Subject: draft-ietf-httpbis-client-hints-06

From: HTTP Working Group <[email-masked]>
Date: Sun, 22 Jul 2018 16:03:37 +0000

HTTP Client Hints
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06

3.1.  The DPR Header Field

https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06#section-3.1

|   The "DPR" request header field is a number that indicates the
|   client's current Device Pixel Ratio (DPR), which is the ratio of
|   physical pixels over CSS px (Section 5.2 of [CSSVAL]) of the layout
|   viewport (Section 9.1.1 of [CSS2]) on the device.
|
|     DPR = 1*DIGIT [ "." 1*DIGIT ]
|
|   If DPR occurs in a message more than once, the last value overrides
|   all previous occurrences.

But on elsewhere

https://tools.ietf.org/html/rfc7230#section-3.2.2

|   A recipient MAY combine multiple header fields with the same field
|   name into one "field-name: field-value" pair, without changing the
|   semantics of the message, by appending each subsequent field value to
|   the combined field value in order, separated by a comma. 

So is that saying that if there is several DPR values on
DPR Header Field, last value is used ?

If that in interpreted only that if last DPR header field is used,
and header field is ignored if it does not fit

   DPR = 1*DIGIT [ "." 1*DIGIT ]

syntax, result is different is recipient combines multiple
DPR headers.

3.1.1.  Confirming Selected DPR
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06#section-3.1.1

|   If Content-DPR occurs in a message more than once, the last value
|   overrides all previous occurrences.

( Partially same on here. Refering of value is better however ).

3.1.1.  Confirming Selected DPR
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06#section-3.1.1

|   If Content-DPR occurs in a message more than once, the last value
|   overrides all previous occurrences.

Same in here.

3.2.  The Width Header Field
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06#section-3.2

|                           If Width occurs in a message more than once, the
|   last value overrides all previous occurrences.

( Partially same on here. Refering of value is better however ).

3.3.  The Viewport-Width Header Field
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-06#section-3.3

|   If Viewport-Width occurs in a message more than once, the last value
|   overrides all previous occurrences.

So it should mention that on these header fields also last value
is used when values are ',' -separated.

/ Kari Hurtta