SchOS/kernel/dev/gfx.c

// Drawing and the text console, on whatever display is bound. See include/gfx.h
// for why this is not a driver and does not name one.
//
// It was kernel/dev/vga.c, and the name was the problem: panic.c called
// gfx_fill_rect, console.c called gfx_putc, /dev/fb0 called gfx_fb_phys. None
// of this code is VGA-specific -- it is bitmap drawing over a linear
// framebuffer -- and the one part that genuinely was is now the driver, in
// kernel/drivers/gpu/vga/.
//
// The framebuffer arrives through gfx_attach_scanout() rather than being read
// out of the boot block here. That is the whole of the inversion: a driver
// publishes what it owns, and this file draws on it without knowing what it is.

#include "types.h"
#include "x86.h"
#include "memlayout.h"
#include "defs.h"
#include "theme.h"
#include "font.h"
#include "logo.h"
#include "device.h"
#include "display.h"
#include "gfx.h"

#define BACKSPACE 0x100
#define CHAR_HEIGHT 16
#define CHAR_WIDTH  8
#define COLOR_BG SCH_BG

// The scanout, as published by whichever driver owns the display. Zeroed until
// one does, and every entry point checks `fb` before touching memory -- a
// kernel that panics before any display driver has run still has to be able to
// call in here and do nothing gracefully.
static struct fb_info scanout;
static volatile uchar *fb;

static int cursor_x = 0;
static int cursor_y = 0;
// Current fill color for glyph backgrounds, backspace erase, and scroll --
// normally COLOR_BG, but panic() switches this to paint the whole console a
// solid color (e.g. PSOGM's purple) instead of leaving cream-colored boxes
// around each character.
static uint32 gfx_bg = COLOR_BG;

void
gfx_attach_scanout(const struct fb_info *info)
{
  scanout = *info;
  fb      = info->ptr;
}

const struct fb_info *
gfx_scanout(void)
{
  return fb ? &scanout : 0;
}

void
gfx_set_bg(uint32 color)
{
  gfx_bg = color;
}


// The mode that was actually set. Exported because the resolution is chosen at
// boot now (press R -- see boot/bios/stage2.S), so nothing above may assume it.
uint32
gfx_width(void)
{
  return scanout.width;
}

uint32
gfx_height(void)
{
  return scanout.height;
}

void
gfx_draw_pixel(int x, int y, uint32 color)
{
  if (!fb || x < 0 || x >= scanout.width || y < 0 || y >= scanout.height)
    return;

  uint32 offset = (y * scanout.stride) + (x * (scanout.bpp / 8));

  if (scanout.bpp == 32) {
    *(volatile uint32*)(fb + offset) = color;
  } else if (scanout.bpp == 24) {
    fb[offset]     = color & 0xFF;
    fb[offset + 1] = (color >> 8) & 0xFF;
    fb[offset + 2] = (color >> 16) & 0xFF;
  } else if (scanout.bpp == 16) {
    uint16 c16 = (((color >> 19) & 0x1F) << 11) | (((color >> 10) & 0x3F) << 5) | ((color >> 3) & 0x1F);
    *(volatile uint16*)(fb + offset) = c16;
  }
}

void
gfx_clear(uint32 color)
{
  for (int y = 0; y < scanout.height; y++) {
    for (int x = 0; x < scanout.width; x++) {
      gfx_draw_pixel(x, y, color);
    }
  }
}

void
gfx_draw_char(int x, int y, uchar c, uint32 color)
{
  // No `c > 127` rejection any more: font_data holds 256 Latin-1 glyphs, and
  // a uchar cannot index past them.
  if (!fb) return;

  for (int row = 0; row < CHAR_HEIGHT; row++) {
    uchar row_data = font_data[c][row];
    for (int col = 0; col < CHAR_WIDTH; col++) {
      if (row_data & (0x80 >> col)) {
        gfx_draw_pixel(x + col, y + row, color);
      } else {
        gfx_draw_pixel(x + col, y + row, gfx_bg);
      }
    }
  }
}

