void clear() override;
     virtual void clear_including_history() override;
 
-    virtual void scroll_up() override;
+    virtual void scroll_up(u16 region_top, u16 region_bottom, size_t count) override;
-    virtual void scroll_down() override;
+    virtual void scroll_down(u16 region_top, u16 region_bottom, size_t count) override;
-    virtual void linefeed() override;
     virtual void put_character_at(unsigned row, unsigned column, u32 ch) override;
-    virtual void set_window_title(const String&) override;
 
     virtual void ICH(Parameters) override;
-
-    virtual void IL(Parameters) override;
     virtual void DCH(Parameters) override;
-    virtual void DL(Parameters) override;
 };
 
 class VirtualConsole final : public TTY
@@ -140,8 +135,8 @@ private:
 
     void on_code_point(u32);
 
-    void scroll_down();
+    void scroll_down(u16 region_top, u16 region_bottom, size_t count);
-    void scroll_up();
+    void scroll_up(u16 region_top, u16 region_bottom, size_t count);
     void clear_line(size_t index);
     void put_character_at(unsigned row, unsigned column, u32 ch, const VT::Attribute&);
 

Userland/Libraries/LibVT/Terminal.cpp

@@ -638,8 +638,7 @@ void Terminal::SU(Parameters params)
     if (params.size() >= 1 && params[0] != 0)
         count = params[0];
 
-    for (u16 i = 0; i < count; i++)
+    scroll_up(count);
-        scroll_up();
 }
 
 void Terminal::SD(Parameters params)
@@ -648,8 +647,7 @@ void Terminal::SD(Parameters params)
     if (params.size() >= 1 && params[0] != 0)
         count = params[0];
 
-    for (u16 i = 0; i < count; i++)
+    scroll_down(count);
-        scroll_down();
 }
 
 void Terminal::DECSCUSR(Parameters params)
@@ -681,54 +679,36 @@ void Terminal::DECSCUSR(Parameters params)
     }
 }
 
-#ifndef KERNEL
 void Terminal::IL(Parameters params)
 {
-    unsigned count = 1;
+    size_t count = 1;
     if (params.size() >= 1 && params[0] != 0)
         count = params[0];
-    invalidate_cursor();
+    if (!is_within_scroll_region(cursor_row())) {
-    for (; count > 0; --count) {
+        dbgln("Shenanigans! Tried to insert line outside the scroll region");
-        active_buffer().insert(cursor_row(), make<Line>(m_columns));
+        return;
-        if (m_scroll_region_bottom + 1 < active_buffer().size())
-            active_buffer().remove(m_scroll_region_bottom + 1);
-        else
-            active_buffer().remove(active_buffer().size() - 1);
     }
-
+    scroll_down(cursor_row(), m_scroll_region_bottom, count);
-    m_need_full_flush = true;
 }
-#endif
 
 void Terminal::DA(Parameters)
 {
     emit_string("\033[?1;0c");
 }
 
-#ifndef KERNEL
 void Terminal::DL(Parameters params)
 {
-    int count = 1;
+    size_t count = 1;
     if (params.size() >= 1 && params[0] != 0)
         count = params[0];
-
+    if (!is_within_scroll_region(cursor_row())) {
-    if (count == 1 && cursor_row() == 0) {
+        dbgln("Shenanigans! Tried to delete line outside the scroll region");
-        scroll_up();
         return;
     }
-
+    scroll_up(cursor_row(), m_scroll_region_bottom, count);
-    int max_count = m_rows - (m_scroll_region_top + cursor_row());
-    count = min(count, max_count);
-
-    for (int c = count; c > 0; --c) {
-        active_buffer().remove(cursor_row());
-        if (m_scroll_region_bottom < active_buffer().size())
-            active_buffer().insert(m_scroll_region_bottom, make<Line>(m_columns));
-        else
-            active_buffer().append(make<Line>(m_columns));
-    }
 }
 
+#ifndef KERNEL
 void Terminal::DCH(Parameters params)
 {
     int num = 1;
@@ -765,33 +745,75 @@ void Terminal::linefeed()
 
 void Terminal::carriage_return()
 {
+    dbgln_if(TERMINAL_DEBUG, "Carriage return");
     set_cursor(cursor_row(), 0);
 }
 
-#ifndef KERNEL
+void Terminal::scroll_up(size_t count)
-void Terminal::scroll_up()
 {
-    dbgln_if(TERMINAL_DEBUG, "Scroll up 1 line");
+    scroll_up(m_scroll_region_top, m_scroll_region_bottom, count);
-    // NOTE: We have to invalidate the cursor first.
-    invalidate_cursor();
-    if (m_scroll_region_top == 0 && !m_use_alternate_screen_buffer) {
-        auto line = move(active_buffer().ptr_at(m_scroll_region_top));
-        add_line_to_history(move(line));
-        m_client.terminal_history_changed();
-    }
-    active_buffer().remove(m_scroll_region_top);
-    active_buffer().insert(m_scroll_region_bottom, make<Line>(m_columns));
-    m_need_full_flush = true;
 }
 
