From 2bde53bd461180502320339d642e4d916a2378e6 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <thinkyhead@users.noreply.github.com>
Date: Mon, 26 Feb 2018 22:53:08 -0600
Subject: [PATCH] Add support for BACK button (if any) (#9836)

---
 Marlin/ultralcd.cpp            | 13 +++++++++++--
 Marlin/ultralcd.h              | 28 ++++++++++++++++++++--------
 Marlin/ultralcd_impl_HD44780.h |  3 +--
 3 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/Marlin/ultralcd.cpp b/Marlin/ultralcd.cpp
index aa18f993c..c7d9ef5bf 100644
--- a/Marlin/ultralcd.cpp
+++ b/Marlin/ultralcd.cpp
@@ -4847,11 +4847,9 @@ void lcd_init() {
     #if BUTTON_EXISTS(EN1)
       SET_INPUT_PULLUP(BTN_EN1);
     #endif
-
     #if BUTTON_EXISTS(EN2)
       SET_INPUT_PULLUP(BTN_EN2);
     #endif
-
     #if BUTTON_EXISTS(ENC)
       SET_INPUT_PULLUP(BTN_ENC);
     #endif
@@ -4996,6 +4994,14 @@ void lcd_update() {
       }
     }
     else wait_for_unclick = false;
+
+    #if BUTTON_EXISTS(BACK)
+      if (LCD_BACK_CLICKED) {
+        lcd_quick_feedback();
+        lcd_goto_previous_menu();
+      }
+    #endif
+
   #endif
 
   #if ENABLED(SDSUPPORT) && PIN_EXISTS(SD_DETECT)
@@ -5367,6 +5373,9 @@ void lcd_reset_alert_level() { lcd_status_message_level = 0; }
         #if BUTTON_EXISTS(ENC)
           if (BUTTON_PRESSED(ENC)) newbutton |= EN_C;
         #endif
+        #if BUTTON_EXISTS(BACK)
+          if (BUTTON_PRESSED(BACK)) newbutton |= EN_D;
+        #endif
 
         //
         // Directional buttons
diff --git a/Marlin/ultralcd.h b/Marlin/ultralcd.h
index eac67f581..2ddf4b6f0 100644
--- a/Marlin/ultralcd.h
+++ b/Marlin/ultralcd.h
@@ -40,9 +40,6 @@
     constexpr bool lcd_external_control = false;
   #endif
 
-  #define BUTTON_EXISTS(BN) (defined(BTN_## BN) && BTN_## BN >= 0)
-  #define BUTTON_PRESSED(BN) !READ(BTN_## BN)
-
   extern int16_t lcd_preheat_hotend_temp[2], lcd_preheat_bed_temp[2], lcd_preheat_fan_speed[2];
 
   #if ENABLED(LCD_BED_LEVELING)
@@ -92,6 +89,8 @@
   #endif
 
   #define LCD_UPDATE_INTERVAL 100
+  #define BUTTON_EXISTS(BN) (defined(BTN_## BN) && BTN_## BN >= 0)
+  #define BUTTON_PRESSED(BN) !READ(BTN_## BN)
 
   #if ENABLED(ULTIPANEL)
 
@@ -103,15 +102,24 @@
 
     void lcd_goto_screen(screenFunc_t screen, const uint32_t encoder=0);
 
+    // Encoder click is directly connected
+
     #define BLEN_A 0
     #define BLEN_B 1
-    // Encoder click is directly connected
-    #if BUTTON_EXISTS(ENC)
-      #define BLEN_C 2
-    #endif
+
     #define EN_A (_BV(BLEN_A))
     #define EN_B (_BV(BLEN_B))
-    #define EN_C (_BV(BLEN_C))
+
+    #if BUTTON_EXISTS(ENC)
+      #define BLEN_C 2
+      #define EN_C (_BV(BLEN_C))
+    #endif
+
+    #if BUTTON_EXISTS(BACK)
+      #define BLEN_D 3
+      #define EN_D BIT(BLEN_D)
+      #define LCD_BACK_CLICKED (buttons & EN_D)
+    #endif
 
     extern volatile uint8_t buttons;  // The last-checked buttons in a bit array.
     void lcd_buttons_update();
@@ -209,9 +217,13 @@
                                             )
 
   #elif ENABLED(NEWPANEL)
+
     #define LCD_CLICKED (buttons & EN_C)
+
   #else
+
     #define LCD_CLICKED false
+
   #endif
 
   #if ENABLED(AUTO_BED_LEVELING_UBL) || ENABLED(G26_MESH_VALIDATION)
diff --git a/Marlin/ultralcd_impl_HD44780.h b/Marlin/ultralcd_impl_HD44780.h
index 2bd8536a1..22be37cc4 100644
--- a/Marlin/ultralcd_impl_HD44780.h
+++ b/Marlin/ultralcd_impl_HD44780.h
@@ -73,13 +73,12 @@ extern volatile uint8_t buttons;  //an extended version of the last checked butt
     #define B_DW (BUTTON_DOWN<<B_I2C_BTN_OFFSET)
     #define B_RI (BUTTON_RIGHT<<B_I2C_BTN_OFFSET)
 
+    #undef LCD_CLICKED
     #if BUTTON_EXISTS(ENC)
       // the pause/stop/restart button is connected to BTN_ENC when used
       #define B_ST (EN_C)                            // Map the pause/stop/resume button into its normalized functional name
-      #undef LCD_CLICKED
       #define LCD_CLICKED (buttons&(B_MI|B_RI|B_ST)) // pause/stop button also acts as click until we implement proper pause/stop.
     #else
-      #undef LCD_CLICKED
       #define LCD_CLICKED (buttons&(B_MI|B_RI))
     #endif