master dc5bb72 2/3: Perform cleanup on errors in mouse-drag-track

[Lars Ingebrigtsen]

branch: master
commit dc5bb729589ce10734a1a03536026ded8745eba0
Author: Yuri D'Elia <wavexx@thregr.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Perform cleanup on errors in mouse-drag-track
    
    * lisp/mouse.el (mouse-drag-track): Disable both scroll-margin and
    auto-hscroll-mode in mouse-drag-region and do not re-enable them until
    dragging is over, making selections work as expected when inside the
    margins.
    * lisp/mouse.el (mouse-drag-track): Correctly reset original values
    changed during execution if errors occur.
---
 lisp/mouse.el | 140 ++++++++++++++++++++++++++++++----------------------------
 1 file changed, 73 insertions(+), 67 deletions(-)

diff --git a/lisp/mouse.el b/lisp/mouse.el
index 3c457a3..1cbdaaf 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -1593,75 +1593,81 @@ The region will be defined with mark and point."
          ;; Save original automatic scrolling behavior (see below).
         (auto-hscroll-mode-saved auto-hscroll-mode)
         (scroll-margin-saved scroll-margin)
-         (old-track-mouse track-mouse))
-
-    (setq mouse-selection-click-count click-count)
-
-    ;; Suppress automatic scrolling near the edges while tracking
-    ;; movement, as it interferes with the natural dragging behavior
-    ;; (point will unexpectedly be moved beneath the pointer, making
-    ;; selections in auto-scrolling margins impossible).
-    (setq auto-hscroll-mode nil)
-    (setq scroll-margin 0)
+         (old-track-mouse track-mouse)
+         (cleanup (lambda ()
+                    (setq track-mouse old-track-mouse)
+                    (setq auto-hscroll-mode auto-hscroll-mode-saved)
+                    (setq scroll-margin scroll-margin-saved))))
+    (condition-case err
+        (progn
+          (setq mouse-selection-click-count click-count)
+
+          ;; Suppress automatic scrolling near the edges while tracking
+          ;; movement, as it interferes with the natural dragging behavior
+          ;; (point will unexpectedly be moved beneath the pointer, making
+          ;; selections in auto-scrolling margins impossible).
+          (setq auto-hscroll-mode nil)
+          (setq scroll-margin 0)
+
+          ;; In case the down click is in the middle of some intangible text,
+          ;; use the end of that text, and put it in START-POINT.
+          (if (< (point) start-point)
+             (goto-char start-point))
+          (setq start-point (point))
+
+          ;; Activate the region, using `mouse-start-end' to determine where
+          ;; to put point and mark (e.g., double-click will select a word).
+          (setq-local transient-mark-mode
+                      (if (eq transient-mark-mode 'lambda)
+                          '(only)
+                        (cons 'only transient-mark-mode)))
+          (let ((range (mouse-start-end start-point start-point click-count)))
+            (push-mark (nth 0 range) t t)
+            (goto-char (nth 1 range)))
 
-    ;; In case the down click is in the middle of some intangible text,
-    ;; use the end of that text, and put it in START-POINT.
-    (if (< (point) start-point)
-       (goto-char start-point))
-    (setq start-point (point))
+          (setf (terminal-parameter nil 'mouse-drag-start) start-event)
+          (setq track-mouse t)
 
-    ;; Activate the region, using `mouse-start-end' to determine where
-    ;; to put point and mark (e.g., double-click will select a word).
-    (setq-local transient-mark-mode
-                (if (eq transient-mark-mode 'lambda)
-                    '(only)
-                  (cons 'only transient-mark-mode)))
-    (let ((range (mouse-start-end start-point start-point click-count)))
-      (push-mark (nth 0 range) t t)
-      (goto-char (nth 1 range)))
-
-    (setf (terminal-parameter nil 'mouse-drag-start) start-event)
-    (setq track-mouse t)
-
-    (set-transient-map
-     (let ((map (make-sparse-keymap)))
-       (define-key map [switch-frame] #'ignore)
-       (define-key map [select-window] #'ignore)
-       (define-key map [mouse-movement]
-         (lambda (event) (interactive "e")
-           (let* ((end (event-end event))
-                  (end-point (posn-point end)))
-             (unless (eq end-point start-point)
-               ;; And remember that we have moved, so mouse-set-region can know
-               ;; its event is really a drag event.
-               (setcar start-event 'mouse-movement))
-             (if (and (eq (posn-window end) start-window)
-                      (integer-or-marker-p end-point))
-                 (mouse--drag-set-mark-and-point start-point
-                                                 end-point click-count)
-               (let ((mouse-row (cdr (cdr (mouse-position)))))
-                 (cond
-                  ((null mouse-row))
-                  ((< mouse-row top)
-                   (mouse-scroll-subr start-window (- mouse-row top)
-                                      nil start-point))
-                  ((>= mouse-row bottom)
-                   (mouse-scroll-subr start-window (1+ (- mouse-row bottom))
-                                      nil start-point))))))))
-       map)
-     t (lambda ()
-         (setq track-mouse old-track-mouse)
-         (setq auto-hscroll-mode auto-hscroll-mode-saved)
-         (setq scroll-margin scroll-margin-saved)
-         ;; Don't deactivate the mark when the context menu was invoked
-         ;; by down-mouse-3 immediately after down-mouse-1 and without
-         ;; releasing the mouse button with mouse-1. This allows to use
-         ;; region-related context menu to operate on the selected region.
-         (unless (and context-menu-mode
-                      (eq (car-safe (aref (this-command-keys-vector) 0))
-                          'down-mouse-3))
-           (deactivate-mark)
-           (pop-mark))))))
+          (set-transient-map
+           (let ((map (make-sparse-keymap)))
+             (define-key map [switch-frame] #'ignore)
+             (define-key map [select-window] #'ignore)
+             (define-key map [mouse-movement]
+               (lambda (event) (interactive "e")
+                 (let* ((end (event-end event))
+                        (end-point (posn-point end)))
+                   (unless (eq end-point start-point)
+                     ;; And remember that we have moved, so mouse-set-region 
can know
+                     ;; its event is really a drag event.
+                     (setcar start-event 'mouse-movement))
+                   (if (and (eq (posn-window end) start-window)
+                            (integer-or-marker-p end-point))
+                       (mouse--drag-set-mark-and-point start-point
+                                                       end-point click-count)
+                     (let ((mouse-row (cdr (cdr (mouse-position)))))
+                       (cond
+                        ((null mouse-row))
+                        ((< mouse-row top)
+                         (mouse-scroll-subr start-window (- mouse-row top)
+                                            nil start-point))
+                        ((>= mouse-row bottom)
+                         (mouse-scroll-subr start-window (1+ (- mouse-row 
bottom))
+                                            nil start-point))))))))
+             map)
+           t (lambda ()
+               (funcall cleanup)
+               ;; Don't deactivate the mark when the context menu was invoked
+               ;; by down-mouse-3 immediately after down-mouse-1 and without
+               ;; releasing the mouse button with mouse-1. This allows to use
+               ;; region-related context menu to operate on the selected 
region.
+               (unless (and context-menu-mode
+                            (eq (car-safe (aref (this-command-keys-vector) 0))
+                                'down-mouse-3))
+                 (deactivate-mark)
+                 (pop-mark)))))
+      ;; Cleanup on errors
+      (error (funcall cleanup)
+             (signal (car err) (cdr err))))))
 
 (defun mouse--drag-set-mark-and-point (start click click-count)
   (let* ((range (mouse-start-end start click click-count))