Fix problem with viewing .webp files from .zip buffers

* lisp/image-mode.el (image-toggle-display-image): Make it
possible to view images (via external formatters, like webp) from
zip files (and other archive modes) (bug#39994).

1 files changed, 17 insertions, 6 deletions

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 129529542ae..c417be43da5 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -818,13 +818,21 @@ was inserted."
                       (- (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)))
          (inhibit-read-only t)
          (buffer-undo-list t)
          (modified (buffer-modified-p))
-         props image)
+         props image type)
+
+    ;; If the data in the current buffer isn't from an existing file,
+    ;; but we have a file name (this happens when visiting images from
+    ;; a zip file, for instance), provide a type hint based on the
+    ;; suffix.
+    (when (and data-p filename)
+      (setq data-p (intern (format "image/%s"
+                                   (file-name-extension filename)))))
+    (setq type (if (image--imagemagick-wanted-p filename)
+                   'imagemagick
+                 (image-type file-or-data nil data-p)))
 
     ;; Get the rotation data from the file, if any.
     (when (zerop image-transform-rotation) ; don't reset modified value
@@ -841,10 +849,13 @@ was inserted."
     ;; :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
+                                  :format (and filename data-p))
                   (create-image file-or-data type data-p :scale 1
                                 :max-width max-width
-                                :max-height max-height)))
+                                :max-height max-height
+                                ;; Type hint.
+                                :format (and filename data-p))))
 
     ;; Discard any stale image data before looking it up again.
     (image-flush image)