[sdf] Added functions to get shortest distance from any edge/contour.

* src/sdf/ftsdf,c (sdf_edge_get_min_distance): Added function to get shortest distance
  from any arbitary edge.

* src/sdf/ftsdf.c (sdf_contour_get_min_distance): Added function to get shortest
  distance from a contour. It basically returns the shortest distance from the nearest
  edge.

src/sdf/ftsdf.c

@@ -2505,5 +2505,148 @@
     return error;
   }
 
+  /**************************************************************************
+   *
+   * @Function:
+   *   sdf_edge_get_min_distance
+   *
+   * @Description:
+   *   This is a handy function which can be used to find shortest distance
+   *   from a `point' to any type of `edge'. It checks the edge type and
+   *   then calls the relevant `get_min_distance_' function.
+   *
+   * @Input:
+   *   edge ::
+   *     An edge to which the shortest distance is to be computed.
+   *
+   *   point ::
+   *     Point from which the shortest distance is to be computed.
+   *
+   * @Return:
+   *   out ::
+   *     Signed distance from the `point' to the `edge'.
+   *
+   *   FT_Error ::
+   *     FreeType error, 0 means success.
+   *
+   */
+  static FT_Error
+  sdf_edge_get_min_distance( SDF_Edge*             edge,
+                             FT_26D6_Vec           point,
+                             SDF_Signed_Distance*  out)
+  {
+    FT_Error  error = FT_Err_Ok;
+
+
+    if ( !edge || !out )
+    {
+      error = FT_THROW( Invalid_Argument );
+      goto Exit;
+    }
+
+    /* edge specific distance calculation */
+    switch ( edge->edge_type ) {
+    case SDF_EDGE_LINE:
+      get_min_distance_line( edge, point, out );
+      break;
+    case SDF_EDGE_CONIC:
+      get_min_distance_conic( edge, point, out );
+      break;
+    case SDF_EDGE_CUBIC:
+      get_min_distance_cubic( edge, point, out );
+      break;
+    default:
+        error = FT_THROW( Invalid_Argument );
+    }
+
+  Exit:
+    return error;
+  }
+
+  /* `sdf_generate' is not used at the moment */
+  #if 0
+
+  /**************************************************************************
+   *
+   * @Function:
+   *   sdf_contour_get_min_distance
+   *
+   * @Description:
+   *   This function iterate through all the edges that make up
+   *   the contour and find the shortest distance from a point to
+   *   this contour and assigns it to `out'.
+   *
+   * @Input:
+   *   contour ::
+   *     A contour to which the shortest distance is to be computed.
+   *
+   *   point ::
+   *     Point from which the shortest distance is to be computed.
+   *
+   * @Return:
+   *   out ::
+   *     Signed distance from the `point' to the `contour'.
+   *
+   *   FT_Error ::
+   *     FreeType error, 0 means success.
+   *
+   * @Note:
+   *   The function does not return signed distance for each edge
+   *   which make up the contour, it simply returns the shortest
+   *   of all the edges.
+   *
+   */
+  static FT_Error
+  sdf_contour_get_min_distance( SDF_Contour*          contour,
+                                FT_26D6_Vec           point,
+                                SDF_Signed_Distance*  out)
+  {
+    FT_Error             error  = FT_Err_Ok;
+    SDF_Signed_Distance  min_dist = max_sdf;
+    SDF_Edge*            edge_list;
+
+
+    if ( !contour || !out )
+    {
+      error = FT_THROW( Invalid_Argument );
+      goto Exit;
+    }
+
+    edge_list = contour->edges;
+
+    /* iterate through all the edges manually */
+    while ( edge_list ) {
+      SDF_Signed_Distance  current_dist = max_sdf;
+      FT_16D16             diff;
+    
+    
+      FT_CALL( sdf_edge_get_min_distance( 
+               edge_list,
+               point, &current_dist ) );
+
+      if ( current_dist.distance >= 0 )
+      {
+        diff = current_dist.distance - min_dist.distance;
+
+
+        if ( FT_ABS(diff ) < CORNER_CHECK_EPSILON )
+          min_dist = resolve_corner( min_dist, current_dist );
+        else if ( diff < 0 )
+          min_dist = current_dist;
+      }
+      else
+      {
+        FT_TRACE0(( "sdf_contour_get_min_distance: Overflowed.\n" ));
+      }
+    
+      edge_list = edge_list->next;
+    }
+
+    *out = min_dist;
+  Exit:
+    return error;
+  }
+
+  #endif
 
 /* END */