gecko-dev/gfx/thebes/cairo-xlib-utils.h

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef CAIROXLIBUTILS_H_
#define CAIROXLIBUTILS_H_

#include "cairo.h"
#include <X11/Xlib.h>

CAIRO_BEGIN_DECLS

/**
 * This callback encapsulates Xlib-based rendering. We assume that the
 * execution of the callback is equivalent to compositing some RGBA image of
 * size (bounds_width, bounds_height) onto the drawable at offset (offset_x,
 * offset_y), clipped to the union of the clip_rects if num_rects is greater
 * than zero. This includes the assumption that the same RGBA image
 * is composited if you call the callback multiple times with the same closure,
 * display and visual during a single cairo_draw_with_xlib call.
 *
 * @return True on success, False on non-recoverable error
 */
typedef cairo_bool_t (*cairo_xlib_drawing_callback)(
    void* closure, Screen* screen, Drawable drawable, Visual* visual,
    short offset_x, short offset_y, XRectangle* clip_rects,
    unsigned int num_rects);

/**
 * This structure captures the result of the native drawing, in case the
 * caller may wish to reapply the drawing efficiently later.
 */
typedef struct {
  cairo_surface_t* surface;
  cairo_bool_t uniform_alpha;
  cairo_bool_t uniform_color;
  double alpha;   /* valid only if uniform_alpha is TRUE */
  double r, g, b; /* valid only if uniform_color is TRUE */
} cairo_xlib_drawing_result_t;

/**
 * This type specifies whether the native drawing callback draws all pixels
 * in its bounds opaquely, independent of the contents of the target drawable,
 * or whether it leaves pixels transparent/translucent or depends on the
 * existing contents of the target drawable in some way.
 */
typedef enum _cairo_xlib_drawing_opacity {
  CAIRO_XLIB_DRAWING_OPAQUE,
  CAIRO_XLIB_DRAWING_TRANSPARENT
} cairo_xlib_drawing_opacity_t;

/**
 * This type encodes the capabilities of the native drawing callback.
 *
 * If CAIRO_XLIB_DRAWING_SUPPORTS_OFFSET is set, 'offset_x' and 'offset_y'
 * can be nonzero in the call to the callback; otherwise they will be zero.
 *
 * If CAIRO_XLIB_DRAWING_SUPPORTS_CLIP_RECT is set, then 'num_rects' can be
 * zero or one in the call to the callback. If
 * CAIRO_XLIB_DRAWING_SUPPORTS_CLIP_LIST is set, then 'num_rects' can be
 * anything in the call to the callback. Otherwise 'num_rects' will be zero.
 * Do not set both of these values.
 *
 * If CAIRO_XLIB_DRAWING_SUPPORTS_ALTERNATE_SCREEN is set, then 'screen' can
 * be any screen on any display, otherwise it will be the default screen of
 * the display passed into cairo_draw_with_xlib.
 *
 * If CAIRO_XLIB_DRAWING_SUPPORTS_NONDEFAULT_VISUAL is set, then 'visual' can be
 * any visual, otherwise it will be equal to
 * DefaultVisualOfScreen (screen).
 */
typedef enum {
  CAIRO_XLIB_DRAWING_SUPPORTS_OFFSET = 0x01,
  CAIRO_XLIB_DRAWING_SUPPORTS_CLIP_RECT = 0x02,
  CAIRO_XLIB_DRAWING_SUPPORTS_CLIP_LIST = 0x04,
  CAIRO_XLIB_DRAWING_SUPPORTS_ALTERNATE_SCREEN = 0x08,
  CAIRO_XLIB_DRAWING_SUPPORTS_NONDEFAULT_VISUAL = 0x10
} cairo_xlib_drawing_support_t;

/**
 * Draw Xlib output into any cairo context. All cairo transforms and effects
 * are honored, including the current operator. This is equivalent to a
 * cairo_set_source_surface and then cairo_paint.
 * @param cr the context to draw into
 * @param callback the code to perform Xlib rendering
 * @param closure associated data
 * @param dpy an X display to use in case the cairo context has no associated X
 * display
 * @param width the width of the putative image drawn by the callback
 * @param height the height of the putative image drawn by the callback
 * @param is_opaque set to CAIRO_XLIB_DRAWING_IS_OPAQUE to indicate
 * that all alpha values of the putative image will be 1.0; the pixels drawn
 * into the Drawable must not depend on the prior contents of the Drawable in
 * any way
 * @param capabilities the capabilities of the callback as described above.
 * @param result if non-NULL, we *may* fill in the struct with information about
 * the rendered image. 'surface' may be filled in with a surface representing
 * the image, similar to the target of 'cr'. If 'uniform_alpha' is True then
 * every pixel of the image has the same alpha value 'alpha'. If
 * 'uniform_color' is True then every pixel of the image has the same RGB
 * color (r, g, b). If the image has uniform color and alpha (or alpha is zero,
 * in which case the color is always uniform) then we won't bother returning
 * a surface for it.
 */
void cairo_draw_with_xlib(cairo_t* cr, cairo_xlib_drawing_callback callback,
                          void* closure, Display* dpy, unsigned int width,
                          unsigned int height,
                          cairo_xlib_drawing_opacity_t is_opaque,
                          cairo_xlib_drawing_support_t capabilities,
                          cairo_xlib_drawing_result_t* result);

CAIRO_END_DECLS

#endif /*CAIROXLIBUTILS_H_*/