SVG (E)rase removes all drawing elements

organix · Feb 3, 2025 · 678f904 · 678f904
1 parent 32fb3f4
commit 678f904
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Showing 4 changed files with 16 additions and 5 deletions.
diff --git a/apps/playground/svg_dev_ui.js b/apps/playground/svg_dev_ui.js
@@ -143,7 +143,11 @@ const svg_dev_ui = make_ui("svg-dev-ui", function (element, {
     ]);
 
     function draw(html) {
-        svg_element.innerHTML += html;
+        if (typeof html === "string") {
+            svg_element.innerHTML += html;
+        } else if (html === undefined) {
+            svg_element.innerHTML = "";
+        }
     }
 
     set_background_color(background_color);

diff --git a/docs/svg_drawing.md b/docs/svg_drawing.md
@@ -45,12 +45,13 @@ Prefix     | Parameters                       | Operation
 `f`        | _r_ _g_ _b_ _a_                  | fill pending (followed by `D`)
 `D`        | _r_ _g_ _b_ _a_ _w_ _cap_ _join_ | draw stroke _w_ wide (0=butt, 1=round, 2=square)
 `f`        | _r_ _g_ _b_ _a_ _w_ _cap_ _join_ | draw pending (followed by `F`)
+`E`        | &mdash;                          | erase all drawing elements
 
 Standard: `AaCcHhLlMmQqSsTtVvZz`
 
-Extended: `DdFfX`
+Extended: `DdFfXE`
 
-Unused: `BbEeGgIiJjKkNnOoPpRrUuWwxYy`
+Unused: `BbeGgIiJjKkNnOoPpRrUuWwxYy`
 
 ## I/O Interface
 

diff --git a/lib/svg_drawing.js b/lib/svg_drawing.js
@@ -5,14 +5,17 @@
 
 // The API is described in `svg_drawing.md`.
 
+/*jslint long */
+
 const join = [ "butt", "round", "square" ];  // linecap and linejoin attributes
 
 function svg_drawing(add_html) {
     // The `svg_drawing` function returns a call-back function
     // that processes a fixnum `code` from the command stream.
 
     // The `add_html` function is called (with a String argument)
-    // to append HTML elements to an SVG drawing.
+    // to append HTML elements to an SVG drawing. If the argument
+    // is `undefined`, all drawing elements are erased.
 
     let next = parse_start;  // parser state-machine (strategy pattern)
     let cmd, nargs, args, path, text, stroke;  // parser context
@@ -35,6 +38,9 @@ function svg_drawing(add_html) {
             nargs = 3;
             args = [];
             next = parse_text_args;
+        } else if (char === "E") {
+            add_html(undefined);
+            next = parse_start;
         }
     }
 

diff --git a/site/index.html b/site/index.html
@@ -137,7 +137,7 @@ <h2><span>🔑</span> Security</h2>
             </ul>
             <p>
                 Addresses are opaque.
-                They can be used only to generate an asynchronous event,
+                They can only be used to generate an asynchronous event,
                 not to access memory.
             </p>
         </details>