Re: [gnomemm] Gnome::Canvas::Item custom drawing

[Paul Davis <paul linuxaudiosystems com>]

>Hi all, I'm trying to write a class derived from a Gnome::Canvas::Item
>such as Gnome::Canvas::Rect.
>
>I would like to override the drawing method to draw resizing handles
>around the object when it is selected inside of my Gnome::CanvasAA
>object.
>
>My understanding is that I should override the update_vfunc() method and
>do my own drawing there. The only documentation I have shows a drawing
>method using libart_lgpl's SVP arrays. However, the sources actually
>uses a GnomeCanvasPathDef method. Either way, I get stuck for the
>following reasons:
>
>1) SVP arrays, I can't get the fill_svp in anyway from the C++ classes.
>The c code puts it in GnomeCanvasShapePriv private structure, so I'd
>rather not use that directly.
>
>2) with the PathDef method, I can't find a way to set the PathDef to the
>shape from the C++ classes (the c code calls
>'gnome_canvas_shape_set_path_def()')
>
>Can someone put me on the right track, please.

i've been using the GtkCanvas (the C backport of the old GnomeCanvas
to pure GTK+) for more than a year. i have several custom C-level
canvas items that do their own drawing, and they use a set of macros
that i isolated from another project. the macros get passed the rgb
buffer that is passed to the item update widget, and they handle just
about any straight line/box/rectangle requirements. for anti-aliasing
and curved surfaces, libart_lgpl is still required. i enclose them
below - perhaps they will be useful to you. note that most of them do
bounds checking, so you do not need to do this in the code that uses
them.

--p

/*
    Copyright (C) 2000 EMC Capital Management, Inc.
  
    Developed by Jon Trowbridge <trow gnu org> and
    Havoc Pennington <hp pobox com>.
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id: rgb_macros.h,v 1.1 2001/09/26 13:24:26 pbd Exp $
*/

#ifndef __gtk_ardour_rgb_macros_h__
#define __gtk_ardour_rgb_macros_h__

/*
  Some convenient macros for drawing into an RGB buffer.
  Beware of side effects, code-bloat, and all of the other classic
  cpp-perils...
*/

