slightly update slice demo

Former-commit-id: e819986

Author: xhlulu

apps/dash-vtk-explorer/demos/slice-rendering/app.py

@@ -30,7 +30,7 @@ def custom_card(children):
     return dbc.Card(
         html.Div(children, style={"height": "100%"}),
         body=True,
-        style={"height": "70vh"},
+        style={"height": "100%"},
     )
 
 
@@ -106,15 +106,18 @@ def custom_card(children):
 
 app.layout = dbc.Container(
     fluid=True,
-    style={"padding-top": "15px"},
+    style={"height": "calc(100vh - 30px)"},
     children=[
-        controls,
-        html.Br(),
+        html.Div(
+            style={"height": "20%", "display": "flex", "align-items": "center"},
+            children=[html.Br(), controls, html.Br(),],
+        ),
         dbc.Row(
-            [
+            style={"height": "80%"},
+            children=[
                 dbc.Col(width=6, children=custom_card(slice_view)),
                 dbc.Col(width=6, children=custom_card(volume_view)),
-            ]
+            ],
         ),
     ],
 )

apps/dash-vtk-explorer/explorer.py

@@ -74,7 +74,7 @@ def prepend_callback_list(ls: list, prefix: str) -> list:
 
 
 def Header(name, app):
-    title = html.H3(name, style={"display": "inline-flex"})
+    title = html.H2(name, style={"display": "inline-flex"})
     logo = html.Img(
         src=app.get_asset_url("dash-logo.png"),
         style={