fix buffer content and update when data arrives during update

flipcontrol_esp32/include/image.h

@@ -43,6 +43,8 @@ private:
 
     void serialPrintInt(uint16_t source);
 
+    bool isBuffersEqual();
+    
 
 
 public:

flipcontrol_esp32/src/image.cpp

@@ -657,11 +657,12 @@ UpdateReturn Image::updateByColumn(bool clearFirst, bool optimizeClear, bool opt
         }
 
     }else{ //odd counter numbers are for setting
-        uint16_t _colSet=backBuffer[x]& ~frontBuffer[x];
+        uint16_t backBuffer_x=backBuffer[x]; //store buffer, because it may change when different data arrives during setting dots
+        uint16_t _colSet=backBuffer_x& ~frontBuffer[x];
         if (!optimizeSet || _colSet>0) { //at least on dot has to be set in this column (if optimize is enabled)
             flipdot.selectColumnSet(x); //lower column number is on the left
             if (!optimizeSet) {
-                flipdot.setRow(backBuffer[x]); //flip all set dots in this column
+                flipdot.setRow(backBuffer_x); //flip all set dots in this column
             }else{           
                 flipdot.setRow(_colSet); //flip only currently not set dots in this column that have to be set
             }
@@ -671,7 +672,7 @@ UpdateReturn Image::updateByColumn(bool clearFirst, bool optimizeClear, bool opt
             }
             lastUpdateMillis=millis();
 
-            frontBuffer[x]=backBuffer[x]; //flip current column in buffer
+            frontBuffer[x]=backBuffer_x; //flip current column in buffer
         }
     }
 
@@ -685,11 +686,24 @@ UpdateReturn Image::updateByColumn(bool clearFirst, bool optimizeClear, bool opt
         flag_updating=false;
         update_counter=0;
         flag_redraw=false;
+        if (!isBuffersEqual()) {
+            flag_updating=true; //update again if buffers not equal
+            return updating;
+        }
+        
         return finished; //finished
     }
     return updating; //not finished
 }
 
+bool Image::isBuffersEqual() {
+    for (uint8_t x=0;x<COLUMNS;x++) {
+        if (frontBuffer[x]!=backBuffer[x]) {
+            return false;
+        }
+    }
+    return true;
+}
 
 void Image::loop_testDots() {