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

    cbox.yMax = (cbox.yMax + 63) & -64;

    width = (unsigned int) ((cbox.xMax - cbox.xMin) >> 6);
    height = (unsigned int) ((cbox.yMax - cbox.yMin) >> 6);
    stride = (width * hmul + 3) & ~3;

    if (width * height == 0) {
	cairo_format_t format;
	/* Looks like fb handles zero-sized images just fine */
	switch (font_options->antialias) {
	case CAIRO_ANTIALIAS_NONE:
	    format = CAIRO_FORMAT_A1;
	    break;
	case CAIRO_ANTIALIAS_SUBPIXEL:
	    format= CAIRO_FORMAT_ARGB32;
	    break;
	case CAIRO_ANTIALIAS_DEFAULT:
	case CAIRO_ANTIALIAS_GRAY:
	default:
	    format = CAIRO_FORMAT_A8;
	    break;
	}

	(*surface) = (cairo_image_surface_t *)
	    cairo_image_surface_create_for_data (NULL, format, 0, 0, 0);
	if ((*surface)->base.status)
	    return CAIRO_STATUS_NO_MEMORY;
    } else  {

	matrix.xx = matrix.yy = 0x10000L;
	matrix.xy = matrix.yx = 0;

	switch (font_options->antialias) {
	case CAIRO_ANTIALIAS_NONE:
	    bitmap.pixel_mode = FT_PIXEL_MODE_MONO;
	    bitmap.num_grays  = 1;
	    stride = ((width + 31) & -32) >> 3;
	    break;
	case CAIRO_ANTIALIAS_DEFAULT:
	case CAIRO_ANTIALIAS_GRAY:
	    bitmap.pixel_mode = FT_PIXEL_MODE_GRAY;
	    bitmap.num_grays  = 256;
	    stride = (width + 3) & -4;
	    break;
	case CAIRO_ANTIALIAS_SUBPIXEL:
	    switch (font_options->subpixel_order) {
	    case CAIRO_SUBPIXEL_ORDER_RGB:
	    case CAIRO_SUBPIXEL_ORDER_BGR:
	    default:
		matrix.xx *= 3;
		hmul = 3;
		subpixel = TRUE;
		break;
	    case CAIRO_SUBPIXEL_ORDER_VRGB:
	    case CAIRO_SUBPIXEL_ORDER_VBGR:
		matrix.yy *= 3;
		vmul = 3;
		subpixel = TRUE;
		break;
	    }
	    FT_Outline_Transform (outline, &matrix);

	    bitmap.pixel_mode = FT_PIXEL_MODE_GRAY;
	    bitmap.num_grays  = 256;
	    stride = (width * hmul + 3) & -4;
	}

	bitmap.pitch = stride;
	bitmap.width = width * hmul;
	bitmap.rows = height * vmul;
	bitmap.buffer = calloc (1, stride * bitmap.rows);

	if (bitmap.buffer == NULL) {
	    return CAIRO_STATUS_NO_MEMORY;
	}

	FT_Outline_Translate (outline, -cbox.xMin*hmul, -cbox.yMin*vmul);

	if (FT_Outline_Get_Bitmap (glyphslot->library, outline, &bitmap) != 0) {
	    free (bitmap.buffer);
	    return CAIRO_STATUS_NO_MEMORY;
	}

	status = _get_bitmap_surface (&bitmap, TRUE, font_options, surface);
	if (status)
	    return status;
    }

    /*
     * Note: the font's coordinate system is upside down from ours, so the
     * Y coordinate of the control box needs to be negated.
     */
    cairo_surface_set_device_offset (&(*surface)->base,
				     floor ((double) cbox.xMin / 64.0),
				     floor (-(double) cbox.yMax / 64.0));

    return CAIRO_STATUS_SUCCESS;
}

/* Converts a bitmap (or other) FT_GlyphSlot into an image */
static cairo_status_t
_render_glyph_bitmap (FT_Face		      face,
		      cairo_font_options_t   *font_options,
		      cairo_image_surface_t **surface)
{
    FT_GlyphSlot glyphslot = face->glyph;
    cairo_status_t status = CAIRO_STATUS_SUCCESS;
    FT_Error error;