#define RGB_TO_UINT(r,g,b) ((((guint)(r))<<16)|(((guint)(g))<<8)|((guint)(b)))
#define RGB_TO_RGBA(x,a) (((x) << 8) | ((((guint)a) & 0xff)))
#define RGBA_TO_UINT(r,g,b,a) RGB_TO_RGBA(RGB_TO_UINT(r,g,b), a)
#define RGB_WHITE  RGB_TO_UINT(0xff, 0xff, 0xff)
#define RGB_BLACK  RGB_TO_UINT(0x00, 0x00, 0x00)
#define RGB_RED    RGB_TO_UINT(0xff, 0x00, 0x00)
#define RGB_GREEN  RGB_TO_UINT(0x00, 0xff, 0x00)
#define RGB_BLUE   RGB_TO_UINT(0x00, 0x00, 0xff)
#define RGB_YELLOW RGB_TO_UINT(0xff, 0xff, 0x00)
#define RGB_VIOLET RGB_TO_UINT(0xff, 0x00, 0xff)
#define RGB_CYAN   RGB_TO_UINT(0x00, 0xff, 0xff)
#define RGBA_WHITE  RGB_TO_RGBA(RGB_WHITE, 0xff)
#define RGBA_BLACK  RGB_TO_RGBA(RGB_BLACK, 0xff)
#define RGBA_RED    RGB_TO_RGBA(RGB_RED, 0xff)
#define RGBA_GREEN  RGB_TO_RGBA(RGB_GREEN, 0xff)
#define RGBA_BLUE   RGB_TO_RGBA(RGB_BLUE, 0xff)
#define RGBA_YELLOW RGB_TO_RGBA(RGB_YELLOW, 0xff)
#define RGBA_VIOLET RGB_TO_RGBA(RGB_VIOLET, 0xff)
#define RGBA_CYAN   RGB_TO_RGBA(RGB_CYAN, 0xff)
#define RGB_GREY(x) RGB_TO_UINT(x,x,x)
#define RGBA_GREY(x) RGB_TO_RGBA(RGB_GREY(x), 0xff)
#define UINT_RGBA_R(x) (((guint)(x))>>24)
#define UINT_RGBA_G(x) ((((guint)(x))>>16)&0xff)
#define UINT_RGBA_B(x) ((((guint)(x))>>8)&0xff)
#define UINT_RGBA_A(x) (((guint)(x))&0xff)
#define UINT_RGBA_CHANGE_R(x, r) (((x)&(~(0xff<<24)))|(((r)&0xff)<<24))
#define UINT_RGBA_CHANGE_G(x, g) (((x)&(~(0xff<<16)))|(((g)&0xff)<<16))
#define UINT_RGBA_CHANGE_B(x, b) (((x)&(~(0xff<<8)))|(((b)&0xff)<<8))
#define UINT_RGBA_CHANGE_A(x, a) (((x)&(~0xff))|((a)&0xff))
#define UINT_TO_RGB(u,r,g,b) \
{ (*(r)) = ((u)>>16)&0xff; (*(g)) = ((u)>>8)&0xff; (*(b)) = (u)&0xff; }
#define UINT_TO_RGBA(u,r,g,b,a) \
{ UINT_TO_RGB(((u)>>8),r,g,b); (*(a)) = (u)&0xff; }
#define MONO_INTERPOLATE(v1, v2, t) ((gint)rint((v2)*(t)+(v1)*(1-(t))))
#define UINT_INTERPOLATE(c1, c2, t) \
  RGBA_TO_UINT( MONO_INTERPOLATE(UINT_RGBA_R(c1), UINT_RGBA_R(c2), t), \
		MONO_INTERPOLATE(UINT_RGBA_G(c1), UINT_RGBA_G(c2), t), \
		MONO_INTERPOLATE(UINT_RGBA_B(c1), UINT_RGBA_B(c2), t), \
		MONO_INTERPOLATE(UINT_RGBA_A(c1), UINT_RGBA_A(c2), t) )
#define PIXEL_RGB(p, r, g, b) \
{((guchar*)(p))[0]=(r); ((guchar*)(p))[1]=(g); ((guchar*)(p))[2]=(b);}
#define PIXEL_RGBA(p, r, g, b, a) \
{ if ((a)>=0xff) { PIXEL_RGB(p,r,g,b) } \
  else if ((a)>0) { \
    guint pixel_tmp; \
    pixel_tmp = ((guchar*)(p))[0]; \
    ((guchar*)(p))[0] = pixel_tmp + ((((r)-pixel_tmp)*(a)+0x80) >> 8); \
    pixel_tmp = ((guchar*)(p))[1]; \
    ((guchar*)(p))[1] = pixel_tmp + ((((g)-pixel_tmp)*(a)+0x80) >> 8); \
    pixel_tmp = ((guchar*)(p))[2]; \
    ((guchar*)(p))[2] = pixel_tmp + ((((b)-pixel_tmp)*(a)+0x80) >> 8); }}
#define PIXEL_RGB_UINT(p, i) \
UINT_TO_RGB((i), ((guchar*)p), ((guchar*)p)+1, ((guchar*)p)+2)
#define PIXEL_RGBA_UINT(p, i) \
  PIXEL_RGBA((p), ((i)>>24)&0xff, ((i)>>16)&0xff, ((i)>>8)&0xff, (i)&0xff)
#define PIXEL_BLACK(p) PIXEL_RGB(p,0,0,0)
#define PIXEL_WHITE(p) PIXEL_RGB(p,0xff,0xff,0xff)
#define PIXEL_GREY(p,g) PIXEL_RGB(p,g,g,g)
#define PIXEL_GREYA(p,g,a) PIXEL_RGBA(p,g,g,g,a)
#define BUF_PTR(inbuf, ptx, pty) \
 ((inbuf)->buf + 3*((ptx)-(inbuf)->rect.x0) + (inbuf)->buf_rowstride*((pty)-(inbuf)->rect.y0))
#define BUF_INBOUNDS_X(inbuf, ptx) \
((inbuf)->rect.x0 <= (ptx) && (ptx) < (inbuf)->rect.x1)
