fix error in process filter: Cannot resize window

1 files changed, 12 insertions, 3 deletions

diff --git a/generic/proof-utils.el b/generic/proof-utils.el
index d2cf760c..be5fee6e 100644
--- a/generic/proof-utils.el
+++ b/generic/proof-utils.el
@@ -431,14 +431,23 @@ or if the window is the only window of its frame."
 	    ;; buffers?  Probably not an issue for us, but one
 	    ;; wonders at the shrink to fit strategy.
 	    ;; NB: way to calculate pixel fraction?
-	    (+ extraline (count-lines (point-min) (point-max)))))
+	    (+ extraline (count-lines (point-min) (point-max))))
+	   (safe-desired-height
+	    ;; Under certain circumstances (involving a non-nil
+	    ;; line-spacing), a desired-height of 1 (which happens
+	    ;; quite often, eg for an empty response buffer) gives an
+	    ;; error inside set-window-text-height. The reason for
+	    ;; this is quite complicated, it involves rounding issues
+	    ;; and emacs' habbit to sometimes resize a window by 2
+	    ;; pixels.
+	    (max 2 desired-height)))
 	;; Let's shrink or expand.  Uses new GNU Emacs function.
 	(let ((window-size-fixed nil))
 	  (set-window-text-height window
 				  ;; As explained earlier: use abs-max-height
 				  ;; but only if that makes it display all.
-				  (if (> desired-height absolute-max-height)
-				      max-height desired-height)))
+				  (if (> safe-desired-height absolute-max-height)
+				      max-height safe-desired-height)))
 	(if (window-live-p window)
 	    (progn
 	      (if (>= (window-text-height window) desired-height)