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Use the VGA start address for fast VirtualConsole scrolling.

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Instead of memcpy'ing the entire screen every time we press enter at the
bottom, use the VGA start address register to make a "view" onto the
underlying memory that moves downward as we scroll.

Eventually we run out of memory and have to reset to the start of the
buffer. That's when we memcpy everything. It would be cool if there was
some way to get the hardware to act like a ring buffer with automatic
wrapping here but I don't know how to do that.
This commit is contained in:
Andreas Kling 2018-11-09 21:18:03 +01:00
parent 8a865c11ec
commit 3e3de67f02
6 changed files with 76 additions and 26 deletions
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55
Kernel/VirtualConsole.cpp
View file

@ -63,12 +63,13 @@ void VirtualConsole::set_active(bool b)
m_active = b;
if (!m_active) {
memcpy(m_buffer, s_vga_buffer, 80 * 25 * 2);
memcpy(m_buffer, m_current_vga_window, 80 * 25 * 2);
return;
}
memcpy(s_vga_buffer, m_buffer, 80 * 25 * 2);
vga_set_cursor(m_cursor_row, m_cursor_column);
set_vga_start_row(0);
vga_set_cursor(m_cursor_row, m_cursor_column, m_current_vga_start_address);
Keyboard::the().setClient(this);
}
@ -282,15 +283,31 @@ void VirtualConsole::execute_escape_sequence(byte final)
m_intermediates.clear();
}
void VirtualConsole::clear_vga_row(word row)
{
word* linemem = (word*)&m_current_vga_window[row * 160];
for (word i = 0; i < 80; ++i)
linemem[i] = 0x0720;
}
void VirtualConsole::scroll_up()
{
if (m_cursor_row == (m_rows - 1)) {
memcpy(m_buffer, m_buffer + 160, 160 * 24);
word* linemem = (word*)&m_buffer[24 * 160];
for (word i = 0; i < 80; ++i)
linemem[i] = 0x0720;
if (m_active)
vga_scroll_up();
if (m_active) {
if (m_vga_start_row >= 160) {
memcpy(s_vga_buffer, m_current_vga_window + 160, 80 * 24 * 2);
set_vga_start_row(0);
clear_vga_row(24);
} else {
set_vga_start_row(m_vga_start_row + 1);
clear_vga_row(24);
}
} else {
memcpy(m_buffer, m_buffer + 160, 160 * 24);
word* linemem = (word*)&m_buffer[24 * 160];
for (word i = 0; i < 80; ++i)
linemem[i] = 0x0720;
}
} else {
++m_cursor_row;
}
@ -304,7 +321,7 @@ void VirtualConsole::set_cursor(unsigned row, unsigned column)
m_cursor_row = row;
m_cursor_column = column;
if (m_active)
vga_set_cursor(m_cursor_row, m_cursor_column);
vga_set_cursor(m_cursor_row, m_cursor_column, m_current_vga_start_address);
}
void VirtualConsole::put_character_at(unsigned row, unsigned column, byte ch)
@ -312,10 +329,14 @@ void VirtualConsole::put_character_at(unsigned row, unsigned column, byte ch)
ASSERT(row < m_rows);
ASSERT(column < m_columns);
word cur = (row * 160) + (column * 2);
m_buffer[cur] = ch;
m_buffer[cur + 1] = m_current_attribute;
if (m_active)
vga_putch_at(row, column, ch, m_current_attribute);
if (m_active) {
word cur = (row * 160) + (column * 2);
m_current_vga_window[cur] = ch;
m_current_vga_window[cur + 1] = m_current_attribute;
} else {
m_buffer[cur] = ch;
m_buffer[cur + 1] = m_current_attribute;
}
}
void VirtualConsole::on_char(byte ch, bool shouldEmit)
@ -416,3 +437,11 @@ String VirtualConsole::ttyName() const
ksprintf(buf, "/dev/tty%u", m_index);
return String(buf);
}
void VirtualConsole::set_vga_start_row(word row)
{
m_vga_start_row = row;
m_current_vga_start_address = row * 80;
m_current_vga_window = s_vga_buffer + row * 160;
vga_set_start_address(m_current_vga_start_address);
}