Add support for backlog with no delay

[emontnemery]

Description:

Add support for executing backlog with no delay without setting SetOption34 = 0

The delay defined by SetOption34 is omitted for any command in a backlog sequence following immediately after the special command NoDelay.
This must be used with care, and only for simple commands.

The main driver is to allow HomeAssistant to more precisely control lights, in particular transitions (Fade and Speed in Tasmota).

Example:

Disable fade, and turn off a light without any delays:
Backlog NoDelay;Fade 0;NoDelay;Power4 OFF
Enable fade, and turn on a light without any additional delays:
Backlog NoDelay;Fade 1;NoDelay;Speed 4;NoDelay;Power4 ON

Checklist:

• The pull request is done against the latest dev branch
• Only relevant files were touched
• Only one feature/fix was added per PR.
• The code change is tested and works on Tasmota core ESP8266 V.2.7.4.3
• The code change is tested and works on core ESP32 V.1.12.2
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[arendst]

I like the idea but would like to play with backlog_delay value in order to execute the next command removing the code execution redundancy.

Let me have a look before optionally merging this.

[arendst]

Thx. Implemented my way.

[emontnemery]

@arendst I first implemented your way, because as you mention code is much cleaner.

However, it doesn't work because with this way there is a delay between handling of the Backlog command itself and until BacklogLoop starts processing the first command in the Backlog.

What could work, while still keeping the NoDelay handling only in BacklogLoop, is to allow BacklogLoop to check if the next command is NoDelay.

What I mean is: revert 29e73da and instead do something like this:

void BacklogLoop(void) {
  if (TimeReached(backlog_delay) || NextCommandNoDelay()) {

Let me know if you want me to give it a try?

[arendst]

@emontnemery How about leaving the commit and add the following to support_command.ino:

    }
//    ResponseCmndChar(D_JSON_APPENDED);
    mqtt_data[0] = '\0';
    backlog_delay = 0;
  } else {

So add line 347 with backlog_delay = 0;

[emontnemery]

@arendst that is the perfect solution if the delay between the backlog command itself and the first command in the backlog is not needed!

By the way, I think this line in your solution also needs to be changed, to handle if user ends the backlog sequence with NoDelay?

-      } while (nodelay_detected);
+      } while (!BACKLOG_EMPTY && nodelay_detected);

Edit: OK, so it's fixed in 074aec0, great!