src/display/inkscape-cairo.cpp

   1 /*
   2  * Helper functions to use cairo with inkscape
   3  *
   4  * Copyright (C) 2007 bulia byak
   5  * Copyright (C) 2008 Johan Engelen
   6  *
   7  * Released under GNU GPL
   8  *
   9  */
  10
  11 #include <cairo.h>
  12
  13 #ifdef HAVE_CONFIG_H
  14 # include <config.h>
  15 #endif
  16 #include <libnr/n-art-bpath.h>
  17 #include <libnr/nr-matrix-ops.h>
  18 #include <libnr/nr-matrix-fns.h>
  19 #include <libnr/nr-pixblock.h>
  20 #include <libnr/nr-convert2geom.h>
  21 #include "../style.h"
  22 #include "nr-arena.h"
  23 #include "sp-canvas.h"
  24 #include <2geom/pathvector.h>
  25 #include <2geom/matrix.h>
  26 #include <2geom/point.h>
  27 #include <2geom/path.h>
  28 #include <2geom/transforms.h>
  29 #include <2geom/sbasis-to-bezier.h>
  30
  31 /** Creates a cairo context to render to the given pixblock on the given area */
  32 cairo_t *
  33 nr_create_cairo_context_for_data (NRRectL *area, NRRectL *buf_area, unsigned char *px, unsigned int rowstride)
  34 {
  35     if (!nr_rect_l_test_intersect (buf_area, area))
  36         return NULL;
  37
  38     NRRectL clip;
  39     nr_rect_l_intersect (&clip, buf_area, area);
  40     unsigned char *dpx = px + (clip.y0 - buf_area->y0) * rowstride + 4 * (clip.x0 - buf_area->x0);
  41     int width = area->x1 - area->x0;
  42     int height = area->y1 - area->y0;
  43     // even though cairo cannot draw in nonpremul mode, select ARGB32 for R8G8B8A8N as the closest; later eliminate R8G8B8A8N everywhere
  44     cairo_surface_t* cst = cairo_image_surface_create_for_data
  45         (dpx,
  46          CAIRO_FORMAT_ARGB32,
  47          width,
  48          height,
  49          rowstride);
  50     cairo_t *ct = cairo_create (cst);
  51
  52     return ct;
  53 }
  54
  55 /** Creates a cairo context to render to the given SPCanvasBuf on the given area */
  56 cairo_t *
  57 nr_create_cairo_context_canvasbuf (NRRectL */*area*/, SPCanvasBuf *b)
  58 {
  59     return nr_create_cairo_context_for_data (&(b->rect), &(b->rect), b->buf, b->buf_rowstride);
  60 }
  61
  62
  63 /** Creates a cairo context to render to the given NRPixBlock on the given area */
  64 cairo_t *
  65 nr_create_cairo_context (NRRectL *area, NRPixBlock *pb)
  66 {
  67     return nr_create_cairo_context_for_data (area, &(pb->area), NR_PIXBLOCK_PX (pb), pb->rs);
  68 }
  69
  70 /** Feeds path-creating calls to the cairo context translating them from the SPCurve, with the given transform and shift */
  71 void
  72 feed_curve_to_cairo (cairo_t *ct, NArtBpath const *bpath, NR::Matrix trans, NR::Maybe<NR::Rect> area, bool optimize_stroke, double stroke_width)
  73 {
  74     NR::Point next(0,0), last(0,0);
  75     if (!area || area->isEmpty())
  76         return;
  77     NR::Point shift = area->min();
  78     NR::Rect view = *area;
  79     view.growBy (stroke_width);
  80     NR::Rect swept;
  81     bool  closed = false;
  82     NR::Point startpath(0,0);
  83     for (int i = 0; bpath[i].code != NR_END; i++) {
  84         switch (bpath[i].code) {
  85             case NR_MOVETO_OPEN:
  86             case NR_MOVETO:
  87                 if (closed) {
  88                     // we cannot use close_path because some of the curves/lines may have been optimized out
  89                     cairo_line_to(ct, startpath[NR::X], startpath[NR::Y]);
  90                 }
  91                 next[NR::X] = bpath[i].x3;
  92                 next[NR::Y] = bpath[i].y3;
  93                 next *= trans;
  94                 last = next;
  95                 next -= shift;
  96                 if (bpath[i].code == NR_MOVETO) {
  97                     // remember the start point of the subpath, for closing it later
  98                     closed = true;
  99                     startpath = next;
 100                 } else {
 101                     closed = false;
 102                 }
 103                 cairo_move_to(ct, next[NR::X], next[NR::Y]);
 104                 break;
 105
 106             case NR_LINETO:
 107                 next[NR::X] = bpath[i].x3;
