path: root/src/ftcrfont.c

/* ftcrfont.c -- FreeType font driver on cairo.
   Copyright (C) 2015-2019 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */


#include <config.h>
#include <stdio.h>
#include <math.h>
#include <cairo-ft.h>

#include "lisp.h"
#include "xterm.h"
#include "blockinput.h"
#include "composite.h"
#include "font.h"
#include "ftfont.h"
#include "pdumper.h"

#define METRICS_NCOLS_PER_ROW	(128)

enum metrics_status
  {
    METRICS_INVALID = -1,    /* metrics entry is invalid */
  };

#define METRICS_STATUS(metrics)	((metrics)->ascent + (metrics)->descent)
#define METRICS_SET_STATUS(metrics, status) \
  ((metrics)->ascent = 0, (metrics)->descent = (status))

static int
ftcrfont_glyph_extents (struct font *font,
                        unsigned glyph,
                        struct font_metrics *metrics)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  int row, col;
  struct font_metrics *cache;

  row = glyph / METRICS_NCOLS_PER_ROW;
  col = glyph % METRICS_NCOLS_PER_ROW;
  if (row >= ftcrfont_info->metrics_nrows)
    {
      ftcrfont_info->metrics =
	xrealloc (ftcrfont_info->metrics,
		  sizeof (struct font_metrics *) * (row + 1));
      memset (ftcrfont_info->metrics + ftcrfont_info->metrics_nrows, 0,
	      (sizeof (struct font_metrics *)
	       * (row + 1 - ftcrfont_info->metrics_nrows)));
      ftcrfont_info->metrics_nrows = row + 1;
    }
  if (ftcrfont_info->metrics[row] == NULL)
    {
      struct font_metrics *new;
      int i;

      new = xmalloc (sizeof (struct font_metrics) * METRICS_NCOLS_PER_ROW);
      for (i = 0; i < METRICS_NCOLS_PER_ROW; i++)
	METRICS_SET_STATUS (new + i, METRICS_INVALID);
      ftcrfont_info->metrics[row] = new;
    }
  cache = ftcrfont_info->metrics[row] + col;

  if (METRICS_STATUS (cache) == METRICS_INVALID)
    {
      cairo_glyph_t cr_glyph = {.index = glyph};
      cairo_text_extents_t extents;

      cairo_scaled_font_glyph_extents (ftcrfont_info->cr_scaled_font,
				       &cr_glyph, 1, &extents);
      cache->lbearing = floor (extents.x_bearing);
      cache->rbearing = ceil (extents.width + extents.x_bearing);
      cache->width = lround (extents.x_advance);
      cache->ascent = ceil (- extents.y_bearing);
      cache->descent = ceil (extents.height + extents.y_bearing);
    }

  if (metrics)
    *metrics = *cache;

  return cache->width;
}

static Lisp_Object
ftcrfont_list (struct frame *f, Lisp_Object spec)
{
  return ftfont_list2 (f, spec, Qftcr);
}

static Lisp_Object
ftcrfont_match (struct frame *f, Lisp_Object spec)
{
  return ftfont_match2 (f, spec, Qftcr);
}

static Lisp_Object
ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
{
  FcResult result;
  Lisp_Object val, filename, font_object;
  FcPattern *pat, *match;
  struct font_info *ftcrfont_info;
  struct font *font;
  double size = 0;
  cairo_font_face_t *font_face;
  cairo_font_extents_t extents;
  FT_Face ft_face;
  FcMatrix *matrix;

  val = assq_no_quit (QCfont_entity, AREF (entity, FONT_EXTRA_INDEX));
  if (! CONSP (val))
    return Qnil;
  val = XCDR (val);
  filename = XCAR (val);
  size = XFIXNUM (AREF (entity, FONT_SIZE_INDEX));
  if (size == 0)
    size = pixel_size;

  block_input ();

  pat = ftfont_entity_pattern (entity, pixel_size);
  FcConfigSubstitute (NULL, pat, FcMatchPattern);
  FcDefaultSubstitute (pat);
  match = FcFontMatch (NULL, pat, &result);
  ftfont_fix_match (pat, match);

