graphics: preventing cursorxy(32,80) from scrolling the screen

assets/disk0/tvdos/bin/command.js

@@ -50,7 +50,7 @@ function greet() {
         con.color_pair(0,253);
         print(" ".repeat(greetLeftPad)+welcome_text+" ".repeat(greetRightPad));
         con.color_pair(253,255);
-        con.addch(16);
+        con.addch(16);print('  ');
         con.move(3,1);
     }
     else
@@ -434,7 +434,7 @@ if (goInteractive) {
                     if (isNaN(errorlevel)) errorlevel = 2;
                 }
                 catch (e) {
-                    printerrln("\n"+e);
+                    printerrln("\n"+(e.stack || e));
                     if (errorlevel === 0 || isNaN(errorlevel)) {
                         errorlevel = 1; // generic failure
                     }

assets/disk0/tvdos/tuidev/demo.js

@@ -0,0 +1,76 @@
+/*
+Screen:
+===================
+Titlebar
+===================
+
+C A N V A S
+
+===================
+
+there are usually two separate canvases: main-screen and menu-screen
+*/
+
+class SimpleScreen {
+
+    constructor(title) {
+        this.title = title;
+        this.termWidth = con.getmaxyx()[1];
+        this.termHeight = con.getmaxyx()[0];
+    }
+
+    drawTitlebar() {
+
+        let titleLeftPad = (this.termWidth - this.title.length - 6) >> 1;
+        let titleRightPad = this.termWidth - titleLeftPad - this.title.length - 6;
+
+        con.move(1,1);
+        con.color_pair(253,255);
+        print('  ');con.addch(17);
+        con.color_pair(0,253);
+        print(" ".repeat(titleLeftPad)+this.title+" ".repeat(titleRightPad));
+        con.color_pair(253,255);
+        con.addch(16);print('  ');
+    }
+    redraw() {
+        con.color_pair(239,255);
+        con.clear();
+        this.drawTitlebar();
+        if (this.canvas !== undefined) this.canvas.redraw();
+    }
+    update() {
+        if (this.canvas !== undefined) this.canvas.update();
+    }
+}
+
+class Canvas {
+    constructor(identifier) {
+        this.id = identifier;
+    }
+    redraw() {}
+    update() {}
+}
+
+class Demo extends SimpleScreen {
+    constructor(title) {
+        super(title);
+        let mainCanvas = new Canvas("main");
+        mainCanvas.redraw = () => {
+
+        }
+        mainCanvas.update = () => {
+            con.move(2 + (Math.random()*(this.termHeight - 1)), 1 + (Math.random()*this.termWidth));
+            con.addch(0xB3 + (Math.random()*39));
+        }
+
+        this.mainCanvas = mainCanvas
+        this.canvas = this.mainCanvas;
+    }
+}
+
+let s = new Demo("Ctrl-C to exit");
+s.redraw();
+while (!con.hitterminate()) {
+    s.update();
+}
+con.clear();