 108                 next[NR::Y] = bpath[i].y3;
 109                 next *= trans;
 110                 if (optimize_stroke) {
 111                     swept = NR::Rect(last, next);
 112                     //std::cout << "swept: " << swept;
 113                     //std::cout << "view: " << view;
 114                     //std::cout << "intersects? " << (swept.intersects(view)? "YES" : "NO") << "\n";
 115                 }
 116                 last = next;
 117                 next -= shift;
 118                 if (!optimize_stroke || swept.intersects(view))
 119                     cairo_line_to(ct, next[NR::X], next[NR::Y]);
 120                 else
 121                     cairo_move_to(ct, next[NR::X], next[NR::Y]);
 122                 break;
 123
 124             case NR_CURVETO: {
 125                 NR::Point  tm1, tm2, tm3;
 126                 tm1[0]=bpath[i].x1;
 127                 tm1[1]=bpath[i].y1;
 128                 tm2[0]=bpath[i].x2;
 129                 tm2[1]=bpath[i].y2;
 130                 tm3[0]=bpath[i].x3;
 131                 tm3[1]=bpath[i].y3;
 132                 tm1 *= trans;
 133                 tm2 *= trans;
 134                 tm3 *= trans;
 135                 if (optimize_stroke) {
 136                     swept = NR::Rect(last, last);
 137                     swept.expandTo(tm1);
 138                     swept.expandTo(tm2);
 139                     swept.expandTo(tm3);
 140                 }
 141                 last = tm3;
 142                 tm1 -= shift;
 143                 tm2 -= shift;
 144                 tm3 -= shift;
 145                 if (!optimize_stroke || swept.intersects(view))
 146                     cairo_curve_to (ct, tm1[NR::X], tm1[NR::Y], tm2[NR::X], tm2[NR::Y], tm3[NR::X], tm3[NR::Y]);
 147                 else
 148                     cairo_move_to(ct, tm3[NR::X], tm3[NR::Y]);
 149                 break;
 150             }
 151
 152             default:
 153                 break;
 154         }
 155     }
 156 }
 157
 158
 159 static void
 160 feed_curve_to_cairo(cairo_t *cr, Geom::Curve const &c, Geom::Matrix & trans, Geom::Rect view, bool optimize_stroke)
 161 {
 162     if( dynamic_cast<Geom::LineSegment const*>(&c) ||
 163         dynamic_cast<Geom::HLineSegment const*>(&c) ||
 164         dynamic_cast<Geom::VLineSegment const*>(&c) )
 165     {
 166         Geom::Point end_tr = c.finalPoint() * trans;
 167         if (!optimize_stroke) {
 168             cairo_line_to(cr, end_tr[0], end_tr[1]);
 169         } else {
 170             Geom::Rect swept(c.initialPoint()*trans, end_tr);
 171             if (swept.intersects(view)) {
 172                 cairo_line_to(cr, end_tr[0], end_tr[1]);
 173             } else {
 174                 cairo_move_to(cr, end_tr[0], end_tr[1]);
 175             }
 176         }
 177     }
 178     else if(Geom::QuadraticBezier const *quadratic_bezier = dynamic_cast<Geom::QuadraticBezier const*>(&c)) {
 179         std::vector<Geom::Point> points = quadratic_bezier->points();
 180         points[0] *= trans;
 181         points[1] *= trans;
 182         points[2] *= trans;
 183         Geom::Point b1 = points[0] + (2./3) * (points[1] - points[0]);
 184         Geom::Point b2 = b1 + (1./3) * (points[2] - points[0]);
 185         if (!optimize_stroke) {
 186             cairo_curve_to(cr, b1[0], b1[1], b2[0], b2[1], points[2][0], points[2][1]);
 187         } else {
 188             Geom::Rect swept(points[0], points[2]);
 189             swept.expandTo(points[1]);
 190             if (swept.intersects(view)) {
 191                 cairo_curve_to(cr, b1[0], b1[1], b2[0], b2[1], points[2][0], points[2][1]);
 192             } else {
 193                 cairo_move_to(cr, points[2][0], points[2][1]);
 194             }
 195         }
 196     }
 197     else if(Geom::CubicBezier const *cubic_bezier = dynamic_cast<Geom::CubicBezier const*>(&c)) {
 198         std::vector<Geom::Point> points = cubic_bezier->points();
 199         //points[0] *= trans; // don't do this one here for fun: it is only needed for optimized strokes
 200         points[1] *= trans;
 201         points[2] *= trans;