  FcPatternDestroy (pat);
  font_face = cairo_ft_font_face_create_for_pattern (match);
  if (!font_face)
    {
      unblock_input ();
      FcPatternDestroy (match);
      return Qnil;
    }
  cairo_matrix_t font_matrix, ctm;
  cairo_matrix_init_scale (&font_matrix, pixel_size, pixel_size);
  cairo_matrix_init_identity (&ctm);
  cairo_font_options_t *options = cairo_font_options_create ();
  cairo_scaled_font_t *scaled_font
    = cairo_scaled_font_create (font_face, &font_matrix, &ctm, options);
  cairo_font_face_destroy (font_face);
  cairo_font_options_destroy (options);
  unblock_input ();

  font_object = font_build_object (VECSIZE (struct font_info),
				   AREF (entity, FONT_TYPE_INDEX),
				   entity, size);
  ASET (font_object, FONT_FILE_INDEX, filename);
  font = XFONT_OBJECT (font_object);
  font->pixel_size = size;
#ifdef HAVE_HARFBUZZ
  if (EQ (AREF (font_object, FONT_TYPE_INDEX), Qftcrhb))
    font->driver = &ftcrhbfont_driver;
  else
#endif	/* HAVE_HARFBUZZ */
  font->driver = &ftcrfont_driver;
  font->encoding_charset = font->repertory_charset = -1;

  ftcrfont_info = (struct font_info *) font;
  ftcrfont_info->cr_scaled_font = scaled_font;

  /* This means that there's no need of transformation.  */
  ftcrfont_info->matrix.xx = 0;
  if (FcPatternGetMatrix (match, FC_MATRIX, 0, &matrix) == FcResultMatch)
    {
      ftcrfont_info->matrix.xx = 0x10000L * matrix->xx;
      ftcrfont_info->matrix.yy = 0x10000L * matrix->yy;
      ftcrfont_info->matrix.xy = 0x10000L * matrix->xy;
      ftcrfont_info->matrix.yx = 0x10000L * matrix->yx;
    }

  ftcrfont_info->metrics = NULL;
  ftcrfont_info->metrics_nrows = 0;

  block_input ();
  cairo_glyph_t stack_glyph;
  font->min_width = font->average_width = font->space_width = 0;
  for (char c = 32; c < 127; c++)
    {
      cairo_glyph_t *glyphs = &stack_glyph;
      int num_glyphs = 1;
      cairo_status_t status =
	cairo_scaled_font_text_to_glyphs (ftcrfont_info->cr_scaled_font,
					  0, 0, &c, 1, &glyphs, &num_glyphs,
					  NULL, NULL, NULL);

      /* In order to simulate the Xft behavior, we use metrics of
	 glyph ID 0 if there is no glyph for an ASCII printable.  */
      if (status != CAIRO_STATUS_SUCCESS)
	stack_glyph.index = 0;
      else if (glyphs != &stack_glyph)
	{
	  cairo_glyph_free (glyphs);
	  stack_glyph.index = 0;
	}
      int this_width = ftcrfont_glyph_extents (font, stack_glyph.index, NULL);
      if (this_width > 0
	  && (! font->min_width
	      || font->min_width > this_width))
	font->min_width = this_width;
      if (c == 32)
	font->space_width = this_width;
      font->average_width += this_width;
    }
  font->average_width /= 95;

  cairo_scaled_font_extents (ftcrfont_info->cr_scaled_font, &extents);
  font->ascent = lround (extents.ascent);
  val = assq_no_quit (QCminspace, AREF (entity, FONT_EXTRA_INDEX));
  if (!(CONSP (val) && NILP (XCDR (val))))
    {
      font->descent = lround (extents.descent);
      font->height = font->ascent + font->descent;
    }
  else
    {
      font->height = lround (extents.height);
      font->descent = font->height - font->ascent;
    }

  ft_face = cairo_ft_scaled_font_lock_face (scaled_font);
  if (XFIXNUM (AREF (entity, FONT_SIZE_INDEX)) == 0)
    {
      int upEM = ft_face->units_per_EM;

      font->underline_position = -ft_face->underline_position * size / upEM;
      font->underline_thickness = ft_face->underline_thickness * size / upEM;
      if (font->underline_thickness > 2)
	font->underline_position -= font->underline_thickness / 2;
    }
  else
    {
      font->underline_position = -1;
      font->underline_thickness = 0;
    }
#ifdef HAVE_LIBOTF
  ftcrfont_info->maybe_otf = (ft_face->face_flags & FT_FACE_FLAG_SFNT) != 0;
  ftcrfont_info->otf = NULL;
#endif	/* HAVE_LIBOTF */
#ifdef HAVE_HARFBUZZ
  ftcrfont_info->hb_font = NULL;
#endif	/* HAVE_HARFBUZZ */
  if (ft_face->units_per_EM)
    ftcrfont_info->bitmap_position_unit = 0;
  else
    ftcrfont_info->bitmap_position_unit = (extents.height
					   / ft_face->size->metrics.height);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;
  unblock_input ();

  font->baseline_offset = 0;
  font->relative_compose = 0;
  font->default_ascent = 0;
  font->vertical_centering = false;

  return font_object;
}

static void
ftcrfont_close (struct font *font)
{
  if (font_data_structures_may_be_ill_formed ())
    return;

  struct font_info *ftcrfont_info = (struct font_info *) font;

  block_input ();
#ifdef HAVE_LIBOTF
  if (ftcrfont_info->otf)
    {
      OTF_close (ftcrfont_info->otf);
      ftcrfont_info->otf = NULL;
    }
#endif
#ifdef HAVE_HARFBUZZ
  if (ftcrfont_info->hb_font)
    {
      hb_font_destroy (ftcrfont_info->hb_font);
      ftcrfont_info->hb_font = NULL;
    }
#endif
  for (int i = 0; i < ftcrfont_info->metrics_nrows; i++)
    if (ftcrfont_info->metrics[i])
      xfree (ftcrfont_info->metrics[i]);
  if (ftcrfont_info->metrics)
    xfree (ftcrfont_info->metrics);
  cairo_scaled_font_destroy (ftcrfont_info->cr_scaled_font);
  unblock_input ();
}

static int
ftcrfont_has_char (Lisp_Object font, int c)
{
  if (FONT_ENTITY_P (font))
    return ftfont_has_char (font, c);

  return -1;
}

static unsigned
ftcrfont_encode_char (struct font *font, int c)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  unsigned code = FONT_INVALID_CODE;
  unsigned char utf8[MAX_MULTIBYTE_LENGTH];
  unsigned char *p = utf8;
  cairo_glyph_t stack_glyph;
  cairo_glyph_t *glyphs = &stack_glyph;
  int num_glyphs = 1;

  CHAR_STRING_ADVANCE (c, p);
  if (cairo_scaled_font_text_to_glyphs (ftcrfont_info->cr_scaled_font, 0, 0,
					(char *) utf8, p - utf8,
					&glyphs, &num_glyphs,
					NULL, NULL, NULL)
      == CAIRO_STATUS_SUCCESS)
    {
      if (glyphs != &stack_glyph)
	cairo_glyph_free (glyphs);
      else if (stack_glyph.index)
	code = stack_glyph.index;
    }

  return code;
}

static void
ftcrfont_text_extents (struct font *font,
                       const unsigned *code,
                       int nglyphs,
                       struct font_metrics *metrics)
{
  int width, i;

  block_input ();
  width = ftcrfont_glyph_extents (font, code[0], metrics);
  for (i = 1; i < nglyphs; i++)
    {
      struct font_metrics m;
      int w = ftcrfont_glyph_extents (font, code[i], metrics ? &m : NULL);

