* new ui/DisplayDriver classes (just SSD1306Display impl for now)

* companion radio: now with optional UITask (enabled by DISPLAY_CLASS config in target/env)

src/helpers/ui/DisplayDriver.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <stdint.h>
+
+class DisplayDriver {
+  int _w, _h;
+protected:
+  DisplayDriver(int w, int h) { _w = w; _h = h; }
+public:
+  enum Color { DARK, LIGHT };
+
+  int width() const { return _w; }
+  int height() const { return _h; }
+
+  virtual bool isOn() = 0;
+  virtual void turnOn() = 0;
+  virtual void turnOff() = 0;
+  virtual void startFrame(Color bkg = DARK) = 0;
+  virtual void setTextSize(int sz) = 0;
+  virtual void setColor(Color c) = 0;
+  virtual void setCursor(int x, int y) = 0;
+  virtual void print(const char* str) = 0;
+  virtual void fillRect(int x, int y, int w, int h) = 0;
+  virtual void drawRect(int x, int y, int w, int h) = 0;
+  virtual void drawXbm(int x, int y, const uint8_t* bits, int w, int h) = 0;
+  virtual void endFrame() = 0;
+};