void
gfx_puts(int x, int y, char *s, uint32 color)
{
  while (*s) {
    gfx_putc((uchar)*s, color);
    s++;
  }
}

void
gfx_putc(int c, uint32 color)
{
  if (!fb) return;

  if (c == BACKSPACE || c == 0x08 || c == '\b' || c == 127) {
    if (cursor_x >= CHAR_WIDTH) {
      cursor_x -= CHAR_WIDTH;
      for (int i = 0; i < CHAR_HEIGHT; i++) {
        for (int j = 0; j < CHAR_WIDTH; j++) {
          gfx_draw_pixel(cursor_x + j, cursor_y + i, gfx_bg);
        }
      }
    }
    return;
  }

  if (c == '\n') {
    cursor_x = 0;
    cursor_y += CHAR_HEIGHT;
  } else if (c == '\r') {
    cursor_x = 0;
  } else if (c == '\t') {
    // Advance to the next multiple of eight columns, erasing as it goes so a
    // tab overwrites rather than skipping over stale characters.
    //
    // There was no tab case at all, so '\t' fell through to gfx_draw_char and
    // was drawn as glyph 9 -- which in CP437 is a hollow circle. Pressing Tab
    // printed a circle. Same for every other control character: the font has
    // a picture for each of them, and none of those pictures is what the
    // character means.
    int col = cursor_x / CHAR_WIDTH;
    int stop = (col + 8) & ~7;
    while (col < stop && cursor_x < (int)scanout.width) {
      for (int i = 0; i < CHAR_HEIGHT; i++)
        for (int j = 0; j < CHAR_WIDTH; j++)
          gfx_draw_pixel(cursor_x + j, cursor_y + i, gfx_bg);
      cursor_x += CHAR_WIDTH;
      col++;
    }
  } else if (c < 32) {
    return;                 // any other control character: not a glyph
  } else {
    gfx_draw_char(cursor_x, cursor_y, (uchar)c, color);
    cursor_x += CHAR_WIDTH;
  }

  if (cursor_x >= scanout.width) {
    cursor_x = 0;
    cursor_y += CHAR_HEIGHT;
  }

  if (cursor_y > (scanout.height - CHAR_HEIGHT)) {
    uint32 line_size = scanout.stride * CHAR_HEIGHT;
    uint32 total_size = scanout.stride * scanout.height;
    uint32 copy_size = total_size - line_size;

    memmove((void*)fb, (void*)(fb + line_size), copy_size);

    for (int y = scanout.height - CHAR_HEIGHT; y < scanout.height; y++) {
      for (int x = 0; x < scanout.width; x++) {
        gfx_draw_pixel(x, y, gfx_bg);
      }
    }
    cursor_y = scanout.height - CHAR_HEIGHT;
  }
}

void
gfx_screen_reset(void)
{
  gfx_bg = COLOR_BG;
  gfx_clear(COLOR_BG);
  cursor_x = 0;
  cursor_y = 0;
}

/* ------------------------------------------------------------------ */
/* Drawing primitives for the crash screen                             */
/*                                                                     */
/* The crash screen lays itself out rather than printing, which needs  */
/* two things the console never did: filled shapes, and text at an     */
/* absolute position that leaves the cursor alone.                     */
/* ------------------------------------------------------------------ */

int
gfx_ready(void)
{
  return fb != 0;
}

void
gfx_dims(int *w, int *h)
{
  if (w) *w = (int)scanout.width;
  if (h) *h = (int)scanout.height;
}

int gfx_char_w(void) { return CHAR_WIDTH; }
int gfx_char_h(void) { return CHAR_HEIGHT; }