 202         points[3] *= trans;
 203         if (!optimize_stroke) {
 204             cairo_curve_to(cr, points[1][0], points[1][1], points[2][0], points[2][1], points[3][0], points[3][1]);
 205         } else {
 206             points[0] *= trans;  // didn't transform this point yet
 207             Geom::Rect swept(points[0], points[3]);
 208             swept.expandTo(points[1]);
 209             swept.expandTo(points[2]);
 210             if (swept.intersects(view)) {
 211                 cairo_curve_to(cr, points[1][0], points[1][1], points[2][0], points[2][1], points[3][0], points[3][1]);
 212             } else {
 213                 cairo_move_to(cr, points[3][0], points[3][1]);
 214             }
 215         }
 216     }
 217 //    else if(Geom::EllipticalArc const *svg_elliptical_arc = dynamic_cast<Geom::EllipticalArc *>(c)) {
 218 //        //TODO: get at the innards and spit them out to cairo
 219 //    }
 220     else {
 221         //this case handles sbasis as well as all other curve types
 222         Geom::Path sbasis_path = path_from_sbasis(c.toSBasis(), 0.1);
 223
 224         //recurse to convert the new path resulting from the sbasis to svgd
 225         for(Geom::Path::iterator iter = sbasis_path.begin(); iter != sbasis_path.end(); ++iter) {
 226             feed_curve_to_cairo(cr, *iter, trans, view, optimize_stroke);
 227         }
 228     }
 229 }
 230
 231
 232 /** Feeds path-creating calls to the cairo context translating them from the SPCurve, with the given transform and shift */
 233 void
 234 feed_path_to_cairo (cairo_t *ct, Geom::Path const &path, Geom::Matrix trans, NR::Maybe<NR::Rect> area, bool optimize_stroke, double stroke_width)
 235 {
 236     if (!area || area->isEmpty())
 237         return;
 238     if (path.empty())
 239         return;
 240
 241     // Transform all coordinates to coords within "area"
 242     Geom::Point shift = to_2geom(area->min());
 243     NR::Rect view = *area;
 244     view.growBy (stroke_width);
 245     view = view * from_2geom(Geom::Translate(-shift));
 246     //  Pass transformation to feed_curve, so that we don't need to create a whole new path.
 247     Geom::Matrix transshift(trans * Geom::Translate(-shift));
 248
 249     Geom::Point initial = path.initialPoint() * transshift;
 250     cairo_move_to(ct, initial[0], initial[1] );
 251
 252     for(Geom::Path::const_iterator cit = path.begin(); cit != path.end_open(); ++cit) {
 253         feed_curve_to_cairo(ct, *cit, transshift, to_2geom(view), optimize_stroke);
 254     }
 255
 256     if (path.closed()) {
 257         cairo_line_to(ct, initial[0], initial[1]);
 258         // I think we should use cairo_close_path(ct) here but it doesn't work. (the closing line is not rendered completely)
 259         /* according to cairo documentation:
 260            The behavior of cairo_close_path() is distinct from simply calling cairo_line_to() with the equivalent coordinate
 261            in the case of stroking. When a closed sub-path is stroked, there are no caps on the ends of the sub-path. Instead,
 262            there is a line join connecting the final and initial segments of the sub-path.
 263         */
 264     }
 265 }
 266
 267 /** Feeds path-creating calls to the cairo context translating them from the SPCurve, with the given transform and shift */
 268 void
 269 feed_pathvector_to_cairo (cairo_t *ct, Geom::PathVector const &pathv, Geom::Matrix trans, NR::Maybe<NR::Rect> area, bool optimize_stroke, double stroke_width)
 270 {
 271     if (!area || area->isEmpty())
 272         return;
 273     if (pathv.empty())
 274         return;
 275
 276     for(Geom::PathVector::const_iterator it = pathv.begin(); it != pathv.end(); ++it) {
 277         feed_path_to_cairo(ct, *it, trans, area, optimize_stroke, stroke_width);
 278     }
 279 }
 280
 281 /*
 282   Local Variables:
 283   mode:c++
 284   c-file-style:"stroustrup"
 285   c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
 286   indent-tabs-mode:nil
 287   fill-column:99
 288   End:
 289 */
 290 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :