cairo-win32-font.c

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

	 * of the font.
	 */
	status = _cairo_win32_scaled_font_select_unscaled_font (&scaled_font->base, hdc);
	if (GetGlyphOutlineW (hdc, _cairo_scaled_glyph_index (scaled_glyph),
			      GGO_METRICS | GGO_GLYPH_INDEX,
			      &metrics, 0, NULL, &matrix) == GDI_ERROR) {
	  status = _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_init_glyph_metrics:GetGlyphOutlineW");
	  memset (&metrics, 0, sizeof (GLYPHMETRICS));
	}
	_cairo_win32_scaled_font_done_unscaled_font (&scaled_font->base);

	extents.x_bearing = (double)metrics.gmptGlyphOrigin.x / scaled_font->em_square;
	extents.y_bearing = - (double)metrics.gmptGlyphOrigin.y / scaled_font->em_square;
	extents.width = (double)metrics.gmBlackBoxX / scaled_font->em_square;
	extents.height = (double)metrics.gmBlackBoxY / scaled_font->em_square;
	extents.x_advance = (double)metrics.gmCellIncX / scaled_font->em_square;
	extents.y_advance = (double)metrics.gmCellIncY / scaled_font->em_square;
    }

    _cairo_scaled_glyph_set_metrics (scaled_glyph,
				     &scaled_font->base,
				     &extents);

    return CAIRO_STATUS_SUCCESS;
}

/* Not currently used code, but may be useful in the future if we add
 * back the capability to the scaled font backend interface to get the
 * actual device space bbox rather than computing it from the
 * font-space metrics.
 */
#if 0
static cairo_status_t
_cairo_win32_scaled_font_glyph_bbox (void		 *abstract_font,
				     const cairo_glyph_t *glyphs,
				     int                  num_glyphs,
				     cairo_box_t         *bbox)
{
    static const MAT2 matrix = { { 0, 1 }, { 0, 0 }, { 0, 0 }, { 0, 1 } };
    cairo_win32_scaled_font_t *scaled_font = abstract_font;
    int x1 = 0, x2 = 0, y1 = 0, y2 = 0;

    if (num_glyphs > 0) {
	HDC hdc = _get_global_font_dc ();
	GLYPHMETRICS metrics;
	cairo_status_t status;
	int i;

	if (!hdc)
	    return CAIRO_STATUS_NO_MEMORY;

	status = cairo_win32_scaled_font_select_font (&scaled_font->base, hdc);
	if (status)
	    return status;

	for (i = 0; i < num_glyphs; i++) {
	    int x = floor (0.5 + glyphs[i].x);
	    int y = floor (0.5 + glyphs[i].y);

	    GetGlyphOutlineW (hdc, glyphs[i].index, GGO_METRICS | GGO_GLYPH_INDEX,
			     &metrics, 0, NULL, &matrix);

	    if (i == 0 || x1 > x + metrics.gmptGlyphOrigin.x)
		x1 = x + metrics.gmptGlyphOrigin.x;
	    if (i == 0 || y1 > y - metrics.gmptGlyphOrigin.y)
		y1 = y - metrics.gmptGlyphOrigin.y;
	    if (i == 0 || x2 < x + metrics.gmptGlyphOrigin.x + (int)metrics.gmBlackBoxX)
		x2 = x + metrics.gmptGlyphOrigin.x + (int)metrics.gmBlackBoxX;
	    if (i == 0 || y2 < y - metrics.gmptGlyphOrigin.y + (int)metrics.gmBlackBoxY)
		y2 = y - metrics.gmptGlyphOrigin.y + (int)metrics.gmBlackBoxY;
	}

	cairo_win32_scaled_font_done_font (&scaled_font->base);
    }

    bbox->p1.x = _cairo_fixed_from_int (x1);
    bbox->p1.y = _cairo_fixed_from_int (y1);
    bbox->p2.x = _cairo_fixed_from_int (x2);
    bbox->p2.y = _cairo_fixed_from_int (y2);

    return CAIRO_STATUS_SUCCESS;
}
#endif

typedef struct {
    cairo_win32_scaled_font_t *scaled_font;
    HDC hdc;

    cairo_array_t glyphs;
    cairo_array_t dx;

    int start_x;
    int last_x;
    int last_y;
} cairo_glyph_state_t;

static void
_start_glyphs (cairo_glyph_state_t        *state,
	       cairo_win32_scaled_font_t  *scaled_font,
	       HDC                         hdc)
{
    state->hdc = hdc;
    state->scaled_font = scaled_font;