    /* According to the FreeType docs, glyphslot->format could be
     * something other than FT_GLYPH_FORMAT_OUTLINE or
     * FT_GLYPH_FORMAT_BITMAP. Calling FT_Render_Glyph gives FreeType
     * the opportunity to convert such to
     * bitmap. FT_GLYPH_FORMAT_COMPOSITE will not be encountered since
     * we avoid the FT_LOAD_NO_RECURSE flag.
     */
    error = FT_Render_Glyph (glyphslot, FT_RENDER_MODE_NORMAL);
    if (error)
	return CAIRO_STATUS_NO_MEMORY;

    status = _get_bitmap_surface (&glyphslot->bitmap, FALSE, font_options, surface);
    if (status)
	return status;

    /*
     * Note: the font's coordinate system is upside down from ours, so the
     * Y coordinate of the control box needs to be negated.
     */
    cairo_surface_set_device_offset (&(*surface)->base,
				     glyphslot->bitmap_left,
				     -glyphslot->bitmap_top);

    return status;
}

static cairo_status_t
_transform_glyph_bitmap (cairo_matrix_t         * shape,
			 cairo_image_surface_t ** surface)
{
    cairo_matrix_t original_to_transformed;
    cairo_matrix_t transformed_to_original;
    cairo_image_surface_t *old_image;
    cairo_surface_t *image;
    double x[4], y[4];
    double origin_x, origin_y;
    int origin_width, origin_height;
    int i;
    int x_min, y_min, x_max, y_max;
    int width, height;
    cairo_status_t status;
    cairo_surface_pattern_t pattern;

    /* We want to compute a transform that takes the origin
     * (device_x_offset, device_y_offset) to 0,0, then applies
     * the "shape" portion of the font transform
     */
    original_to_transformed = *shape;
    
    cairo_surface_get_device_offset (&(*surface)->base, &origin_x, &origin_y);
    origin_width = cairo_image_surface_get_width (&(*surface)->base);
    origin_height = cairo_image_surface_get_height (&(*surface)->base);

    cairo_matrix_translate (&original_to_transformed,
			    origin_x, origin_y);

    /* Find the bounding box of the original bitmap under that
     * transform
     */
    x[0] = 0;            y[0] = 0;
    x[1] = origin_width; y[1] = 0;
    x[2] = origin_width; y[2] = origin_height;
    x[3] = 0;            y[3] = origin_height;

    for (i = 0; i < 4; i++)
      cairo_matrix_transform_point (&original_to_transformed,
				    &x[i], &y[i]);

    x_min = floor (x[0]);   y_min = floor (y[0]);
    x_max =  ceil (x[0]);   y_max =  ceil (y[0]);

    for (i = 1; i < 4; i++) {
	if (x[i] < x_min)
	    x_min = floor (x[i]);
	if (x[i] > x_max)
	    x_max = ceil (x[i]);
	if (y[i] < y_min)
	    y_min = floor (y[i]);
	if (y[i] > y_max)
	    y_max = ceil (y[i]);
    }

    /* Adjust the transform so that the bounding box starts at 0,0 ...
     * this gives our final transform from original bitmap to transformed
     * bitmap.
     */
    original_to_transformed.x0 -= x_min;
    original_to_transformed.y0 -= y_min;

    /* Create the transformed bitmap
     */
    width = x_max - x_min;
    height = y_max - y_min;

    transformed_to_original = original_to_transformed;
    status = cairo_matrix_invert (&transformed_to_original);
    if (status)
	return status;

    /* We need to pad out the width to 32-bit intervals for cairo-xlib-surface.c */
    width = (width + 3) & ~3;
    image = cairo_image_surface_create (CAIRO_FORMAT_A8, width, height);
    if (image->status)
	return CAIRO_STATUS_NO_MEMORY;

    /* Initialize it to empty
     */
    _cairo_surface_fill_rectangle (image, CAIRO_OPERATOR_CLEAR,
				   CAIRO_COLOR_TRANSPARENT,
				   0, 0,
				   width, height);

    /* Draw the original bitmap transformed into the new bitmap
     */
    _cairo_pattern_init_for_surface (&pattern, &(*surface)->base);
    cairo_pattern_set_matrix (&pattern.base, &transformed_to_original);

    _cairo_surface_composite (CAIRO_OPERATOR_OVER,
			      &pattern.base, NULL, image,
			      0, 0, 0, 0, 0, 0,
			      width,
			      height);

    _cairo_pattern_fini (&pattern.base);

