Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Refine some wording for clarity and explicitness #3

Draft
wants to merge 1 commit into
base: gh-pages
Choose a base branch
from
Draft

Refine some wording for clarity and explicitness #3

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
18 changes: 9 additions & 9 deletions README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,18 +2,22 @@

**[SVG paths](https://www.w3.org/TR/SVG/paths.html)** can be daunting at first,
but upon closer examination,
most of the commands can be understood pretty intuitively.
most of the path data commands
(provided in the `d` attribute of a `<path>` element)
can be understood pretty intuitively.

The syntax of the
**[arc command](https://www.w3.org/TR/SVG/paths.html#PathDataEllipticalArcCommands)**,
however, seems to be an exception.
This repo provides some resources that hopefully make its syntax clearer.
however, seems to be an exception,
in that it defies easy interpretation even to the trained eye.
This project provides some resources that hopefully make its syntax clearer.

## Explanation

The awkward
[syntax of the arc command](https://www.w3.org/TR/SVG/implnote.html#ArcSyntax)
is due to it being designed to match the structure of the other SVG path commands,
is due to it being designed to match the structure of the other
[path data commands](https://www.w3.org/TR/SVG/paths.html#PathData),
all of which consist of one or more pairs of (x,y) coordinates,
the last one being the coordinates of the new "current point" of the "pen"
(to follow the analogy of a [plotter](https://en.wikipedia.org/wiki/Plotter)).
Expand All @@ -31,14 +35,10 @@ is as providing parameters to a
**[constraint solver](https://en.wikipedia.org/wiki/Constraint_programming)**:
the arc has to follow an ellipse
with a given **width/height ratio** (x-radius vs. y-radius),
with a given **rotation**<sup>†</sup>, and that passes through the **start point**
with a given **orientation**, and that passes through the **start point**
given at the end of the preceding path command, and the **end point**
given at the end of the arc command.

><sup>†</sup>Note that the rotation maintains the start and end points,
whereas a rotation with the transform attribute (outside the path description)
would cause the entire path, including the start and end points, to be rotated.

These restrictions (with a few
[adjustments to prevent unsolvable constraints](https://www.w3.org/TR/SVG/implnote.html#ArcOutOfRangeParameters))
result in two possible ellipses,
Expand Down