service cleanup after removing return FRAMETIME (#5443)

Clean-up and simplification of strip.service() after individual effect FRAMETIME was removed.
* Activation "_frametime" is now the same for all effects, so effects scheduling based on individual frametime is not needed any more
* Special handling for mode_static is obsolete, because the solid effect does not have a different timing any more
* Ensures a safe fallback segment after servicing to avoid stale state.
* Brightness changes use a capped refresh threshold to avoid excessive redraws.

Author: softhack007

wled00/FX_fcn.cpp

@@ -1266,16 +1266,16 @@ void WS2812FX::finalizeInit() {
 
 void WS2812FX::service() {
   unsigned long nowUp = millis(); // Be aware, millis() rolls over every 49 days
-  now = nowUp + timebase;
   unsigned long elapsed = nowUp - _lastServiceShow;
-  if (_suspend || elapsed <= MIN_FRAME_DELAY) return;   // keep wifi alive - no matter if triggered or unlimited
-  if (!_triggered && (_targetFps != FPS_UNLIMITED)) {   // unlimited mode = no frametime
-    if (elapsed < _frametime) return;                   // too early for service
-  }
+  bool timeToShow = (elapsed >= _frametime);                        // all segments are running at the same speed
+  if (_triggered || _targetFps == FPS_UNLIMITED) timeToShow = true; // unlimited mode = no frametime; strip.trigger() can overrule timing
 
-  bool doShow = false;
+  now = nowUp + timebase;                               // common time base for all effects
+  if (!timeToShow) return;                              // too early for service
+  if (_suspend || elapsed <= MIN_FRAME_DELAY) return;   // keep wifi alive - no matter if triggered or unlimited
 
   _isServicing = true;
+  bool doShow = _triggered;    // true if ≥1 active segment was processed (and strip was not suspended mid-loop), or trigger received → triggers show()
   for (size_t i = 0; i < _segments.size(); i++) {
     Segment &seg = _segments[i];
     _segment_index = i;
@@ -1286,13 +1286,10 @@ void WS2812FX::service() {
     // reset the segment runtime data if needed
     seg.resetIfRequired();
 
-    if (!seg.isActive()) continue;
-
-    // last condition ensures all solid segments are updated at the same time
-    if (nowUp > _lastServiceShow + _frametime || _triggered || (doShow && seg.mode == FX_MODE_STATIC))
-    {
+    if (seg.isActive()) {
+      // current segment is active -> re-run effect, and remember that show() call is necessary
+      // if we arrive here, its always showtime (timeToShow == true)
       doShow = true;
-
       if (!seg.freeze) { //only run effect function if not frozen
         // Effect blending
         uint16_t prog = seg.progress();
@@ -1318,6 +1315,7 @@ void WS2812FX::service() {
     }
   }
   _segment_index = 0;     // segment index is only valid while effects are serviced
+  _currentSegment = &_segments[0]; // safe fallback to prevent stale pointer - SEGMENT/SEGENV should not be used outside of the service loop
 
   #ifdef WLED_DEBUG
   if ((_targetFps != FPS_UNLIMITED) && (millis() - nowUp > _frametime)) DEBUG_PRINTF_P(PSTR("Slow effects %u/%d.\n"), (unsigned)(millis()-nowUp), (int)_frametime);
@@ -1754,7 +1752,7 @@ void WS2812FX::setBrightness(uint8_t b, bool direct) {
   BusManager::setBrightness(scaledBri(b));
   if (!direct) {
     unsigned long t = millis();
-    if (t - _lastShow > MIN_SHOW_DELAY) trigger(); //apply brightness change immediately if no refresh soon
+    if (t - _lastShow > min(_frametime, uint16_t(FRAMETIME_FIXED))) trigger(); //apply brightness change immediately if no refresh soon, but don't speed up above 42fps
   }
 }