Doc: Describe the experimental language client plugin

Change-Id: I14e227a242dc101f9e535f56da52beddb5bc325a
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

doc/src/editors/creator-coding.qdoc

@@ -89,6 +89,13 @@
 
     \list
 
+        \li \l{Using Language Servers}
+
+            The experimental language client provides code completion,
+            highlighting of the symbol under cursor, and jumping to the symbol
+            definition for other programming languages besides C++. In addition,
+            it integrates diagnostics from the language server.
+
         \li \l{Editing MIME Types}
 
             \QC uses the MIME type of a file to determine which mode and editor

doc/src/editors/creator-only/creator-fakevim.qdoc

@@ -27,7 +27,7 @@
     \contentspage index.html
     \previouspage creator-editor-options-text.html
     \page creator-editor-fakevim.html
-    \nextpage creator-mime-types.html
+    \nextpage creator-language-servers.html
 
     \title Using FakeVim Mode
 

doc/src/editors/creator-only/creator-language-server.qdoc

@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Creator documentation.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Free Documentation License Usage
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file. Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
+**
+****************************************************************************/
+
+/*!
+    \contentspage index.html
+    \previouspage creator-editor-fakevim.html
+    \page creator-language-servers.html
+    \nextpage creator-mime-types.html
+
+    \title Using Language Servers
+
+    For several programming languages, a \e {language server} is available
+    that provides information about the code to IDEs as long as they support
+    communication via the language server protocol (LSP). This enables the
+    IDE to provide code completion, highlighting of the symbol under cursor,
+    and jumping to the symbol definition, as well as to integrate diagnostics
+    from the language server.
+
+    By providing a client for the language server protocol, \QC can support
+    the above features for several other programming languages besides C++.
+    However, the experimental client does support language servers that
+    require special handling.
+
+    \QC uses the \l{https://www.iana.org/assignments/media-types/media-types.xhtml}
+    {MIME type} of the file to determine which language server to start when you
+    open a file for editing. Add new MIME types as filters for language servers.
+    For more information about how \QC uses MIME types, see
+    \l {Editing MIME Types}.
+
+    The experimental language service client has been mostly tested with Python.
+    If problems arise when you try some other language, please select
+    \uicontrol Help > \uicontrol {Report Bug} to report them in the Qt Bug
+    Tracker. The reports should include \QC console output with the environment
+    variable \c {QT_LOGGING_RULES=qtc.languageclient.*=true} set.
+
+    To use a language server:
+
+    \list 1
+
+        \li Enable the language server client by selecting \uicontrol Help >
+            \uicontrol {About Plugins} > \uicontrol {Other Languages} >
+            \uicontrol {Language Client} (or \uicontrol {Qt Creator} >
+            \uicontrol {About Plugins} > \uicontrol {Other Languages} >
+            \uicontrol {Language Client} on \macos).
+        \li Restart \QC to load the language client plugin.
+        \li Select \uicontrol Tools > \uicontrol Options >
+            \uicontrol {Language Client} > \uicontrol Add (or
+            \uicontrol {Qt Creator} > \uicontrol {Language Client} >
+            \uicontrol Add on \macos) to add language servers.
+        \li In the \uicontrol Name field, enter a name for the language server.
+        \li Select the \uicontrol Enabled check box.
+        \li In the \uicontrol {MIME Type} field, enter the filter for files that
+            the lanaguage server will handle. When you start typing the filter
+            name, a list of predefined filters appears where you can select a
+            filter.
+        \li In the \uicontrol Executable field, enter the path to the language
+            server executable.
+        \li In the \uicontrol Arguments field, enter any required command line
+            arguments.
+    \endlist
+*/

doc/src/editors/creator-only/creator-mime-types.qdoc

@@ -31,16 +31,16 @@
 
 /*!
     \contentspage index.html
-    \previouspage creator-editor-fakevim.html
+    \previouspage creator-language-servers.html
     \page creator-mime-types.html
     \nextpage creator-modeling.html
 
     \title Editing MIME Types
 
-    \QC uses the \l{http://en.wikipedia.org/wiki/Internet_media_type}
-    {Internet media type} (MIME type) of the file to determine which mode and
-    editor to use for opening the file. For example, \QC opens C++ source and
-    header files in the C++ editor, and Qt widget based UI files (.ui) in \QD.
+    \QC uses the \l{https://www.iana.org/assignments/media-types/media-types.xhtml}
+    {MIME type} of the file to determine which mode and editor to use for
+    opening the file. For example, \QC opens C++ source and header files in
+    the C++ editor, and Qt widget based UI files (.ui) in \QD.
 
     To identify the MIME type of a file, \QC uses matching by pattern and
     matching by contents. First, \QC looks at the filename to check whether it

doc/src/qtcreator-toc.qdoc

@@ -141,6 +141,7 @@
                 \li \l{Specifying Text Editor Settings}
                 \li \l{Using FakeVim Mode}
             \endlist
+            \li \l{Using Language Servers}
             \li \l{Editing MIME Types}
             \li \l{Modeling}
             \li \l{Editing State Charts}