Allow AsyncPowerOn

* The display takes 16ms to power on
  During this time we can render the
  content and finally display it
* The call is optional if we do not call
  it then the old code path is used
* Moved the init to constructor

src/Display.cpp

@@ -38,6 +38,14 @@ void WatchyDisplay::initWatchy() {
   init(0, displayFullInit, 2, true);
 }
 
+void WatchyDisplay::asyncPowerOn() {
+  // This is expensive if unused
+  if (!waitingPowerOn && !_hibernating) {
+    _InitDisplay();
+    _PowerOnAsync();
+  }
+}
+
 void WatchyDisplay::setDarkBorder(bool dark) {
   if (_hibernating) return;
   darkBorder = dark;
@@ -349,31 +357,52 @@ void WatchyDisplay::_setPartialRamArea(uint16_t x, uint16_t y, uint16_t w, uint1
   _endTransfer();
 }
 
+void WatchyDisplay::_PowerOnAsync()
+{
+  if (_power_is_on)
+    return;
+  _startTransfer();
+  _transferCommand(0x22);
+  _transfer(0xf8);
+  _transferCommand(0x20);
+  _endTransfer();
+  waitingPowerOn = true;
+  _power_is_on = true;
+}
+
 void WatchyDisplay::_PowerOn()
 {
-  if (!_power_is_on)
+  if (waitingPowerOn)
   {
-    _startTransfer();
-    _transferCommand(0x22);
-    _transfer(0xf8);
-    _transferCommand(0x20);
-    _endTransfer();
+    waitingPowerOn = false;
     _waitWhileBusy("_PowerOn", power_on_time);
   }
+  if (_power_is_on)
+    return;
+  _startTransfer();
+  _transferCommand(0x22);
+  _transfer(0xf8);
+  _transferCommand(0x20);
+  _endTransfer();
+  _waitWhileBusy("_PowerOn", power_on_time);
   _power_is_on = true;
 }
 
 void WatchyDisplay::_PowerOff()
 {
-  if (_power_is_on)
+  if (waitingPowerOn)
   {
-    _startTransfer();
-    _transferCommand(0x22);
-    _transfer(0x83);
-    _transferCommand(0x20);
-    _endTransfer();
-    _waitWhileBusy("_PowerOff", power_off_time);
+    waitingPowerOn = false;
+    _waitWhileBusy("_PowerOn", power_on_time);
   }
+  if (!_power_is_on)
+    return;
+  _startTransfer();
+  _transferCommand(0x22);
+  _transfer(0x83);
+  _transferCommand(0x20);
+  _endTransfer();
+  _waitWhileBusy("_PowerOff", power_off_time);
   _power_is_on = false;
   _using_partial_mode = false;
 }

src/Display.h

@@ -37,6 +37,9 @@ class WatchyDisplay : public GxEPD2_EPD
     WatchyDisplay();
     void initWatchy();
     void setDarkBorder(bool darkBorder);
+    void asyncPowerOn();
+    void _PowerOnAsync();
+    bool waitingPowerOn = false;
     static void busyCallback(const void *);
     // methods (virtual)
     //  Support for Bitmaps (Sprites) to Controller Buffer and to Screen

src/Watchy.cpp

@@ -594,6 +594,8 @@ void Watchy::showAccelerometer() {
 
 void Watchy::showWatchFace(bool partialRefresh) {
   display.setFullWindow();
+  // At this point it is sure we are going to update
+  display.epd2.asyncPowerOn();
   drawWatchFace();
   display.display(partialRefresh); // partial refresh
   guiState = WATCHFACE_STATE;