Pikchr

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Comment:Improved boundry box estimation for arcs. Response to forum post ed93cba38d.
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SHA3-256: 9b9b3133644ff804f8312bb839ad4eb43d1eb1869558f7a3a50b788b2c4a706a
User & Date: drh 2025-03-19 12:41:21.100
Context
2025-03-19
16:19
A more precise computation of the bounding box for an arc. (check-in: 8a43b02014 user: drh tags: trunk)
12:41
Improved boundry box estimation for arcs. Response to forum post ed93cba38d. (check-in: 9b9b313364 user: drh tags: trunk)
2025-03-13
11:15
Updates to the download page to reflect the fact that "pikchr.c" is no longer stored in the source tree. (check-in: 6d099ccfa5 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to pikchr.y.
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}
/* Hack: Arcs are here rendered as quadratic Bezier curves rather
** than true arcs.  Multiple reasons: (1) the legacy-PIC parameters
** that control arcs are obscure and I could not figure out what they
** mean based on available documentation.  (2) Arcs are rarely used,
** and so do not seem that important.
*/
static PPoint arcControlPoint(int cw, PPoint f, PPoint t, PNum rScale){
  PPoint m;
  PNum dx, dy;
  m.x = 0.5*(f.x+t.x);
  m.y = 0.5*(f.y+t.y);
  dx = t.x - f.x;
  dy = t.y - f.y;
  if( cw ){
    m.x -= 0.5*rScale*dy;
    m.y += 0.5*rScale*dx;
  }else{
    m.x += 0.5*rScale*dy;
    m.y -= 0.5*rScale*dx;
  }
  return m;
}
static void arcCheck(Pik *p, PObj *pObj){
  PPoint m;
  if( p->nTPath>2 ){
    pik_error(p, &pObj->errTok, "arc geometry error");
    return;
  }
  m = arcControlPoint(pObj->cw, p->aTPath[0], p->aTPath[1], 0.5);


  pik_bbox_add_xy(&pObj->bbox, m.x, m.y);
}
static void arcRender(Pik *p, PObj *pObj){
  PPoint f, m, t;
  if( pObj->nPath<2 ) return;
  if( pObj->sw<0.0 ) return;
  f = pObj->aPath[0];
  t = pObj->aPath[1];
  m = arcControlPoint(pObj->cw,f,t,1.0);
  if( pObj->larrow ){
    pik_draw_arrowhead(p,&m,&f,pObj);
  }
  if( pObj->rarrow ){
    pik_draw_arrowhead(p,&m,&t,pObj);
  }
  pik_append_xy(p,"<path d=\"M", f.x, f.y);








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}
/* Hack: Arcs are here rendered as quadratic Bezier curves rather
** than true arcs.  Multiple reasons: (1) the legacy-PIC parameters
** that control arcs are obscure and I could not figure out what they
** mean based on available documentation.  (2) Arcs are rarely used,
** and so do not seem that important.
*/
static PPoint arcControlPoint(int cw, PPoint f, PPoint t, PNum rScale, PNum rPct){
  PPoint m;
  PNum dx, dy;
  m.x = rPct*(f.x+t.x);
  m.y = rPct*(f.y+t.y);
  dx = t.x - f.x;
  dy = t.y - f.y;
  if( cw ){
    m.x -= 0.5*rScale*dy;
    m.y += 0.5*rScale*dx;
  }else{
    m.x += 0.5*rScale*dy;
    m.y -= 0.5*rScale*dx;
  }
  return m;
}
static void arcCheck(Pik *p, PObj *pObj){
  PPoint m;
  if( p->nTPath>2 ){
    pik_error(p, &pObj->errTok, "arc geometry error");
    return;
  }
  m = arcControlPoint(pObj->cw, p->aTPath[0], p->aTPath[1], 0.5, 0.25);
  pik_bbox_add_xy(&pObj->bbox, m.x, m.y);
  m = arcControlPoint(pObj->cw, p->aTPath[0], p->aTPath[1], 0.5, 0.75);
  pik_bbox_add_xy(&pObj->bbox, m.x, m.y);
}
static void arcRender(Pik *p, PObj *pObj){
  PPoint f, m, t;
  if( pObj->nPath<2 ) return;
  if( pObj->sw<0.0 ) return;
  f = pObj->aPath[0];
  t = pObj->aPath[1];
  m = arcControlPoint(pObj->cw,f,t,1.0,0.5);
  if( pObj->larrow ){
    pik_draw_arrowhead(p,&m,&f,pObj);
  }
  if( pObj->rarrow ){
    pik_draw_arrowhead(p,&m,&t,pObj);
  }
  pik_append_xy(p,"<path d=\"M", f.x, f.y);
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