Kernel+LibVT: Implement left-right scrolling

This commit implements the left/right scrolling used in the `ICH`/`DCH`
escape sequences for `VirtualConsole`. This brings us one step closer to
VT420/xterm compatibility.

We can now finally remove the last escape sequence related `ifdef`s.

4 files changed, 68 insertions, 43 deletions

diff --git a/Kernel/TTY/VirtualConsole.cpp b/Kernel/TTY/VirtualConsole.cpp
index 8acc248f9f..e4c50127cb 100644
--- a/Kernel/TTY/VirtualConsole.cpp
+++ b/Kernel/TTY/VirtualConsole.cpp
@@ -86,14 +86,14 @@ void ConsoleImpl::clear_in_line(u16 row, u16 first_column, u16 last_column)
     m_client.clear_in_line(row, first_column, last_column);
 }
 
-void ConsoleImpl::ICH(Parameters)
+void ConsoleImpl::scroll_left(u16 row, u16 column, size_t count)
 {
-    // FIXME: Implement this
+    m_client.scroll_left(row, column, count);
 }
 
-void ConsoleImpl::DCH(Parameters)
+void ConsoleImpl::scroll_right(u16 row, u16 column, size_t count)
 {
-    // FIXME: Implement this
+    m_client.scroll_right(row, column, count);
 }
 
 void VirtualConsole::set_graphical(bool graphical)
@@ -425,6 +425,28 @@ void VirtualConsole::scroll_down(u16 region_top, u16 region_bottom, size_t count
         m_lines[row].dirty = true;
 }
 
+void VirtualConsole::scroll_left(u16 row, u16 column, size_t count)
+{
+    VERIFY(row < rows());
+    VERIFY(column < columns());
+    count = min<size_t>(count, columns() - column);
+    memmove(&cell_at(column, row), &cell_at(column + count, row), sizeof(Cell) * (columns() - column - count));
+    for (size_t i = column + count; i < columns(); ++i)
+        cell_at(i, row).clear();
+    m_lines[row].dirty = true;
+}
+
+void VirtualConsole::scroll_right(u16 row, u16 column, size_t count)
+{
+    VERIFY(row < rows());
+    VERIFY(column < columns());
+    count = min<size_t>(count, columns() - column);
+    memmove(&cell_at(column + count, row), &cell_at(column, row), sizeof(Cell) * (columns() - column - count));
+    for (size_t i = column; i < column + count; ++i)
+        cell_at(i, row).clear();
+    m_lines[row].dirty = true;
+}
+
 void VirtualConsole::clear_in_line(u16 row, u16 first_column, u16 last_column)
 {
     VERIFY(row < rows());
diff --git a/Kernel/TTY/VirtualConsole.h b/Kernel/TTY/VirtualConsole.h
index a25c5a3731..4acd096f05 100644
--- a/Kernel/TTY/VirtualConsole.h
+++ b/Kernel/TTY/VirtualConsole.h
@@ -39,11 +39,10 @@ private:
 
     virtual void scroll_up(u16 region_top, u16 region_bottom, size_t count) override;
     virtual void scroll_down(u16 region_top, u16 region_bottom, size_t count) override;
+    virtual void scroll_left(u16 row, u16 column, size_t count) override;
+    virtual void scroll_right(u16 row, u16 column, size_t count) override;
     virtual void put_character_at(unsigned row, unsigned column, u32 ch) override;
     virtual void clear_in_line(u16 row, u16 first_column, u16 last_column) override;
-
-    virtual void ICH(Parameters) override;
-    virtual void DCH(Parameters) override;
 };
 
 class VirtualConsole final : public TTY
@@ -138,6 +137,8 @@ private:
 
     void scroll_down(u16 region_top, u16 region_bottom, size_t count);
     void scroll_up(u16 region_top, u16 region_bottom, size_t count);
+    void scroll_left(u16 row, u16 column, size_t count);
+    void scroll_right(u16 row, u16 column, size_t count);
     void clear_line(size_t index)
     {
         clear_in_line(index, 0, m_console_impl.columns() - 1);
diff --git a/Userland/Libraries/LibVT/Terminal.cpp b/Userland/Libraries/LibVT/Terminal.cpp
index 5641e44cfc..5e72d1dd8e 100644
--- a/Userland/Libraries/LibVT/Terminal.cpp
+++ b/Userland/Libraries/LibVT/Terminal.cpp
@@ -692,27 +692,15 @@ void Terminal::DL(Parameters params)
     scroll_up(cursor_row(), m_scroll_region_bottom, count);
 }
 
-#ifndef KERNEL
 void Terminal::DCH(Parameters params)
 {
     int num = 1;
     if (params.size() >= 1 && params[0] != 0)
         num = params[0];
 
