[RP] [PATCH] Fix: exclude degenerate case from frame overlap

[Antoine Busque]

The current implementation of the find_frame_* functions considered
the degenerate case of frame overlap (i.e. a single pixel overlap, or
in other words, one frame beginning where the other ends) as valid.

This led to issues where certain frames would be impossible to reach
via focus* commands, since another frame with single pixel overlap
would be focused onto instead.

An easy way to reproduce such a case is to split one screen into 4
frames, by doing one vertical split and then two horizontal splits, or
vice versa. In the current implementation, the bottom-right frame is
unreachable via directional focus commands, since either the top-right
(when trying to focusright from the bottom-left) or bottom-left (when
trying to focusdown from the top-right) frames are focused onto, due
to a single pixel overlap.

Therefore, this patch excludes the degenerate case from being
considered as a valid frame overlap.

Signed-off-by: Antoine Busque <address@hidden>
---
 src/split.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/src/split.c b/src/split.c
index eed0f50..1c7d8b5 100644
--- a/src/split.c
+++ b/src/split.c
@@ -1000,6 +1000,28 @@ show_frame_message (char *msg)
   sbuf_free (msgbuf);
 }
 
+static int
+frames_overlap_horizontal (rp_frame *f1, rp_frame *f2)
+{
+  int f1_right = frame_right_abs (f1);
+  int f2_right = frame_right_abs (f2);
+  int f1_left = frame_left_abs (f1);
+  int f2_left = frame_left_abs (f2);
+
+  return f1_left < f2_right && f2_left < f1_right;
+}
+
+static int
+frames_overlap_vertical (rp_frame *f1, rp_frame *f2)
+{
+  int f1_bottom = frame_bottom_abs (f1);
+  int f2_bottom = frame_bottom_abs (f2);
+  int f1_top = frame_top_abs (f1);
+  int f2_top = frame_top_abs (f2);
+
+  return f1_top < f2_bottom && f2_top < f1_bottom;
+}
+
 rp_frame *
 find_frame_up (rp_frame *frame)
 {
@@ -1011,7 +1033,7 @@ find_frame_up (rp_frame *frame)
       list_for_each_entry (cur, &s->frames, node)
         {
           if (frame_top_abs (frame) == frame_bottom_abs (cur))
-            if (frame_right_abs (frame) >= frame_left_abs (cur) && 
frame_left_abs (frame) <= frame_right_abs (cur))
+            if (frames_overlap_horizontal (frame, cur))
               return cur;
         }
     }
@@ -1030,7 +1052,7 @@ find_frame_down (rp_frame *frame)
       list_for_each_entry (cur, &s->frames, node)
         {
           if (frame_bottom_abs (frame) == frame_top_abs (cur))
-            if (frame_right_abs (frame) >= frame_left_abs (cur) && 
frame_left_abs (frame) <= frame_right_abs (cur))
+            if (frames_overlap_horizontal (frame, cur))
               return cur;
         }
     }
@@ -1049,7 +1071,7 @@ find_frame_left (rp_frame *frame)
       list_for_each_entry (cur, &s->frames, node)
         {
           if (frame_left_abs (frame) == frame_right_abs (cur))
-            if (frame_bottom_abs (frame) >= frame_top_abs (cur) && 
frame_top_abs (frame) <= frame_bottom_abs (cur))
+            if (frames_overlap_vertical (frame, cur))
               return cur;
         }
     }
@@ -1068,7 +1090,7 @@ find_frame_right (rp_frame *frame)
       list_for_each_entry (cur, &s->frames, node)
         {
           if (frame_right_abs (frame) == frame_left_abs (cur))
-            if (frame_bottom_abs (frame) >= frame_top_abs (cur) && 
frame_top_abs (frame) <= frame_bottom_abs (cur))
+            if (frames_overlap_vertical (frame, cur))
               return cur;
         }
     }
-- 
2.16.1