Fix erasing of arrow highlight (XB)

On large board with long-range oblique moves (like in Grande Acedrex)
the head of the arrow was not always erased (and not always drawn either).
This was partly due to the arrow pointing to a corner of the target square
even if the path was nearly orthogonal, while the damage trail is always
assumed to connect the square centers. Having the arrow point more
precisely and widening the damage trail a bit solved the problem.

diff --git a/board.c b/board.c
index e8111dd..f2b0643 100644 (file)
--- a/board.c
+++ b/board.c
@@ -1190,10 +1190,10 @@ ArrowDamage (int s_col, int s_row, int d_col, int d_row)
     int hor, vert, i, n = partnerUp * twoBoards;
     hor = 64*s_col + 32; vert = 64*s_row + 32;
     for(i=0; i<= 64; i++) {
-            damage[n][vert+6>>6][hor+6>>6] |= 2;
-            damage[n][vert-6>>6][hor+6>>6] |= 2;
-            damage[n][vert+6>>6][hor-6>>6] |= 2;
-            damage[n][vert-6>>6][hor-6>>6] |= 2;
+            damage[n][vert+8>>6][hor+8>>6] |= 2;
+            damage[n][vert-8>>6][hor+8>>6] |= 2;
+            damage[n][vert+8>>6][hor-8>>6] |= 2;
+            damage[n][vert-8>>6][hor-8>>6] |= 2;
             hor += d_col - s_col; vert += d_row - s_row;
     }
 }
@@ -1212,20 +1212,20 @@ DrawArrowBetweenSquares (int s_col, int s_row, int d_col, int d_row)
     SquareToPos( s_row, s_col, &s_x, &s_y);
     SquareToPos( d_row, d_col, &d_x, &d_y);
 
-    if( d_y > s_y ) {
+    if( d_y > s_y && d_y - s_y > abs(d_x - s_x)/2) {
         d_y += squareSize / 2 - squareSize / 4; // [HGM] round towards same centers on all sides!
     }
-    else if( d_y < s_y ) {
+    else if( d_y < s_y && s_y - d_y > abs(d_x - d_y)/2) {
         d_y += squareSize / 2 + squareSize / 4;
     }
     else {
         d_y += squareSize / 2;
     }
 
-    if( d_x > s_x ) {
+    if( d_x > s_x && d_x - s_x > abs(d_y - s_y)/2) {
         d_x += squareSize / 2 - squareSize / 4;
     }
-    else if( d_x < s_x ) {
+    else if( d_x < s_x && s_x - d_x > abs(d_y - s_y)/2) {
         d_x += squareSize / 2 + squareSize / 4;
     }
     else {