Enter shutter lock if release and focus are both pressed.

During remote control, if focus button is held and release is pressed,
enter shutter lock.
Exit shutter lock if either focus or release are clicked.

src/furble.ino

@@ -167,45 +167,67 @@ static void remote_interval(Furble::Device *device) {
 }
 
 static void remote_control(Furble::Device *device) {
+
+  static bool shutter_lock = false;
+
   Serial.println("Remote Control");
 
 #ifdef M5STACK_CORE2
-  ez.msgBox("Remote Shutter", "", "Release#Focus#Back", false);
+  ez.msgBox("Remote Shutter", "Lock: Focus+Release", "Release#Focus#Back", false);
 #else
-  ez.msgBox("Remote Shutter", "Back: Power", "Release#Focus", false);
+  ez.msgBox("Remote Shutter", "Lock: Focus+Release\nBack: Power", "Release#Focus", false);
 #endif
   do {
     M5.update();
 
     update_geodata(device);
 
     if (M5.BtnPWR.wasClicked() || M5.BtnC.wasPressed()) {
+      if (shutter_lock) {
+        // ensure shutter is released on exit
+        device->shutterRelease();
+      }
       Serial.println("Exit shutter");
       break;
     }
 
-    if (M5.BtnA.wasPressed()) {
-      device->shutterPress();
-      Serial.println("shutterPress()");
-      continue;
-    }
-
-    if (M5.BtnA.wasReleased()) {
-      device->shutterRelease();
-      Serial.println("shutterRelease()");
-      continue;
-    }
-
-    if (M5.BtnB.wasPressed()) {
-      device->focusPress();
-      Serial.println("focusPress()");
-      continue;
-    }
-
-    if (M5.BtnB.wasReleased()) {
-      device->focusRelease();
-      Serial.println("focusRelease()");
-      continue;
+    if (shutter_lock) {
+      // release shutter if either shutter or focus is pressed
+      if (M5.BtnA.wasClicked() || M5.BtnB.wasClicked()) {
+         shutter_lock = false;
+         device->shutterRelease();
+         Serial.println("shutterRelease(unlock)");
+      }
+    } else {
+      if (M5.BtnA.wasPressed()) {
+        device->shutterPress();
+        Serial.println("shutterPress()");
+        continue;
+      }
+
+      if (M5.BtnA.wasReleased()) {
+        // focus + shutter = shutter lock
+        if (M5.BtnB.isPressed()) {
+           shutter_lock = true;
+           Serial.println("shutter lock");
+        } else {
+          device->shutterRelease();
+          Serial.println("shutterRelease()");
+        }
+        continue;
+      }
+
+      if (M5.BtnB.wasPressed()) {
+        device->focusPress();
+        Serial.println("focusPress()");
+        continue;
+      }
+
+      if (M5.BtnB.wasReleased()) {
+        device->focusRelease();
+        Serial.println("focusRelease()");
+        continue;
+      }
     }
 
     ez.yield();