cairo-ft-font.c

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

    if (unscaled == NULL)
	return;

    if (unscaled->from_face) {
	/* See comments in _ft_font_face_destroy about the "zombie" state
	 * for a _ft_font_face.
	 */
	if (unscaled->faces && !unscaled->faces->unscaled)
	    cairo_font_face_destroy (&unscaled->faces->base);
    } else {
	cairo_ft_unscaled_font_map_t *font_map;

	font_map = _cairo_ft_unscaled_font_map_lock ();
	/* All created objects must have been mapped in the font map. */
	assert (font_map != NULL);

	_cairo_hash_table_remove (font_map->hash_table,
				  &unscaled->base.hash_entry);

	_font_map_release_face_lock_held (font_map, unscaled);
	_cairo_ft_unscaled_font_fini (unscaled);

	_cairo_ft_unscaled_font_map_unlock ();
    }
}

static cairo_bool_t
_has_unlocked_face (void *entry)
{
    cairo_ft_unscaled_font_t *unscaled = entry;

    return (unscaled->lock == 0 && unscaled->face);
}

/* Ensures that an unscaled font has a face object. If we exceed
 * MAX_OPEN_FACES, try to close some.
 *
 * This differs from _cairo_ft_scaled_font_lock_face in that it doesn't
 * set the scale on the face, but just returns it at the last scale.
 */
FT_Face
_cairo_ft_unscaled_font_lock_face (cairo_ft_unscaled_font_t *unscaled)
{
    cairo_ft_unscaled_font_map_t *font_map;
    FT_Face face = NULL;

    if (unscaled->face) {
	unscaled->lock++;
	return unscaled->face;
    }

    /* If this unscaled font was created from an FT_Face then we just
     * returned it above. */
    assert (!unscaled->from_face);

    font_map = _cairo_ft_unscaled_font_map_lock ();
    assert (font_map != NULL);

    while (font_map->num_open_faces >= MAX_OPEN_FACES)
    {
	cairo_ft_unscaled_font_t *entry;

	entry = _cairo_hash_table_random_entry (font_map->hash_table,
						_has_unlocked_face);
	if (entry == NULL)
	    break;

	_font_map_release_face_lock_held (font_map, entry);
    }

    if (FT_New_Face (font_map->ft_library,
		     unscaled->filename,
		     unscaled->id,
		     &face) != FT_Err_Ok)
	goto FAIL;

    unscaled->face = face;
    unscaled->lock++;

    font_map->num_open_faces++;

 FAIL:
    _cairo_ft_unscaled_font_map_unlock ();

    return face;
}

/* Unlock unscaled font locked with _cairo_ft_unscaled_font_lock_face
 */
void
_cairo_ft_unscaled_font_unlock_face (cairo_ft_unscaled_font_t *unscaled)
{
    assert (unscaled->lock > 0);

    unscaled->lock--;
}

static void
_compute_transform (cairo_ft_font_transform_t *sf,
		    cairo_matrix_t      *scale)
{
    cairo_matrix_t normalized = *scale;
    double tx, ty;

    /* The font matrix has x and y "scale" components which we extract and
     * use as character scale values. These influence the way freetype
     * chooses hints, as well as selecting different bitmaps in
     * hand-rendered fonts. We also copy the normalized matrix to
     * freetype's transformation.
     */

    _cairo_matrix_compute_scale_factors (&normalized,
					 &sf->x_scale, &sf->y_scale,
					 /* XXX */ 1);

    if (sf->x_scale != 0 && sf->y_scale != 0) {
	cairo_matrix_scale (&normalized, 1.0 / sf->x_scale, 1.0 / sf->y_scale);

	_cairo_matrix_get_affine (&normalized,
				  &sf->shape[0][0], &sf->shape[0][1],
				  &sf->shape[1][0], &sf->shape[1][1],
				  &tx, &ty);
    } else {
	sf->shape[0][0] = sf->shape[1][1] = 1.0;
	sf->shape[0][1] = sf->shape[1][0] = 0.0;
    }
}

/* Temporarily scales an unscaled font to the give scale. We catch
 * scaling to the same size, since changing a FT_Face is expensive.
 */
static void
_cairo_ft_unscaled_font_set_scale (cairo_ft_unscaled_font_t *unscaled,
				   cairo_matrix_t	      *scale)
{
    cairo_ft_font_transform_t sf;
    FT_Matrix mat;
    FT_UInt pixel_width, pixel_height;
    FT_Error error;

    assert (unscaled->face != NULL);

    if (unscaled->have_scale &&
	scale->xx == unscaled->current_scale.xx &&
	scale->yx == unscaled->current_scale.yx &&
	scale->xy == unscaled->current_scale.xy &&
	scale->yy == unscaled->current_scale.yy)
	return;

    unscaled->have_scale = TRUE;
    unscaled->current_scale = *scale;