#define BUF_INBOUNDS_Y(inbuf, pty) \
((inbuf)->rect.y0 <= (pty) && (pty) < (inbuf)->rect.y1)
#define PAINT_DOT(inbuf, colr, colg, colb,ptx, pty) \
{ \
  guchar* pd_p; \
  if (BUF_INBOUNDS_X(inbuf, ptx) && BUF_INBOUNDS_Y(inbuf, pty)) { \
    pd_p = BUF_PTR(inbuf, ptx, pty); \
    PIXEL_RGB(pd_p, (colr), (colg), (colb)); \
  } \
}
#define PAINT_DOTA(inbuf, colr, colg, colb, cola, ptx, pty) \
{ \
  guchar* pd_p; \
  if (BUF_INBOUNDS_X(inbuf, ptx) && BUF_INBOUNDS_Y(inbuf, pty)) { \
    pd_p = BUF_PTR(inbuf, ptx, pty); \
    PIXEL_RGBA(pd_p, (colr), (colg), (colb), (cola)); \
  } \
}
#define PAINT_HORIZ(inbuf, colr, colg, colb, ptx0, ptx1, pty) \
{ \
  GtkCanvasBuf* ph_buf = (inbuf); \
  guchar* ph_p; \
  gint ph_a0, ph_a1; \
  gint ph_colr=(colr), ph_colg=(colg), ph_colb=(colb); \
\
  ph_a0 = MAX(ph_buf->rect.x0, (ptx0)); \
  ph_a1 = MIN(ph_buf->rect.x1, (ptx1)); \
\
  if (ph_a0 < ph_a1 && BUF_INBOUNDS_Y(ph_buf, pty)) { \
    ph_p = BUF_PTR(ph_buf, ph_a0, pty); \
    while (ph_a0 < ph_a1) { \
      PIXEL_RGB(ph_p, ph_colr, ph_colg, ph_colb); \
      ++ph_a0; \
      ph_p += 3; \
    } \
  } \
}
#define PAINT_HORIZA(inbuf, colr, colg, colb, cola, ptx0, ptx1, pty) \
{ \
  GtkCanvasBuf* ph_buf = (inbuf); \
  guchar* ph_p; \
  gint ph_a0, ph_a1; \
  gint ph_colr=(colr), ph_colg=(colg), ph_colb=(colb), ph_cola=(cola); \
\
  ph_a0 = MAX(ph_buf->rect.x0, (ptx0)); \
  ph_a1 = MIN(ph_buf->rect.x1, (ptx1)); \
\
  if (ph_a0 < ph_a1 && BUF_INBOUNDS_Y(ph_buf, pty)) { \
    ph_p = BUF_PTR(ph_buf, ph_a0, pty); \
    while (ph_a0 < ph_a1) { \
      PIXEL_RGBA(ph_p, ph_colr, ph_colg, ph_colb, ph_cola); \
      ++ph_a0; \
      ph_p += 3; \
    } \
  } \
}
#define PAINT_VERT(inbuf, colr, colg, colb, ptx, pty0, pty1) \
{ \
  GtkCanvasBuf* pv_buf = (inbuf); \
  guchar* pv_p; \
  gint pv_b0, pv_b1; \
  gint pv_colr=(colr), pv_colg=(colg), pv_colb=(colb);\
\
  pv_b0 = MAX(pv_buf->rect.y0, (pty0)); \
  pv_b1 = MIN(pv_buf->rect.y1, (pty1)); \
\
 if (pv_b0 < pv_b1 && BUF_INBOUNDS_X(pv_buf, ptx)) { \
    pv_p = BUF_PTR(pv_buf, ptx, pv_b0); \
    while (pv_b0 < pv_b1) { \
      PIXEL_RGB(pv_p, pv_colr, pv_colg, pv_colb); \
      ++pv_b0; \
      pv_p += pv_buf->buf_rowstride; \
    } \
  } \
}
#define FAST_PAINT_VERT(inbuf, colr, colg, colb, ptx, pty0, pty1) \
{ \
  GtkCanvasBuf* fpv_buf = (inbuf); \
  guchar* fpv_p; \
  gint fpv_b0, fpv_b1; \
\
  fpv_b0 = MAX(fpv_buf->rect.y0, (pty0)); \
  fpv_b1 = MIN(fpv_buf->rect.y1, (pty1)); \
\
  fpv_p = BUF_PTR(fpv_buf, ptx, fpv_b0); \
\
  while (fpv_b0 < fpv_b1) { \
      PIXEL_RGB(fpv_p, colr, colg, colb); \
      ++fpv_b0; \
      fpv_p += fpv_buf->buf_rowstride; \
  } \
}
#define PAINT_VERTA(inbuf, colr, colg, colb, cola, ptx, pty0, pty1) \
{ \
  GtkCanvasBuf* pv_buf = (inbuf); \
  guchar* pv_p; \
  gint pv_b0, pv_b1; \
  gint pv_colr=(colr), pv_colg=(colg), pv_colb=(colb), pv_cola=(cola);\
\
  pv_b0 = MAX(pv_buf->rect.y0, (pty0)); \
  pv_b1 = MIN(pv_buf->rect.y1, (pty1)); \
\
 if (pv_b0 < pv_b1 && BUF_INBOUNDS_X(pv_buf, ptx)) { \
    pv_p = BUF_PTR(pv_buf, ptx, pv_b0); \
    while (pv_b0 < pv_b1) { \
      PIXEL_RGBA(pv_p, pv_colr, pv_colg, pv_colb, pv_cola); \
      ++pv_b0; \
      pv_p += pv_buf->buf_rowstride; \
    } \
  } \
}

