add a helper to wait and show a dialog if needed

use this in snaplist view. cancellation with asyncio is mindbending!

subiquity/ui/views/snaplist.py

@@ -13,6 +13,7 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import asyncio
 import datetime
 import logging
 
@@ -246,34 +247,6 @@ class SnapInfoView(WidgetWrap):
         return self.pile.render(size, focus)
 
 
-class FetchingInfo(WidgetWrap):
-
-    def __init__(self, parent, snap, aio_loop):
-        self.parent = parent
-        self.spinner = Spinner(aio_loop, style='dots')
-        self.spinner.start()
-        self.closed = False
-        text = _("Fetching info for {snap}").format(snap=snap.name)
-        # | text |
-        # 12    34
-        self.width = len(text) + 4
-        cancel = cancel_btn(label=_("Cancel"), on_press=self.close)
-        super().__init__(
-            LineBox(
-                Pile([
-                    ('pack', Text(' ' + text)),
-                    ('pack', self.spinner),
-                    ('pack', button_pile([cancel])),
-                    ])))
-
-    def close(self, sender=None):
-        if self.closed:
-            return
-        self.closed = True
-        self.spinner.stop()
-        self.parent.remove_overlay()
-
-
 class FetchingFailed(WidgetWrap):
 
     def __init__(self, row, snap):
@@ -294,7 +267,7 @@ class FetchingFailed(WidgetWrap):
 
     def load(self, sender=None):
         self.close()
-        self.row.load_info()
+        schedule_task(self.row.load_info())
 
     def close(self, sender=None):
         if self.closed:
@@ -331,25 +304,18 @@ class SnapCheckBox(CheckBox):
                     on_press=self.parent.show_main_screen)],
                 focus_buttons=False))
 
-    async def wait(self, t, fi):
-        await t
-        fi.close()
+    async def load_info(self):
+        app = self.parent.controller.app
+        await app.wait_with_text_dialog(
+            asyncio.shield(
+                self.parent.controller.get_snap_info_task(self.snap)),
+            _("Fetching info for {snap}").format(snap=self.snap.name),
+            can_cancel=True)
         self.loaded()
 
-    def load_info(self):
-        t = self.parent.controller.get_snap_info_task(self.snap)
-
-        if t.done():
-            self.loaded()
-            return
-        fi = FetchingInfo(
-            self.parent, self.snap, self.parent.controller.app.aio_loop)
-        self.parent.show_overlay(fi, width=fi.width)
-        schedule_task(self.wait(t, fi))
-
     def keypress(self, size, key):
         if key.startswith("enter"):
-            self.load_info()
+            schedule_task(self.load_info())
         else:
             return super().keypress(size, key)
 

subiquitycore/tui.py

@@ -29,6 +29,7 @@ from subiquitycore.palette import (
     )
 from subiquitycore.screen import make_screen
 from subiquitycore.tuicontroller import Skip
+from subiquitycore.ui.utils import LoadingDialog
 from subiquitycore.ui.frame import SubiquityCoreUI
 from subiquitycore.utils import arun_command
 
@@ -161,6 +162,30 @@ class TuiApplication(Application):
     def show_progress(self):
         raise NotImplementedError
 
+    async def wait_with_text_dialog(self, awaitable, message,
+                                    *, can_cancel=False):
+        ld = None
+
+        task_to_cancel = None
+        if can_cancel:
+            if not isinstance(awaitable, asyncio.Task):
+                async def w():
+                    return await awaitable
+                task_to_cancel = self.aio_loop.create_task(w())
+            else:
+                task_to_cancel = awaitable
+
+        def show_load():
+            nonlocal ld
+            ld = LoadingDialog(
+                self.ui.body, self.aio_loop, message, task_to_cancel)
+            self.ui.body.show_overlay(ld, width=ld.width)
+
+        def hide_load():
+            ld.close()
+
+        await self._wait_with_indication(awaitable, show_load, hide_load)
+
     async def _move_screen(self, increment, coro):
         if coro is not None:
             await coro

subiquitycore/ui/utils.py

@@ -23,6 +23,7 @@ from urwid import (
     AttrMap,
     CompositeCanvas,
     connect_signal,
+    LineBox,
     Padding as _Padding,
     SelectableIcon,
     Text,
@@ -30,8 +31,16 @@ from urwid import (
     WidgetDisable,
     )
 
-from subiquitycore.ui.buttons import other_btn
-from subiquitycore.ui.container import ListBox, Pile
+from subiquitycore.ui.buttons import (
+    cancel_btn,
+    other_btn,
+    )
+from subiquitycore.ui.container import (
+    ListBox,
+    Pile,
+    WidgetWrap,
+    )
+from subiquitycore.ui.spinner import Spinner
 from subiquitycore.ui.stretchy import Stretchy
 from subiquitycore.ui.table import TableRow
 from subiquitycore.ui.width import widget_width
@@ -352,3 +361,33 @@ class SomethingFailed(Stretchy):
 
     def close(self, sender):
         self.parent.remove_overlay()
+
+
+class LoadingDialog(WidgetWrap):
+
+    def __init__(self, parent, aio_loop, msg, task_to_cancel):
+        self.parent = parent
+        self.spinner = Spinner(aio_loop, style='dots')
+        self.spinner.start()
+        self.closed = False
+        # | text |
+        # 12    34
+        self.width = len(msg) + 4
+        widgets = [
+            ('pack', Text(' ' + msg)),
+            ('pack', self.spinner),
+            ]
+        if task_to_cancel is not None:
+            self.task_to_cancel = task_to_cancel
+            cancel = cancel_btn(label=_("Cancel"), on_press=self.close)
+            widgets.append(('pack', button_pile([cancel])))
+        super().__init__(LineBox(Pile(widgets)))
+
+    def close(self, sender=None):
+        if self.closed:
+            return
+        if sender is not None:
+            self.task_to_cancel.cancel()
+        self.closed = True
+        self.spinner.stop()
+        self.parent.remove_overlay()