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

	if (!GetOutlineTextMetrics (hdc, otm_size, otm)) {
	    _cairo_win32_print_gdi_error ("_win32_scaled_font_get_unscaled_hfont:GetOutlineTextMetrics");
	    free (otm);
	    return NULL;
	}

	scaled_font->em_square = otm->otmEMSquare;
	free (otm);

	logfont = scaled_font->logfont;
	logfont.lfHeight = -scaled_font->em_square;
	logfont.lfWidth = 0;
	logfont.lfEscapement = 0;
	logfont.lfOrientation = 0;
	logfont.lfQuality = scaled_font->quality;

	scaled_font->unscaled_hfont = CreateFontIndirectW (&logfont);
	if (!scaled_font->unscaled_hfont) {
	    _cairo_win32_print_gdi_error ("_win32_scaled_font_get_unscaled_hfont:CreateIndirect");
	    return NULL;
	}
    }

    return scaled_font->unscaled_hfont;
}

static cairo_status_t
_cairo_win32_scaled_font_select_unscaled_font (cairo_scaled_font_t *scaled_font,
					       HDC                  hdc)
{
    cairo_status_t status;
    HFONT hfont;
    HFONT old_hfont = NULL;

    hfont = _win32_scaled_font_get_unscaled_hfont ((cairo_win32_scaled_font_t *)scaled_font, hdc);
    if (!hfont)
	return CAIRO_STATUS_NO_MEMORY;

    old_hfont = SelectObject (hdc, hfont);
    if (!old_hfont)
	return _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_select_unscaled_font");

    status = _win32_scaled_font_set_identity_transform (hdc);
    if (status) {
	SelectObject (hdc, old_hfont);
	return status;
    }

    SetMapMode (hdc, MM_TEXT);

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_win32_scaled_font_done_unscaled_font (cairo_scaled_font_t *scaled_font)
{
}

/* implement the font backend interface */

static cairo_status_t
_cairo_win32_scaled_font_create_toy (cairo_toy_font_face_t *toy_face,
				     const cairo_matrix_t        *font_matrix,
				     const cairo_matrix_t        *ctm,
				     const cairo_font_options_t  *options,
				     cairo_scaled_font_t        **scaled_font_out)
{
    LOGFONTW logfont;
    cairo_scaled_font_t *scaled_font;
    uint16_t *face_name;
    int face_name_len;
    cairo_status_t status;

    status = _cairo_utf8_to_utf16 (toy_face->family, -1,
				   &face_name, &face_name_len);
    if (status)
	return status;

    if (face_name_len > LF_FACESIZE - 1) {
	free (face_name);
	return CAIRO_STATUS_INVALID_STRING;
    }

    memcpy (logfont.lfFaceName, face_name, sizeof (uint16_t) * (face_name_len + 1));
    free (face_name);

    logfont.lfHeight = 0;	/* filled in later */
    logfont.lfWidth = 0;	/* filled in later */
    logfont.lfEscapement = 0;	/* filled in later */
    logfont.lfOrientation = 0;	/* filled in later */

    switch (toy_face->weight) {
    case CAIRO_FONT_WEIGHT_NORMAL:
    default:
	logfont.lfWeight = FW_NORMAL;
	break;
    case CAIRO_FONT_WEIGHT_BOLD:
	logfont.lfWeight = FW_BOLD;
	break;
    }

    switch (toy_face->slant) {
    case CAIRO_FONT_SLANT_NORMAL:
    default:
	logfont.lfItalic = FALSE;
	break;
    case CAIRO_FONT_SLANT_ITALIC:
    case CAIRO_FONT_SLANT_OBLIQUE:
	logfont.lfItalic = TRUE;
	break;
    }

    logfont.lfUnderline = FALSE;
    logfont.lfStrikeOut = FALSE;
    /* The docs for LOGFONT discourage using this, since the
     * interpretation is locale-specific, but it's not clear what
     * would be a better alternative.
     */
    logfont.lfCharSet = DEFAULT_CHARSET;
    logfont.lfOutPrecision = OUT_DEFAULT_PRECIS;
    logfont.lfClipPrecision = CLIP_DEFAULT_PRECIS;
    logfont.lfQuality = DEFAULT_QUALITY; /* filled in later */
    logfont.lfPitchAndFamily = DEFAULT_PITCH | FF_DONTCARE;

    if (!logfont.lfFaceName)
	return CAIRO_STATUS_NO_MEMORY;

    scaled_font = _win32_scaled_font_create (&logfont, NULL, &toy_face->base,
					     font_matrix, ctm, options);
    if (!scaled_font)
	return CAIRO_STATUS_NO_MEMORY;

