cairo-xlib-surface.c

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

	ximage->bitmap_bit_order != native_byte_order) {
	_swap_ximage_bits (ximage);
	if (ximage->bitmap_bit_order == ximage->byte_order)
	    return;
    }

    if (ximage->byte_order == native_byte_order)
	return;

    switch (ximage->bits_per_pixel) {
    case 1:
	unit_bytes = ximage->bitmap_unit / 8;
	break;
    case 8:
    case 16:
    case 32:
	unit_bytes = ximage->bits_per_pixel / 8;
	break;
    default:
        /* This could be hit on some uncommon but possible cases,
	 * such as bpp=4. These are cases that libpixman can't deal
	 * with in any case.
	 */
	ASSERT_NOT_REACHED;
    }

    switch (unit_bytes) {
    case 1:
	return;
    case 2:
	_swap_ximage_2bytes (ximage);
	break;
    case 4:
	_swap_ximage_4bytes (ximage);
	break;
    default:
	ASSERT_NOT_REACHED;
    }
}

static cairo_status_t
_get_image_surface (cairo_xlib_surface_t    *surface,
		    cairo_rectangle_int16_t *interest_rect,
		    cairo_image_surface_t  **image_out,
		    cairo_rectangle_int16_t *image_rect)
{
    cairo_image_surface_t *image;
    XImage *ximage;
    int x1, y1, x2, y2;
    cairo_format_masks_t masks;
    cairo_format_t format;

    x1 = 0;
    y1 = 0;
    x2 = surface->width;
    y2 = surface->height;

    if (interest_rect) {
	cairo_rectangle_int16_t rect;

	rect.x = interest_rect->x;
	rect.y = interest_rect->y;
	rect.width = interest_rect->width;
	rect.height = interest_rect->height;

	if (rect.x > x1)
	    x1 = rect.x;
	if (rect.y > y1)
	    y1 = rect.y;
	if (rect.x + rect.width < x2)
	    x2 = rect.x + rect.width;
	if (rect.y + rect.height < y2)
	    y2 = rect.y + rect.height;

	if (x1 >= x2 || y1 >= y2) {
	    *image_out = NULL;
	    return CAIRO_STATUS_SUCCESS;
	}
    }

    if (image_rect) {
	image_rect->x = x1;
	image_rect->y = y1;
	image_rect->width = x2 - x1;
	image_rect->height = y2 - y1;
    }

    /* XXX: This should try to use the XShm extension if available */

    if (surface->use_pixmap == 0)
    {
	cairo_xlib_error_func_t old_handler;

	old_handler = XSetErrorHandler (_noop_error_handler);

	ximage = XGetImage (surface->dpy,
			    surface->drawable,
			    x1, y1,
			    x2 - x1, y2 - y1,
			    AllPlanes, ZPixmap);

	XSetErrorHandler (old_handler);

	/* If we get an error, the surface must have been a window,
	 * so retry with the safe code path.
	 */
	if (!ximage)
	    surface->use_pixmap = CAIRO_ASSUME_PIXMAP;
    }
    else
    {
	surface->use_pixmap--;
	ximage = NULL;
    }

    if (!ximage)
    {

	/* XGetImage from a window is dangerous because it can
	 * produce errors if the window is unmapped or partially
	 * outside the screen. We could check for errors and
	 * retry, but to keep things simple, we just create a
	 * temporary pixmap
	 */
	Pixmap pixmap = XCreatePixmap (surface->dpy,
				       surface->drawable,
				       x2 - x1, y2 - y1,
				       surface->depth);
	_cairo_xlib_surface_ensure_gc (surface);

	XCopyArea (surface->dpy, surface->drawable, pixmap, surface->gc,
		   x1, y1, x2 - x1, y2 - y1, 0, 0);

	ximage = XGetImage (surface->dpy,
			    pixmap,
			    0, 0,
			    x2 - x1, y2 - y1,
			    AllPlanes, ZPixmap);

	XFreePixmap (surface->dpy, pixmap);
    }
    if (!ximage)
	return CAIRO_STATUS_NO_MEMORY;

    _swap_ximage_to_native (ximage);

    /*
     * Compute the pixel format masks from either a visual or a
     * XRenderFormat, failing we assume the drawable is an
     * alpha-only pixmap as it could only have been created
     * that way through the cairo_xlib_surface_create_for_bitmap
     * function.
     */
    if (surface->visual) {
	masks.bpp = ximage->bits_per_pixel;
	masks.alpha_mask = 0;
	masks.red_mask = surface->visual->red_mask;
	masks.green_mask = surface->visual->green_mask;
	masks.blue_mask = surface->visual->blue_mask;
    } else if (surface->xrender_format) {
	masks.bpp = ximage->bits_per_pixel;
	masks.red_mask = (unsigned long)surface->xrender_format->direct.redMask << surface->xrender_format->direct.red;
	masks.green_mask = (unsigned long)surface->xrender_format->direct.greenMask << surface->xrender_format->direct.green;
	masks.blue_mask = (unsigned long)surface->xrender_format->direct.blueMask << surface->xrender_format->direct.blue;
	masks.alpha_mask = (unsigned long)surface->xrender_format->direct.alphaMask << surface->xrender_format->direct.alpha;
    } else {
	masks.bpp = ximage->bits_per_pixel;
	masks.red_mask = 0;
	masks.green_mask = 0;
	masks.blue_mask = 0;
	if (surface->depth < 32)
	    masks.alpha_mask = (1 << surface->depth) - 1;
	else
	    masks.alpha_mask = 0xffffffff;
    }

