bug#41886: 27.1; Rotated image doesn't fit to window height

[Juri Linkov]

Version: 27.1
Tags: patch

I found a bug in image-mode on emacs-27.

Using the default value 't' of 'image-transform-resize'
(that means to fit the image to the window height and width),
when an image has exif-orientation 90 and visited in image-mode,
it's rotated, but doesn't fit to the window height,
only the upper half of the image is displayed.
The patch that fixes this problem:

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index b82c066918..019f6e20ce 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -810,8 +810,12 @@ image-toggle-display-image
            filename))
         ;; If we have a `fit-width' or a `fit-height', don't limit
         ;; the size of the image to the window size.
-        (edges (and (eq image-transform-resize t)
-                    (window-inside-pixel-edges (get-buffer-window))))
+        (edges (when (eq image-transform-resize t)
+                 (window-inside-pixel-edges (get-buffer-window))))
+        (max-width (when edges
+                     (- (nth 2 edges) (nth 0 edges))))
+        (max-height (when edges
+                      (- (nth 3 edges) (nth 1 edges))))
         (type (if (image--imagemagick-wanted-p filename)
                   'imagemagick
                 (image-type file-or-data nil data-p)))
@@ -827,14 +831,18 @@ image-toggle-display-image
                  (ignore-error exif-error
                    (exif-parse-buffer)))
                 0.0)))
+    ;; Swap width and height when changing orientation
+    ;; between portrait and landscape.
+    (when (and edges (memq (truncate image-transform-rotation) '(90 270)))
+      (setq max-width (prog1 max-height (setq max-height max-width))))
 
     ;; :scale 1: If we do not set this, create-image will apply
     ;; default scaling based on font size.
     (setq image (if (not edges)
                    (create-image file-or-data type data-p :scale 1)
                  (create-image file-or-data type data-p :scale 1
-                               :max-width (- (nth 2 edges) (nth 0 edges))
-                               :max-height (- (nth 3 edges) (nth 1 edges)))))
+                               :max-width max-width
+                               :max-height max-height)))
 
     ;; Discard any stale image data before looking it up again.
     (image-flush image)