Optimize e-paper refresh behavior and make deprecated image logic future

proof.

esphome/epaperframe.yaml

@@ -51,6 +51,13 @@ api:
 # Include ArduinoJson support for the compact calendar event feed.
 json:
 
+# Prevent refreshes when Home Assistant republishes unchanged calendar data.
+globals:
+  - id: last_rendered_calendar_entries
+    type: std::string
+    restore_value: no
+    initial_value: '""'
+
 ota:
   platform: esphome
   password: !secret ota
@@ -222,6 +229,17 @@ text_sensor:
     entity_id: sensor.epaper_kalenderdaten
     attribute: entries
     id: calendar_entries
+    on_value:
+      then:
+        - if:
+            condition:
+              and:
+                - display.is_displaying_page: calendar
+                - lambda: return x != id(last_rendered_calendar_entries);
+            then:
+              - lambda: id(last_rendered_calendar_entries) = x;
+              - component.update: epaper
+
 
   # Home Assistant selects one quote per day from its local quote library.
   - platform: homeassistant
@@ -243,14 +261,19 @@ time:
           - output.turn_on: power_key
           - delay: 0.5s
           - output.turn_off: power_key
-      # Every 10 minutes
+      # Environmental readings need their regular refresh. Calendar updates are
+      # instead triggered by changed event data while that page is active.
       - seconds: 0
         minutes: /10
         then:
-          - logger.log:
-              level: INFO
-              format: "Timer based screen refresh"
-          - component.update: epaper
+          - if:
+              condition:
+                display.is_displaying_page: environment
+              then:
+                - logger.log:
+                    level: INFO
+                    format: "Timer based environment screen refresh"
+                - component.update: epaper
       - seconds: 10
         minutes: 0
         hours: 0
@@ -721,11 +744,12 @@ font:
       ]
 
 image:
-  - file: "epaperframe/C1024_logo_flat_bw.png"
+  - platform: file
+    file: "epaperframe/C1024_logo_flat_bw.png"
     id: c1024_logo
     type: binary
     resize: 77x40
-    invert_alpha: True
+    invert_alpha: true
 
 spi:
   clk_pin: 23