This should explode in multiple ways. Let's see.

src/graphics/eink/Backlight/LatchingBacklight.cpp

@@ -0,0 +1,108 @@
+#ifdef MESHTASTIC_INCLUDE_NICHE_GRAPHICS
+
+#include "./LatchingBacklight.h"
+
+#include "assert.h"
+
+#include "sleep.h"
+
+using namespace NicheGraphics::Drivers;
+
+// Private constructor
+// Called by getInstance
+LatchingBacklight::LatchingBacklight()
+{
+    // Attach the deep sleep callback
+    deepSleepObserver.observe(&notifyDeepSleep);
+}
+
+// Get access to (or create) the singleton instance of this class
+LatchingBacklight *LatchingBacklight::getInstance()
+{
+    // Instantiate the class the first time this method is called
+    static LatchingBacklight *const singletonInstance = new LatchingBacklight;
+
+    return singletonInstance;
+}
+
+// Which pin controls the backlight?
+// Is the light active HIGH (default) or active LOW?
+void LatchingBacklight::setPin(uint8_t pin, bool activeWhen)
+{
+    this->pin = pin;
+    this->logicActive = activeWhen;
+
+    pinMode(pin, OUTPUT);
+    off(); // Explicit off seem required by T-Echo?
+}
+
+// Called when device is shutting down
+// Ensures the backlight is off
+int LatchingBacklight::beforeDeepSleep(void *unused)
+{
+    // Contingency only
+    // - pin wasn't set
+    if (pin != static_cast<uint8_t>(-1)) {
+        off();
+        pinMode(pin, INPUT); // High impedance - unnecessary?
+    } else
+        LOG_WARN("LatchingBacklight instantiated, but pin not set");
+    return 0; // Continue with deep sleep
+}
+
+// Turn the backlight on *temporarily*
+// This should be used for momentary illumination, such as while a button is held
+// The effect on the backlight is the same; peek and latch are separated to simplify short vs long press button handling
+void LatchingBacklight::peek()
+{
+    assert(pin != static_cast<uint8_t>(-1));
+    digitalWrite(pin, logicActive); // On
+    on = true;
+    latched = false;
+}
+
+// Turn the backlight on, and keep it on
+// This should be used when the backlight should remain active, even after user input ends
+// e.g. when enabled via the menu
+// The effect on the backlight is the same; peek and latch are separated to simplify short vs long press button handling
+void LatchingBacklight::latch()
+{
+    assert(pin != static_cast<uint8_t>(-1));
+
+    // Blink if moving from peek to latch
+    // Indicates to user that the transition has taken place
+    if (on && !latched) {
+        digitalWrite(pin, !logicActive); // Off
+        delay(25);
+        digitalWrite(pin, logicActive); // On
+        delay(25);
+        digitalWrite(pin, !logicActive); // Off
+        delay(25);
+    }
+
+    digitalWrite(pin, logicActive); // On
+    on = true;
+    latched = true;
+}
+
+// Turn the backlight off
+// Suitable for ending both peek and latch
+void LatchingBacklight::off()
+{
+    assert(pin != static_cast<uint8_t>(-1));
+    digitalWrite(pin, !logicActive); // Off
+    on = false;
+    latched = false;
+}
+
+bool LatchingBacklight::isOn()
+{
+    return on;
+}
+
+bool LatchingBacklight::isLatched()
+{
+    return latched;
+}
+
+#endif