Simplify encoder handling (#18754)

Marlin/src/lcd/ultralcd.cpp

   bool MarlinUI::wait_for_move; // = false
 #endif
 
+constexpr uint8_t epps = ENCODER_PULSES_PER_STEP;
+
 #if HAS_SPI_LCD
   #if ENABLED(STATUS_MESSAGE_SCROLLING)
     uint8_t MarlinUI::status_scroll_offset; // = 0
           #endif
           {
             #if HAS_LCD_MENU
-                   if (RRK(EN_KEYPAD_UP))     encoderPosition -= ENCODER_PULSES_PER_STEP;
-              else if (RRK(EN_KEYPAD_DOWN))   encoderPosition += ENCODER_PULSES_PER_STEP;
+                   if (RRK(EN_KEYPAD_UP))     encoderPosition -= epps;
+              else if (RRK(EN_KEYPAD_DOWN))   encoderPosition += epps;
               else if (RRK(EN_KEYPAD_LEFT))   { MenuItem_back::action(); quick_feedback(); }
               else if (RRK(EN_KEYPAD_RIGHT))  encoderPosition = 0;
             #else
-                   if (RRK(EN_KEYPAD_UP)   || RRK(EN_KEYPAD_LEFT))  encoderPosition -= ENCODER_PULSES_PER_STEP;
-              else if (RRK(EN_KEYPAD_DOWN) || RRK(EN_KEYPAD_RIGHT)) encoderPosition += ENCODER_PULSES_PER_STEP;
+                   if (RRK(EN_KEYPAD_UP)   || RRK(EN_KEYPAD_LEFT))  encoderPosition -= epps;
+              else if (RRK(EN_KEYPAD_DOWN) || RRK(EN_KEYPAD_RIGHT)) encoderPosition += epps;
             #endif
           }
         #endif
         RESET_STATUS_TIMEOUT();
         if (touch_buttons & (EN_A | EN_B)) {              // Menu arrows, in priority
           if (ELAPSED(ms, next_button_update_ms)) {
-            encoderDiff = (ENCODER_STEPS_PER_MENU_ITEM) * (ENCODER_PULSES_PER_STEP) * encoderDirection;
+            encoderDiff = (ENCODER_STEPS_PER_MENU_ITEM) * epps * encoderDirection;
             if (touch_buttons & EN_A) encoderDiff *= -1;
             TERN_(AUTO_BED_LEVELING_UBL, external_encoder());
             next_button_update_ms = ms + repeat_delay;    // Assume the repeat delay
       #if ENCODER_PULSES_PER_STEP > 1
         // When reversing the encoder direction, a movement step can be missed because
         // encoderDiff has a non-zero residual value, making the controller unresponsive.
-        // The fix clears the residual value when the encoder is reversed.
+        // The fix clears the residual value when the encoder is idle.
         // Also check if past half the threshold to compensate for missed single steps.
         static int8_t lastEncoderDiff;
-        int8_t prevDiff = lastEncoderDiff;
-        lastEncoderDiff = encoderDiff;  // Store before updating encoderDiff to save actual steps
-
-        // When not past threshold, and reversing... or past half the threshold
-        if (WITHIN(abs_diff, 1, (ENCODER_PULSES_PER_STEP) - 1)  // Not past threshold
-          && (abs_diff > (ENCODER_PULSES_PER_STEP) / 2          // Passed half the threshold? Done! Call it a full step.
-            || (ABS(encoderDiff - prevDiff) >= (ENCODER_PULSES_PER_STEP)  // A big change when abs_diff is small implies reverse
-                && ABS(prevDiff) < (ENCODER_PULSES_PER_STEP)    // ...especially when starting from a partial or no step.
-               )
-             )
-        ) {
-          abs_diff = ENCODER_PULSES_PER_STEP;
-          encoderDiff = (encoderDiff < 0 ? -1 : 1) * abs_diff;  // Treat as full step
+
+        // Timeout? No decoder change since last check. 10 or 20 times per second.
+        if (encoderDiff == lastEncoderDiff && abs_diff <= epps / 2)   // Same direction & size but not over a half-step?
+          encoderDiff = 0;                                            // Clear residual pulses.
+        else if (WITHIN(abs_diff, epps / 2 + 1, epps - 1)) {          // Past half of threshold?
+          abs_diff = epps;                                            // Treat as a full step size
+          encoderDiff = (encoderDiff < 0 ? -1 : 1) * abs_diff;        // ...in the spin direction.
         }
+        lastEncoderDiff = encoderDiff;
       #endif
 
-      const bool encoderPastThreshold = (abs_diff >= (ENCODER_PULSES_PER_STEP));
+      const bool encoderPastThreshold = (abs_diff >= epps);
       if (encoderPastThreshold || lcd_clicked) {
         if (encoderPastThreshold) {
 
             int32_t encoderMultiplier = 1;
 
             if (encoderRateMultiplierEnabled) {
-              const float encoderMovementSteps = float(abs_diff) / (ENCODER_PULSES_PER_STEP);
+              const float encoderMovementSteps = float(abs_diff) / epps;
 
               if (lastEncoderMovementMillis) {
                 // Note that the rate is always calculated between two passes through the
 
           #endif // ENCODER_RATE_MULTIPLIER
 
-          encoderPosition += (encoderDiff * encoderMultiplier) / (ENCODER_PULSES_PER_STEP);
+          encoderPosition += (encoderDiff * encoderMultiplier) / epps;
           encoderDiff = 0;
         }
 
         //
         #if ANY_BUTTON(UP, DWN, LFT, RT)
 
-          const int8_t pulses = (ENCODER_PULSES_PER_STEP) * encoderDirection;
+          const int8_t pulses = epps * encoderDirection;
 
           if (false) {
             // for the else-ifs below
       const int8_t xdir = col < (LCD_WIDTH ) / 2 ? -1 : 1,
                    ydir = row < (LCD_HEIGHT) / 2 ? -1 : 1;
       if (on_edit_screen)
-        encoderDiff = (ENCODER_PULSES_PER_STEP) * ydir;
+        encoderDiff = epps * ydir;
       else if (screen_items > 0) {
         // Last 3 cols act as a scroll :-)
         if (col > (LCD_WIDTH) - 5)
           // 2 * LCD_HEIGHT to scroll to bottom of next page. (LCD_HEIGHT would only go 1 item down.)
-          encoderDiff = (ENCODER_PULSES_PER_STEP) * (encoderLine - encoderTopLine + 2 * (LCD_HEIGHT)) * ydir;
+          encoderDiff = epps * (encoderLine - encoderTopLine + 2 * (LCD_HEIGHT)) * ydir;
         else
-          encoderDiff = (ENCODER_PULSES_PER_STEP) * (row - encoderPosition + encoderTopLine);
+          encoderDiff = epps * (row - encoderPosition + encoderTopLine);
       }
       else if (!on_status_screen())
-        encoderDiff = (ENCODER_PULSES_PER_STEP) * xdir;
+        encoderDiff = epps * xdir;
     }
 
   #endif