From 62f845a94e7f84b1e2525c18ac3c9f5c0ae63010 Mon Sep 17 00:00:00 2001
From: Will Miles <will@willmiles.net>
Date: Mon, 18 Mar 2024 19:46:33 -0400
Subject: [PATCH] DDP: Support sources that don't push

If the source never sends the push flag, WLED buffers the update but
never publishes it to the LEDs.  This causes the confusing case where
the peek display shows one thing but the LEDs themselves something else.

Add a static flag that tracks if we've seen a push from the source;
until we do, apply every update as soon as it's received, per the DDP
specification.
---
 wled00/e131.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/wled00/e131.cpp b/wled00/e131.cpp
index ec2efb50e..a67a672c2 100644
--- a/wled00/e131.cpp
+++ b/wled00/e131.cpp
@@ -11,6 +11,7 @@
 //DDP protocol support, called by handleE131Packet
 //handles RGB data only
 void handleDDPPacket(e131_packet_t* p) {
+  static bool ddpSeenPush = false;  // have we seen a push yet?
   int lastPushSeq = e131LastSequenceNumber[0];
 
   //reject late packets belonging to previous frame (assuming 4 packets max. before push)
@@ -34,6 +35,7 @@ void handleDDPPacket(e131_packet_t* p) {
   uint16_t c = 0;
   if (p->flags & DDP_TIMECODE_FLAG) c = 4; //packet has timecode flag, we do not support it, but data starts 4 bytes later
 
+  if (realtimeMode != REALTIME_MODE_DDP) ddpSeenPush = false; // just starting, no push yet
   realtimeLock(realtimeTimeoutMs, REALTIME_MODE_DDP);
 
   if (!realtimeOverride || (realtimeMode && useMainSegmentOnly)) {
@@ -44,7 +46,8 @@ void handleDDPPacket(e131_packet_t* p) {
   }
 
   bool push = p->flags & DDP_PUSH_FLAG;
-  if (push) {
+  ddpSeenPush |= push;
+  if (!ddpSeenPush || push) { // if we've never seen a push, or this is one, render display
     e131NewData = true;
     byte sn = p->sequenceNum & 0xF;
     if (sn) e131LastSequenceNumber[0] = sn;