    _cairo_array_init (&state->glyphs, sizeof (WCHAR));
    _cairo_array_init (&state->dx, sizeof (int));
}

static cairo_status_t
_flush_glyphs (cairo_glyph_state_t *state)
{
    cairo_status_t status;
    int dx = 0;
    WCHAR * elements;
    int * dx_elements;

    status = _cairo_array_append (&state->dx, &dx);
    if (status)
	return status;

    elements = _cairo_array_index (&state->glyphs, 0);
    dx_elements = _cairo_array_index (&state->dx, 0);
    if (!ExtTextOutW (state->hdc,
		      state->start_x, state->last_y,
		      ETO_GLYPH_INDEX,
		      NULL,
		      elements,
		      state->glyphs.num_elements,
		      dx_elements)) {
	return _cairo_win32_print_gdi_error ("_flush_glyphs");
    }

    _cairo_array_truncate (&state->glyphs, 0);
    _cairo_array_truncate (&state->dx, 0);

    return CAIRO_STATUS_SUCCESS;
}

static cairo_status_t
_add_glyph (cairo_glyph_state_t *state,
	    unsigned long        index,
	    double               device_x,
	    double               device_y)
{
    cairo_status_t status;
    double user_x = device_x;
    double user_y = device_y;
    WCHAR glyph_index = index;
    int logical_x, logical_y;

    cairo_matrix_transform_point (&state->scaled_font->device_to_logical, &user_x, &user_y);

    logical_x = floor (user_x + 0.5);
    logical_y = floor (user_y + 0.5);

    if (state->glyphs.num_elements > 0) {
	int dx;

	if (logical_y != state->last_y) {
	    status = _flush_glyphs (state);
	    if (status)
		return status;
	    state->start_x = logical_x;
	}

	dx = logical_x - state->last_x;
	status = _cairo_array_append (&state->dx, &dx);
	if (status)
	    return status;
    } else {
	state->start_x = logical_x;
    }

    state->last_x = logical_x;
    state->last_y = logical_y;

    status = _cairo_array_append (&state->glyphs, &glyph_index);
    if (status)
	return status;

    return CAIRO_STATUS_SUCCESS;
}

static void
_finish_glyphs (cairo_glyph_state_t *state)
{
    _flush_glyphs (state);

    _cairo_array_fini (&state->glyphs);
    _cairo_array_fini (&state->dx);
}

static cairo_status_t
_draw_glyphs_on_surface (cairo_win32_surface_t     *surface,
			 cairo_win32_scaled_font_t *scaled_font,
			 COLORREF                   color,
			 int                        x_offset,
			 int                        y_offset,
			 const cairo_glyph_t       *glyphs,
			 int                 	    num_glyphs)
{
    cairo_glyph_state_t state;
    cairo_status_t status = CAIRO_STATUS_SUCCESS;
    int i;

    if (!SaveDC (surface->dc))
	return _cairo_win32_print_gdi_error ("_draw_glyphs_on_surface:SaveDC");

    status = cairo_win32_scaled_font_select_font (&scaled_font->base, surface->dc);
    if (status)
	goto FAIL1;

    SetTextColor (surface->dc, color);
    SetTextAlign (surface->dc, TA_BASELINE | TA_LEFT);
    SetBkMode (surface->dc, TRANSPARENT);

    _start_glyphs (&state, scaled_font, surface->dc);

    for (i = 0; i < num_glyphs; i++) {
	status = _add_glyph (&state, glyphs[i].index,
			     glyphs[i].x - x_offset, glyphs[i].y - y_offset);
	if (status)
	    goto FAIL2;
    }

 FAIL2:
    _finish_glyphs (&state);
    cairo_win32_scaled_font_done_font (&scaled_font->base);
 FAIL1:
    RestoreDC (surface->dc, -1);

    return status;
}

/* Duplicate the green channel of a 4-channel mask in the alpha channel, then
 * invert the whole mask.
 */
static void
_compute_argb32_mask_alpha (cairo_win32_surface_t *mask_surface)
{
    cairo_image_surface_t *image = (cairo_image_surface_t *)mask_surface->image;
    int i, j;

    for (i = 0; i < image->height; i++) {
	uint32_t *p = (uint32_t *) (image->data + i * image->stride);
	for (j = 0; j < image->width; j++) {
	    *p = 0xffffffff ^ (*p | ((*p & 0x0000ff00) << 16));
	    p++;
	}
    }
}

/* Invert a mask
 */
static void
_invert_argb32_mask (cairo_win32_surface_t *mask_surface)
{
    cairo_image_surface_t *image = (cairo_image_surface_t *)mask_surface->image;
    int i, j;

    for (i = 0; i < image->height; i++) {
	uint32_t *p = (uint32_t *) (image->data + i * image->stride);
	for (j = 0; j < image->width; j++) {
	    *p = 0xffffffff ^ *p;
	    p++;
	}
    }
}

