Handle edge cases for E-Ink screensaver (#3518)

* remove redundant logic

* Handle special screens for old EInkDisplayClass

* Handle special screens for EInkDynamicDisplay class

* Join an async refresh in progress to avoid skipping screensaver

* attempt trunk fix

src/graphics/EInkDynamicDisplay.h

@@ -119,20 +119,30 @@ class EInkDynamicDisplay : public EInkDisplay, protected concurrency::NotifiedWo
 
     // Conditional - async full refresh - only with modified meshtastic/GxEPD2
 #if defined(HAS_EINK_ASYNCFULL)
+  public:
+    void joinAsyncRefresh(); // Main thread joins an async refresh already in progress. Blocks, then runs post-update code
+
+  protected:
     void pollAsyncRefresh();          // Run the post-update code if the hardware is ready
     void checkBusyAsyncRefresh();     // Check if display is busy running an async full-refresh (rejecting new frames)
     void awaitRefresh();              // Hold control while an async refresh runs
     void endUpdate() override {}      // Disable base-class behavior of running post-update immediately after forceDisplay()
     bool asyncRefreshRunning = false; // Flag, checked by checkBusyAsyncRefresh()
 #else
+  public:
+    void joinAsyncRefresh() {} // Dummy method
+
+  protected:
     void pollAsyncRefresh() {} // Dummy method. In theory, not reachable
 #endif
 };
 
-// Tidier calls to addFrameFlag() from outside class
+// Hide the ugly casts used in Screen.cpp
 #define EINK_ADD_FRAMEFLAG(display, flag) static_cast<EInkDynamicDisplay *>(display)->addFrameFlag(EInkDynamicDisplay::flag)
+#define EINK_JOIN_ASYNCREFRESH(display) static_cast<EInkDynamicDisplay *>(display)->joinAsyncRefresh()
 
 #else // !USE_EINK_DYNAMICDISPLAY
 // Dummy-macro, removes the need for include guards
 #define EINK_ADD_FRAMEFLAG(display, flag)
+#define EINK_JOIN_ASYNCREFRESH(display)
 #endif