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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Add the geopoly_svg() SQL function.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | geojson
Files: files | file ages | folders
SHA3-256: 318ba5f0c52596fc5ceed23a2b7b1ca18644449809890bfed47ab4ee01075060
User & Date: drh 2018-05-12 21:09:31
Context
2018-05-12
23:31
Resolve issues with floating-point round-off error in the geopoly_overlap() routine. check-in: a3c6696f user: drh tags: geojson
21:09
Add the geopoly_svg() SQL function. check-in: 318ba5f0 user: drh tags: geojson
20:28
Preliminary tests show geopoly_overlap() is working. check-in: 77bb7b7d user: drh tags: geojson
Changes
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Changes to ext/misc/geopoly.c.

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    }
    sqlite3_str_appendf(x, "[%!g,%!g]]", p->a[0], p->a[1]);
    sqlite3_result_text(context, sqlite3_str_finish(x), -1, sqlite3_free);
    sqlite3_free(p);
  }
}




































/*
** Implementation of the geopoly_area(X) function.
**
** If the input is a well-formed Geopoly BLOB then return the area
** enclosed by the polygon.  If the polygon circulates clockwise instead
** of counterclockwise (as it should) then return the negative of the
................................................................................
    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
    int nArg;
    const char *zName;
  } aFunc[] = {
     { geopolyAreaFunc,          1,    "geopoly_area"     },
     { geopolyBlobFunc,          1,    "geopoly_blob"     },
     { geopolyJsonFunc,          1,    "geopoly_json"     },

     { geopolyWithinFunc,        3,    "geopoly_within"   },
     { geopolyOverlapFunc,       2,    "geopoly_overlap"  },
     { geopolyDebugFunc,         1,    "geopoly_debug"    },
  };
  int i;
  SQLITE_EXTENSION_INIT2(pApi);
  (void)pzErrMsg;  /* Unused parameter */







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    }
    sqlite3_str_appendf(x, "[%!g,%!g]]", p->a[0], p->a[1]);
    sqlite3_result_text(context, sqlite3_str_finish(x), -1, sqlite3_free);
    sqlite3_free(p);
  }
}

/*
** SQL function:     geopoly_svg(X, ....)
**
** Interpret X as a polygon and render it as a SVG <polyline>.
** Additional arguments are added as attributes to the <polyline>.
*/
static void geopolySvgFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  GeoPoly *p = geopolyFuncParam(context, argv[0]);
  if( p ){
    sqlite3 *db = sqlite3_context_db_handle(context);
    sqlite3_str *x = sqlite3_str_new(db);
    int i;
    char cSep = '\'';
    sqlite3_str_appendf(x, "<polyline points=");
    for(i=0; i<p->nVertex; i++){
      sqlite3_str_appendf(x, "%c%g,%g", cSep, p->a[i*2], p->a[i*2+1]);
      cSep = ' ';
    }
    sqlite3_str_appendf(x, " %g,%g'", p->a[0], p->a[1]);
    for(i=1; i<argc; i++){
      const char *z = (const char*)sqlite3_value_text(argv[i]);
      if( z && z[0] ){
        sqlite3_str_appendf(x, " %s", z);
      }
    }
    sqlite3_str_appendf(x, "></polyline>");
    sqlite3_result_text(context, sqlite3_str_finish(x), -1, sqlite3_free);
    sqlite3_free(p);
  }
}

/*
** Implementation of the geopoly_area(X) function.
**
** If the input is a well-formed Geopoly BLOB then return the area
** enclosed by the polygon.  If the polygon circulates clockwise instead
** of counterclockwise (as it should) then return the negative of the
................................................................................
    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
    int nArg;
    const char *zName;
  } aFunc[] = {
     { geopolyAreaFunc,          1,    "geopoly_area"     },
     { geopolyBlobFunc,          1,    "geopoly_blob"     },
     { geopolyJsonFunc,          1,    "geopoly_json"     },
     { geopolySvgFunc,          -1,    "geopoly_svg"      },
     { geopolyWithinFunc,        3,    "geopoly_within"   },
     { geopolyOverlapFunc,       2,    "geopoly_overlap"  },
     { geopolyDebugFunc,         1,    "geopoly_debug"    },
  };
  int i;
  SQLITE_EXTENSION_INIT2(pApi);
  (void)pzErrMsg;  /* Unused parameter */