New functions svg-text and svg-remove

* doc/lispref/display.texi (SVG Images): Document svg-remove.

* doc/lispref/display.texi (SVG Images): Document svg-text.

* lisp/svg.el (svg-remove): New function.
(svg-text): New function.

doc/lispref/display.texi

@@ -5350,6 +5350,24 @@ that describe the outer circumference of the polygon.
 @end lisp
 @end defun
 
+@defun svg-text svg text &rest args
+Add a text to @var{svg}.
+
+@lisp
+(svg-text
+ svg "This is a text"
+ :font-size "40"
+ :font-weight "bold"
+ :stroke "black"
+ :fill "white"
+ :font-family "impact"
+ :letter-spacing "4pt"
+ :x 300
+ :y 400
+ :stroke-width 1)
+@end lisp
+@end defun
+
 @defun svg-embed svg image image-type datap &rest args
 Add an embedded (raster) image to @var{svg}.  If @var{datap} is
 @code{nil}, @var{IMAGE} should be a file name; if not, it should be a
@@ -5363,6 +5381,10 @@ binary string containing the image data.  @var{image-type} should be a
 @end lisp
 @end defun
 
+@defun svg-remove svg id
+Remove the element with identifier @code{id} from the @code{svg}.
+@end defun
+
 Finally, the @code{svg-image} takes an SVG object as its parameter and
 returns an image object suitable for use in functions like
 @code{insert-image}.  Here's a complete example that creates and

lisp/svg.el

@@ -27,6 +27,7 @@
 (require 'cl-lib)
 (require 'xml)
 (require 'dom)
+(require 'subr-x)
 
 (defun svg-create (width height &rest args)
   "Create a new, empty SVG image with dimensions WIDTHxHEIGHT.
@@ -149,13 +150,22 @@ otherwise.  IMAGE-TYPE should be a MIME image type, like
     `((xlink:href . ,(svg--image-data image image-type datap))
       ,@(svg--arguments svg args)))))
 
+(defun svg-text (svg text &rest args)
+  "Add TEXT to SVG."
+  (svg--append
+   svg
+   (dom-node
+    'text
+    `(,@(svg--arguments svg args))
+    text)))
+
 (defun svg--append (svg node)
   (let ((old (and (dom-attr node 'id)
 		  (dom-by-id svg
                              (concat "\\`" (regexp-quote (dom-attr node 'id))
                                      "\\'")))))
     (if old
-	(dom-set-attributes old (dom-attributes node))
+	(setcdr (car old) (cdr node))
       (dom-append-child svg node)))
   (svg-possibly-update-image svg))
 
@@ -237,16 +247,26 @@ If the SVG is later changed, the image will also be updated."
 
 (defun svg-print (dom)
   "Convert DOM into a string containing the xml representation."
-  (insert (format "<%s" (car dom)))
-  (dolist (attr (nth 1 dom))
-    ;; Ignore attributes that start with a colon.
-    (unless (= (aref (format "%s" (car attr)) 0) ?:)
-      (insert (format " %s=\"%s\"" (car attr) (cdr attr)))))
-  (insert ">")
-  (dolist (elem (nthcdr 2 dom))
-    (insert " ")
-    (svg-print elem))
-  (insert (format "</%s>" (car dom))))
+  (if (stringp dom)
+      (insert dom)
+    (insert (format "<%s" (car dom)))
+    (dolist (attr (nth 1 dom))
+      ;; Ignore attributes that start with a colon.
+      (unless (= (aref (format "%s" (car attr)) 0) ?:)
+        (insert (format " %s=\"%s\"" (car attr) (cdr attr)))))
+    (insert ">")
+    (dolist (elem (nthcdr 2 dom))
+      (insert " ")
+      (svg-print elem))
+    (insert (format "</%s>" (car dom)))))
+
+(defun svg-remove (svg id)
+  "Remove the element identified by ID from SVG."
+  (when-let ((node (car (dom-by-id
+                         svg
+                         (concat "\\`" (regexp-quote id)
+                                 "\\'")))))
+    (dom-remove-node svg node)))
 
 (provide 'svg)