    *scaled_font_out = scaled_font;

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_win32_scaled_font_fini (void *abstract_font)
{
    cairo_win32_scaled_font_t *scaled_font = abstract_font;

    if (scaled_font == NULL)
	return;

    if (scaled_font->scaled_hfont && scaled_font->delete_scaled_hfont)
	DeleteObject (scaled_font->scaled_hfont);

    if (scaled_font->unscaled_hfont)
	DeleteObject (scaled_font->unscaled_hfont);
}

static cairo_int_status_t
_cairo_win32_scaled_font_text_to_glyphs (void		*abstract_font,
					 double		x,
					 double		y,
					 const char	*utf8,
					 cairo_glyph_t **glyphs,
					 int		*num_glyphs)
{
    cairo_win32_scaled_font_t *scaled_font = abstract_font;
    uint16_t *utf16;
    int n16;
    GCP_RESULTSW gcp_results;
    unsigned int buffer_size, i;
    WCHAR *glyph_indices = NULL;
    int *dx = NULL;
    cairo_status_t status = CAIRO_STATUS_SUCCESS;
    double x_pos, y_pos;
    double x_incr, y_incr;
    HDC hdc = NULL;

    /* Compute a vector in user space along the baseline of length one logical space unit */
    x_incr = 1;
    y_incr = 0;
    cairo_matrix_transform_distance (&scaled_font->base.font_matrix, &x_incr, &y_incr);
    x_incr /= scaled_font->logical_scale;
    y_incr /= scaled_font->logical_scale;

    status = _cairo_utf8_to_utf16 (utf8, -1, &utf16, &n16);
    if (status)
	return status;

    gcp_results.lStructSize = sizeof (GCP_RESULTS);
    gcp_results.lpOutString = NULL;
    gcp_results.lpOrder = NULL;
    gcp_results.lpCaretPos = NULL;
    gcp_results.lpClass = NULL;

    buffer_size = MAX (n16 * 1.2, 16);		/* Initially guess number of chars plus a few */
    if (buffer_size > INT_MAX) {
	status = CAIRO_STATUS_NO_MEMORY;
	goto FAIL1;
    }

    hdc = _get_global_font_dc ();
    if (!hdc) {
	status = CAIRO_STATUS_NO_MEMORY;
	goto FAIL1;
    }

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

    while (TRUE) {
	if (glyph_indices) {
	    free (glyph_indices);
	    glyph_indices = NULL;
	}
	if (dx) {
	    free (dx);
	    dx = NULL;
	}

	glyph_indices = malloc (sizeof (WCHAR) * buffer_size);
	dx = malloc (sizeof (int) * buffer_size);
	if (!glyph_indices || !dx) {
	    status = CAIRO_STATUS_NO_MEMORY;
	    goto FAIL2;
	}

	gcp_results.nGlyphs = buffer_size;
	gcp_results.lpDx = dx;
	gcp_results.lpGlyphs = glyph_indices;

	if (!GetCharacterPlacementW (hdc, utf16, n16,
				     0,
				     &gcp_results,
				     GCP_DIACRITIC | GCP_LIGATE | GCP_GLYPHSHAPE | GCP_REORDER)) {
	    status = _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_text_to_glyphs");
	    goto FAIL2;
	}

	if (gcp_results.lpDx && gcp_results.lpGlyphs)
	    break;

	/* Too small a buffer, try again */

	buffer_size *= 1.5;
	if (buffer_size > INT_MAX) {
	    status = CAIRO_STATUS_NO_MEMORY;
	    goto FAIL2;
	}
    }

    *num_glyphs = gcp_results.nGlyphs;
    *glyphs = malloc (sizeof (cairo_glyph_t) * gcp_results.nGlyphs);
    if (!*glyphs) {
	status = CAIRO_STATUS_NO_MEMORY;
	goto FAIL2;
    }

    x_pos = x;
    y_pos = y;

    for (i = 0; i < gcp_results.nGlyphs; i++) {
	(*glyphs)[i].index = glyph_indices[i];
	(*glyphs)[i].x = x_pos ;
	(*glyphs)[i].y = y_pos;

	x_pos += x_incr * dx[i];
	y_pos += y_incr * dx[i];
    }

 FAIL2:
    if (glyph_indices)
	free (glyph_indices);
    if (dx)
	free (dx);

    cairo_win32_scaled_font_done_font (&scaled_font->base);

 FAIL1:
    free (utf16);

    return status;
}

static cairo_status_t
_cairo_win32_scaled_font_set_metrics (cairo_win32_scaled_font_t *scaled_font)
{
    cairo_status_t status;
    cairo_font_extents_t extents;