/* ------------------------------------------------------------------ */
/* Framebuffer geometry                                                */
/*                                                                     */
/* Whatever the attached scanout says, rather than anything read from  */
/* the boot block here -- the driver that owns the display is the only */
/* thing that knows where the pixels are. See kernel/dev/fb.c for the  */
/* device these back.                                                  */
/* ------------------------------------------------------------------ */

uint64 gfx_fb_phys(void) { return scanout.phys; }

// Bytes of framebuffer, measured in scanlines rather than as
// width * height * bpp/8 -- the two differ whenever the card pads its rows,
// and it is the stride that says how far apart two rows really are.
uint64 gfx_fb_size(void)
{
  if (!fb)
    return 0;
  return (uint64)scanout.stride * (uint64)scanout.height;
}

uint32 gfx_fb_stride(void) { return scanout.stride; }
uint32 gfx_fb_bpp(void)    { return scanout.bpp; }

volatile uchar *gfx_fb_ptr(void) { return fb; }

/* ------------------------------------------------------------------ */
/* Cursor addressing and erasing                                       */
/*                                                                     */
/* What an ANSI escape parser needs and gfx_putc alone cannot give it: */
/* the ability to put the cursor somewhere specific and to erase a     */
/* region without writing spaces over it. See kernel/core/console.c.   */
/* ------------------------------------------------------------------ */

int gfx_cols(void) { return scanout.width  ? (int)(scanout.width  / CHAR_WIDTH)  : 0; }
int gfx_rows(void) { return scanout.height ? (int)(scanout.height / CHAR_HEIGHT) : 0; }

void
gfx_cursor_get(int *col, int *row)
{
  if (col) *col = cursor_x / CHAR_WIDTH;
  if (row) *row = cursor_y / CHAR_HEIGHT;
}

// Clamped rather than validated: an escape sequence is untrusted input that
// arrives from any program that can write to the terminal, and "CUP to row
// 9999" should put the cursor on the last row, not off the end of the
// framebuffer.
void
gfx_cursor_set(int col, int row)
{
  int maxc = gfx_cols(), maxr = gfx_rows();

  if (maxc <= 0 || maxr <= 0)
    return;
  if (col < 0) col = 0;
  if (row < 0) row = 0;
  if (col >= maxc) col = maxc - 1;
  if (row >= maxr) row = maxr - 1;

  cursor_x = col * CHAR_WIDTH;
  cursor_y = row * CHAR_HEIGHT;
}

// Fill a run of character cells with the background colour.
static void
erase_cells(int col, int row, int count)
{
  int maxc = gfx_cols();

  while (count-- > 0) {
    int x = col * CHAR_WIDTH, y = row * CHAR_HEIGHT;
    for (int i = 0; i < CHAR_HEIGHT; i++)
      for (int j = 0; j < CHAR_WIDTH; j++)
        gfx_draw_pixel(x + j, y + i, gfx_bg);
    if (++col >= maxc) { col = 0; row++; }
  }
}

// ED -- erase in display. 0: cursor to end, 1: start to cursor, 2: all.
void
gfx_erase_display(int mode)
{
  int col, row, maxc = gfx_cols(), maxr = gfx_rows();

  gfx_cursor_get(&col, &row);
  switch (mode) {
  case 0: erase_cells(col, row, (maxr - row) * maxc - col); break;
  case 1: erase_cells(0, 0, row * maxc + col + 1);          break;
  default: gfx_clear(gfx_bg);                               break;
  }
}

// EL -- erase in line. Same three modes, bounded to the current row.
void
gfx_erase_line(int mode)
{
  int col, row, maxc = gfx_cols();

  gfx_cursor_get(&col, &row);
  switch (mode) {
  case 0: erase_cells(col, row, maxc - col); break;
  case 1: erase_cells(0, row, col + 1);      break;
  default: erase_cells(0, row, maxc);        break;
  }
}

