implement proper picking (by the frame and diagonals) in outline mode

diff --git a/src/display/nr-arena-image.cpp b/src/display/nr-arena-image.cpp
index d91733dc75bd24753311b3b317afd2c0a16a245f..32e29ac07d05b9438eeed5738bc74928d75b2501 100644 (file)
--- a/src/display/nr-arena-image.cpp
+++ b/src/display/nr-arena-image.cpp
@@ -263,6 +263,27 @@ nr_arena_image_render (cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPixBlock
        return item->state;
 }
 
+/** Calculates the closest distance from p to the segment a1-a2*/
+double 
+distance_to_segment (NR::Point p, NR::Point a1, NR::Point a2)
+{
+       // calculate sides of the triangle and their squares
+       double d1 = NR::L2(p - a1); 
+       double d1_2 = d1 * d1;
+       double d2 = NR::L2(p - a2);
+       double d2_2 = d2 * d2;
+       double a = NR::L2(a1 - a2); 
+       double a_2 = a * a;
+
+       // if one of the angles at the base is > 90, return the corresponding side
+       if (d1_2 + a_2 <= d2_2) return d1;
+       if (d2_2 + a_2 <= d1_2) return d2;
+
+       // otherwise calculate the height to the base
+       double peri = (a + d1 + d2)/2;
+       return (2*sqrt(peri * (peri - a) * (peri - d1) * (peri - d2))/a);
+}
+
 static NRArenaItem *
 nr_arena_image_pick (NRArenaItem *item, NR::Point p, double delta, unsigned int sticky)
 {
@@ -270,20 +291,39 @@ nr_arena_image_pick (NRArenaItem *item, NR::Point p, double delta, unsigned int
 
        if (!image->px) return NULL;
 
-       unsigned char * const pixels = image->px;
-       const int width = image->pxw;
-       const int height = image->pxh;
-       const int rowstride = image->pxrs;
-       NR::Point tp = p * image->grid2px;
-       const int ix = (int)(tp[NR::X]);
-       const int iy = (int)(tp[NR::Y]);
+       bool outline = (item->arena->rendermode == RENDERMODE_OUTLINE);
+
+       if (outline) {
+
+               // frame
+               if (distance_to_segment (p, image->c00, image->c10) < delta) return item;
+               if (distance_to_segment (p, image->c10, image->c11) < delta) return item;
+               if (distance_to_segment (p, image->c11, image->c01) < delta) return item;
+               if (distance_to_segment (p, image->c01, image->c00) < delta) return item;
+
+               // diagonals
+               if (distance_to_segment (p, image->c00, image->c11) < delta) return item;
+               if (distance_to_segment (p, image->c10, image->c01) < delta) return item;
 
-       if ((ix < 0) || (iy < 0) || (ix >= width) || (iy >= height))
                return NULL;
 
-       unsigned char *pix_ptr = pixels + iy * rowstride + ix * 4;
-       // is the alpha not transparent?
-       return (pix_ptr[3] > 0) ? item : NULL;
+       } else {
+
+               unsigned char * const pixels = image->px;
+               const int width = image->pxw;
+               const int height = image->pxh;
+               const int rowstride = image->pxrs;
+               NR::Point tp = p * image->grid2px;
+               const int ix = (int)(tp[NR::X]);
+               const int iy = (int)(tp[NR::Y]);
+
+               if ((ix < 0) || (iy < 0) || (ix >= width) || (iy >= height))
+                       return NULL;
+
+               unsigned char *pix_ptr = pixels + iy * rowstride + ix * 4;
+               // is the alpha not transparent?
+               return (pix_ptr[3] > 0) ? item : NULL;
+       }
 }
 
 /* Utility */