[doc] Use RTD theme. (#7346)

doc/_static/custom.css

@@ -1,23 +1,31 @@
-div.breathe-sectiondef.container {
-  width: 100%;
+@import url('theme.css');
+
+/* Logo background */
+.wy-side-nav-search, .wy-side-nav-search img {
+    background-color: #ffffff !important;
 }
 
-div.literal-block-wrapper.container {
-  width: 100%;
+.highlight {
+  background: #f1f3f4;
 }
 
-.red {
-  color: red;
+.navbar {
+  background: #ffffff;
 }
 
-table {
-  border: 0;
+.navbar-nav {
+  background: #ffffff;
 }
 
-td, th {
-  padding: 1px 8px 1px 5px;
-  border-top: 0;
-  border-bottom: 1px solid #aaa;
-  border-left: 0;
-  border-right: 0;
+/* side bar */
+.wy-nav-side {
+  background: #f1f3f4;
+}
+
+.wy-menu-vertical a {
+  color: #707070;
+}
+
+.wy-side-nav-search div.version {
+  color: #404040;
 }

doc/build.rst

@@ -522,14 +522,7 @@ XGBoost uses `Sphinx <https://www.sphinx-doc.org/en/stable/>`_ for documentation
 
 * Python dependencies
 
-  - sphinx
-  - breathe
-  - guzzle_sphinx_theme
-  - recommonmark
-  - mock
-  - sh
-  - graphviz
-  - matplotlib
+  Checkout the ``requirements.txt`` file under ``doc/``
 
 Under ``xgboost/doc`` directory, run ``make <format>`` with ``<format>`` replaced by the format you want.  For a list of supported formats, run ``make help`` under the same directory.
 

doc/conf.py

@@ -19,7 +19,6 @@ import sys
 import re
 import os
 import subprocess
-import guzzle_sphinx_theme
 
 git_branch = os.getenv('SPHINX_GIT_BRANCH', default=None)
 if not git_branch:
@@ -33,6 +32,7 @@ if not git_branch:
 else:
     git_branch = [git_branch]
 print('git_branch = {}'.format(git_branch[0]))
+
 try:
     filename, _ = urllib.request.urlretrieve(
         'https://s3-us-west-2.amazonaws.com/xgboost-docs/{}.tar.bz2'.format(
@@ -169,17 +169,13 @@ todo_include_todos = False
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme_path = guzzle_sphinx_theme.html_theme_path()
-html_theme = 'guzzle_sphinx_theme'
+html_theme = "sphinx_rtd_theme"
+html_theme_options = {"logo_only": True}
 
-# Register the theme as an extension to generate a sitemap.xml
-extensions.append("guzzle_sphinx_theme")
 
-# Guzzle theme options (see theme.conf for more information)
-html_theme_options = {
-    # Set the name of the project to appear in the sidebar
-    "project_nav_name": "XGBoost"
-}
+html_logo = "https://raw.githubusercontent.com/dmlc/dmlc.github.io/master/img/logo-m/xgboost.png"
+
+html_css_files = ["css/custom.css"]
 
 html_sidebars = {
   '**': ['logo-text.html', 'globaltoc.html', 'searchbox.html']
@@ -201,8 +197,7 @@ latex_elements = {
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
-  (master_doc, '%s.tex' % project, project,
-   author, 'manual'),
+  (master_doc, '%s.tex' % project, project, author, 'manual'),
 ]
 
 intersphinx_mapping = {

doc/requirements.txt

@@ -1,6 +1,6 @@
 sphinx>=2.1
 mock
-guzzle_sphinx_theme
+sphinx_rtd_theme
 breathe
 sh>=1.12.14
 matplotlib>=2.1

doc/xgboost_doc.yml

@@ -10,6 +10,6 @@ dependencies:
   - matplotlib
   - pip:
     - breathe
-    - guzzle_sphinx_theme
+    - sphinx_rtd_theme
     - pydot-ng
     - graphviz

tests/ci_build/conda_env/cpu_test.yml

@@ -35,6 +35,6 @@ dependencies:
 - pip:
   - shap
   - ipython                     # required by shap at import time.
-  - guzzle_sphinx_theme
+  - sphinx_rtd_theme
   - datatable
   - modin[all]

tests/ci_build/conda_env/macos_cpu_test.yml

@@ -32,5 +32,5 @@ dependencies:
 - boto3
 - awscli
 - pip:
-  - guzzle_sphinx_theme
+  - sphinx_rtd_theme
   - datatable