/* Paint a solid-colored box into a GtkCanvasBuf (clipping as necessary).
   The box contains (ptx0,pty0), but not (ptx1, pty1).
   Each macro arg should appear exactly once in the body of the code. */
#define PAINT_BOX(inbuf, colr, colg, colb, cola, ptx0, pty0, ptx1, pty1) \
{ \
  GtkCanvasBuf* pb_buf = (inbuf); \
  guchar* pb_p; \
  guchar* pb_pp; \
  gint pb_a0, pb_a1, pb_b0, pb_b1, pb_i, pb_j; \
  gint pb_colr=(colr), pb_colg=(colg), pb_colb=(colb), pb_cola=(cola); \
\
  pb_a0 = MAX(pb_buf->rect.x0, (ptx0)); \
  pb_a1 = MIN(pb_buf->rect.x1, (ptx1)); \
  pb_b0 = MAX(pb_buf->rect.y0, (pty0)); \
  pb_b1 = MIN(pb_buf->rect.y1, (pty1)); \
\
  if (pb_a0 < pb_a1 && pb_b0 < pb_b1) { \
    pb_p = BUF_PTR(pb_buf, pb_a0, pb_b0); \
    for (pb_j=pb_b0; pb_j<pb_b1; ++pb_j) { \
      pb_pp = pb_p; \
      for (pb_i=pb_a0; pb_i<pb_a1; ++pb_i) { \
        PIXEL_RGBA(pb_pp, pb_colr, pb_colg, pb_colb, pb_cola); \
        pb_pp += 3; \
      } \
      pb_p += pb_buf->buf_rowstride; \
    } \
  } \
}

#endif /* __gtk_ardour_rgb_macros_h__ */