    TEXTMETRIC metrics;
    HDC hdc;

    hdc = _get_global_font_dc ();
    if (!hdc)
	return CAIRO_STATUS_NO_MEMORY;

    if (scaled_font->preserve_axes) {
	/* For 90-degree rotations (including 0), we get the metrics
	 * from the GDI in logical space, then convert back to font space
	 */
	status = cairo_win32_scaled_font_select_font (&scaled_font->base, hdc);
	if (status)
	    return status;
	GetTextMetrics (hdc, &metrics);
	cairo_win32_scaled_font_done_font (&scaled_font->base);

	extents.ascent = metrics.tmAscent / scaled_font->logical_scale;
	extents.descent = metrics.tmDescent / scaled_font->logical_scale;

	extents.height = (metrics.tmHeight + metrics.tmExternalLeading) / scaled_font->logical_scale;
	extents.max_x_advance = metrics.tmMaxCharWidth / scaled_font->logical_scale;
	extents.max_y_advance = 0;

    } else {
	/* For all other transformations, we use the design metrics
	 * of the font. The GDI results from GetTextMetrics() on a
	 * transformed font are inexplicably large and we want to
	 * avoid them.
	 */
	status = _cairo_win32_scaled_font_select_unscaled_font (&scaled_font->base, hdc);
	if (status)
	    return status;
	GetTextMetrics (hdc, &metrics);
	_cairo_win32_scaled_font_done_unscaled_font (&scaled_font->base);

	extents.ascent = (double)metrics.tmAscent / scaled_font->em_square;
	extents.descent = metrics.tmDescent * scaled_font->em_square;
	extents.height = (double)(metrics.tmHeight + metrics.tmExternalLeading) / scaled_font->em_square;
	extents.max_x_advance = (double)(metrics.tmMaxCharWidth) / scaled_font->em_square;
	extents.max_y_advance = 0;

    }

    _cairo_scaled_font_set_metrics (&scaled_font->base, &extents);

    return CAIRO_STATUS_SUCCESS;
}

static cairo_status_t
_cairo_win32_scaled_font_init_glyph_metrics (cairo_win32_scaled_font_t *scaled_font,
					     cairo_scaled_glyph_t      *scaled_glyph)
{
    static const MAT2 matrix = { { 0, 1 }, { 0, 0 }, { 0, 0 }, { 0, 1 } };
    GLYPHMETRICS metrics;
    cairo_status_t status;
    cairo_text_extents_t extents;
    HDC hdc;

    hdc = _get_global_font_dc ();
    if (!hdc)
	return CAIRO_STATUS_NO_MEMORY;

    if (scaled_font->preserve_axes) {
	/* If we aren't rotating / skewing the axes, then we get the metrics
	 * from the GDI in device space and convert to font space.
	 */
	status = cairo_win32_scaled_font_select_font (&scaled_font->base, hdc);
	if (status)
	    return status;
	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_font (&scaled_font->base);

	if (scaled_font->swap_axes) {
	    extents.x_bearing = - metrics.gmptGlyphOrigin.y / scaled_font->y_scale;
	    extents.y_bearing = metrics.gmptGlyphOrigin.x / scaled_font->x_scale;
	    extents.width = metrics.gmBlackBoxY / scaled_font->y_scale;
	    extents.height = metrics.gmBlackBoxX / scaled_font->x_scale;
	    extents.x_advance = metrics.gmCellIncY / scaled_font->x_scale;
	    extents.y_advance = metrics.gmCellIncX / scaled_font->y_scale;
	} else {
	    extents.x_bearing = metrics.gmptGlyphOrigin.x / scaled_font->x_scale;
	    extents.y_bearing = - metrics.gmptGlyphOrigin.y / scaled_font->y_scale;
	    extents.width = metrics.gmBlackBoxX / scaled_font->x_scale;
	    extents.height = metrics.gmBlackBoxY / scaled_font->y_scale;
	    extents.x_advance = metrics.gmCellIncX / scaled_font->x_scale;
	    extents.y_advance = metrics.gmCellIncY / scaled_font->y_scale;
	}

	if (scaled_font->swap_x) {
	    extents.x_bearing = (- extents.x_bearing - extents.width);
	    extents.x_advance = - extents.x_advance;
	}

	if (scaled_font->swap_y) {
	    extents.y_bearing = (- extents.y_bearing - extents.height);
	    extents.y_advance = - extents.y_advance;
	}

    } else {
	/* For all other transformations, we use the design metrics