X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/puzzles/blobdiff_plain/4a9957b631033dd550ade368dddad95fbc9d115d..dbdfc6eadd04c4c91c9ff11c57f0559fb12611ca:/misc.c

diff --git a/misc.c b/misc.c
index 81aa011..11c842c 100644
--- a/misc.c
+++ b/misc.c
@@ -280,6 +280,35 @@ int c2pos(int w, int h, int cx, int cy)
     return -1; /* not reached */
 }
 
+int c2diff(int w, int h, int cx, int cy, int button)
+{
+    int diff = 0;
+
+    assert(IS_CURSOR_MOVE(button));
+
+    /* Obvious moves around edge. */
+    if (cy == -1)
+        diff = (button == CURSOR_RIGHT) ? +1 : (button == CURSOR_LEFT) ? -1 : diff;
+    if (cy == h)
+        diff = (button == CURSOR_RIGHT) ? -1 : (button == CURSOR_LEFT) ? +1 : diff;
+    if (cx == -1)
+        diff = (button == CURSOR_UP) ? +1 : (button == CURSOR_DOWN) ? -1 : diff;
+    if (cx == w)
+        diff = (button == CURSOR_UP) ? -1 : (button == CURSOR_DOWN) ? +1 : diff;
+
+    if (button == CURSOR_LEFT && cx == w && (cy == 0 || cy == h-1))
+        diff = (cy == 0) ? -1 : +1;
+    if (button == CURSOR_RIGHT && cx == -1 && (cy == 0 || cy == h-1))
+        diff = (cy == 0) ? +1 : -1;
+    if (button == CURSOR_DOWN && cy == -1 && (cx == 0 || cx == w-1))
+        diff = (cx == 0) ? -1 : +1;
+    if (button == CURSOR_UP && cy == h && (cx == 0 || cx == w-1))
+        diff = (cx == 0) ? +1 : -1;
+
+    debug(("cx,cy = %d,%d; w%d h%d, diff = %d", cx, cy, w, h, diff));
+    return diff;
+}
+
 void pos2c(int w, int h, int pos, int *cx, int *cy)
 {
     int max = w+h+w+h;