bug#41222: 27.1; Auto-resizing of images in image-mode

[Juri Linkov <juri@linkov.net>]

This is a followup to the emacs-devel thread
https://lists.gnu.org/archive/html/emacs-devel/2020-04/msg00777.html

I noticed that image-mode still lacks one needed command:
some image viewers have a menu item titled “Normal Size C-0” or
“Original Size C-0”.  Here's is the patch that implements it:

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 480b2e6b26..45007289c8 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -456,6 +456,7 @@ image-mode-map
     (define-key map "sb" 'image-transform-fit-both)
     (define-key map "ss" 'image-transform-set-scale)
     (define-key map "sr" 'image-transform-set-rotation)
+    (define-key map "so" 'image-transform-original)
     (define-key map "s0" 'image-transform-reset)
 
     ;; Multi-frame keys
@@ -521,6 +522,8 @@ image-mode-map
 	 :help "Rotate the image"]
 	["Set Rotation..." image-transform-set-rotation
 	 :help "Set rotation angle of the image"]
+	["Original Size" image-transform-original
+	 :help "Reset image to original size"]
 	["Reset Transformations" image-transform-reset
 	 :help "Reset all image transformations"]
 	"--"
@@ -1382,6 +1385,13 @@ image-transform-set-rotation
   (setq image-transform-rotation (float (mod rotation 360)))
   (image-toggle-display-image))
 
+(defun image-transform-original ()
+  "Display the current image with the original size and rotation."
+  (interactive)
+  (setq image-transform-resize nil
+	image-transform-scale 1)
+  (image-toggle-display-image))
+
 (defun image-transform-reset ()
   "Display the current image with the default size and rotation."
   (interactive)


BTW, like ‘image-auto-resize-on-window-resize’ was added recently to
image-mode.el, is there a need to add a similar option to man.el
to allow customization of auto-resizing of Man buffers as well?
Maybe something like:

diff --git a/lisp/man.el b/lisp/man.el
index 5278a1a84d..a614cac536 100644
--- a/lisp/man.el
+++ b/lisp/man.el
@@ -1579,7 +1579,8 @@ Man-mode
   (set (make-local-variable 'outline-level) (lambda () 1))
   (set (make-local-variable 'bookmark-make-record-function)
        'Man-bookmark-make-record)
-  (add-hook 'window-state-change-functions #'Man--window-state-change nil t))
+  (when Man-fit-to-window-on-window-resize
+    (add-hook 'window-state-change-functions #'Man--window-state-change nil t)))
 
 (defun Man-build-section-list ()
   "Build the list of manpage sections."