Rage hacking on TerminalWidget.

There's some really hideous plumbing with globals going on here, but my
priority right now is getting a basic VT100 terminal emulator working.

Widgets/TerminalWidget.cpp

@@ -1,18 +1,47 @@
 #include "TerminalWidget.h"
 #include "Painter.h"
+#include <unistd.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+
+extern int g_fd;
+TerminalWidget* g_tw;
 
 TerminalWidget::TerminalWidget(Widget* parent)
     : Widget(parent)
 {
+    g_tw = this;
+    
     setRect({ 100, 300, columns() * 8, rows() * 8 });
-    m_screen = new CharacterWithAttributes[rows() * columns() * 2]; 
+    printf("rekt: %d x %d\n", width(), height());
+    m_screen = new CharacterWithAttributes[rows() * columns()]; 
     for (unsigned row = 0; row < m_rows; ++row) {
         for (unsigned column = 0; column < m_columns; ++column) {
             at(row, column).character = ' ';
             at(row, column).attribute = 0x07;
         }
     }
-    onReceive(String("Serenity/OS").toByteBuffer());
+    g_fd = getpt();
+    grantpt(g_fd);
+    unlockpt(g_fd);
+    char buf[1024];
+    ptsname_r(g_fd, buf, sizeof(buf));
+
+    if (fork() == 0) {
+        close(g_fd);
+        setsid();
+        int fd = open(buf, O_RDWR);
+        dup2(fd, 0);
+        dup2(fd, 1);
+        dup2(fd, 2);
+        signal(SIGWINCH, SIG_IGN);
+        ioctl(fd, TIOCSCTTY);
+        execl("/bin/bash", "bash", nullptr);
+        ASSERT_NOT_REACHED();
+    }
+
+    signal(SIGCHLD, SIG_IGN);
 }
 
 TerminalWidget::~TerminalWidget()
@@ -53,17 +82,52 @@ void TerminalWidget::onReceive(const ByteBuffer& buffer)
 
 void TerminalWidget::onReceive(byte ch)
 {
-    at(m_cursorRow, m_cursorColumn).character = ch;
-    printf("%2u,%2u -> ", m_cursorRow, m_cursorColumn);
-    if (++m_cursorColumn > m_columns) {
-        m_cursorColumn = 0;
+    //printf("receive %02x\n", ch);
+    auto scrollScreen = [&] () {
+        memmove(m_screen, m_screen + columns(), (m_rows - 1) * columns() * sizeof(CharacterWithAttributes));
+        memset(m_screen + (m_rows - 1) * columns(), ' ', columns() * sizeof(CharacterWithAttributes) * 2);
+    };
+
+    auto addChar = [&] (byte ch) {
+        at(m_cursorRow, m_cursorColumn).character = ch;
+        if (++m_cursorColumn > m_columns) {
+            m_cursorColumn = 0;
+            if (m_cursorRow < (m_rows - 1)) {
+                ++m_cursorRow;
+            } else {
+                scrollScreen();
+            }
+        }
+    };
+
+    if (ch == '\n') {
         if (m_cursorRow < (m_rows - 1)) {
             ++m_cursorRow;
         } else {
-            // FIXME: Scroll it!
-            ASSERT_NOT_REACHED();
+            scrollScreen();
         }
+    } else if (ch == '\r') {
+        m_cursorColumn = 0;
+    } else if (ch == '\t') {
+        while ((m_cursorColumn % 8) != 0 && m_cursorColumn < m_columns) {
+            addChar(' ');
+        }
+    } else {
+        addChar(ch);
     }
-    printf("%2u,%2u\n", m_cursorRow, m_cursorColumn);
+    update();
+}
+
+void TerminalWidget::onKeyDown(KeyEvent& event)
+{
+    char buf[] = { 0, 0 };
+    buf[0] = event.key();
+    write(g_fd, buf, 2);
+    return Widget::onKeyDown(event);
+}
+
+void TerminalWidget::onKeyUp(KeyEvent& event)
+{
+    return Widget::onKeyUp(event);
 }