x/tools/cmd/godoc: improve accessibility

[jimmyfrasche]

This is a meta issue for improving the accessibility of godoc.

• need hover/focus styles for buttons and button-like links (easy, but requires design)
• insufficient contrast on date stamp for blog entries (easy)
• malformed definition lists (easy)
• embedded playground buttons not in focus order (easy)
• Mobile menu needs better keyboard and screen reader support (moderate)
• missing lang on html tag (difficult)
• UI exposed by -analysis=pointer,type inaccessible by keyboard and screen reader (very difficult)
• expanding/collapsing section inaccessible by keyboard (difficult, in progress)
• expanding/collapsing sections announce state glyph but not state (difficult, in progress)
• insufficient contrast on default focus ring for top level menu
• links can only be identified by color https://golang.org/cl/69150
• missing label and submit button on search form https://golang.org/cl/69190
• insufficient contrast for placeholder text in search form https://golang.org/cl/69190
• permalinks are insufficiently labeled https://golang.org/cl/69210
• images without alt attribute https://golang.org/cl/69130
• package docs skips heading level 3 https://golang.org/cl/69171

If you discover an issue not in the above list, please report it here so that it can be addressed.

If you want to help out and aren't sure where to start or just want to make sure that tools you create are as accessible possible, see (or update!) WebAccessibilityResourcesAndTips on the wiki.

[gopherbot]

Change https://golang.org/cl/69130 mentions this issue: godoc: add alt attr to gopher on main package index

[gopherbot]

Change https://golang.org/cl/69150 mentions this issue: godoc: better distinguish links and link state

[gopherbot]

Change https://golang.org/cl/69190 mentions this issue: godoc: add label and button to search bar

[gopherbot]

Change https://golang.org/cl/69210 mentions this issue: godoc: accessible permalinks

[gopherbot]

Change https://golang.org/cl/69171 mentions this issue: godoc: avoid skipping heading level in package docs

[jimmyfrasche]

I created a wiki page for anyone who wants to help out or to make sure that tools they create are as accessible as possible: https://github.com/golang/go/wiki/WebAccessibilityResourcesAndTips

@jimmyfrasche IMO the underline effects in CL 69150 makes the docs look messy, especially in the package table of contents. I'm curious if anyone else feels that way.

[jimmyfrasche]

@bontibon The purpose is to distinguish between clickable and not clickable elements. That means having to distinguishing them by both shape and color. This helps users who have trouble seeing certain colors, a monochrome display, and new users who haven't acclimated to the fact that you can click "func Count(s, substr string) int" but not "Package strings" despite them both being the same blue.

[dsnet]

I find the underlines fairly hard to read. Perhaps we should keep the underline, but make it an opacity of 30% or something.