Optimise menu to only redrew necessary parts

src/Menu.cpp

@@ -9,6 +9,7 @@ RTC_DATA_ATTR uint8_t Menu::m_numPages = 0;
 RTC_DATA_ATTR uint8_t Menu::m_currentPage = 0;
 RTC_DATA_ATTR uint8_t Menu::m_numMenuItemsinCurrentPage = 0;
 RTC_DATA_ATTR uint8_t Menu::m_currentMenuItem = 0;
+RTC_DATA_ATTR uint8_t Menu::m_prevMenuItem = 0;
 
 Menu::Menu()
 {
@@ -110,8 +111,22 @@ void Menu::Redraw(bool partialRefresh)
     return;
   }
 
+  bool hasTitle = false;
+  bool hasBody = false;
+
+  if (m_pages[m_currentPage].title.length() > 0) {
+    hasTitle = true;
+  }
+
+  if (m_pages[m_currentPage].body.length() > 0) {
+    hasBody = true;
+  }
+
   m_display->setFullWindow();  
+
+  if (!partialRefresh) {
     m_display->fillScreen(GxEPD_WHITE);
+  }
 
   if (m_pages.size() > 0) {
     bool hasTitle = false;
@@ -120,10 +135,8 @@ void Menu::Redraw(bool partialRefresh)
     uint16_t top = 5;
 
     if (m_pages[m_currentPage].title.length() > 0) {
-      hasTitle = true;
-
-      m_display->setFont(&FreeSansBold9pt7b);
       m_display->setTextColor(GxEPD_BLACK);
+      m_display->setFont(&FreeSansBold9pt7b);
       int16_t x, y;
       uint16_t w, h;
 
@@ -139,8 +152,10 @@ void Menu::Redraw(bool partialRefresh)
       }
 
       m_display->setCursor(x, 15);
+      if (!partialRefresh) {
         m_display->print(m_pages[m_currentPage].title.c_str());
         m_display->drawLine(5, 20, m_display->width() - 10, 20, GxEPD_BLACK);
+      }
 
       top += 35;
     }
@@ -154,9 +169,14 @@ void Menu::Redraw(bool partialRefresh)
       m_display->setTextWrap(false);
       m_display->getTextBounds(m_pages[m_currentPage].body.c_str(), 0, 0, &x, &y, &w, &h);
       m_display->setCursor(5, top);
+
+      if (!partialRefresh) {
         m_display->print(m_pages[m_currentPage].body.c_str());
+      }
       top += h - 5;
+      if (!partialRefresh) {
         m_display->drawLine(5, top, m_display->width() - 10, top, GxEPD_BLACK);
+      }
       top += 5;
     }
 
@@ -165,19 +185,30 @@ void Menu::Redraw(bool partialRefresh)
       uint16_t w, h;
       m_display->getTextBounds(m_pages[m_currentPage].menuItems[i].title.c_str(), 5, top, &x, &y, &w, &h);
 
+      bool draw = false;
+
       if (i == m_currentMenuItem) {
         m_display->fillRect(5, top, m_display->width() - 15, h + 6, GxEPD_BLACK);
         m_display->setTextColor(GxEPD_WHITE);
+        draw = true;
       } else {
+        if (!partialRefresh || (m_prevMenuItem != m_currentMenuItem && i == m_prevMenuItem)) {
+          m_display->fillRect(5, top, m_display->width() - 15, h + 6, GxEPD_WHITE);
           m_display->setTextColor(GxEPD_BLACK);
+          draw = true;
+        }
       }
 
+      if (draw) {
         m_display->setFont(&FreeSans9pt7b);
         m_display->setCursor(x, top + 15);
         m_display->print(m_pages[m_currentPage].menuItems[i].title.c_str());
+      }
 
       top += h + 5;
     }
+
+    m_prevMenuItem = m_currentMenuItem;
   }
 
   m_display->display(partialRefresh);
@@ -187,6 +218,7 @@ void Menu::Reset()
 {
   m_currentPage = 0;
   m_currentMenuItem = 0;
+  m_prevMenuItem = 0;
   m_numPages = m_pages.size();
 
   if (m_numPages) {

src/Menu.h

@@ -45,6 +45,6 @@ private:
 
   static RTC_DATA_ATTR WatchyDisplay * m_display;
   static RTC_DATA_ATTR std::function<void()> m_exitCallback;
-  static RTC_DATA_ATTR uint8_t m_numPages, m_currentPage, m_numMenuItemsinCurrentPage, m_currentMenuItem;
+  static RTC_DATA_ATTR uint8_t m_numPages, m_currentPage, m_numMenuItemsinCurrentPage, m_currentMenuItem, m_prevMenuItem;
   std::vector<MenuPage> m_pages;
 };