Bare metal VGA: minor improvements (#608)

libc/vga/tty.c

@@ -93,7 +93,7 @@ static wchar_t *Wcs(struct Tty *tty)
 
 void _StartTty(struct Tty *tty, unsigned short yn, unsigned short xn,
                unsigned short starty, unsigned short startx,
-               void *vccs, wchar_t *wcs) {
+               unsigned char chr_ht, void *vccs, wchar_t *wcs) {
   struct VgaTextCharCell *ccs = vccs;
   memset(tty, 0, sizeof(struct Tty));
   SetYn(tty, yn);
@@ -103,8 +103,11 @@ void _StartTty(struct Tty *tty, unsigned short yn, unsigned short xn,
     starty = yn - 1;
   if (startx >= xn)
     startx = xn - 1;
+  if (chr_ht > 32)
+    chr_ht = 32;
   tty->y = starty;
   tty->x = startx;
+  tty->chr_ht = chr_ht;
   if (SetWcs(tty, wcs)) {
     size_t n = (size_t)yn * xn, i;
     for (i = 0; i < n; ++i)
@@ -143,66 +146,27 @@ static wchar_t *GetXlatLineDrawing(void) {
   return xlat;
 }
 
-static void XlatAlphabet(wchar_t xlat[128], int a, int b) {
-  unsigned i;
-  for (i = 0; i < 128; ++i) {
-    if ('a' <= i && i <= 'z') {
-      xlat[i] = i - 'a' + a;
-    } else if ('A' <= i && i <= 'Z') {
-      xlat[i] = i - 'A' + b;
-    } else {
-      xlat[i] = i;
-    }
-  }
-}
-
 static wchar_t *GetXlatItalic(void) {
-  static bool once;
+  /* Unimplemented.  Simply output normal non-italicized characters for now. */
-  static wchar_t xlat[128];
+  return GetXlatAscii();
-  if (!once) {
-    XlatAlphabet(xlat, L'𝑎', L'𝐴');
-    once = true;
-  }
-  return xlat;
 }
 
 static wchar_t *GetXlatBoldItalic(void) {
-  static bool once;
+  /*
-  static wchar_t xlat[128];
+   * Unimplemented.  Simply output high-intensity non-italicized characters
-  if (!once) {
+   * for now.
-    XlatAlphabet(xlat, L'𝒂', L'𝑨');
+   */
-    once = true;
+  return GetXlatAscii();
-  }
-  return xlat;
 }
 
 static wchar_t *GetXlatBoldFraktur(void) {
-  static bool once;
+  /* Unimplemented. */
-  static wchar_t xlat[128];
+  return GetXlatAscii();
-  if (!once) {
-    XlatAlphabet(xlat, L'𝖆', L'𝕬');
-    once = true;
-  }
-  return xlat;
 }
 
 static wchar_t *GetXlatFraktur(void) {
-  unsigned i;
+  /* Unimplemented. */
-  static bool once;
+  return GetXlatAscii();
-  static wchar_t xlat[128];
-  if (!once) {
-    for (i = 0; i < ARRAYLEN(xlat); ++i) {
-      if ('A' <= i && i <= 'Z') {
-        xlat[i] = L"𝔄𝔅ℭ𝔇𝔈𝔉𝔊ℌℑ𝔍𝔎𝔏𝔐𝔑𝔒𝔓𝔔ℜ𝔖𝔗𝔘𝔙𝔚𝔛𝔜ℨ"[i - 'A'];
-      } else if ('a' <= i && i <= 'z') {
-        xlat[i] = i - 'a' + L'𝔞';
-      } else {
-        xlat[i] = i;
-      }
-    }
-    once = true;
-  }
-  return xlat;
 }
 
 static wchar_t *GetXlatDoubleWidth(void) {
@@ -258,15 +222,33 @@ static void TtySetCodepage(struct Tty *tty, char id) {
   }
 }
 