/* Compute an alpha-mask from a monochrome RGB24 image
 */
static cairo_surface_t *
_compute_a8_mask (cairo_win32_surface_t *mask_surface)
{
    cairo_image_surface_t *image24 = (cairo_image_surface_t *)mask_surface->image;
    cairo_image_surface_t *image8;
    int i, j;

    image8 = (cairo_image_surface_t *)cairo_image_surface_create (CAIRO_FORMAT_A8,
								  image24->width, image24->height);
    if (image8->base.status)
	return NULL;

    for (i = 0; i < image24->height; i++) {
	uint32_t *p = (uint32_t *) (image24->data + i * image24->stride);
	unsigned char *q = (unsigned char *) (image8->data + i * image8->stride);

	for (j = 0; j < image24->width; j++) {
	    *q = 255 - ((*p & 0x0000ff00) >> 8);
	    p++;
	    q++;
	}
    }

    return &image8->base;
}

static cairo_status_t
_cairo_win32_scaled_font_glyph_init (void		       *abstract_font,
				     cairo_scaled_glyph_t      *scaled_glyph,
				     cairo_scaled_glyph_info_t  info)
{
    cairo_win32_scaled_font_t *scaled_font = abstract_font;
    cairo_status_t status;

    if ((info & CAIRO_SCALED_GLYPH_INFO_METRICS) != 0) {
	status = _cairo_win32_scaled_font_init_glyph_metrics (scaled_font, scaled_glyph);
	if (status)
	    return status;
    }

    if ((info & CAIRO_SCALED_GLYPH_INFO_SURFACE) != 0) {
	ASSERT_NOT_REACHED;
    }

    if ((info & CAIRO_SCALED_GLYPH_INFO_PATH) != 0) {
	status = _cairo_win32_scaled_font_init_glyph_path (scaled_font, scaled_glyph);
	if (status)
	    return status;
    }

    return CAIRO_STATUS_SUCCESS;
}

static cairo_int_status_t
_cairo_win32_scaled_font_show_glyphs (void		       *abstract_font,
				      cairo_operator_t    	op,
				      cairo_pattern_t          *pattern,
				      cairo_surface_t          *generic_surface,
				      int                 	source_x,
				      int                 	source_y,
				      int			dest_x,
				      int			dest_y,
				      unsigned int		width,
				      unsigned int		height,
				      const cairo_glyph_t      *glyphs,
				      int                 	num_glyphs)
{
    cairo_win32_scaled_font_t *scaled_font = abstract_font;
    cairo_win32_surface_t *surface = (cairo_win32_surface_t *)generic_surface;
    cairo_status_t status;

    if (width == 0 || height == 0)
	return CAIRO_STATUS_SUCCESS;

    if (_cairo_surface_is_win32 (generic_surface) &&
	surface->format == CAIRO_FORMAT_RGB24 &&
	op == CAIRO_OPERATOR_OVER &&
	_cairo_pattern_is_opaque_solid (pattern)) {

	cairo_solid_pattern_t *solid_pattern = (cairo_solid_pattern_t *)pattern;

	/* When compositing OVER on a GDI-understood surface, with a
	 * solid opaque color, we can just call ExtTextOut directly.
	 */
	COLORREF new_color;

	new_color = RGB (((int)solid_pattern->color.red_short) >> 8,
			 ((int)solid_pattern->color.green_short) >> 8,
			 ((int)solid_pattern->color.blue_short) >> 8);

	status = _draw_glyphs_on_surface (surface, scaled_font, new_color,
					  0, 0,
					  glyphs, num_glyphs);

	return status;
    } else {
	/* Otherwise, we need to draw using software fallbacks. We create a mask
	 * surface by drawing the the glyphs onto a DIB, black-on-white then
	 * inverting. GDI outputs gamma-corrected images so inverted black-on-white
	 * is very different from white-on-black. We favor the more common
	 * case where the final output is dark-on-light.
	 */
	cairo_win32_surface_t *tmp_surface;
	cairo_surface_t *mask_surface;
	cairo_surface_pattern_t mask;
	RECT r;

	tmp_surface = (cairo_win32_surface_t *)cairo_win32_surface_create_with_dib (CAIRO_FORMAT_ARGB32, width, height);
	if (tmp_surface->base.status)
	    return CAIRO_STATUS_NO_MEMORY;

	r.left = 0;
	r.top = 0;
	r.right = width;
	r.bottom = height;
	FillRect (tmp_surface->dc, &r, GetStockObject (WHITE_BRUSH));

	_draw_glyphs_on_surface (tmp_surface, scaled_font, RGB (0, 0, 0),
				 dest_x, dest_y,
				 glyphs, num_glyphs);