Improve documentation of 'display-monitor-attributes-

* doc/lispref/frames.texi (Multiple Terminals):
* lisp/frame.el (display-monitor-attributes-list): Better
documentation of what the 'source' key means on X.  (Bug#75936)

(cherry picked from commit 6d7e7899d84600de3aa4bb5e4cb4013e48f7a8b5)

diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index e30d1c9982044ef467af9d5c125cf2cd7e09cba5..bc2d6b07ae8342679c690436f052b8b6afa9c344 100644 (file)
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -427,7 +427,12 @@ Name of the physical monitor as @var{string}.
 
 @item source
 Source of the multi-monitor information as @var{string};
-e.g., @samp{XRandR 1.5}, @samp{XRandr} or @samp{Xinerama}.
+on X, it could be @samp{XRandR 1.5}, @samp{XRandr}, @samp{Xinerama},
+@samp{Gdk}, or @samp{fallback}.  The last value of @samp{source} means
+that Emacs was built without GTK and without XRandR or Xinerama
+extensions, in which case the information about multiple physical
+monitors will be provided as if they all as a whole formed a single
+monitor.
 @end table
 
 @var{x}, @var{y}, @var{width}, and @var{height} are integers.

diff --git a/lisp/frame.el b/lisp/frame.el
index 4bc8b4c05dbaba3d10d740650d16d0a96c3a6f2f..62faaf80be9b578e6e3ab9a65658cd4d184243cb 100644 (file)
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2543,6 +2543,10 @@ details depend on the platform and environment.
 The `source' attribute describes the source from which the
 information was obtained.  On X, this may be one of: \"Gdk\",
 \"XRandR 1.5\", \"XRandr\", \"Xinerama\", or \"fallback\".
+If it is \"fallback\", it means Emacs was built without GTK
+and without XrandR or Xinerama extensions, in which case the
+information about multiple physical monitors will be provided
+as if they all as a whole formed a single monitor.
 
 A frame is dominated by a physical monitor when either the
 largest area of the frame resides in the monitor, or the monitor