+/**
+ * Map the currently active foreground & background colors & terminal
+ * configuration to a VGA text character attribute byte.
+ *
+ * @see VGA_USE_BLINK macro (libc/vga/vga.internal.h)
+ * @see drivers/tty/vt/vt.c in Linux 5.9.14 source code
+ */
 static uint8_t TtyGetVgaAttr(struct Tty *tty)
 {
-  uint8_t attr = tty->fg | tty->bg << 4;
+  uint8_t attr;
-  if ((tty->pr & kTtyBold) != 0)
+  if ((tty->pr & kTtyFlip) == 0)
-    attr |= 0x08;
+    attr = tty->fg | tty->bg << 4;
+  else
+    attr = tty->bg | tty->fg << 4;
 #ifdef VGA_USE_BLINK
+  /*
+   * If blinking is enabled, we can only have the 8 dark background color
+   * codes (0 to 7).  Simply map any bright background color (8 to 15) to
+   * its corresponding dark color, & call it a day.  This is a bit more
+   * simplistic than what Linux does, but should be enough.
+   */
+  attr &= ~0x80;
   if ((tty->pr & kTtyBlink) != 0)
     attr |= 0x80;
 #endif
+  if ((tty->pr & kTtyBold) != 0)
+    attr |= 0x08;
   return attr;
 }
 
@@ -639,37 +621,23 @@ static void TtyCsiN(struct Tty *tty) {
 
 /**
  * Map the given (R, G, B) triplet to one of the 16 basic foreground colors
- * or one of the 8 (or 16) background colors.
+ * or one of the 16 background colors.
  *
- * @see VGA_USE_BLINK macro (libc/vga/vga.internal.h)
  * @see drivers/tty/vt/vt.c in Linux 5.9.14 source code
  */
-static uint8_t TtyMapTrueColor(uint8_t r, uint8_t g, uint8_t b, bool as_fg)
+static uint8_t TtyMapTrueColor(uint8_t r, uint8_t g, uint8_t b)
 {
-  uint8_t hue = 0;
+  uint8_t hue = 0, max = MAX(MAX(r, g), b);
-#ifdef VGA_USE_BLINK
+  if (r > max / 2)
-  if (!as_fg) {
+    hue |= 4;
-    if (r >= 128)
+  if (g > max / 2)
-      hue |= 4;
+    hue |= 2;
-    if (g >= 128)
+  if (b > max / 2)
-      hue |= 2;
+    hue |= 1;
-    if (b >= 128)
+  if (hue == 7 && max <= 0x55)
-      hue |= 1;
+    hue = 8;
-  } else
+  else if (max > 0xaa)
-#endif
+    hue |= 8;
-  {
-    uint8_t max = MAX(MAX(r, g), b);
-    if (r > max / 2)
-      hue |= 4;
-    if (g > max / 2)
-      hue |= 2;
-    if (b > max / 2)
-      hue |= 1;
-    if (hue == 7 && max <= 0x55)
-      hue = 8;
-    else if (max > 0xaa)
-      hue |= 8;
-  }
   return hue;
 }
 
@@ -679,7 +647,7 @@ static uint8_t TtyMapTrueColor(uint8_t r, uint8_t g, uint8_t b, bool as_fg)
  *
  * @see drivers/tty/vt/vt.c in Linux 5.9.14 source code
  */
-static uint8_t TtyMapXtermColor(uint8_t color, bool as_fg)
+static uint8_t TtyMapXtermColor(uint8_t color)
 {
   uint8_t r, g, b;
   if (color < 8) {
@@ -699,7 +667,7 @@ static uint8_t TtyMapXtermColor(uint8_t color, bool as_fg)
     r = color * 0x55 / 2;
   } else
     r = g = b = (unsigned)color * 10 - 2312;
-  return TtyMapTrueColor(r, g, b, as_fg);
+  return TtyMapTrueColor(r, g, b);
 }
 
