Rework the image property getter/setters

* doc/lispref/display.texi (Defining Images): Document the
renamed `image-get/set-property' functions.

* lisp/image.el (image--set-property): Rename from
image-set-property.
(image-property): Declare a setf form.
(image-property): Rename from `image-get-property'.

2 files changed, 12 insertions, 7 deletions

diff --git a/lisp/image.el b/lisp/image.el
index 3522c5bc75c..96afa98bb3e 100644
--- a/lisp/image.el
+++ b/lisp/image.el
@@ -435,10 +435,9 @@ Image file names that are not absolute are searched for in the
                        (image-compute-scaling-factor image-scaling-factor)))
 	    props)))
 
-(defun image-set-property (image property value)
+(defun image--set-property (image property value)
   "Set PROPERTY in IMAGE to VALUE.
-If VALUE is nil, PROPERTY is removed from IMAGE.  IMAGE is
-returned."
+Internal use only."
   (if (null value)
       (while (cdr image)
         ;; IMAGE starts with the symbol `image', and the rest is a
@@ -451,8 +450,13 @@ returned."
     (plist-put (cdr image) property value))
   image)
 
-(defun image-get-property (image property)
-  "Return the value of PROPERTY in IMAGE."
+(defun image-property (image property)
+  "Return the value of PROPERTY in IMAGE.
+Properties can be set with
+
+  (setf (image-property IMAGE PROPERTY) VALUE)
+If VALUE is nil, PROPERTY is removed from IMAGE."
+  (declare (gv-setter image--set-property))
   (plist-get (cdr image) property))
 
 (defun image-compute-scaling-factor (scaling)
diff --git a/lisp/net/shr.el b/lisp/net/shr.el
index 6352d384184..4c3dfc4fdeb 100644
--- a/lisp/net/shr.el
+++ b/lisp/net/shr.el
@@ -1536,7 +1536,7 @@ The preference is a float determined from `shr-prefer-media-type'."
                             (- (nth 2 edges) (nth 0 edges))))))
          (max-height (and edges
                           (truncate (* shr-max-image-proportion
-				(- (nth 3 edges) (nth 1 edges))))))
+                                       (- (nth 3 edges) (nth 1 edges))))))
          svg image)
     (when (and max-width
                (> width max-width))
@@ -1551,7 +1551,8 @@ The preference is a float determined from `shr-prefer-media-type'."
     (svg-rectangle svg 0 0 width height :gradient "background"
                    :stroke-width 2 :stroke-color "black")
     (let ((image (svg-image svg)))
-      (image-set-property image :ascent 100))))
+      (setf (image-property image :ascent) 100)
+      image)))
 
 (defun shr-tag-pre (dom)
   (let ((shr-folding-mode 'none)