Rollup merge of #90487 - NoraCodes:nora/how-to-read-rustdoc, r=jyn514

Add a chapter on reading Rustdoc output

Includes documentation for:
 - general page structure
 - navigation
 - searching
 - themes
 - deep-linking

Doesn't include docs on the settings page.

Per https://github.com/rust-lang/rust/issues/90309

src/doc/rustdoc/src/SUMMARY.md

@@ -1,6 +1,7 @@
 # The Rustdoc Book
 
 - [What is rustdoc?](what-is-rustdoc.md)
+- [How to read rustdoc output](how-to-read-rustdoc.md)
 - [How to write documentation](how-to-write-documentation.md)
 - [What to include (and exclude)](what-to-include.md)
 - [Command-line arguments](command-line-arguments.md)

src/doc/rustdoc/src/how-to-read-rustdoc.md

@@ -0,0 +1,107 @@
+# How to read rustdoc output
+
+Rustdoc's HTML output includes a friendly and useful navigation interface which
+makes it easier for users to navigate and understand your code.
+This chapter covers the major features of that interface,
+and is a great starting point for documentation authors and users alike.
+
+## Structure
+
+The `rustdoc` output is divided into three sections.
+Along the left side of each page is a quick navigation bar,
+which shows contextual information about the current entry.
+The rest of the page is taken up by the search interface at the top
+and the documentation for the current item below that.
+
+## The Item Documentation
+
+The majority of the screen is taken up with the documentation text for the item
+currently being viewed.
+At the top is some at-a-glance info and controls:
+
+- the type and name of the item,
+  such as "Struct `std::time::Duration`",
+- a button to copy the item's path to the clipboard,
+  which is a clipboard item
+- a button to collapse or expand the top-level documentation for that item
+  (`[+]` or `[-]`),
+- a link to the source code (`[src]`),
+  if [configured](the-doc-attribute.html#html_no_source),
+  and present (the source may not be available if
+  the documentation was created with `cargo doc --no-deps`),
+- and the version in which the item became stable,
+  if it's a stable item in the standard library.
+
+Below this is the main documentation for the item,
+including a definition or function signature if appropriate,
+followed by a list of fields or variants for Rust types.
+Finally, the page lists associated functions and trait implementations,
+including automatic and blanket implementations that `rustdoc` knows about.
+
+### Navigation
+
+Subheadings, variants, fields, and many other things in this documentation
+are anchors and can be clicked on and deep-linked to,
+which is a great way to communicate exactly what you're talking about.
+The typograpical character "§" appears next to lines with anchors on them
+when hovered or given keyboard focus.
+
+## The Navigation Bar
+
+For example, when looking at documentation for the crate root,
+it shows all the crates documented in the documentation bundle,
+and quick links to the modules, structs, traits, functions, and macros available
+from the current crate.
+At the top, it displays a [configurable logo](the-doc-attribute.html#html_logo_url)
+alongside the current crate's name and version,
+or the current item whose documentation is being displayed.
+
+## The Theme Picker and Search Interface
+
+When viewing `rustdoc`'s output in a browser with JavaScript enabled,
+a dynamic interface appears at the top of the page.
+To the left is the theme picker, denoted with a paint-brush icon,
+and the search interface, help screen, and options appear to the right of that.
+
+### The Theme Picker
+
+Clicking on the theme picker provides a list of themes -
+by default `ayu`, `light`, and `dark` -
+which are available for viewing.
+
+### The Search Interface
+
+Typing in the search bar instantly searches the available documentation for
+the string entered with a fuzzy matching algorithm that is tolerant of minor
+typos.
+
+By default, the search results give are "In Names",
+meaning that the fuzzy match is made against the names of items.
+Matching names are shown on the left, and the first few words of their
+descriptions are given on the right.
+By clicking an item, you will navigate to its particular documentation.
+
+There are two other sets of results, shown as tabs in the search results pane.
+"In Parameters" shows matches for the string in the types of parameters to
+functions, and "In Return Types" shows matches in the return types of functions.
+Both are very useful when looking for a function whose name you can't quite
+bring to mind when you know the type you have or want.
+
+When typing in the search bar, you can prefix your search term with a type
+followed by a colon (such as `mod:`) to restrict the results to just that
+kind of item. (The available items are listed in the help popup.)
+
+### Shortcuts
+
+Pressing `S` while focused elsewhere on the page will move focus to the
+search bar, and pressing `?` shows the help screen,
+which includes all these shortcuts and more.
+Pressing `T` focuses the theme picker.
+
+When the search results are focused,
+the left and right arrows move between tabs and the up and down arrows move
+among the results.
+Pressing the enter or return key opens the highlighted result.
+
+When looking at the documentation for an item, the plus and minus keys expand
+and collapse all sections in the document.