From c28c662bcd3f93fcecf64db9e6282ac83f477109 Mon Sep 17 00:00:00 2001
From: Trivalik <3148279+trivalik@users.noreply.github.com>
Date: Sun, 12 Feb 2023 05:14:53 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=9A=B8=20Negative=20temperature=20display?=
 =?UTF-8?q?=20option=20(#25036)?=
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Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>
---
 Marlin/Configuration_adv.h                  |  3 +++
 Marlin/src/lcd/HD44780/marlinui_HD44780.cpp | 14 ++++++++++--
 Marlin/src/lcd/dogm/status_screen_DOGM.cpp  | 24 +++++++++++++++------
 3 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/Marlin/Configuration_adv.h b/Marlin/Configuration_adv.h
index 31cbd678bfd4..a9e6d4928f07 100644
--- a/Marlin/Configuration_adv.h
+++ b/Marlin/Configuration_adv.h
@@ -1455,6 +1455,9 @@
   // Show the E position (filament used) during printing
   //#define LCD_SHOW_E_TOTAL
 
+  // Display a negative temperature instead of "err"
+  //#define SHOW_TEMPERATURE_BELOW_ZERO
+
   /**
    * LED Control Menu
    * Add LED Control to the LCD menu
diff --git a/Marlin/src/lcd/HD44780/marlinui_HD44780.cpp b/Marlin/src/lcd/HD44780/marlinui_HD44780.cpp
index 9445198a22c1..9093fa3eab9e 100644
--- a/Marlin/src/lcd/HD44780/marlinui_HD44780.cpp
+++ b/Marlin/src/lcd/HD44780/marlinui_HD44780.cpp
@@ -537,7 +537,7 @@ FORCE_INLINE void _draw_axis_value(const AxisEnum axis, const char *value, const
  */
 FORCE_INLINE void _draw_heater_status(const heater_id_t heater_id, const char prefix, const bool blink) {
   #if HAS_HEATED_BED
-    const bool isBed = TERN(HAS_HEATED_CHAMBER, heater_id == H_BED, heater_id < 0);
+    const bool isBed = heater_id == H_BED;
     const celsius_t t1 = (isBed ? thermalManager.wholeDegBed()  : thermalManager.wholeDegHotend(heater_id)),
                     t2 = (isBed ? thermalManager.degTargetBed() : thermalManager.degTargetHotend(heater_id));
   #else
@@ -546,7 +546,17 @@ FORCE_INLINE void _draw_heater_status(const heater_id_t heater_id, const char pr
 
   if (prefix >= 0) lcd_put_lchar(prefix);
 
-  lcd_put_u8str(t1 < 0 ? "err" : i16tostr3rj(t1));
+  if (t1 >= 0)
+    lcd_put_u8str(ui16tostr3rj(t1));
+  else {
+    #if ENABLED(SHOW_TEMPERATURE_BELOW_ZERO)
+      char * const str = i16tostr3rj(t1);
+      lcd_put_u8str(&str[1]);
+    #else
+      lcd_put_u8str(F("err"));
+    #endif
+  }
+
   lcd_put_u8str(F("/"));
 
   #if !HEATER_IDLE_HANDLER
diff --git a/Marlin/src/lcd/dogm/status_screen_DOGM.cpp b/Marlin/src/lcd/dogm/status_screen_DOGM.cpp
index 8bdba4234282..721dcb63ffbe 100644
--- a/Marlin/src/lcd/dogm/status_screen_DOGM.cpp
+++ b/Marlin/src/lcd/dogm/status_screen_DOGM.cpp
@@ -192,14 +192,26 @@
 #define PROGRESS_BAR_WIDTH (LCD_PIXEL_WIDTH - PROGRESS_BAR_X)
 
 FORCE_INLINE void _draw_centered_temp(const celsius_t temp, const uint8_t tx, const uint8_t ty) {
-  if (temp < 0)
-    lcd_put_u8str(tx - 3 * (INFO_FONT_WIDTH) / 2 + 1, ty, F("err"));
+  const char *str;
+  uint8_t len;
+  if (temp >= 0) {
+    str = i16tostr3left(temp);
+    len = strlen(str);
+    lcd_moveto(tx + 1 - len * (INFO_FONT_WIDTH) / 2, ty);
+  }
   else {
-    const char *str = i16tostr3rj(temp);
-    const uint8_t len = str[0] != ' ' ? 3 : str[1] != ' ' ? 2 : 1;
-    lcd_put_u8str(tx - len * (INFO_FONT_WIDTH) / 2 + 1, ty, &str[3-len]);
-    lcd_put_lchar(LCD_STR_DEGREE[0]);
+    #if ENABLED(SHOW_TEMPERATURE_BELOW_ZERO)
+      str = i16tostr3left((-temp) % 100);
+      len = strlen(str) + 1;
+      lcd_moveto(tx + 1 - len * (INFO_FONT_WIDTH) / 2, ty);
+      lcd_put_lchar('-');
+    #else
+      lcd_put_u8str(tx + 1 - 3 * (INFO_FONT_WIDTH) / 2, ty, F("err"));
+      return;
+    #endif
   }
+  lcd_put_u8str(str);
+  lcd_put_lchar(LCD_STR_DEGREE[0]);
 }
 
 #if DO_DRAW_FLOWMETER