display a permanent warning when using IE

HISTORY.md

@@ -8,6 +8,7 @@
 * **Notable Changes:**
     * made "i" upvar inside FOR loop's C-Shape slot mutable by user script
     * prevent switching to another sprite if a block editor is open (so local blocks of different sprites don't mix)
+    * display a permanent warning when using IE
 * **Notable Fixes:**
     * typing strings into the search-field again shows relevant blocks (regression from IME)
     * fixed project dialog's search-field behevior (regression from IME)
@@ -26,6 +27,7 @@
 * gui: prevent switching to another sprite if a block editor is open (so local blocks of different sprites don't mix)
 * updated German translation
 * gui: simplified asset loading scheduler
+* gui: display a permenent warning when using IE
 
 ### 2019-10-14
 * morphic: new "reactToInput" text-editing event

src/gui.js

@@ -550,6 +550,8 @@ IDE_Morph.prototype.openIn = function (world) {
     } else {
         interpretUrlAnchors.call(this);
     }
+
+    this.warnAboutIE();
 };
 
 // IDE_Morph construction
@@ -6002,6 +6004,42 @@ IDE_Morph.prototype.prompt = function (message, callback, choices, key) {
     );
 };
 
+// IDE_Morph bracing against IE
+
+IDE_Morph.prototype.warnAboutIE = function () {
+    var dlg, txt;
+    if (this.isIE()) {
+        dlg = new DialogBoxMorph();
+        txt = new TextMorph(
+            'Please do not use Internet Explorer.\n' +
+                'Snap! runs best in a web-standards\n' +
+                'compliant browser',
+            dlg.fontSize,
+            dlg.fontStyle,
+            true,
+            false,
+            'center',
+            null,
+            null,
+            MorphicPreferences.isFlat ? null : new Point(1, 1),
+            new Color(255, 255, 255)
+        );
+
+        dlg.key = 'IE-Warning';
+        dlg.labelString = "Internet Explorer";
+        dlg.createLabel();
+        dlg.addBody(txt);
+        dlg.drawNew();
+        dlg.fixLayout();
+        dlg.popUp(this.world());
+    }
+};
+
+IDE_Morph.prototype.isIE = function () {
+    var ua = navigator.userAgent;
+    return ua.indexOf("MSIE ") > -1 || ua.indexOf("Trident/") > -1;
+};
+
 // ProjectDialogMorph ////////////////////////////////////////////////////
 
 // ProjectDialogMorph inherits from DialogBoxMorph: