Implement scrolling console

src/modules/main/console.cpp

@@ -0,0 +1,109 @@
+#include "console.h"
+
+console::console(const font &f, const screen &s, void *scratch, size_t len) :
+	m_font(f),
+	m_screen(s),
+	m_size(s.width() / f.width(), s.height() / f.height()),
+	m_fg(0xffffffff),
+	m_bg(0x00000000),
+	m_first(0),
+	m_length(len),
+	m_data(static_cast<char *>(scratch))
+{
+	if (len < m_size.size()) {
+		m_data = nullptr;
+	}
+
+	const unsigned count = m_size.size();
+	for (unsigned i = 0; i < count; ++i)
+		m_data[i] = 0;
+	repaint();
+}
+
+char *
+console::line_pointer(unsigned line)
+{
+	if (!m_data) return nullptr;
+	return m_data + ((m_first + line) % m_size.y) * m_size.x;
+}
+
+void
+console::repaint()
+{
+	m_screen.fill(m_bg);
+	if (!m_data) return;
+
+	for (unsigned y = 0; y < m_size.y; ++y) {
+		const char *line = line_pointer(y);
+		for (unsigned x = 0; x < m_size.x; ++x) {
+			m_font.draw_glyph(
+				m_screen,
+				line[x] ? line[x] : ' ',
+				m_fg,
+				m_bg,
+				x * m_font.width(),
+				y * m_font.height());
+		}
+	}
+}
+
+void
+console::scroll(unsigned lines)
+{
+	if (!m_data) {
+		m_pos.x = 0;
+		m_pos.y = 0;
+	} else {
+		unsigned bytes = lines * m_size.x;
+		char *line = line_pointer(0);
+		for (unsigned i = 0; i < bytes; ++i)
+			*line++ = 0;
+
+		m_first = (m_first + lines) % m_size.y;
+		m_pos.y -= lines;
+	}
+	repaint();
+}
+
+size_t
+console::puts(const char *message)
+{
+	char *line = line_pointer(m_pos.y);
+
+	while (message && *message) {
+		const unsigned x = m_pos.x * m_font.width();
+		const unsigned y = m_pos.y * m_font.height();
+		const char c = *message++;
+
+		switch (c) {
+		case '\t':
+			m_pos.x = (m_pos.x + 4) / 4 * 4;
+			break;
+
+		case '\r':
+			m_pos.x = 0;
+			break;
+
+		case '\n':
+			m_pos.x = 0;
+			m_pos.y++;
+			break;
+
+		default:
+			if (m_data) line[m_pos.x] = c;
+			m_font.draw_glyph(m_screen, c, m_fg, m_bg, x, y);
+			m_pos.x++;
+		}
+
+		if (m_pos.x >= m_size.x) {
+			m_pos.x = m_pos.x % m_size.x;
+			m_pos.y++;
+		}
+
+		if (m_pos.y >= m_size.y) {
+			scroll(1);
+			line = line_pointer(m_pos.y);
+		}
+	}
+}
+