-void Terminal::scroll_down()
+void Terminal::scroll_down(size_t count)
 {
-    dbgln_if(TERMINAL_DEBUG, "Scroll down 1 line");
+    scroll_down(m_scroll_region_top, m_scroll_region_bottom, count);
+}
+
+#ifndef KERNEL
+// Insert `count` blank lines at the bottom of the region. Text moves up, top lines get added to the scrollback.
+void Terminal::scroll_up(u16 region_top, u16 region_bottom, size_t count)
+{
+    VERIFY(region_top <= region_bottom);
+    VERIFY(region_bottom < rows());
+    // Only the specified region should be affected.
+    size_t region_size = region_bottom - region_top + 1;
+    count = min(count, region_size);
+    dbgln_if(TERMINAL_DEBUG, "Scroll up {} lines in region {}-{}", count, region_top, region_bottom);
     // NOTE: We have to invalidate the cursor first.
     invalidate_cursor();
-    active_buffer().remove(m_scroll_region_bottom);
+
-    active_buffer().insert(m_scroll_region_top, make<Line>(m_columns));
+    if (!m_use_alternate_screen_buffer && max_history_size() != 0)
-    m_need_full_flush = true;
+        for (size_t i = 0; i < count; ++i)
+            add_line_to_history(move(active_buffer().ptr_at(region_top + i)));
+
+    if (count == region_size) {
+        for (u16 row = region_top; row <= region_bottom; ++row)
+            active_buffer()[row].clear(Attribute());
+        return;
+    }
+
+    active_buffer().remove(region_top, count);
+    for (size_t i = 0; i < count; ++i)
+        active_buffer().insert(region_bottom - count + i + 1, make<Line>(m_columns));
+    for (u16 row = region_top; row <= region_bottom; ++row)
+        active_buffer()[row].set_dirty(true);
+    if (!m_use_alternate_screen_buffer && max_history_size() != 0)
+        m_client.terminal_history_changed();
+}
+
+// Insert `count` blank lines at the top of the region. Text moves down. Does not affect the scrollback buffer.
+void Terminal::scroll_down(u16 region_top, u16 region_bottom, size_t count)
+{
+    VERIFY(region_top <= region_bottom);
+    VERIFY(region_bottom < rows());
+    // Only the specified region should be affected.
+    size_t region_size = region_bottom - region_top + 1;
+    count = min(count, region_size);
+    dbgln_if(TERMINAL_DEBUG, "Scroll down {} lines in region {}-{}", count, region_top, region_bottom);
+    // NOTE: We have to invalidate the cursor first.
+    invalidate_cursor();
+
+    if (count == region_size) {
+        for (u16 row = region_top; row <= region_bottom; ++row)
+            active_buffer()[row].set_dirty(true);
+        return;
+    }
+
+    active_buffer().remove(region_bottom - count + 1, count);
+    for (size_t i = 0; i < count; ++i)
+        active_buffer().insert(region_top, make<Line>(m_columns));
+    for (u16 row = region_top; row <= region_bottom; ++row)
+        active_buffer()[row].set_dirty(true);
 }
 
 void Terminal::put_character_at(unsigned row, unsigned column, u32 code_point)

Userland/Libraries/LibVT/Terminal.h

@@ -171,6 +171,11 @@ public:
         return m_needs_bracketed_paste;
     };
 
+    bool is_within_scroll_region(u16 line) const
+    {
+        return line >= m_scroll_region_top && line <= m_scroll_region_bottom;
+    }
+
 protected:
     // ^EscapeSequenceExecutor
     virtual void emit_code_point(u32) override;
@@ -199,18 +204,17 @@ protected:
     };
 
     void carriage_return();
-#ifndef KERNEL
+    inline void scroll_up(size_t count = 1);
-    void scroll_up();
+    inline void scroll_down(size_t count = 1);
-    void scroll_down();
     void linefeed();
+#ifndef KERNEL
+    void scroll_up(u16 region_top, u16 region_bottom, size_t count);
+    void scroll_down(u16 region_top, u16 region_bottom, size_t count);
     void put_character_at(unsigned row, unsigned column, u32 ch);
-    void set_window_title(const String&);
 #else
-    virtual void scroll_up() = 0;
+    virtual void scroll_up(u16 region_top, u16 region_bottom, size_t count) = 0;
-    virtual void scroll_down() = 0;
+    virtual void scroll_down(u16 region_top, u16 region_bottom, size_t count) = 0;
-    virtual void linefeed() = 0;
     virtual void put_character_at(unsigned row, unsigned column, u32 ch) = 0;
-    virtual void set_window_title(const String&) = 0;
 #endif
 
     void unimplemented_control_code(u8);
@@ -307,18 +311,18 @@ protected:
     // SD - Scroll Down (called "Pan Up" in VT510)
     void SD(Parameters);
 
-#ifndef KERNEL
     // IL - Insert Line
     void IL(Parameters);
+
+#ifndef KERNEL
     // DCH - Delete Character
     void DCH(Parameters);
+#else
+    virtual void DCH(Parameters) = 0;
+#endif
+
     // DL - Delete Line
     void DL(Parameters);
-#else
-    virtual void IL(Parameters) = 0;
-    virtual void DCH(Parameters) = 0;
-    virtual void DL(Parameters) = 0;
-#endif
 
     // CHA - Cursor Horizontal Absolute
     void CHA(Parameters);