PFW-1523 Implement S parameter for M79

Change in memory:
Flash: +112 bytes
SRAM: +3 bytes

Firmware/Marlin_main.cpp

@@ -5857,12 +5857,22 @@ Sigma_Exit:
     Restart the printer-host enable keepalive timer. While the timer has not expired, the printer will enable host specific features.
     #### Usage
 
-        M79
+        M79 [ S ]
     #### Parameters
-       None
+       - `S` - Quoted string containing two characters e.g. "PL"
     */
     case 79:
         M79_timer_restart();
+
+        if (code_seen('S'))
+        {
+            unquoted_string str = unquoted_string(strchr_pointer);
+            if (str.WasFound())
+            {
+                ResetHostStatusScreenName();
+                SetHostStatusScreenName(str.GetUnquotedString());
+            }
+        }
         break;
 
     /*!

Firmware/host.cpp

@@ -1,8 +1,23 @@
+#include <string.h>
 #include "Configuration_adv.h"
 #include "host.h"
 #include "Timer.h"
 
 static LongTimer M79_timer;
+static char host_status_screen_name[3];
+
+void SetHostStatusScreenName(const char * name) {
+    strncpy(host_status_screen_name, name, 2);
+    host_status_screen_name[2] = '\0';
+}
+
+char * GetHostStatusScreenName() {
+    return host_status_screen_name;
+}
+
+void ResetHostStatusScreenName() {
+    memset(host_status_screen_name, 0, sizeof(host_status_screen_name));
+}
 
 void M79_timer_restart() {
     M79_timer.start();

Firmware/host.h

@@ -1,5 +1,15 @@
 #pragma once
 
+/// Assigns host name with up to two characters which will be shown on
+/// the UI when printing. The function forces the third byte to be null delimiter.
+void SetHostStatusScreenName(const char * name);
+
+/// Returns a pointer to the host name
+char * GetHostStatusScreenName();
+
+/// Reset the memory to NULL when the host name should not be used
+void ResetHostStatusScreenName();
+
 /// Restart the M79 timer
 void M79_timer_restart();
 

Firmware/ultralcd.cpp

@@ -19,7 +19,7 @@
 #include "menu.h"
 
 #include "backlight.h"
-
+#include "host.h"
 #include "util.h"
 #include "mesh_bed_leveling.h"
 #include "mesh_bed_calibration.h"
@@ -359,8 +359,7 @@ void lcdui_print_feedrate(void)
 // Print percent done in form "USB---%", " SD---%", "   ---%" (7 chars total)
 void lcdui_print_percent_done(void)
 {
-	const char* src = usb_timer.running()?_N("USB"):(IS_SD_PRINTING?_N(" SD"):_N("   "));
+	const char* src = usb_timer.running()?_N(" HO"):(IS_SD_PRINTING?_N(" SD"):_N("   "));
-	char per[4];
 	bool num = IS_SD_PRINTING || (printer_active() && (print_percent_done_normal != PRINT_PERCENT_DONE_INIT));
 	if (!num || heating_status != HeatingStatus::NO_HEATING) // either not printing or heating
 	{
@@ -375,8 +374,18 @@ void lcdui_print_percent_done(void)
 			return; //do not also print the percentage
 		}
 	}
-	sprintf_P(per, num?_N("%3d"):_N("---"), calc_percent_done());
+
-	lcd_printf_P(_N("%3S%3s%%"), src, per);
+    if (M79_timer_get_status() && GetHostStatusScreenName())
+    {
+        // Overwrite the name
+        char * hostName = GetHostStatusScreenName();
+        lcd_space(1);    // Blank space
+        lcd_print(hostName); // Two characters
+    } else {
+        lcd_printf_P(PSTR("%3S"), src);
+    }
+
+    lcd_printf_P(num ? _N("%3d%%"):_N("---%%"), calc_percent_done());
 }
 
 // Print extruder status (5 chars total)