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Using enums to avoid default true in "settings dictionaries" (#466, #467, #471)

From: Adam Bergkvist <adam.bergkvist@ericsson.com>
Date: Wed, 17 Feb 2016 09:34:30 +0000
To: "public-media-capture@w3.org" <public-media-capture@w3.org>
Message-ID: <A222C88B6882744D8D4B9681B31588902957B60F@ESESSMB307.ericsson.se>
Hi

We currently have three PRs (#466 [1], #467 [2], #471 [3]) that attempt 
to solve the "avoid having true as default value" problem [4] for 
dictionaries by replacing them with enums. This mail tries to summarize 
the situation and present some options going forward. The goal is to be 
somewhat consistent so we can use the outcome of this discusion to make 
future decisions.

#467 [2] and #471 [3] present similar cases where we have an attribute 
with a "boolean-like" name and the enum would have two values represent 
"on" and "off".

- boolean voiceActivityDetection = true;
+ RTCVoiceActivityOption voiceActivityDetection = "enabled";
(other value is "disabled)

- boolean ordered = true;
+ (boolean or RTCDataChannelOrdered) ordered = "ordered";
(other value is "unordered")

About the above changes:
* It solves the "true as default value" problem.

* Verbosity without extra clarity. We don't get the clarity you get when 
replacing a boolean function argument with an enum (e.g. f(true) vs 
f("enableFeature")) here since we're dealing with dictionaries that 
always have the member name in front of the value (e.g. ordered: "ordered").

* In the case of ordered, the RTCDataChannel has a property that 
reflects the setting. Developers might expect the expression dc.ordered 
to work as is, but it evaluates to true for both "ordered" and "unordered".

An alternative approach could be to keep the boolean types but rephrase 
the names to indicate that they are turning off a feature that is on by 
default. For example

boolean unordered = false;
boolean disableVoiceActivityDetection = false;

Our options: Keep the current (1), switch to enums (2) or keep boolean 
but change the names (3).

#471 [3] is a bit different since it aims to replace two boolean 
properties with a single enum with four values.

- boolean send = true;
- boolean receive = true;
+ RTCRtpTransceiverDirection direction = "sendrecv";
(other values: "sendonly", "recvonly" and "inactive")

Alternative approaches:

(C) Negate the names and keep booleans.

boolean deactivateSender = false;
boolean deactivateReceiver = false;

(D) Use two separate values with on/off-like enum values.

RTCRtpActivity sender = "active";
RTCRtpActivity receiver = "active";
(other value "inactive")

Our options: Let's call what's in the spec currently approach (A), and 
the enum proposal in PR #471 (B). The rest is listed above.

/Adam

[1] https://github.com/w3c/webrtc-pc/pull/466
[2] https://github.com/w3c/webrtc-pc/pull/467
[3] https://github.com/w3c/webrtc-pc/pull/471
[4] http://heycam.github.io/webidl/#idl-dictionaries
Received on Wednesday, 17 February 2016 09:35:06 UTC

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