Keep New Thread controls reachable below its scrolling form

src/toad/widgets/comms_command_dialog.py

@@ -30,7 +30,13 @@
 from textual.worker import Worker, WorkerFailed
 from toad.forms.editors import MultilineEditor, ValueEditor
 from toad.forms.form_view import InlineFormView
-from toad.native_style import AutoWidth, EllipsisOverflow, SideMargin
+from toad.native_style import (
+    AutoWidth,
+    DockedBottom,
+    EllipsisOverflow,
+    FillHeight,
+    SideMargin,
+)
 from toad.screens.modal import (
     CenteredScreen,
     DismissibleScreen,
@@ -168,13 +174,17 @@ def apply_native_layout(self) -> None:
         self.styles.padding = (1, 2)
 
 
+class CommandFormScroll(FillHeight, VerticalScroll):
+    """The form scrolls within the space left above its fixed command footer."""
+
+
 class CommandTitle(EllipsisOverflow, Static):
     def apply_native_layout(self) -> None:
         super().apply_native_layout()
         self.styles.max_height = 3
 
 
-class CommandButtons(Horizontal):
+class CommandButtons(DockedBottom, Horizontal):
     def apply_native_layout(self) -> None:
         super().apply_native_layout()
         self.styles.height = 3
@@ -231,10 +241,10 @@ def __init__(self, definition: TargetAction, target: str, fields: tuple[TargetFi
     def compose(self) -> ComposeResult:
         with CommandBox():
             yield CommandTitle(f"{self.definition.label} — {self.target}", markup=False)
-            with VerticalScroll():
+            with CommandFormScroll():
                 yield CommandConfirmation('', markup=False)
                 yield self.form
-            yield CommandConfirmed('I confirm this operation')
+                yield CommandConfirmed('I confirm this operation')
             with CommandButtons():
                 yield ApplyCommandButton('Apply', variant='primary')
                 yield CancelCommandButton('Cancel')

tests/textual/test_application_actions_in_the_running_app.py

@@ -16,7 +16,11 @@
 from toad.preferences import SETTINGS
 from toad.screens.keymap import KeymapScreen
 from toad.screens.settings import SettingsScreen
-from toad.widgets.comms_command_dialog import CatalogField, CatalogFieldSelection
+from toad.widgets.comms_command_dialog import (
+    CatalogField,
+    CatalogFieldSelection,
+    CommandFormScroll,
+)
 from toad.widgets.comms_sidebar import CommsSidebar, NewSessionButton
 from toad.widgets.footer import ToadFooter
 from toad.widgets.session_tabs import SessionTabClose
@@ -180,8 +184,20 @@ def call(self, request):
             parameter = dialog.choices['model'].parameter
             assert selection.current == FieldCodec.encode(parameter.value)
             assert selection.choices == tuple(choice for choice in parameter.options if choice.value is not None)
+            await ui.textual[1].resize_terminal(80, 24)
+            await ui.step()
             button = dialog.query_one(ApplyCommandButton)
             await ui.until(lambda: not button.disabled, why="the command values to be accepted")
+            await ui.until_clickable(button, why="the fixed create control to remain visible before scrolling")
+            lower = next(reversed(dialog.form.values.values())).editor
+            lower.scroll_visible(animate=False, immediate=True)
+            assert isinstance(lower, ChoicesEditor)
+            await ui.step()
+            await ui.textual[1].click(lower, offset=(3, 1))
+            await ui.until(lambda: lower.expanded, why="the scrolled lower field to open its actual choices")
+            await ui.press('escape')
+            assert dialog.query_one(CommandFormScroll).scroll_y > 0
+            await ui.until_clickable(button, why="the fixed create control to remain visible after scrolling")
             editor = dialog.form.values["name"].editor
             editor.scroll_visible(animate=False, immediate=True)
             await ui.until_clickable(editor, why="the name editor to be visible")