fix: cooldown period during the display shutdown display sequence

Observed to prevent border pixels from being locked in place with some residual charge?

src/graphics/niche/InkHUD/Applets/System/Logo/LogoApplet.cpp

@@ -95,8 +95,10 @@ void InkHUD::LogoApplet::onShutdown()
 
     inverted = true;
     inkhud->forceUpdate(Drivers::EInk::FULL, false);
+    delay(1000); // Cooldown. Back to back updates aren't great for health.
     inverted = false;
     inkhud->forceUpdate(Drivers::EInk::FULL, false);
+    delay(1000); // Cooldown
 
     // Prepare for the powered-off screen now
     // We can change these values because the initial "shutting down" screen has already rendered at this point
@@ -108,6 +110,19 @@ void InkHUD::LogoApplet::onShutdown()
     // This is then drawn by InkHUD::Events::onShutdown, with a blocking FULL update, after InkHUD's flash write is complete
 }
 
+void InkHUD::LogoApplet::onReboot()
+{
+    bringToForeground();
+
+    textLeft = "";
+    textRight = "";
+    textTitle = "Rebooting...";
+    fontTitle = fontSmall;
+
+    inkhud->forceUpdate(Drivers::EInk::FULL, false);
+    // Perform the update right now, waiting here until complete
+}
+
 int32_t InkHUD::LogoApplet::runOnce()
 {
     sendToBackground();

src/graphics/niche/InkHUD/Applets/System/Logo/LogoApplet.h

@@ -25,6 +25,7 @@ class LogoApplet : public SystemApplet, public concurrency::OSThread
     void onForeground() override;
     void onBackground() override;
     void onShutdown() override;
+    void onReboot() override;
 
   protected:
     int32_t runOnce() override;

src/graphics/niche/InkHUD/Events.cpp

@@ -95,6 +95,7 @@ int InkHUD::Events::beforeDeepSleep(void *unused)
     // We're updating to show that one now.
 
     inkhud->forceUpdate(Drivers::EInk::UpdateTypes::FULL, false);
+    delay(1000); // Cooldown, before potentially yanking display power
 
     return 0; // We agree: deep sleep now
 }
@@ -111,16 +112,16 @@ int InkHUD::Events::beforeReboot(void *unused)
         a->onDeactivate();
         a->onShutdown();
     }
-    for (Applet *sa : inkhud->systemApplets) {
+    for (SystemApplet *sa : inkhud->systemApplets) {
         // Note: no onDeactivate. System applets are always active.
-        sa->onShutdown();
+        sa->onReboot();
     }
 
     inkhud->persistence->saveSettings();
     inkhud->persistence->saveLatestMessage();
 
     // Note: no forceUpdate call here
-    // Because OSThread will not be given another chance to run before reboot, this means that no display update will occur
+    // We don't have any final screen to draw, although LogoApplet::onReboot did already display a "rebooting" screen
 
     return 0; // No special status to report. Ignored anyway by this Observable
 }

src/graphics/niche/InkHUD/SystemApplet.h

@@ -26,6 +26,8 @@ class SystemApplet : public Applet
     bool lockRendering = false; // - prevent other applets from being rendered during an update
     bool lockRequests = false;  // - prevent other applets from triggering display updates
 
+    virtual void onReboot() { onShutdown(); } // - handle reboot specially
+
     // Other system applets may take precedence over our own system applet though
     // The order an applet is passed to WindowManager::addSystemApplet determines this hierarchy (added earlier = higher rank)