    /* Now update the cache entry for the new bitmap, recomputing
     * the origin based on the final transform.
     */
    origin_x = - origin_x;
    origin_y = - origin_y;
    cairo_matrix_transform_point (&original_to_transformed,
				  &origin_x, &origin_y);

    old_image = (*surface);
    (*surface) = (cairo_image_surface_t *)image;
    cairo_surface_destroy (&old_image->base);

    cairo_surface_set_device_offset (&(*surface)->base,
				     - floor (origin_x + 0.5),
				     - floor (origin_y + 0.5));
    return status;
}

static const cairo_unscaled_font_backend_t cairo_ft_unscaled_font_backend = {
    _cairo_ft_unscaled_font_destroy,
#if 0
    _cairo_ft_unscaled_font_create_glyph
#endif
};

/* cairo_ft_scaled_font_t */

typedef struct _cairo_ft_scaled_font {
    cairo_scaled_font_t base;
    cairo_ft_unscaled_font_t *unscaled;
    cairo_ft_options_t ft_options;
} cairo_ft_scaled_font_t;

const cairo_scaled_font_backend_t cairo_ft_scaled_font_backend;

/* The load flags passed to FT_Load_Glyph control aspects like hinting and
 * antialiasing. Here we compute them from the fields of a FcPattern.
 */
static cairo_ft_options_t
_get_pattern_ft_options (FcPattern *pattern)
{
    FcBool antialias, vertical_layout, hinting, autohint, bitmap, embolden;
    cairo_ft_options_t ft_options;
    int rgba;
#ifdef FC_HINT_STYLE
    int hintstyle;
#endif

    _cairo_font_options_init_default (&ft_options.base);
    ft_options.load_flags = FT_LOAD_DEFAULT;
    ft_options.extra_flags = 0;

#ifndef FC_EMBEDDED_BITMAP
#define FC_EMBEDDED_BITMAP "embeddedbitmap"
#endif

    /* Check whether to force use of embedded bitmaps */
    if (FcPatternGetBool (pattern,
			  FC_EMBEDDED_BITMAP, 0, &bitmap) != FcResultMatch)
	bitmap = FcFalse;

    /* disable antialiasing if requested */
    if (FcPatternGetBool (pattern,
			  FC_ANTIALIAS, 0, &antialias) != FcResultMatch)
	antialias = FcTrue;
    
    if (antialias) {
	if (!bitmap)
	    ft_options.load_flags |= FT_LOAD_NO_BITMAP;
	
	/* disable hinting if requested */
	if (FcPatternGetBool (pattern,
			      FC_HINTING, 0, &hinting) != FcResultMatch)
	    hinting = FcTrue;

	if (FcPatternGetInteger (pattern,
				 FC_RGBA, 0, &rgba) != FcResultMatch)
	    rgba = FC_RGBA_UNKNOWN;

	switch (rgba) {
	case FC_RGBA_RGB:
	    ft_options.base.subpixel_order = CAIRO_SUBPIXEL_ORDER_RGB;
	    break;
	case FC_RGBA_BGR:
	    ft_options.base.subpixel_order = CAIRO_SUBPIXEL_ORDER_BGR;
	    break;
	case FC_RGBA_VRGB:
	    ft_options.base.subpixel_order = CAIRO_SUBPIXEL_ORDER_VRGB;
	    break;
	case FC_RGBA_VBGR:
	    ft_options.base.subpixel_order = CAIRO_SUBPIXEL_ORDER_VBGR;
	    break;
	case FC_RGBA_UNKNOWN:
	case FC_RGBA_NONE:
	default:
	    break;
	}

	if (ft_options.base.subpixel_order != CAIRO_SUBPIXEL_ORDER_DEFAULT)
	    ft_options.base.antialias = CAIRO_ANTIALIAS_SUBPIXEL;

#ifdef FC_HINT_STYLE    
	if (FcPatternGetInteger (pattern, 
				 FC_HINT_STYLE, 0, &hintstyle) != FcResultMatch)
	    hintstyle = FC_HINT_FULL;

	if (!hinting)
	    hintstyle = FC_HINT_NONE;

	switch (hintstyle) {
	case FC_HINT_NONE:
	    ft_options.base.hint_style = CAIRO_HINT_STYLE_NONE;	
	    break;
	case FC_HINT_SLIGHT:
	    ft_options.base.hint_style = CAIRO_HINT_STYLE_SLIGHT;
	    break;
	case FC_HINT_MEDIUM:
	default:
	    ft_options.base.hint_style = CAIRO_HINT_STYLE_MEDIUM;
	    break;
	case FC_HINT_FULL:
	    ft_options.base.hint_style = CAIRO_HINT_STYLE_FULL;
	    break;
	}
#else /* !FC_HINT_STYLE */
	if (!hinting) {
	    ft_options.base.hint_style = CAIRO_HINT_STYLE_NONE;
	}
#endif /* FC_FHINT_STYLE */
    } else {
	ft_options.base.antialias = CAIRO_ANTIALIAS_NONE;
    }