      if (metrics)
	{
	  if (width + m.lbearing < metrics->lbearing)
	    metrics->lbearing = width + m.lbearing;
	  if (width + m.rbearing > metrics->rbearing)
	    metrics->rbearing = width + m.rbearing;
	  if (m.ascent > metrics->ascent)
	    metrics->ascent = m.ascent;
	  if (m.descent > metrics->descent)
	    metrics->descent = m.descent;
	}
      width += w;
    }
  unblock_input ();

  if (metrics)
    metrics->width = width;
}

static int
ftcrfont_get_bitmap (struct font *font, unsigned int code,
		     struct font_bitmap *bitmap, int bits_per_pixel)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;

  if (ftcrfont_info->bitmap_position_unit)
    return -1;

  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  int result = ftfont_get_bitmap (font, code, bitmap, bits_per_pixel);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;

  return result;
}

static int
ftcrfont_anchor_point (struct font *font, unsigned int code, int idx,
		       int *x, int *y)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;

  if (ftcrfont_info->bitmap_position_unit)
    return -1;

  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  int result = ftfont_anchor_point (font, code, idx, x, y);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;

  return result;
}

#ifdef HAVE_LIBOTF
static Lisp_Object
ftcrfont_otf_capability (struct font *font)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  Lisp_Object result = ftfont_otf_capability (font);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;

  return result;
}
#endif

#if defined HAVE_M17N_FLT && defined HAVE_LIBOTF
static Lisp_Object
ftcrfont_shape (Lisp_Object lgstring, Lisp_Object direction)
{
  struct font *font = CHECK_FONT_GET_OBJECT (LGSTRING_FONT (lgstring));
  struct font_info *ftcrfont_info = (struct font_info *) font;

  if (ftcrfont_info->bitmap_position_unit)
    return make_fixnum (0);

  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  Lisp_Object result = ftfont_shape (lgstring, direction);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;

  return result;
}
#endif

#if defined HAVE_OTF_GET_VARIATION_GLYPHS || defined HAVE_FT_FACE_GETCHARVARIANTINDEX
static int
ftcrfont_variation_glyphs (struct font *font, int c, unsigned variations[256])
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  int result = ftfont_variation_glyphs (font, c, variations);
  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;

  return result;
}
#endif	/* HAVE_OTF_GET_VARIATION_GLYPHS || HAVE_FT_FACE_GETCHARVARIANTINDEX */

static int
ftcrfont_draw (struct glyph_string *s,
               int from, int to, int x, int y, bool with_background)
{
  struct frame *f = s->f;
  struct face *face = s->face;
  struct font_info *ftcrfont_info = (struct font_info *) s->font;
  cairo_t *cr;
  cairo_glyph_t *glyphs;
  int len = to - from;
  int i;

  block_input ();

  cr = x_begin_cr_clip (f, s->gc);

  if (with_background)
    {
      x_set_cr_source_with_gc_background (f, s->gc);
      cairo_rectangle (cr, x, y - FONT_BASE (face->font),
		       s->width, FONT_HEIGHT (face->font));
      cairo_fill (cr);
    }

  glyphs = alloca (sizeof (cairo_glyph_t) * len);
  for (i = 0; i < len; i++)
    {
      glyphs[i].index = s->char2b[from + i];
      glyphs[i].x = x;
      glyphs[i].y = y;
      x += (s->padding_p ? 1 : ftcrfont_glyph_extents (s->font,
                                                       glyphs[i].index,
                                                       NULL));
    }

  x_set_cr_source_with_gc_foreground (f, s->gc);
  cairo_set_scaled_font (cr, ftcrfont_info->cr_scaled_font);
  cairo_show_glyphs (cr, glyphs, len);

  x_end_cr_clip (f);

  unblock_input ();

  return len;
}

#ifdef HAVE_HARFBUZZ

static Lisp_Object
ftcrhbfont_list (struct frame *f, Lisp_Object spec)
{
  return ftfont_list2 (f, spec, Qftcrhb);
}

