Add alternate gauge view for energy monitor

Allow button B to toggle a persisted page-one gauge view with
configurable grid and solar power limits.

esphome/energymonitor.yaml

@@ -1,6 +1,8 @@
 substitutions:
   name: "energymonitor"
   friendly_name: "Energy Monitor"
+  grid_power_gauge_max_w: "5000.0"
+  balcony_solar_gauge_max_w: "800.0"
 
 esphome:
   name: ${name}
@@ -137,6 +139,10 @@ globals:
     type: bool
     restore_value: false
     initial_value: 'false'
+  - id: page_one_gauge_view
+    type: bool
+    restore_value: true
+    initial_value: 'false'
 
 sensor:
   # WiFi signal strength
@@ -175,6 +181,18 @@ binary_sensor:
   - platform: wireguard
     enabled:
       name: 'WireGuard Enabled'
+  # M5Stack Core button B (middle) toggles the alternate gauge view on page one.
+  - platform: gpio
+    pin:
+      number: GPIO38
+      mode: INPUT
+      inverted: true
+    id: button_middle
+    on_press:
+      then:
+        - lambda: id(page_one_gauge_view) = !id(page_one_gauge_view);
+        - component.update: tft
+
   # M5Stack Core button A (left). GPIO39 is input-only and has an external pull-up.
   - platform: gpio
     pin:
@@ -250,7 +268,7 @@ display:
       }
       it.printf(312, 8, id(font_icon), wifi_color, TextAlign::TOP_RIGHT, "%s", wifi_icon);
 
-      if (id(page_index) == 0) {
+      if (id(page_index) == 0 && !id(page_one_gauge_view)) {
         it.printf(12, 12, id(font_small), Color::WHITE, "Netzleistung");
         if (id(grid_power).has_state()) {
           const Color grid_power_color = id(grid_power).state >= 0
@@ -292,6 +310,48 @@ display:
           it.printf(308, 168, id(font_value), Color(255, 170, 40), TextAlign::TOP_RIGHT,
                     "-- W");
         }
+      } else if (id(page_index) == 0) {
+        // One shared gauge with two parallel curved bars: grid on the outside, solar inside.
+        const Color gauge_background = Color(42, 42, 42);
+        const int gauge_center_x = 160;
+        const int gauge_center_y = 188;
+
+        // The outer band represents the absolute grid-power value with its signed color.
+        float grid_power_value = id(grid_power).has_state() ? id(grid_power).state : 0.0f;
+        float grid_power_magnitude = grid_power_value < 0.0f ? -grid_power_value : grid_power_value;
+        int grid_gauge_percent = static_cast<int>(grid_power_magnitude * 100.0f / ${grid_power_gauge_max_w});
+        if (grid_gauge_percent > 100) grid_gauge_percent = 100;
+        const Color grid_gauge_color = grid_power_value >= 0.0f
+            ? Color(143, 190, 223)  // #8FBEDF
+            : Color(150, 110, 217); // #966ED9
+        it.filled_gauge(gauge_center_x, gauge_center_y, 140, 122, 100, gauge_background);
+        it.filled_gauge(gauge_center_x, gauge_center_y, 140, 122, grid_gauge_percent, grid_gauge_color);
+
+        // The inner band is solar power, normalized against the 800 W inverter maximum.
+        float solar_power_value = id(balcony_solar_power).has_state() ? id(balcony_solar_power).state : 0.0f;
+        int solar_gauge_percent = static_cast<int>(solar_power_value * 100.0f / ${balcony_solar_gauge_max_w});
+        if (solar_gauge_percent < 0) solar_gauge_percent = 0;
+        if (solar_gauge_percent > 100) solar_gauge_percent = 100;
+        const Color solar_gauge_color = Color(255, 170, 40); // #FFAA28
+        it.filled_gauge(gauge_center_x, gauge_center_y, 116, 98, 100, gauge_background);
+        it.filled_gauge(gauge_center_x, gauge_center_y, 116, 98, solar_gauge_percent, solar_gauge_color);
+
+        it.printf(gauge_center_x, 102, id(font_small), Color::WHITE, TextAlign::TOP_CENTER,
+                  "Netzleistung");
+        if (id(grid_power).has_state()) {
+          it.printf(gauge_center_x, 120, id(font_title), grid_gauge_color, TextAlign::TOP_CENTER,
+                    "%+.0f W", grid_power_value);
+        } else {
+          it.printf(gauge_center_x, 120, id(font_title), Color::WHITE, TextAlign::TOP_CENTER, "-- W");
+        }
+        it.printf(gauge_center_x, 151, id(font_small), Color::WHITE, TextAlign::TOP_CENTER,
+                  "Balkonkraftwerk");
+        if (id(balcony_solar_power).has_state()) {
+          it.printf(gauge_center_x, 169, id(font_title), solar_gauge_color, TextAlign::TOP_CENTER,
+                    "%.0f W", solar_power_value);
+        } else {
+          it.printf(gauge_center_x, 169, id(font_title), solar_gauge_color, TextAlign::TOP_CENTER, "-- W");
+        }
       } else {
         it.printf(160, 45, id(font_title), Color::WHITE, TextAlign::TOP_CENTER,
                   "Weitere Seite");
@@ -304,5 +364,10 @@ display:
                 "< Zurück");
       it.printf(312, 239, id(font_small), Color::WHITE, TextAlign::BOTTOM_RIGHT,
                 "Weiter >");
+      if (id(page_index) == 0) {
         it.printf(160, 239, id(font_small), Color::WHITE, TextAlign::BOTTOM_CENTER,
-                "%d / 2", id(page_index) + 1);
+                  "Ansicht · 1 / 2");
+      } else {
+        it.printf(160, 239, id(font_small), Color::WHITE, TextAlign::BOTTOM_CENTER,
+                  "2 / 2");
+      }