Feature: show power grid usage on display (#658)

* make efficient use of available display area

fix calculation of the text baselines, using getAscent() in favor of
getMaxCharHeight(), which includes ascent and descent. this moves the
first text up and allows to insert margin between the lines until the
display area is fully utilized.

on large displays, if the small diagram is selected, keep the first line
rather low to avoid collision with the diagram y-axis label. in this mode,
there is still more space between the text lines as before, allowing for
improved readability.

* Feature: show power grid usage on display

if the power meter is enabled, the display will use two of three out
of every three-second time slot to show the grid consumption.

closes #620.

src/Display_Graphic.cpp

@@ -4,6 +4,8 @@
  */
 #include "Display_Graphic.h"
 #include "Datastore.h"
+#include "PowerMeter.h"
+#include "Configuration.h"
 #include <NetworkSettings.h>
 #include <map>
 #include <time.h>
@@ -31,6 +33,8 @@ const uint8_t languages[] = {
 static const char* const i18n_offline[] = { "Offline", "Offline", "Offline" };
 static const char* const i18n_current_power_w[] = { "%.0f W", "%.0f W", "%.0f W" };
 static const char* const i18n_current_power_kw[] = { "%.1f kW", "%.1f kW", "%.1f kW" };
+static const char* const i18n_meter_power_w[] = { "grid:   %.0f W", "Netz:   %.0f W", "reseau: %.0f W" };
+static const char* const i18n_meter_power_kw[] = { "grid:   %.1f kW", "Netz:   %.1f kW", "reseau: %.1f kW" };
 static const char* const i18n_yield_today_wh[] = { "today: %4.0f Wh", "Heute: %4.0f Wh", "auj.: %4.0f Wh" };
 static const char* const i18n_yield_total_kwh[] = { "total: %.1f kWh", "Ges.: %.1f kWh", "total: %.1f kWh" };
 static const char* const i18n_date_format[] = { "%m/%d/%Y %H:%M", "%d.%m.%Y %H:%M", "%d/%m/%Y %H:%M" };
@@ -67,11 +71,19 @@ void DisplayGraphicClass::init(Scheduler& scheduler, const DisplayType_t type, c
 
 void DisplayGraphicClass::calcLineHeights()
 {
-    uint8_t yOff = 0;
+    bool diagram = (_isLarge && _diagram_mode == DiagramMode_t::Small);
+    // the diagram needs space. we need to keep
+    // away from the y-axis label in particular.
+    uint8_t yOff = (diagram?7:0);
     for (uint8_t i = 0; i < 4; i++) {
         setFont(i);
-        yOff += (_display->getMaxCharHeight());
+        yOff += _display->getAscent();
         _lineOffsets[i] = yOff;
+        yOff += ((!_isLarge || diagram)?2:3);
+        // the descent is a negative value and moves the *next* line's
+        // baseline. the first line never uses a letter with descent and
+        // we need that space when showing the small diagram.
+        yOff -= ((i == 0 && diagram)?0:_display->getDescent());
     }
 }
 
@@ -252,6 +264,32 @@ void DisplayGraphicClass::loop()
         }
     }
 
+    // the IP and time info in the third line use three-second slots. the
+    // timing for the power meter is chosen such that every third of those
+    // three-second slots is used to NOT overwrite the total inverter energy.
+    bool timing = (_mExtra % 9) >= 3;
+
+    if (showText && Configuration.get().PowerMeter.Enabled && timing && !displayPowerSave) {
+        // erase the third line and print the power meter value instead.
+        // we do it this way to touch as least upstream code as possible
+        // to make maintenance easier.
+        setFont(2);
+        auto lineHeight = _display->getAscent() - _display->getDescent();
+        auto y = _lineOffsets[2] - _display->getAscent();
+        _display->setDrawColor(0);
+        _display->drawBox(0, y, _display->getDisplayWidth(), lineHeight);
+        _display->setDrawColor(1);
+
+        auto acPower = PowerMeter.getPowerTotal(false);
+        if (acPower > 999) {
+            snprintf(_fmtText, sizeof(_fmtText), i18n_meter_power_kw[_display_language], (acPower / 1000));
+        } else {
+            snprintf(_fmtText, sizeof(_fmtText), i18n_meter_power_w[_display_language], acPower);
+        }
+
+        printText(_fmtText, 2);
+    }
+
     _display->sendBuffer();
 
     _mExtra++;

src/WebApi_device.cpp

@@ -184,12 +184,12 @@ void WebApiDeviceClass::onDeviceAdminPost(AsyncWebServerRequest* request)
         config.Led_Single[i].Brightness = min<uint8_t>(100, config.Led_Single[i].Brightness);
     }
 
+    Display.setDiagramMode(static_cast<DiagramMode_t>(config.Display.Diagram.Mode));
     Display.setOrientation(config.Display.Rotation);
     Display.enablePowerSafe = config.Display.PowerSafe;
     Display.enableScreensaver = config.Display.ScreenSaver;
     Display.setContrast(config.Display.Contrast);
     Display.setLanguage(config.Display.Language);
-    Display.setDiagramMode(static_cast<DiagramMode_t>(config.Display.Diagram.Mode));
     Display.Diagram().updatePeriod();
 
     WebApi.writeConfig(retMsg);

src/main.cpp

@@ -135,12 +135,12 @@ void setup()
         pin.display_clk,
         pin.display_cs,
         pin.display_reset);
+    Display.setDiagramMode(static_cast<DiagramMode_t>(config.Display.Diagram.Mode));
     Display.setOrientation(config.Display.Rotation);
     Display.enablePowerSafe = config.Display.PowerSafe;
     Display.enableScreensaver = config.Display.ScreenSaver;
     Display.setContrast(config.Display.Contrast);
     Display.setLanguage(config.Display.Language);
-    Display.setDiagramMode(static_cast<DiagramMode_t>(config.Display.Diagram.Mode));
     Display.setStartupDisplay();
     MessageOutput.println("done");