// Row pointer computed once per row rather than per pixel. The crash screen
// paints a solid card behind the QR symbol, and at 8 pixels per module that is
// tens of thousands of writes going through gfx_draw_pixel's bounds check and
// multiply.
void
gfx_fill_rect(int x0, int y0, int w, int h, uint32 color)
{
  if (!fb)
    return;
  if (x0 < 0) { w += x0; x0 = 0; }
  if (y0 < 0) { h += y0; y0 = 0; }
  if (x0 + w > (int)scanout.width)  w = (int)scanout.width  - x0;
  if (y0 + h > (int)scanout.height) h = (int)scanout.height - y0;
  if (w <= 0 || h <= 0)
    return;

  // Only the 32bpp case gets the fast path; anything else is rare enough that
  // correctness through gfx_draw_pixel is the better trade.
  if (scanout.bpp != 32) {
    for (int y = y0; y < y0 + h; y++)
      for (int x = x0; x < x0 + w; x++)
        gfx_draw_pixel(x, y, color);
    return;
  }
  for (int y = y0; y < y0 + h; y++) {
    volatile uint32 *row = (volatile uint32 *)(fb + y * scanout.stride) + x0;
    for (int x = 0; x < w; x++)
      row[x] = color;
  }
}

void
gfx_fill_circle(int cx, int cy, int r, uint32 color)
{
  for (int dy = -r; dy <= r; dy++)
    for (int dx = -r; dx <= r; dx++)
      if (dx * dx + dy * dy <= r * r)
        gfx_draw_pixel(cx + dx, cy + dy, color);
}

// Text at an absolute position, leaving the console cursor alone. The crash
// screen lays itself out, so gfx_putc's cursor tracking and scrolling are
// exactly what it does not want.
void
gfx_text_at(int x, int y, const char *s, uint32 color)
{
  for (int i = 0; s[i]; i++)
    gfx_draw_char(x + i * CHAR_WIDTH, y, (uchar)s[i], color);
}

// --- Logo ------------------------------------------------------------------
//
// The boot splash's logo is drawn by the *loader*, not here -- see splash() in
// boot/bios/stage2main.c. It has to be, because the kernel does not reach gfx_init()
// until roughly the last 300ms of a 2.8s boot: drawing it here put the logo on
// screen for one frame before console_takeover() wiped it, which is worse than
// not having one.
//
// What lives here is the same drawing code against the same mask, for the
// things that want the mark *after* boot -- the crash screen, and eventually
// whatever schinit shows. Keeping one copy of the compositing logic is why this
// is not simply deleted.

// Blend `fg` over `bg` by coverage a (0..255). Per-channel, integer only: this
// runs before any floating point is safe to touch.
static uint32
blend(uint32 bg, uint32 fg, uint a)
{
  uint32 r = (((fg >> 16) & 0xFF) * a + ((bg >> 16) & 0xFF) * (255 - a)) / 255;
  uint32 g = (((fg >>  8) & 0xFF) * a + ((bg >>  8) & 0xFF) * (255 - a)) / 255;
  uint32 b = (((fg      ) & 0xFF) * a + ((bg      ) & 0xFF) * (255 - a)) / 255;
  return (r << 16) | (g << 8) | b;
}

void
gfx_draw_logo(int x, int y, uint32 color, uint32 bg)
{
  if (!fb)
    return;
  for (int dy = 0; dy < LOGO_H; dy++) {
    for (int dx = 0; dx < LOGO_W; dx++) {
      uint a = LOGO_INK(dy * LOGO_W + dx);
      // Skip the background rather than painting it. The mask is a square but
      // the mark is a circle, so most of it is empty -- and drawing that empty
      // area in bg would stamp a visible box over whatever is underneath.
      if (a == 0)
        continue;
      gfx_draw_pixel(x + dx, y + dy, a == 255 ? color : blend(bg, color, a));
    }
  }
}

// Centred, for callers that own the whole screen.
void
gfx_logo_centered(int cy, uint32 color, uint32 bg)
{
  if (!fb || scanout.width < LOGO_W)
    return;
  gfx_draw_logo(((int)scanout.width - LOGO_W) / 2, cy - LOGO_H / 2, color, bg);
}