-    auto& line = active_buffer()[cursor_row()];
-    num = min(num, static_cast<int>(line.length()) - cursor_column());
-
-    // Move n characters of line to the left
-    for (size_t i = cursor_column(); i < line.length() - num; i++)
-        line.cell_at(i) = line.cell_at(i + num);
-
-    // Fill remainder of line with blanks
-    for (size_t i = line.length() - num; i < line.length(); i++)
-        line.set_code_point(i, ' ');
-
-    line.set_dirty(true);
+    num = min<int>(num, columns() - cursor_column());
+    scroll_left(cursor_row(), cursor_column(), num);
 }
-#endif
 
 void Terminal::linefeed()
 {
@@ -807,6 +795,36 @@ void Terminal::scroll_down(u16 region_top, u16 region_bottom, size_t count)
         active_buffer()[row].set_dirty(true);
 }
 
+// Insert `count` blank cells at the end of the line. Text moves left.
+void Terminal::scroll_left(u16 row, u16 column, size_t count)
+{
+    VERIFY(row < rows());
+    VERIFY(column < columns());
+    count = min<size_t>(count, columns() - column);
+    dbgln_if(TERMINAL_DEBUG, "Scroll left {} columns from line {} column {}", count, row, column);
+
+    auto& line = active_buffer()[row];
+    for (size_t i = column; i < columns() - count; ++i)
+        swap(line.cell_at(i), line.cell_at(i + count));
+    clear_in_line(row, columns() - count, columns() - 1);
+    line.set_dirty(true);
+}
+
+// Insert `count` blank cells after `row`. Text moves right.
+void Terminal::scroll_right(u16 row, u16 column, size_t count)
+{
+    VERIFY(row < rows());
+    VERIFY(column < columns());
+    count = min<size_t>(count, columns() - column);
+    dbgln_if(TERMINAL_DEBUG, "Scroll right {} columns from line {} column {}", count, row, column);
+
+    auto& line = active_buffer()[row];
+    for (int i = columns() - 1; i >= static_cast<int>(column + count); --i)
+        swap(line.cell_at(i), line.cell_at(i - count));
+    clear_in_line(row, column, column + count - 1);
+    line.set_dirty(true);
+}
+
 void Terminal::put_character_at(unsigned row, unsigned column, u32 code_point)
 {
     VERIFY(row < rows());
@@ -883,27 +901,15 @@ void Terminal::DSR(Parameters params)
     }
 }
 
-#ifndef KERNEL
 void Terminal::ICH(Parameters params)
 {
     unsigned num = 1;
     if (params.size() >= 1 && params[0] != 0)
         num = params[0];
-    auto& line = active_buffer()[cursor_row()];
-
-    auto max_insert = static_cast<unsigned>(line.length()) - cursor_column();
-    num = min(num, max_insert);
-    // Move characters after cursor to the right
-    for (int i = line.length() - num - 1; i >= cursor_column(); --i)
-        line.cell_at(i + num) = line.cell_at(i);
 
-    // Fill n characters after cursor with blanks
-    for (unsigned i = 0; i < num; ++i)
-        line.set_code_point(cursor_column() + i, ' ');
-
-    line.set_dirty(true);
+    num = min<unsigned>(num, columns() - cursor_column());
+    scroll_right(cursor_row(), cursor_column(), num);
 }
-#endif
 
 void Terminal::on_input(u8 byte)
 {
diff --git a/Userland/Libraries/LibVT/Terminal.h b/Userland/Libraries/LibVT/Terminal.h
index def255546e..ea719935ba 100644
--- a/Userland/Libraries/LibVT/Terminal.h
+++ b/Userland/Libraries/LibVT/Terminal.h
@@ -216,11 +216,15 @@ protected:
 #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 scroll_left(u16 row, u16 column, size_t count);
+    void scroll_right(u16 row, u16 column, size_t count);
     void put_character_at(unsigned row, unsigned column, u32 ch);
     void clear_in_line(u16 row, u16 first_column, u16 last_column);
 #else
     virtual void scroll_up(u16 region_top, u16 region_bottom, size_t count) = 0;
     virtual void scroll_down(u16 region_top, u16 region_bottom, size_t count) = 0;
+    virtual void scroll_left(u16 row, u16 column, size_t count) = 0;
+    virtual void scroll_right(u16 row, u16 column, size_t count) = 0;
     virtual void put_character_at(unsigned row, unsigned column, u32 ch) = 0;
     virtual void clear_in_line(u16 row, u16 first_column, u16 last_column) = 0;
 #endif
@@ -306,12 +310,8 @@ protected:
     // DECSCUSR - Set Cursor Style
     void DECSCUSR(Parameters);
 
-#ifndef KERNEL
     // ICH - Insert Character
     void ICH(Parameters);
-#else
-    virtual void ICH(Parameters) = 0;
-#endif
 
     // SU - Scroll Up (called "Pan Down" in VT510)
     void SU(Parameters);
@@ -322,12 +322,8 @@ protected:
     // 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);