    /* force autohinting if requested */
    if (FcPatternGetBool (pattern,
			  FC_AUTOHINT, 0, &autohint) != FcResultMatch)
	autohint = FcFalse;

    if (autohint)
	ft_options.load_flags |= FT_LOAD_FORCE_AUTOHINT;

    if (FcPatternGetBool (pattern,
			  FC_VERTICAL_LAYOUT, 0, &vertical_layout) != FcResultMatch)
	vertical_layout = FcFalse;

    if (vertical_layout)
	ft_options.load_flags |= FT_LOAD_VERTICAL_LAYOUT;
    
#ifndef FC_EMBOLDEN
#define FC_EMBOLDEN "embolden"
#endif
    if (FcPatternGetBool (pattern,
			  FC_EMBOLDEN, 0, &embolden) != FcResultMatch)
	embolden = FcFalse;
    
    if (embolden)
	ft_options.extra_flags |= CAIRO_FT_OPTIONS_EMBOLDEN;

    return ft_options;
}

static void
_cairo_ft_options_merge (cairo_ft_options_t *options,
			 cairo_ft_options_t *other)
{
    int load_flags = other->load_flags;
    int load_target = FT_LOAD_TARGET_NORMAL;

    /* clear load target mode */
    load_flags &= ~(FT_LOAD_TARGET_(FT_LOAD_TARGET_MODE(other->load_flags)));
    
    if (load_flags & FT_LOAD_NO_HINTING)
	other->base.hint_style = CAIRO_HINT_STYLE_NONE;

    if (other->base.antialias == CAIRO_ANTIALIAS_NONE ||
	options->base.antialias == CAIRO_ANTIALIAS_NONE) {
	options->base.antialias = CAIRO_ANTIALIAS_NONE;
	options->base.subpixel_order = CAIRO_SUBPIXEL_ORDER_DEFAULT;
    }

    if (other->base.antialias == CAIRO_ANTIALIAS_SUBPIXEL &&
	(options->base.antialias == CAIRO_ANTIALIAS_DEFAULT || 
	 options->base.antialias == CAIRO_ANTIALIAS_GRAY)) {
	options->base.antialias = CAIRO_ANTIALIAS_SUBPIXEL;
	options->base.subpixel_order = other->base.subpixel_order;
    }

    if (options->base.hint_style == CAIRO_HINT_STYLE_DEFAULT)
	options->base.hint_style = other->base.hint_style;

    if (other->base.hint_style == CAIRO_HINT_STYLE_NONE)
	options->base.hint_style = CAIRO_HINT_STYLE_NONE;

    if (options->base.antialias == CAIRO_ANTIALIAS_NONE) {
	if (options->base.hint_style == CAIRO_HINT_STYLE_NONE)
	    load_flags |= FT_LOAD_NO_HINTING;
	else
	    load_target = FT_LOAD_TARGET_MONO;
	load_flags |= FT_LOAD_MONOCHROME;
    } else {
	switch (options->base.hint_style) {
	case CAIRO_HINT_STYLE_NONE:
	    load_flags |= FT_LOAD_NO_HINTING;
	    break;
	case CAIRO_HINT_STYLE_SLIGHT:
	    load_target = FT_LOAD_TARGET_LIGHT;
	    break;
	case CAIRO_HINT_STYLE_MEDIUM:
	    break;
	case CAIRO_HINT_STYLE_FULL:
	case CAIRO_HINT_STYLE_DEFAULT:
	    if (options->base.antialias == CAIRO_ANTIALIAS_SUBPIXEL) {
		switch (options->base.subpixel_order) {
		case CAIRO_SUBPIXEL_ORDER_DEFAULT:
		case CAIRO_SUBPIXEL_ORDER_RGB:
		case CAIRO_SUBPIXEL_ORDER_BGR:
		    load_target |= FT_LOAD_TARGET_LCD;
		    break;
		case CAIRO_SUBPIXEL_ORDER_VRGB:
		case CAIRO_SUBPIXEL_ORDER_VBGR:
		    load_target |= FT_LOAD_TARGET_LCD_V;
		break;
		}
	    }
	    break;
	}
    }

    options->load_flags = load_flags | load_target;
    options->extra_flags = other->extra_flags;
}