Draw content in display loop only when needed

Example for splash screen.

Marlin/dogm_lcd_implementation.h

@@ -186,7 +186,7 @@ char lcd_printPGM(const char* str) {
   return n;
 }
 
-static int8_t show_splashscreed = 2;
+int8_t show_splashscreen = 2;
 
 static void lcd_implementation_init()
 {
@@ -221,8 +221,12 @@ static void lcd_implementation_init()
 
 	u8g.firstPage();
 	do {
-    if (show_splashscreed) {
+    switch (show_splashscreen) {
+      case 2 : {
         u8g.drawBitmapP(offx, offy, START_BMPBYTEWIDTH, START_BMPHEIGHT, start_bmp);
+        break;
+      }
+      case 1 : {
         lcd_setFont(FONT_MENU);
         #ifndef STRING_SPLASH_LINE2
           u8g.drawStr(txt1X, u8g.getHeight() - DOG_CHAR_HEIGHT, STRING_SPLASH_LINE1);
@@ -231,8 +235,11 @@ static void lcd_implementation_init()
           u8g.drawStr(txt1X, u8g.getHeight() - DOG_CHAR_HEIGHT*3/2, STRING_SPLASH_LINE1);
           u8g.drawStr(txt2X, u8g.getHeight() - DOG_CHAR_HEIGHT*1/2, STRING_SPLASH_LINE2);
         #endif
-      show_splashscreed--;
+        break;
+      }
+      break;  
     }  
+    if (show_splashscreen) show_splashscreen--;
 	} while (u8g.nextPage());
 }