    /*
     * Prefer to use a standard pixman format instead of the
     * general masks case.
     */
    if (_CAIRO_MASK_FORMAT (&masks, &format))
    {
	image = (cairo_image_surface_t*)
	    cairo_image_surface_create_for_data ((unsigned char *) ximage->data,
						 format,
						 ximage->width,
						 ximage->height,
						 ximage->bytes_per_line);
	if (image->base.status)
	    goto FAIL;
    }
    else
    {
	/*
	 * XXX This can't work.  We must convert the data to one of the
	 * supported pixman formats.  Pixman needs another function
	 * which takes data in an arbitrary format and converts it
	 * to something supported by that library.
	 */
	image = (cairo_image_surface_t*)
	    _cairo_image_surface_create_with_masks ((unsigned char *) ximage->data,
						    &masks,
						    ximage->width,
						    ximage->height,
						    ximage->bytes_per_line);
	if (image->base.status)
	    goto FAIL;
    }

    /* Let the surface take ownership of the data */
    _cairo_image_surface_assume_ownership_of_data (image);
    ximage->data = NULL;
    XDestroyImage (ximage);

    *image_out = image;
    return CAIRO_STATUS_SUCCESS;

 FAIL:
    XDestroyImage (ximage);
    return CAIRO_STATUS_NO_MEMORY;
}

static void
_cairo_xlib_surface_ensure_src_picture (cairo_xlib_surface_t    *surface)
{
    if (!surface->src_picture)
	surface->src_picture = XRenderCreatePicture (surface->dpy,
						     surface->drawable,
						     surface->xrender_format,
						     0, NULL);
}

static void
_cairo_xlib_surface_set_picture_clip_rects (cairo_xlib_surface_t *surface)
{
    if (surface->have_clip_rects)
	XRenderSetPictureClipRectangles (surface->dpy, surface->dst_picture,
					 0, 0,
					 surface->clip_rects,
					 surface->num_clip_rects);
}

static void
_cairo_xlib_surface_set_gc_clip_rects (cairo_xlib_surface_t *surface)
{
    if (surface->have_clip_rects)
	XSetClipRectangles(surface->dpy, surface->gc,
			   0, 0,
			   surface->clip_rects,
			   surface->num_clip_rects, YXSorted);
}

static void
_cairo_xlib_surface_ensure_dst_picture (cairo_xlib_surface_t    *surface)
{
    if (!surface->dst_picture) {
	surface->dst_picture = XRenderCreatePicture (surface->dpy,
						     surface->drawable,
						     surface->xrender_format,
						     0, NULL);
	_cairo_xlib_surface_set_picture_clip_rects (surface);
    }

}

static void
_cairo_xlib_surface_ensure_gc (cairo_xlib_surface_t *surface)
{
    XGCValues gcv;

    if (surface->gc)
	return;

    gcv.graphics_exposures = False;
    surface->gc = XCreateGC (surface->dpy, surface->drawable,
			     GCGraphicsExposures, &gcv);
    _cairo_xlib_surface_set_gc_clip_rects (surface);
}

static cairo_status_t
_draw_image_surface (cairo_xlib_surface_t   *surface,
		     cairo_image_surface_t  *image,
		     int                    dst_x,
		     int                    dst_y)
{
    XImage ximage;
    int bpp, alpha, red, green, blue;
    int native_byte_order = _native_byte_order_lsb () ? LSBFirst : MSBFirst;

    pixman_format_get_masks (pixman_image_get_format (image->pixman_image),
			     &bpp, &alpha, &red, &green, &blue);

    ximage.width = image->width;
    ximage.height = image->height;
    ximage.format = ZPixmap;
    ximage.data = (char *)image->data;
    ximage.byte_order = native_byte_order;
    ximage.bitmap_unit = 32;	/* always for libpixman */
    ximage.bitmap_bit_order = native_byte_order;
    ximage.bitmap_pad = 32;	/* always for libpixman */
    ximage.depth = image->depth;
    ximage.bytes_per_line = image->stride;
    ximage.bits_per_pixel = bpp;
    ximage.red_mask = red;
    ximage.green_mask = green;
    ximage.blue_mask = blue;
    ximage.xoffset = 0;

    XInitImage (&ximage);

    _cairo_xlib_surface_ensure_gc (surface);
    XPutImage(surface->dpy, surface->drawable, surface->gc,
	      &ximage, 0, 0, dst_x, dst_y,
	      image->width, image->height);

    return CAIRO_STATUS_SUCCESS;