    _compute_transform (&sf, scale);

    unscaled->x_scale = sf.x_scale;
    unscaled->y_scale = sf.y_scale;

    mat.xx = DOUBLE_TO_16_16(sf.shape[0][0]);
    mat.yx = - DOUBLE_TO_16_16(sf.shape[0][1]);
    mat.xy = - DOUBLE_TO_16_16(sf.shape[1][0]);
    mat.yy = DOUBLE_TO_16_16(sf.shape[1][1]);

    unscaled->have_shape = (mat.xx != 0x10000 ||
			    mat.yx != 0x00000 ||
			    mat.xy != 0x00000 ||
			    mat.yy != 0x10000);

    cairo_matrix_init (&unscaled->current_shape,
		       sf.shape[0][0], sf.shape[0][1],
		       sf.shape[1][0], sf.shape[1][1],
		       0.0, 0.0);

    FT_Set_Transform(unscaled->face, &mat, NULL);

    if ((unscaled->face->face_flags & FT_FACE_FLAG_SCALABLE) != 0) {
	pixel_width = sf.x_scale;
	pixel_height = sf.y_scale;
	error = FT_Set_Char_Size (unscaled->face,
				  sf.x_scale * 64.0,
				  sf.y_scale * 64.0,
				  0, 0);
    } else {
	double min_distance = DBL_MAX;
	int i;
	int best_i = 0;

	pixel_width = pixel_height = 0;

	for (i = 0; i < unscaled->face->num_fixed_sizes; i++) {
#if HAVE_FT_BITMAP_SIZE_Y_PPEM
	    double size = unscaled->face->available_sizes[i].y_ppem / 64.;
#else
	    double size = unscaled->face->available_sizes[i].height;
#endif
	    double distance = fabs (size - sf.y_scale);

	    if (distance <= min_distance) {
		min_distance = distance;
		best_i = i;
	    }
	}
#if HAVE_FT_BITMAP_SIZE_Y_PPEM
	error = FT_Set_Char_Size (unscaled->face,
				  unscaled->face->available_sizes[best_i].x_ppem,
				  unscaled->face->available_sizes[best_i].y_ppem,
				  0, 0);
	if (error)
#endif
	    error = FT_Set_Pixel_Sizes (unscaled->face,
					unscaled->face->available_sizes[best_i].width,
					unscaled->face->available_sizes[best_i].height);
    }

    assert (error == 0);
}

/* Empirically-derived subpixel filtering values thanks to Keith
 * Packard and libXft. */
static const int    filters[3][3] = {
    /* red */
#if 0
    {    65538*4/7,65538*2/7,65538*1/7 },
    /* green */
    {    65536*1/4, 65536*2/4, 65537*1/4 },
    /* blue */
    {    65538*1/7,65538*2/7,65538*4/7 },
#endif
    {    65538*9/13,65538*3/13,65538*1/13 },
    /* green */
    {    65538*1/6, 65538*4/6, 65538*1/6 },
    /* blue */
    {    65538*1/13,65538*3/13,65538*9/13 },
};

/* Fills in val->image with an image surface created from @bitmap
 */
static cairo_status_t
_get_bitmap_surface (FT_Bitmap		     *bitmap,
		     cairo_bool_t	      own_buffer,
		     cairo_font_options_t    *font_options,
		     cairo_image_surface_t  **surface)
{
    int width, height, stride;
    unsigned char *data;
    int format = CAIRO_FORMAT_A8;
    cairo_bool_t subpixel = FALSE;

    width = bitmap->width;
    height = bitmap->rows;

    switch (bitmap->pixel_mode) {
    case FT_PIXEL_MODE_MONO:
	stride = (((width + 31) & ~31) >> 3);
	if (own_buffer) {
	    data = bitmap->buffer;
	    assert (stride == bitmap->pitch);
	} else {
	    data = malloc (stride * height);
	    if (!data)
		return CAIRO_STATUS_NO_MEMORY;

	    if (stride == bitmap->pitch) {
		memcpy (data, bitmap->buffer, stride * height);
	    } else {
		int i;
		unsigned char *source, *dest;

		source = bitmap->buffer;
		dest = data;
		for (i = height; i; i--) {
		    memcpy (dest, source, bitmap->pitch);
		    memset (dest + bitmap->pitch, '\0', stride - bitmap->pitch);

		    source += bitmap->pitch;
		    dest += stride;
		}
	    }
	}

#ifndef WORDS_BIGENDIAN
	{
	    unsigned char   *d = data;
	    int		count = stride * height;

	    while (count--) {
		*d = CAIRO_BITSWAP8 (*d);
		d++;
	    }
	}
#endif
	format = CAIRO_FORMAT_A1;
	break;

    case FT_PIXEL_MODE_LCD:
    case FT_PIXEL_MODE_LCD_V:
    case FT_PIXEL_MODE_GRAY:
	switch (font_options->antialias) {
	case CAIRO_ANTIALIAS_DEFAULT:
	case CAIRO_ANTIALIAS_GRAY:
	case CAIRO_ANTIALIAS_NONE:
	default:
	    stride = bitmap->pitch;
	    if (own_buffer) {
		data = bitmap->buffer;
	    } else {
		data = malloc (stride * height);
		if (!data)
		    return CAIRO_STATUS_NO_MEMORY;
		memcpy (data, bitmap->buffer, stride * height);
	    }
	    format = CAIRO_FORMAT_A8;
	    break;
	case CAIRO_ANTIALIAS_SUBPIXEL: {
	    int		    x, y;
	    unsigned char   *in_line, *out_line, *in;
	    unsigned int    *out;
	    unsigned int    red, green, blue;
	    int		    rf, gf, bf;
	    int		    s;
	    int		    o, os;
	    unsigned char   *data_rgba;
	    unsigned int    width_rgba, stride_rgba;
	    int		    vmul = 1;
	    int		    hmul = 1;

