only report video capture as "on" when the camera actually records something

HISTORY.md

@@ -4,10 +4,12 @@
 * **New Features:**
 * **Notable Changes:**
 * **Notable Fixes:**
+    * only report video capture as "on" when the camera actually records something
 * **Translation Updates:**
 
 ### 2019-11-18
 * new dev version
+* threads: only report video capture as "on" when the camera actually records something
 
 ## v5.3.6:
 * **Notable Fix:**

snap.html

@@ -7,7 +7,7 @@
         <script type="text/javascript" src="src/morphic.js?version=2019-11-12"></script>
         <script type="text/javascript" src="src/widgets.js?version=2019-10-16"></script>
         <script type="text/javascript" src="src/blocks.js?version=2019-11-12"></script>
-        <script type="text/javascript" src="src/threads.js?version=2019-11-13"></script>
+        <script type="text/javascript" src="src/threads.js?version=2019-11-18"></script>
         <script type="text/javascript" src="src/objects.js?version=2019-11-15"></script>
         <script type="text/javascript" src="src/gui.js?version=2019-11-18"></script>
         <script type="text/javascript" src="src/paint.js?version=2019-06-27"></script>

src/threads.js

@@ -61,7 +61,7 @@ StageMorph, SpriteMorph, StagePrompterMorph, Note, modules, isString, copy,
 isNil, WatcherMorph, List, ListWatcherMorph, alert, console, TableMorph, Color,
 TableFrameMorph, ColorSlotMorph, isSnapObject, Map, newCanvas, Symbol*/
 
-modules.threads = '2019-November-13';
+modules.threads = '2019-November-18';
 
 var ThreadManager;
 var Process;
@@ -2099,7 +2099,11 @@ Process.prototype.reportGlobalFlag = function (name) {
     case 'flat line ends':
         return SpriteMorph.prototype.useFlatLineEnds;
     case 'video capture':
-        return !isNil(stage.projectionSource);
+        return !isNil(stage.projectionSource) &&
+            stage.projectionLayer()
+                .getContext('2d')
+                .getImageData(0, 0, 1, 1)
+                .data[3] > 0;
     case 'mirror video':
         return stage.mirrorVideo;
     default: