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[css3-images] linear-gradient keywords and angles are opposite

From: Brian Manthos <brianman@microsoft.com>
Date: Tue, 7 Jun 2011 18:34:59 +0000
To: "www-style@w3.org" <www-style@w3.org>
Message-ID: <FA122FEC823D524CB516E4E0374D9DCF1FB130EE@TK5EX14MBXC136.redmond.corp.microsoft.com>
Something was bugging me about the linear gradient keywords, and I think I narrowed it down.

The same issue applies to the Working Draft and the Editor's Draft.

For now, let's use the Working Draft:
http://www.w3.org/TR/css3-images/

# The gradient-line may be specified in two different ways. The
# first is by specifying the angle the gradient-line should assume;
# this uses the standard algebraic notation for angles where 0deg
# points to the right, 90deg points up, and positive angles go
# counterclockwise. The starting-point and ending-point of the
# gradient-line are determined by extending a line in both
# direction from the center of the box at the angle specified.
# [1]In the direction of the angle, the ending-point is the point on
# the gradient-line where a line drawn perpendicular to the
# gradient-line would intersect the corner of the box in that
# direction. The starting-point is determined identically, except
# in the opposite direction of the angle.[/1]
#
# The [2]second way is to simply provide a side or corner of the box
# that the gradient should start[/2] at; the gradient will then
# automatically angle itself to [3]extend from the specified side or
# corner to the opposite[/3] side or corner in a straight line. To be
# precise, the gradient is converted to the angle form described
# in the previous paragraph at used-value time. If a 'left',
# 'bottom', 'right', or 'top' is given, the used value of the gradient
# is 0deg, 90deg, 180deg, or 270 deg, respectively. If a corner is
# given, the used value of the gradient is the angle necessary to
# place the starting-point of the gradient in that corner of the box. 


Paraphrasing [1]:
When specified via angle, the angle can be understood as both the direction ("toward the <angle>") and the ending point ("ends at <angle>").

Paraphrasing [2] and [3]:
When specified via keyword, the keyword can be understood as both opposite direction ("away from the <keyword(s)>") and the starting point ("starts at  <keyword>").


Is it intentional that these two ways of specifying gradient-line are opposite?
Received on Tuesday, 7 June 2011 18:35:31 GMT

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