Merge "Add an Escher demo"

app/escher_demo.cpp

@@ -0,0 +1,37 @@
+extern "C" {
+#include <assert.h>
+#include <escher.h>
+#include <stdlib.h>
+#include <ion.h>
+}
+
+class MyTextView : public View {
+  using View::View;
+public:
+  void drawRect(KDRect frame) override;
+};
+
+void MyTextView::drawRect(KDRect frame) {
+  KDPoint zero = {0, 0};
+  KDDrawString("Hello, world!", zero, 0);
+}
+
+void ion_app() {
+  KDRect wholeScreen = {0, 0, 100, 100};
+  KDColor a = 0x55;
+  View * window = new SolidColorView(wholeScreen, a);
+  KDRect textRect = {0, 0, 50, 50};
+  MyTextView * textView = new MyTextView(textRect);
+  window->addSubview(textView);
+
+  window->draw();
+
+  while (1) {
+    ion_sleep();
+    textRect.y = textRect.y+1;
+    textView->setFrame(textRect);
+  }
+
+  delete textView;
+  delete window;
+}