fix(signcol): handle edge case with maximum value

50250542 failed to consider that the maximum passed to buf_signcols
is window scoped whereas the signcols value is buffer scoped. This can
lead to a bug where the signcolumn becomes incorrect if:
- global signcolumn is set to auto:N
- signcolumn in a window is changed locally to auto:M where M > N
- the buffer has a line with M or greater signs.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index dd40623af2..9e82b4e80b 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -5495,11 +5495,19 @@ static int buf_signcols_inner(buf_T *buf, int maximum)
 
 int buf_signcols(buf_T *buf, int maximum)
 {
+  // The maximum can be determined from 'signcolumn' which is window scoped so
+  // need to invalidate signcols if the maximum is greater than the previous
+  // maximum.
+  if (maximum > buf->b_signcols_max) {
+    buf->b_signcols_valid = false;
+  }
+
   if (!buf->b_signcols_valid) {
     int signcols = buf_signcols_inner(buf, maximum);
     // Check if we need to redraw
     if (signcols != buf->b_signcols) {
       buf->b_signcols = signcols;
+      buf->b_signcols_max = maximum;
       redraw_buf_later(buf, NOT_VALID);
     }