Describe diff preferences in review UI documentation

Change-Id: I61b4692a3f8656ecbbcc2eb31746ba9a0537dbd9
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/user-review-ui.txt

@@ -710,14 +710,12 @@ the Git web browser.
 image::images/user-review-ui-side-by-side-diff-screen-project-and-file.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-project-and-file.png"]
 
 The checkbox in front of the project name and the file name allows the
-patch to be marked as reviewed.
+patch to be marked as reviewed. The link:#mark-reviewed[Mark Reviewed]
+diff preference allows to control whether the files should be
+automatically marked as reviewed when they are viewed.
 
 image::images/user-review-ui-side-by-side-diff-screen-reviewed.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-reviewed.png"]
 
-Syntax coloring is supported for many languages and file types.
-
-image::images/user-review-ui-side-by-side-diff-screen-syntax-coloring.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-syntax-coloring.png"]
-
 The scrollbar shows patch diffs and inline comments as annotations.
 This provides a good overview of the lines in the patch that are
 relevant for reviewing. By clicking on an annotation one can quickly
@@ -777,8 +775,8 @@ To link to a line in the old file version, '@a<line-number>' must be
 appended to the patch link. These links can be used to directly link to
 certain inline comments.
 
-If the diff preference `Expand All Comments` is set to `Expand`, all
+If the diff preference link:#expand-all-comments[Expand All Comments]
-inline comments will be automatically expanded.
+is set to `Expand`, all inline comments will be automatically expanded.
 
 image::images/user-review-ui-side-by-side-diff-screen-inline-comments.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-inline-comments.png"]
 
@@ -877,6 +875,140 @@ level comment.
 
 image::images/user-review-ui-side-by-side-diff-screen-file-level-commented.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-file-level-commented.png"]
 
+[[diff-preferences]]
+=== Diff Preferences
+
+There are several options to control how patch diffs should be
+rendered. Users can configure their preferences in the diff
+preferences. The diff preferences can be accessed by clicking on the
+settings icon in the screen header.
+
+image::images/user-review-ui-side-by-side-diff-screen-preferences.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-preferences.png"]
+
+The diff preferences popup allows to change the diff preferences.
+By clicking on the `Save` button changes to the diff preferences are
+saved permanently. Clicking on the `Apply` button applies the new
+diff preferences to the current screen, but they are discarded when the
+screen is refreshed. The `Save` button is only available if the user is
+signed in.
+
+image::images/user-review-ui-side-by-side-diff-screen-preferences-popup.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-preferences-popup.png"]
+
+The following diff preferences can be configured:
+
+- `Theme`:
++
+Controls the theme that is used to render the file content.
++
+E.g. users could choose to work with a dark theme.
++
+image::images/user-review-ui-side-by-side-diff-screen-dark-theme.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-dark-theme.png"]
+
+- `Ignore Whitespace`:
++
+Controls whether differences in whitespace should be ignored or not.
++
+** `None`:
++
+All differences in whitespace are highlighted.
++
+** `At Line End`:
++
+Whitespace differences at the end of lines are ignored.
++
+** `Leading, At Line End`:
++
+Whitespace differences at the beginning and end of lines are ignored.
++
+** `All`:
++
+All differences in whitespace are ignored.
+
+- `Tab Width`:
++
+Controls how many spaces should be displayed for a tab.
+
+- `Columns`:
++
+Sets the preferred line length. At this position a vertical dashed line
+is displayed so that one can easily detect lines the exceed the
+preferred line length.
++
+image::images/user-review-ui-side-by-side-diff-screen-column.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-column.png"]
+
+- `Lines Of Context`:
++
+The number of context lines that should be displayed before and after
+any diff. If the `entire file` checkbox is selected, the full file is
+rendered.
++
+Skipped common lines can be expanded by clicking on the placeholder for
+the skipped lines.
++
+Clicking on "... skipped <n> common lines ..." expands the complete
+block of skipped lines.
++
+If many lines are skipped there are additional links to expand the
+context by ten lines before and after the skipped block.
++
+image::images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png"]
+
+- `Intraline Difference`:
++
+Controls whether intraline differences should be highlighted.
++
+image::images/user-review-ui-side-by-side-diff-screen-intraline-difference.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-intraline-difference.png"]
+
+- `Syntax Highlighting`:
++
+Controls whether syntax highlighting should be enabled.
++
+The language for the syntax highlighting is automatically detected from
+the file extension.
++
+image::images/user-review-ui-side-by-side-diff-screen-syntax-coloring.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-syntax-coloring.png"]
+
+- `Whitespace Errors`:
++
+Controls whether whitespace errors are highlighted.
+
+- `Show Tabs`:
++
+Controls whether tabs are highlighted.
+
+- `Line Numbers`:
++
+Controls whether line numbers are shown.
+
+- `Top Menu`:
++
+Controls whether the top menu is shown.
+
+[[mark-reviewed]]
+- `Mark Reviewed`:
++
+Controls whether the files of the patch set should be automatically
+marked as reviewed when they are viewed.
+
+[[expand-all-comments]]
+- `Expand All Comments`:
++
+Controls whether all comments should be automatically expanded.
+
+- `Render`:
++
+Controls how patch files that exceed the screen size are rendered.
++
+If `Fast` is selected file contents which are outside of the visible
+area are not attached to the browser's DOM tree. This makes the
+rendering fast, but searching by `Ctrl+F` only finds content which is
+in the visible area.
++
+If `Slow` is selected all file contents are attached to the browser's
+DOM tree, which makes the rendering slow for large files. The advantage
+of this setting is that `Ctrl+F` can be used to search in the complete
+file.
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]