Add Streamlit app for mock element slider

Implement a Streamlit app with a slider for mock elements.

Author: lukasmasuch

app/gh-13853/app.py

@@ -0,0 +1,32 @@
+import streamlit as st
+
+num_elements = 10
+
+st.set_page_config(page_title="Mock element Slider", layout="centered")
+
+element_ids = [f"mock-element-{i:02d}" for i in range(num_elements)]
+element_to_idx = {element_id: idx for idx, element_id in enumerate(element_ids)}
+
+url_element_id = st.query_params.get("element_id")
+if (
+    "mock_element_id" not in st.session_state
+    or st.session_state["mock_element_id"] not in element_to_idx
+):
+    st.session_state["mock_element_id"] = (
+        url_element_id if url_element_id in element_to_idx else element_ids[0]
+    )
+
+with st.container(key="mock-element-slider"):
+    st.select_slider(
+        "element",
+        options=element_ids,
+        key="mock_element_id",
+        label_visibility="collapsed",
+    )
+
+st.query_params["element_id"] = st.session_state["mock_element_id"]
+
+current_element_id = st.session_state["mock_element_id"]
+current_idx = element_to_idx[current_element_id]
+with st.popover(f"element `{current_element_id}`"):
+    st.markdown(f"({current_idx}/{num_elements})")