fix: address 4 critical bugs in core utilities and singer logic (sugarlabs#5679)

* fix: address 4 critical bugs in core utilities and singer logic

1. Fix numberOfNotes() crash (ReferenceError) — removed dead code
   referencing undefined variables left over from an incomplete
   refactor to saveState. (turtle-singer.js)

2. Fix rationalSum() silently mutating its input arrays — replaced
   in-place array assignments with local const variables to prevent
   corrupting the caller's note-timing state. (utils.js)

3. Fix safeSVG() only escaping the first special character — added
   the global /g flag to all three regex patterns. (utils.js)

4. Fix doUseCamera() using deprecated navigator.getUserMedia API —
   updated to modern navigator.mediaDevices.getUserMedia() with
   proper promise-based flow and feature detection. (utils.js)

* refactor: adopt CameraManager from upstream PR sugarlabs#5662

Replaced bare hasSetupCamera variable with the CameraManager
module introduced in upstream PR sugarlabs#5662. All internal references
updated from hasSetupCamera to CameraManager.isSetup while
preserving the modern
avigator.mediaDevices.getUserMedia() fix.

Ran prettier on both changed files.

Author: Ashutoshx7

js/turtle-singer.js

@@ -660,18 +660,6 @@ class Singer {
         tur.painter.doPenUp();
         tur.painter.doSetXY(saveState.x, saveState.y);
         tur.painter.doSetHeading(saveState.orientation);
-        tur.painter.doSetXY(saveX, saveY);
-        tur.painter.color = saveColor;
-        tur.painter.value = saveValue;
-        tur.painter.chroma = saveChroma;
-        tur.painter.stroke = saveStroke;
-        tur.painter.canvasAlpha = saveCanvasAlpha;
-        tur.painter.doSetHeading(saveOrientation);
-        tur.painter.penState = savePenState;
-        tur.singer.suppressOutput = saveSuppressStatus;
-        tur.singer.previousTurtleTime = savePrevTurtleTime;
-        tur.singer.turtleTime = saveTurtleTime;
-        tur.singer.whichNoteToCount = saveWhichNoteToCount;
         tur.singer.justCounting.pop();
         tur.butNotThese = {};
 

js/utils/utils.js

@@ -1093,14 +1093,6 @@ let doUseCamera = (args, turtles, turtle, isVideo, cameraID, setCameraID, errorM
     let streaming = false;
     const video = document.querySelector("#camVideo");
     const canvas = document.querySelector("#camCanvas");
-    navigator.getMedia =
-        navigator.getUserMedia ||
-        navigator.mozGetUserMedia ||
-        navigator.webkitGetUserMedia ||
-        navigator.msGetUserMedia;
-    if (navigator.getMedia === undefined) {
-        errorMsg("Your browser does not support the webcam");
-    }
 
     function draw() {
         canvas.width = w;
@@ -1111,24 +1103,23 @@ let doUseCamera = (args, turtles, turtle, isVideo, cameraID, setCameraID, errorM
     }
 
     if (!CameraManager.isSetup) {
-        navigator.getMedia(
-            { video: true, audio: false },
-            stream => {
-                if (navigator.mozGetUserMedia) {
-                    video.mozSrcObject = stream;
-                } else {
-                    video.srcObject = stream;
-                }
+        if (!navigator.mediaDevices || !navigator.mediaDevices.getUserMedia) {
+            errorMsg("Your browser does not support the webcam");
+            return;
+        }
 
+        navigator.mediaDevices
+            .getUserMedia({ video: true, audio: false })
+            .then(stream => {
+                video.srcObject = stream;
                 video.play();
                 CameraManager.isSetup = true;
-            },
-            error => {
+            })
+            .catch(error => {
                 errorMsg("Could not connect to camera");
                 // eslint-disable-next-line no-console
                 console.debug(error);
-            }
-        );
+            });
     } else {
         streaming = true;
         video.play();
@@ -1219,7 +1210,7 @@ function displayMsg(/*blocks, text*/) {
  */
 function safeSVG(label) {
     if (typeof label === "string") {
-        return label.replace(/&/, "&amp;").replace(/</, "&lt;").replace(/>/, "&gt;");
+        return label.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
     } else {
         return label;
     }
@@ -1414,16 +1405,15 @@ let rationalSum = (a, b) => {
     } else {
         objb1 = [b[1], 1];
     }
-
-    a[0] = obja0[0] * obja1[1];
-    a[1] = obja0[1] * obja1[0];
-    b[0] = objb0[0] * objb1[1];
-    b[1] = objb0[1] * objb1[0];
+    // Use local variables to avoid mutating the caller's arrays
+    const a0 = obja0[0] * obja1[1];
+    const a1 = obja0[1] * obja1[0];
+    const b0 = objb0[0] * objb1[1];
+    const b1 = objb0[1] * objb1[0];
 
     // Find the least common denomenator
-    const lcd = LCD(a[1], b[1]);
-    // const c0 = (a[0] * lcd) / a[1] + (b[0] * lcd) / b[1];
-    return [(a[0] * lcd) / a[1] + (b[0] * lcd) / b[1], lcd];
+    const lcd = LCD(a1, b1);
+    return [(a0 * lcd) / a1 + (b0 * lcd) / b1, lcd];
 };
 
 /**