Add navbar version switcher

docs/_static/switcher.json

@@ -0,0 +1,72 @@
+[
+  {
+    "name": "dev",
+    "version": "latest",
+    "url": "https://ctapipe.readthedocs.io/en/latest/"
+  },
+  {
+    "name": "v0.19.2 (stable)",
+    "version": "stable",
+    "url": "https://ctapipe.readthedocs.io/en/stable/"
+  },
+  {
+    "name": "v0.19.3",
+    "version": "v0.19.3",
+    "url": "https://ctapipe.readthedocs.io/en/v0.19.3/"
+  },
+  {
+    "name": "v0.19.2",
+    "version": "v0.19.2",
+    "url": "https://ctapipe.readthedocs.io/en/v0.19.2/"
+  },
+  {
+    "name": "v0.19.1",
+    "version": "v0.19.1",
+    "url": "https://ctapipe.readthedocs.io/en/v0.19.1/"
+  },
+  {
+    "name": "v0.19.0",
+    "version": "v0.19.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.19.0/"
+  },
+  {
+    "name": "v0.18.1",
+    "version": "v0.18.1",
+    "url": "https://ctapipe.readthedocs.io/en/v0.18.1/"
+  },
+  {
+    "name": "v0.18.0",
+    "version": "v0.18.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.18.0/"
+  },
+  {
+    "name": "v0.17.0",
+    "version": "v0.17.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.17.0/"
+  },
+  {
+    "name": "v0.16.0",
+    "version": "v0.16.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.16.0/"
+  },
+  {
+    "name": "v0.15.0",
+    "version": "v0.15.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.15.0/"
+  },
+  {
+    "name": "v0.14.0",
+    "version": "v0.14.0",
+    "url": "https://ctapipe.readthedocs.io/en/v0.14.0/"
+  },
+  {
+    "name": "v0.12.0-rtd",
+    "version": "v0.12.0-rtd",
+    "url": "https://ctapipe.readthedocs.io/en/v0.12.0-rtd/"
+  },
+  {
+    "name": "v0.11.0-rtd",
+    "version": "v0.11.0-rtd",
+    "url": "https://ctapipe.readthedocs.io/en/v0.11.0-rtd/"
+  }
+]

docs/conf.py

@@ -190,6 +190,26 @@ def setup(app):
 todo_include_todos = True
 
 
+# -- Version switcher -----------------------------------------------------
+
+# Define the json_url for our version switcher.
+json_url = "https://ctapipe.readthedocs.io/en/latest/_static/switcher.json"
+
+# Define the version we use for matching in the version switcher.
+version_match = os.environ.get("READTHEDOCS_VERSION")
+# If READTHEDOCS_VERSION doesn't exist, we're not on RTD
+# If it is an integer, we're in a PR build and the version isn't correct.
+if not version_match or version_match.isdigit():
+    # For local development, infer the version to match from the package.
+    if "dev" in release or "rc" in release:
+        version_match = "latest"
+        # We want to keep the relative reference if we are in dev mode
+        # but we want the whole url if we are effectively in a released version
+        json_url = "_static/switcher.json"
+    else:
+        version_match = release
+
+
 # -- Options for HTML output ----------------------------------------------
 
 html_theme = "pydata_sphinx_theme"
@@ -208,7 +228,11 @@ def setup(app):
     },
     "github_url": "https://github.com/cta-observatory/ctapipe",
     "header_links_before_dropdown": 6,
-    "navbar_start": ["navbar-logo"],
+    "navbar_start": ["navbar-logo", "version-switcher"],
+    "switcher": {
+        "version_match": version_match,
+        "json_url": json_url,
+    },
     "use_edit_page_button": True,
     "icon_links_label": "Quick Links",
     "icon_links": [
@@ -226,8 +250,6 @@ def setup(app):
     """,
 }
 
-html_sidebars = {"**": ["sidebar-nav-bs.html", "sidebar-ethical-ads.html"]}
-
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".