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LibVT: Add Alternate Screen Buffer support

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The Alternate Screen Buffer is used by full-screen terminal applications
(like `vim` and `nano`). Its data is stored separately from the normal
buffer, therefore after applications using it exit, everything looks
like it was before, the bottom of their interfaces isn't visible. An
interesting feature is that it does not support scrollback, so it
consumes less memory by not having to allocate lines for history.

Because of the need to save and restore state between the switches, some
correctness issues relating to it were also fixed in this commit.
This commit is contained in:
Daniel Bertalan 2021-05-23 15:47:41 +02:00 • committed by Ali Mohammad Pur
parent cb8d0c8d0d
commit 146bd794eb
3 changed files with 275 additions and 181 deletions
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70
Userland/Libraries/LibVT/Terminal.h
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Daniel Bertalan <dani@danielbertalan.dev>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -71,7 +72,7 @@ public:
void on_input(u8);
void set_cursor(unsigned row, unsigned column);
void set_cursor(unsigned row, unsigned column, bool skip_debug = false);
#ifndef KERNEL
void clear();
@ -93,20 +94,27 @@ public:
}
u16 rows() const { return m_rows; }
u16 cursor_column() const { return m_cursor_column; }
u16 cursor_row() const { return m_cursor_row; }
u16 cursor_column() const { return m_current_state.cursor.column; }
u16 cursor_row() const { return m_current_state.cursor.row; }
#ifndef KERNEL
size_t line_count() const
{
return m_history.size() + m_lines.size();
if (m_use_alternate_screen_buffer)
return m_alternate_screen_buffer.size();
else
return m_history.size() + m_normal_screen_buffer.size();
}
Line& line(size_t index)
{
if (index < m_history.size())
return m_history[(m_history_start + index) % m_history.size()];
return m_lines[index - m_history.size()];
if (m_use_alternate_screen_buffer) {
return m_alternate_screen_buffer[index];
} else {
if (index < m_history.size())
return m_history[(m_history_start + index) % m_history.size()];
return m_normal_screen_buffer[index - m_history.size()];
}
}
const Line& line(size_t index) const
{
@ -115,11 +123,12 @@ public:
Line& visible_line(size_t index)
{
return m_lines[index];
return active_buffer()[index];
}
const Line& visible_line(size_t index) const
{
return m_lines[index];
return active_buffer()[index];
}
size_t max_history_size() const { return m_max_history_lines; }
@ -173,6 +182,22 @@ protected:
virtual void receive_dcs_char(u8 byte) override;
virtual void execute_dcs_sequence() override;
struct CursorPosition {
u16 row { 0 };
u16 column { 0 };
void clamp(u16 max_row, u16 max_column)
{
row = min(row, max_row);
column = min(column, max_column);
}
};
struct BufferState {
Attribute attribute;
CursorPosition cursor;
};
void carriage_return();
#ifndef KERNEL
void scroll_up();
@ -225,7 +250,13 @@ protected:
void SCOSC();
// Restore Saved Cursor Position
void SCORC(Parameters);
void SCORC();
// Save Cursor (and other attributes)
void DECSC();
// Restore Cursor (and other attributes)
void DECRC();
// DECSTBM – Set Top and Bottom Margins ("Scrolling Region")
void DECSTBM(Parameters);
@ -322,19 +353,28 @@ protected:
m_history_start = (m_history_start + 1) % m_history.size();
}
NonnullOwnPtrVector<Line> m_lines;
NonnullOwnPtrVector<Line>& active_buffer() { return m_use_alternate_screen_buffer ? m_alternate_screen_buffer : m_normal_screen_buffer; };
const NonnullOwnPtrVector<Line>& active_buffer() const { return m_use_alternate_screen_buffer ? m_alternate_screen_buffer : m_normal_screen_buffer; };
NonnullOwnPtrVector<Line> m_normal_screen_buffer;
NonnullOwnPtrVector<Line> m_alternate_screen_buffer;
#endif
bool m_use_alternate_screen_buffer { false };
size_t m_scroll_region_top { 0 };
size_t m_scroll_region_bottom { 0 };
u16 m_columns { 1 };
u16 m_rows { 1 };
u16 m_cursor_row { 0 };
u16 m_cursor_column { 0 };
u16 m_saved_cursor_row { 0 };
u16 m_saved_cursor_column { 0 };
BufferState m_current_state;
BufferState m_normal_saved_state;
BufferState m_alternate_saved_state;
// Separate from *_saved_state: some escape sequences only save/restore the cursor position,
// while others impact the text attributes and other state too.
CursorPosition m_saved_cursor_position;
bool m_swallow_current { false };
bool m_stomp { false };