static Lisp_Object
ftcrhbfont_match (struct frame *f, Lisp_Object spec)
{
  return ftfont_match2 (f, spec, Qftcrhb);
}

static hb_font_t *
ftcrhbfont_begin_hb_font (struct font *font, double *position_unit)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;
  FT_Face ft_face = cairo_ft_scaled_font_lock_face (scaled_font);

  ftcrfont_info->ft_size = ft_face->size;
  hb_font_t *hb_font = fthbfont_begin_hb_font (font, position_unit);
  if (ftcrfont_info->bitmap_position_unit)
    *position_unit = ftcrfont_info->bitmap_position_unit;

  return hb_font;
}

static void
ftcrhbfont_end_hb_font (struct font *font, hb_font_t *hb_font)
{
  struct font_info *ftcrfont_info = (struct font_info *) font;
  cairo_scaled_font_t *scaled_font = ftcrfont_info->cr_scaled_font;

  cairo_ft_scaled_font_unlock_face (scaled_font);
  ftcrfont_info->ft_size = NULL;
}

#endif	/* HAVE_HARFBUZZ */


static void syms_of_ftcrfont_for_pdumper (void);

struct font_driver const ftcrfont_driver =
  {
  .type = LISPSYM_INITIALLY (Qftcr),
  .get_cache = ftfont_get_cache,
  .list = ftcrfont_list,
  .match = ftcrfont_match,
  .list_family = ftfont_list_family,
  .open = ftcrfont_open,
  .close = ftcrfont_close,
  .has_char = ftcrfont_has_char,
  .encode_char = ftcrfont_encode_char,
  .text_extents = ftcrfont_text_extents,
  .draw = ftcrfont_draw,
  .get_bitmap = ftcrfont_get_bitmap,
  .anchor_point = ftcrfont_anchor_point,
#ifdef HAVE_LIBOTF
  .otf_capability = ftcrfont_otf_capability,
#endif
#if defined HAVE_M17N_FLT && defined HAVE_LIBOTF
  .shape = ftcrfont_shape,
#endif
#if defined HAVE_OTF_GET_VARIATION_GLYPHS || defined HAVE_FT_FACE_GETCHARVARIANTINDEX
  .get_variation_glyphs = ftcrfont_variation_glyphs,
#endif
  .filter_properties = ftfont_filter_properties,
  .combining_capability = ftfont_combining_capability,
  };
#ifdef HAVE_HARFBUZZ
struct font_driver ftcrhbfont_driver;
#endif	/* HAVE_HARFBUZZ */

void
syms_of_ftcrfont (void)
{
  DEFSYM (Qftcr, "ftcr");
#ifdef HAVE_HARFBUZZ
  DEFSYM (Qftcrhb, "ftcrhb");
  Fput (Qftcr, Qfont_driver_superseded_by, Qftcrhb);
#endif	/* HAVE_HARFBUZZ */
  pdumper_do_now_and_after_load (syms_of_ftcrfont_for_pdumper);
}

static void
syms_of_ftcrfont_for_pdumper (void)
{
  register_font_driver (&ftcrfont_driver, NULL);
#ifdef HAVE_HARFBUZZ
  ftcrhbfont_driver = ftcrfont_driver;
  ftcrhbfont_driver.type = Qftcrhb;
  ftcrhbfont_driver.list = ftcrhbfont_list;
  ftcrhbfont_driver.match = ftcrhbfont_match;
  ftcrhbfont_driver.shape = hbfont_shape;
  ftcrhbfont_driver.combining_capability = hbfont_combining_capability;
  ftcrhbfont_driver.begin_hb_font = ftcrhbfont_begin_hb_font;
  ftcrhbfont_driver.end_hb_font = ftcrhbfont_end_hb_font;
  register_font_driver (&ftcrhbfont_driver, NULL);
#endif	/* HAVE_HARFBUZZ */
}