emacs: show: make buttons select window

Emacs has two button type objects: widgets (as used for saved searches
in notmuch-hello) and buttons as used by parts/citations and id links
in notmuch-show. These two behave subtly differently when clicked with
the mouse: widgets select the window clicked before running the
action, buttons do not.

This patch makes all of these behave the same: clicking always selects
the clicked window. It does this by defining a notmuch-button-type
supertype that the other notmuch buttons can inherit from. This
supertype binds the mouse-action to select the window and then
activate the button.

1 files changed, 15 insertions, 0 deletions

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index d78bcf80..270e3dc6 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -97,6 +97,21 @@ For example, if you wanted to remove an \"inbox\" tag and add an
   :group 'notmuch-search
   :group 'notmuch-show)
 
+;; By default clicking on a button does not select the window
+;; containing the button (as opposed to clicking on a widget which
+;; does). This means that the button action is then executed in the
+;; current selected window which can cause problems if the button
+;; changes the buffer (e.g., id: links) or moves point.
+;;
+;; This provides a button type which overrides mouse-action so that
+;; the button's window is selected before the action is run. Other
+;; notmuch buttons can get the same behaviour by inheriting from this
+;; button type.
+(define-button-type 'notmuch-button-type
+  'mouse-action (lambda (button)
+		  (select-window (posn-window (event-start last-input-event)))
+		  (button-activate button)))
+
 (defun notmuch-version ()
   "Return a string with the notmuch version number."
   (let ((long-string