 static void TtySelectGraphicsRendition(struct Tty *tty) {
@@ -822,13 +790,7 @@ static void TtySelectGraphicsRendition(struct Tty *tty) {
                 break;
               case 100 ... 107:
                 code[0] -= 100 - 40;
-#ifndef VGA_USE_BLINK
-                /*
-                 * If blinking is not enabled in VGA text mode, then we can
-                 * use bright background colors.
-                 */
                 code[0] += 8;
-#endif
                 /* fallthrough */
               case 40 ... 47:
                 tty->bg = code[0] - 40;
@@ -855,7 +817,7 @@ static void TtySelectGraphicsRendition(struct Tty *tty) {
             if (++code[3] == 3) {
               code[3] = 0;
               t = kSgr;
-              tty->fg = TtyMapTrueColor(code[0], code[1], code[2], true);
+              tty->fg = TtyMapTrueColor(code[0], code[1], code[2]);
               tty->pr |= kTtyFg;
               tty->pr |= kTtyTrue;
             }
@@ -864,20 +826,20 @@ static void TtySelectGraphicsRendition(struct Tty *tty) {
             if (++code[3] == 3) {
               code[3] = 0;
               t = kSgr;
-              tty->bg = TtyMapTrueColor(code[0], code[1], code[2], false);
+              tty->bg = TtyMapTrueColor(code[0], code[1], code[2]);
               tty->pr |= kTtyBg;
               tty->pr |= kTtyTrue;
             }
             break;
           case kSgrFgXterm:
             t = kSgr;
-            tty->fg = TtyMapXtermColor(code[0], true);
+            tty->fg = TtyMapXtermColor(code[0]);
             tty->pr |= kTtyFg;
             tty->pr &= ~kTtyTrue;
             break;
           case kSgrBgXterm:
             t = kSgr;
-            tty->bg = TtyMapXtermColor(code[0], false);
+            tty->bg = TtyMapXtermColor(code[0]);
             tty->pr |= kTtyBg;
             tty->pr &= ~kTtyTrue;
             break;
@@ -1081,10 +1043,17 @@ static void TtyEscAppend(struct Tty *tty, char c) {
 }
 
 static void TtyUpdateHwCursor(struct Tty *tty) {
+  unsigned char start = tty->chr_ht - 2, end = tty->chr_ht - 1;
   unsigned short pos = tty->y * Xn(tty) + tty->x;
-  outb(CRTPORT, 0x0e);
+  if ((tty->conf & kTtyNocursor))
+    start |= 1 << 5;
+  outb(CRTPORT, 0x0A);
+  outb(CRTPORT + 1, start);
+  outb(CRTPORT, 0x0B);
+  outb(CRTPORT + 1, end);
+  outb(CRTPORT, 0x0E);
   outb(CRTPORT + 1, (unsigned char)(pos >> 8));
-  outb(CRTPORT, 0x0f);
+  outb(CRTPORT, 0x0F);
   outb(CRTPORT + 1, (unsigned char)pos);
 }
 

libc/vga/vga.internal.h

@@ -109,7 +109,7 @@ struct Tty {
   uint32_t u8;
   uint32_t n8;
   uint32_t pr;
-  uint8_t fg, bg;
+  uint8_t fg, bg, chr_ht;
   uint32_t conf;
   unsigned short savey, savex;
   struct VgaTextCharCell *ccs;
@@ -134,7 +134,8 @@ struct Tty {
 };
 
 void _StartTty(struct Tty *, unsigned short, unsigned short,
-               unsigned short, unsigned short, void *, wchar_t *);
+               unsigned short, unsigned short, unsigned char,
+               void *, wchar_t *);
 ssize_t _TtyRead(struct Tty *, void *, size_t);
 ssize_t _TtyWrite(struct Tty *, const void *, size_t);
 ssize_t _TtyWriteInput(struct Tty *, const void *, size_t);

libc/vga/writev-vga.c

@@ -58,15 +58,23 @@ ssize_t sys_writev_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
 
 __attribute__((__constructor__)) static textstartup void _vga_init(void) {
   void * const vid_buf = (void *)(BANE + 0xb8000ull);
-  /* Get the initial cursor position from the BIOS data area. */
+  /*
+   * Get the initial cursor position from the BIOS data area.  Also get
+   * the height (in scan lines) of each character; this is used to set the
+   * cursor shape.
+   */
   typedef struct {
     unsigned char col, row;
   } bios_curs_pos_t;
   bios_curs_pos_t pos = *(bios_curs_pos_t *)(BANE + 0x0450ull);
+  uint8_t chr_ht = *(uint8_t *)(BANE + 0x0485ull),
+          chr_ht_hi = *(uint8_t *)(BANE + 0x0486ull);
+  if (chr_ht_hi != 0 || chr_ht > 32)
+    chr_ht = 32;
   /*
-   * Initialize our tty structure from the current screen contents & current
+   * Initialize our tty structure from the current screen contents, current
-   * cursor position.
+   * cursor position, & character height.
    */
   _StartTty(&vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
-            vid_buf, vga_wcs);
+            chr_ht, vid_buf, vga_wcs);
 }