From d0ed30ecb6c069b059cdfa0e035431121dffba13 Mon Sep 17 00:00:00 2001
From: "Ben V. Brown" <Ralim@Ralimtek.com>
Date: Sun, 20 Nov 2022 21:16:38 +1100
Subject: [PATCH] Split display checksum out

---
 source/Core/Drivers/OLED.cpp |  1 +
 source/Core/Drivers/OLED.hpp | 21 ++++++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/source/Core/Drivers/OLED.cpp b/source/Core/Drivers/OLED.cpp
index 9210da51..af1ec479 100644
--- a/source/Core/Drivers/OLED.cpp
+++ b/source/Core/Drivers/OLED.cpp
@@ -372,6 +372,7 @@ void OLED::setRotation(bool leftHanded) {
   const int len  = FRAMEBUFFER_START + (OLED_WIDTH * 2);
   I2C_CLASS::Transmit(DEVICEADDR_OLED, screenBuffer, len);
   osDelay(TICKS_10MS);
+  checkDisplayBufferChecksum();
 }
 
 void OLED::setBrightness(uint8_t contrast) {
diff --git a/source/Core/Drivers/OLED.hpp b/source/Core/Drivers/OLED.hpp
index 9912c5df..e51b3c8a 100644
--- a/source/Core/Drivers/OLED.hpp
+++ b/source/Core/Drivers/OLED.hpp
@@ -51,13 +51,9 @@ public:
   static bool isInitDone();
   // Draw the buffer out to the LCD if any content has changed.
   static void refresh() {
-    uint32_t  hash = 0;
-    const int len  = FRAMEBUFFER_START + (OLED_WIDTH * 2);
-    for (int i = 0; i < len; i++) {
-      hash += (i * screenBuffer[i]);
-    }
-    if (hash != displayChecksum) {
-      displayChecksum = hash;
+   
+    if (checkDisplayBufferChecksum()) {
+      const int len  = FRAMEBUFFER_START + (OLED_WIDTH * 2);
       I2C_CLASS::Transmit(DEVICEADDR_OLED, screenBuffer, len);
       // DMA tx time is ~ 20mS Ensure after calling this you delay for at least 25ms
       // or we need to goto double buffering
@@ -118,6 +114,17 @@ public:
   static void transitionScrollDown();
 
 private:
+static bool checkDisplayBufferChecksum(){
+   uint32_t  hash = 0;
+    const int len  = FRAMEBUFFER_START + (OLED_WIDTH * 2);
+    for (int i = 0; i < len; i++) {
+      hash += (i * screenBuffer[i]);
+    }
+
+    bool result =  hash!=displayChecksum;
+    displayChecksum= hash;
+    return result;
+}
   static void         drawChar(uint16_t charCode, FontStyle fontStyle); // Draw a character to the current cursor location
   static void         setFramebuffer(uint8_t *buffer);
   static uint8_t     *firstStripPtr;    // Pointers to the strips to allow for buffer having extra content