Add a basic tab group demo

Punting on getting the Angular Material Tab component working for now.

So just creating a very barebones tab group as a starting point.

demo/main.py

@@ -64,6 +64,7 @@
 import slide_toggle as slide_toggle
 import slider as slider
 import snackbar as snackbar
+import tab_group as tab_group
 import table as table
 import tailwind as tailwind
 import text as text
@@ -112,6 +113,7 @@ class Section:
       Example(name="grid_table"),
       Example(name="headers"),
       Example(name="snackbar"),
+      Example(name="tab_group"),
       Example(name="chat_inputs"),
       Example(name="form_billing"),
       Example(name="form_profile"),

demo/tab_group.py

@@ -0,0 +1,166 @@
+"""Simple tab group example.
+
+- Use this code as a starting point for creating tab group-like functionlity.
+- Extend/Modify it for your specific use case.
+"""
+
+from dataclasses import dataclass, field
+from typing import Callable
+
+import mesop as me
+
+
+@dataclass
+class Tab:
+  label: str
+  content: Callable
+  selected: bool = False
+  disabled: bool = False
+  icon: str | None = None
+
+
+def load(e: me.LoadEvent):
+  me.set_theme_mode("system")
+
+
+@me.stateclass
+class State:
+  selected_tab_index: int = 0
+  disabled_tab_indexes: set[int] = field(default_factory=lambda: {1})
+
+
+@me.page(
+  on_load=load,
+  security_policy=me.SecurityPolicy(
+    allowed_iframe_parents=["https://google.github.io"]
+  ),
+  path="/tab_group",
+)
+def app():
+  with me.box():
+    tab_group(make_tabs(), on_tab_click)
+
+
+def make_tabs() -> list[Tab]:
+  """Helper to make the tabs for the tab group demo."""
+  state = me.state(State)
+  tabs = [
+    Tab(label="Tab 1", icon="home", content=tab_1),
+    Tab(label="Tab 2", content=tab_2),
+    Tab(label="Tab 3", icon="tab", content=tab_3),
+  ]
+  for index, tab in enumerate(tabs):
+    tab.selected = state.selected_tab_index == index
+    tab.disabled = index in state.disabled_tab_indexes
+  return tabs
+
+
+@me.component
+def tab_1():
+  me.text("Tab 1")
+
+
+@me.component
+def tab_2():
+  me.text("Tab 2")
+
+
+@me.component
+def tab_3():
+  me.text("Tab 3")
+
+
+def on_tab_click(e: me.ClickEvent):
+  """Click handler that handles updating the tabs when clicked."""
+  state = me.state(State)
+
+  _, tab_index = e.key.split("-")
+  tab_index = int(tab_index)
+
+  if tab_index == state.selected_tab_index:
+    return
+  if tab_index in state.disabled_tab_indexes:
+    return
+
+  state.selected_tab_index = int(tab_index)
+
+
+@me.component
+def tab_group(tabs: list[Tab], on_tab_click: Callable):
+  """Generates the tab group component
+
+  Args:
+    tabs: Metadata for rendering tabs for the tab group
+    on_tab_click: Event to handle what happens when a tab header is clicked
+  """
+  tab_header(tabs, on_tab_click)
+  tab_content(tabs)
+
+
+@me.component
+def tab_header(tabs: list[Tab], on_tab_click: Callable):
+  """Generates the header for the tab group."""
+  with me.box(
+    style=me.Style(
+      display="flex",
+      width="100%",
+      border=me.Border(
+        bottom=me.BorderSide(
+          width=1, style="solid", color=me.theme_var("outline-variant")
+        )
+      ),
+    )
+  ):
+    for index, tab in enumerate(tabs):
+      with me.box(
+        key=f"tab-{index}",
+        on_click=on_tab_click,
+        style=make_tab_style(tab.selected, tab.disabled),
+      ):
+        if tab.icon:
+          me.icon(tab.icon)
+        me.text(tab.label)
+
+
+@me.component
+def tab_content(tabs: list[Tab]):
+  """Component for rendering the content of the selected tab."""
+  for tab in tabs:
+    if tab.selected:
+      with me.box():
+        tab.content()
+
+
+def make_tab_style(selected: bool, disabled: bool) -> me.Style:
+  """Makes the styles for the tab based on selected/disabled state."""
+  style = make_default_tab_style()
+  if disabled:
+    style.color = me.theme_var("outline")
+    style.cursor = "default"
+  elif selected:
+    style.background = me.theme_var("surface-container")
+    style.border = me.Border(
+      bottom=me.BorderSide(
+        width=2, style="solid", color=me.theme_var("primary")
+      )
+    )
+    style.cursor = "default"
+  return style
+
+
+def make_default_tab_style():
+  """Basic styles shared by different tab state (selected, disabled, default)."""
+  return me.Style(
+    align_items="center",
+    color=me.theme_var("on-surface"),
+    display="flex",
+    cursor="pointer",
+    flex_grow=1,
+    justify_content="center",
+    line_height=1,
+    font_size=14,
+    font_weight="medium",
+    padding=me.Padding.all(16),
+    text_align="center",
+    gap=5,
+  )