Although "deprecated" is a feature (and *will* appear in the features
list), add a special :deprecated: option to generate an eye-catch that
makes this information very hard to miss.

(The intent is to modify qapidoc.py to add this option whenever it
detects that the features list attached to a definition contains the
"deprecated" entry.)

-

RFC: Technically, this object-level option is un-needed and could be
replaced with a standard content-level directive that e.g. qapidoc.py
could insert at the beginning of the content block. I've done it here as
an option to demonstrate how it would be possible to do.

It's a matter of taste for "where" we feel like implementing it.

One benefit of doing it this way is that we can create a single
containing box to set CSS style options controlling the flow of multiple
infoboxes. The other way to achieve that would be to create a directive
that allows us to set multiple options instead, e.g.:

.. qapi:infoboxes:: deprecated unstable

or possibly:

.. qapi:infoboxes::
   :deprecated:
   :unstable:

For now, I've left these as top-level QAPI object options. "Hey, it works."

P.S., I outsourced the CSS ;)

Signed-off-by: Harmonie Snow <harmonie@gmail.com>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 docs/sphinx-static/theme_overrides.css | 25 +++++++++++++++++++++++++
 docs/sphinx/qapi-domain.py             | 24 ++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/docs/sphinx-static/theme_overrides.css b/docs/sphinx-static/theme_overrides.css
index 965ecac54fd..3765cab1b20 100644
--- a/docs/sphinx-static/theme_overrides.css
+++ b/docs/sphinx-static/theme_overrides.css
@@ -208,3 +208,28 @@ div[class^="highlight"] pre {
         color: inherit;
     }
 }
+
+/* QAPI domain theming */
+
+.qapi-infopips {
+    margin-bottom: 1em;
+}
+
+.qapi-infopip {
+    display: inline-block;
+    padding: 0em 0.5em 0em 0.5em;
+    margin: 0.25em;
+}
+
+.qapi-deprecated {
+    background-color: #fffef5;
+    border: solid #fff176 6px;
+    font-weight: bold;
+    padding: 8px;
+    border-radius: 15px;
+    margin: 5px;
+}
+
+.qapi-deprecated::before {
+    content: '⚠️ ';
+}
diff --git a/docs/sphinx/qapi-domain.py b/docs/sphinx/qapi-domain.py
index 6120515bdc8..b33d9927f4d 100644
--- a/docs/sphinx/qapi-domain.py
+++ b/docs/sphinx/qapi-domain.py
@@ -126,6 +126,7 @@ class QAPIObject(ObjectDescription[Signature]):
             "module": directives.unchanged,  # Override contextual module name
             # These are QAPI originals:
             "since": since_validator,
+            "deprecated": directives.flag,
         }
     )
 
@@ -236,6 +237,28 @@ def add_target_and_index(
                     ("single", indextext, node_id, "", None)
                 )
 
+    def _add_infopips(self, contentnode: addnodes.desc_content) -> None:
+        # Add various eye-catches and things that go below the signature
+        # bar, but precede the user-defined content.
+        infopips = nodes.container()
+        infopips.attributes["classes"].append("qapi-infopips")
+
+        def _add_pip(source: str, content: str, classname: str) -> None:
+            node = nodes.container(source)
+            node.append(nodes.Text(content))
+            node.attributes["classes"].extend(["qapi-infopip", classname])
+            infopips.append(node)
+
+        if "deprecated" in self.options:
+            _add_pip(
+                ":deprecated:",
+                f"This {self.objtype} is deprecated.",
+                "qapi-deprecated",
+            )
+
+        if infopips.children:
+            contentnode.insert(0, infopips)
+
     def _merge_adjoining_field_lists(
         self, contentnode: addnodes.desc_content
     ) -> None:
@@ -263,6 +286,7 @@ def _merge_adjoining_field_lists(
             contentnode.remove(child)
 
     def transform_content(self, contentnode: addnodes.desc_content) -> None:
+        self._add_infopips(contentnode)
         self._merge_adjoining_field_lists(contentnode)
 
     def _toc_entry_name(self, sig_node: desc_signature) -> str:
-- 
2.47.0