Merge pull request #1967 from thinkyhead/g4_dwell_message

Use millis_t for progress_bar_ms and expire_status_ms

Marlin/ultralcd.cpp

   #ifdef LCD_PROGRESS_BAR
     millis_t ms = millis();
     #ifndef PROGRESS_MSG_ONCE
-      if (ms > progressBarTick + PROGRESS_BAR_MSG_TIME + PROGRESS_BAR_BAR_TIME) {
-        progressBarTick = ms;
+      if (ms > progress_bar_ms + PROGRESS_BAR_MSG_TIME + PROGRESS_BAR_BAR_TIME) {
+        progress_bar_ms = ms;
       }
     #endif
     #if PROGRESS_MSG_EXPIRE > 0
 
 void lcd_finishstatus(bool persist=false) {
   #ifdef LCD_PROGRESS_BAR
-    progressBarTick = millis();
+    progress_bar_ms = millis();
     #if PROGRESS_MSG_EXPIRE > 0
-      expire_status_ms = persist ? 0 : progressBarTick + PROGRESS_MSG_EXPIRE;
+      expire_status_ms = persist ? 0 : progress_bar_ms + PROGRESS_MSG_EXPIRE;
     #endif
   #endif
   lcdDrawUpdate = 2;

Marlin/ultralcd_implementation_hitachi_HD44780.h

 #include "utf_mapper.h"
 
 #ifdef LCD_PROGRESS_BAR
-  static uint16_t progressBarTick = 0;
+  static millis_t progress_bar_ms = 0;
   #if PROGRESS_MSG_EXPIRE > 0
-    static uint16_t expire_status_ms = 0;
+    static millis_t expire_status_ms = 0;
   #endif
   #define LCD_STR_PROGRESS  "\x03\x04\x05"
 #endif
   #ifdef LCD_PROGRESS_BAR
 
     if (card.isFileOpen()) {
-      if (millis() >= progressBarTick + PROGRESS_BAR_MSG_TIME || !lcd_status_message[0]) {
-        // draw the progress bar
+      // Draw the progress bar if the message has shown long enough
+      // or if there is no message set.
+      if (millis() >= progress_bar_ms + PROGRESS_BAR_MSG_TIME || !lcd_status_message[0]) {
         int tix = (int)(card.percentDone() * LCD_WIDTH * 3) / 100,
           cel = tix / 3, rem = tix % 3, i = LCD_WIDTH;
         char msg[LCD_WIDTH+1], b = ' ';