	    switch (font_options->subpixel_order) {
	    case CAIRO_SUBPIXEL_ORDER_DEFAULT:
	    case CAIRO_SUBPIXEL_ORDER_RGB:
	    case CAIRO_SUBPIXEL_ORDER_BGR:
	    default:
		width /= 3;
		hmul = 3;
		break;
	    case CAIRO_SUBPIXEL_ORDER_VRGB:
	    case CAIRO_SUBPIXEL_ORDER_VBGR:
		vmul = 3;
		height /= 3;
		break;
	    }
	    /*
	     * Filter the glyph to soften the color fringes
	     */
	    width_rgba = width;
	    stride = bitmap->pitch;
	    stride_rgba = (width_rgba * 4 + 3) & ~3;
	    data_rgba = calloc (1, stride_rgba * height);

	    os = 1;
	    switch (font_options->subpixel_order) {
	    case CAIRO_SUBPIXEL_ORDER_VRGB:
		os = stride;
	    case CAIRO_SUBPIXEL_ORDER_DEFAULT:
	    case CAIRO_SUBPIXEL_ORDER_RGB:
	    default:
		rf = 0;
		gf = 1;
		bf = 2;
		break;
	    case CAIRO_SUBPIXEL_ORDER_VBGR:
		os = stride;
	    case CAIRO_SUBPIXEL_ORDER_BGR:
		bf = 0;
		gf = 1;
		rf = 2;
		break;
	    }
	    in_line = bitmap->buffer;
	    out_line = data_rgba;
	    for (y = 0; y < height; y++)
	    {
		in = in_line;
		out = (unsigned int *) out_line;
		in_line += stride * vmul;
		out_line += stride_rgba;
		for (x = 0; x < width * hmul; x += hmul)
		{
		    red = green = blue = 0;
		    o = 0;
		    for (s = 0; s < 3; s++)
		    {
			red += filters[rf][s]*in[x+o];
			green += filters[gf][s]*in[x+o];
			blue += filters[bf][s]*in[x+o];
			o += os;
		    }
		    red = red / 65536;
		    green = green / 65536;
		    blue = blue / 65536;
		    *out++ = (green << 24) | (red << 16) | (green << 8) | blue;
		}
	    }

	    /* Images here are stored in native format. The
	     * backend must convert to its own format as needed
	     */

	    if (own_buffer)
		free (bitmap->buffer);
	    data = data_rgba;
	    stride = stride_rgba;
	    format = CAIRO_FORMAT_ARGB32;
	    subpixel = TRUE;
	    break;
	}
	}
	break;
    case FT_PIXEL_MODE_GRAY2:
    case FT_PIXEL_MODE_GRAY4:
	/* These could be triggered by very rare types of TrueType fonts */
    default:
	return CAIRO_STATUS_NO_MEMORY;
    }

    *surface = (cairo_image_surface_t *)
	cairo_image_surface_create_for_data (data,
					     format,
					     width, height, stride);
    if ((*surface)->base.status) {
	free (data);
	return CAIRO_STATUS_NO_MEMORY;
    }

    if (subpixel)
	pixman_image_set_component_alpha ((*surface)->pixman_image, TRUE);

    _cairo_image_surface_assume_ownership_of_data ((*surface));

    return CAIRO_STATUS_SUCCESS;
}

/* Converts an outline FT_GlyphSlot into an image
 *
 * This could go through _render_glyph_bitmap as well, letting
 * FreeType convert the outline to a bitmap, but doing it ourselves
 * has two minor advantages: first, we save a copy of the bitmap
 * buffer: we can directly use the buffer that FreeType renders
 * into.
 *
 * Second, it may help when we add support for subpixel
 * rendering: the Xft code does it this way. (Keith thinks that
 * it may also be possible to get the subpixel rendering with
 * FT_Render_Glyph: something worth looking into in more detail
 * when we add subpixel support. If so, we may want to eliminate
 * this version of the code path entirely.
 */
static cairo_status_t
_render_glyph_outline (FT_Face                    face,
		       cairo_font_options_t	 *font_options,
		       cairo_image_surface_t	**surface)
{
    FT_GlyphSlot glyphslot = face->glyph;
    FT_Outline *outline = &glyphslot->outline;
    FT_Bitmap bitmap;
    FT_BBox cbox;
    FT_Matrix matrix;
    int hmul = 1;
    int vmul = 1;
    unsigned int width, height, stride;
    cairo_bool_t subpixel = FALSE;
    cairo_status_t status;

    FT_Outline_Get_CBox (outline, &cbox);

    cbox.xMin &= -64;
    cbox.yMin &= -64;
    cbox.xMax = (cbox.xMax + 63) & -64;