}

static cairo_status_t
_cairo_xlib_surface_acquire_source_image (void                    *abstract_surface,
					  cairo_image_surface_t  **image_out,
					  void                   **image_extra)
{
    cairo_xlib_surface_t *surface = abstract_surface;
    cairo_image_surface_t *image;
    cairo_status_t status;

    status = _get_image_surface (surface, NULL, &image, NULL);
    if (status)
	return status;

    *image_out = image;
    *image_extra = NULL;

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_xlib_surface_release_source_image (void                   *abstract_surface,
					  cairo_image_surface_t  *image,
					  void                   *image_extra)
{
    cairo_surface_destroy (&image->base);
}

static cairo_status_t
_cairo_xlib_surface_acquire_dest_image (void                    *abstract_surface,
					cairo_rectangle_int16_t *interest_rect,
					cairo_image_surface_t  **image_out,
					cairo_rectangle_int16_t *image_rect_out,
					void                   **image_extra)
{
    cairo_xlib_surface_t *surface = abstract_surface;
    cairo_image_surface_t *image;
    cairo_status_t status;

    status = _get_image_surface (surface, interest_rect, &image, image_rect_out);
    if (status)
	return status;

    *image_out = image;
    *image_extra = NULL;

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_xlib_surface_release_dest_image (void                    *abstract_surface,
					cairo_rectangle_int16_t *interest_rect,
					cairo_image_surface_t   *image,
					cairo_rectangle_int16_t *image_rect,
					void                    *image_extra)
{
    cairo_xlib_surface_t *surface = abstract_surface;

    /* ignore errors */
    _draw_image_surface (surface, image, image_rect->x, image_rect->y);

    cairo_surface_destroy (&image->base);
}

/*
 * Return whether two xlib surfaces share the same
 * screen.  Both core and Render drawing require this
 * when using multiple drawables in an operation.
 */
static cairo_bool_t
_cairo_xlib_surface_same_screen (cairo_xlib_surface_t *dst,
				 cairo_xlib_surface_t *src)
{
    return dst->dpy == src->dpy && dst->screen == src->screen;
}

static cairo_status_t
_cairo_xlib_surface_clone_similar (void			*abstract_surface,
				   cairo_surface_t	*src,
				   cairo_surface_t     **clone_out)
{
    cairo_xlib_surface_t *surface = abstract_surface;
    cairo_xlib_surface_t *clone;

    if (src->backend == surface->base.backend ) {
	cairo_xlib_surface_t *xlib_src = (cairo_xlib_surface_t *)src;

	if (_cairo_xlib_surface_same_screen (surface, xlib_src)) {
	    *clone_out = cairo_surface_reference (src);

	    return CAIRO_STATUS_SUCCESS;
	}
    } else if (_cairo_surface_is_image (src)) {
	cairo_image_surface_t *image_src = (cairo_image_surface_t *)src;

	clone = (cairo_xlib_surface_t *)
	    _cairo_xlib_surface_create_similar_with_format (surface, image_src->format,
						image_src->width, image_src->height);
	if (clone->base.status)
	    return CAIRO_STATUS_NO_MEMORY;

	_draw_image_surface (clone, image_src, 0, 0);

	*clone_out = &clone->base;

	return CAIRO_STATUS_SUCCESS;
    }

    return CAIRO_INT_STATUS_UNSUPPORTED;
}

static cairo_status_t
_cairo_xlib_surface_set_matrix (cairo_xlib_surface_t *surface,
				cairo_matrix_t	     *matrix)
{
    XTransform xtransform;

    if (!surface->src_picture)
	return CAIRO_STATUS_SUCCESS;

    xtransform.matrix[0][0] = _cairo_fixed_from_double (matrix->xx);
    xtransform.matrix[0][1] = _cairo_fixed_from_double (matrix->xy);
    xtransform.matrix[0][2] = _cairo_fixed_from_double (matrix->x0);

    xtransform.matrix[1][0] = _cairo_fixed_from_double (matrix->yx);
    xtransform.matrix[1][1] = _cairo_fixed_from_double (matrix->yy);
    xtransform.matrix[1][2] = _cairo_fixed_from_double (matrix->y0);

    xtransform.matrix[2][0] = 0;
    xtransform.matrix[2][1] = 0;
    xtransform.matrix[2][2] = _cairo_fixed_from_double (1);

    if (!CAIRO_SURFACE_RENDER_HAS_PICTURE_TRANSFORM (surface))
    {
	static const XTransform identity = { {
	    { 1 << 16, 0x00000, 0x00000 },
	    { 0x00000, 1 << 16, 0x00000 },
	    { 0x00000, 0x00000, 1 << 16 },
	} };

	if (memcmp (&xtransform, &identity, sizeof (XTransform)) == 0)
	    return CAIRO_STATUS_SUCCESS;

	return CAIRO_INT_STATUS_UNSUPPORTED;
    }