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