Extensions: resolve popup glitches when dropping URL's

Use UILayout::template_popup_confirm to replace workarounds that didn't
work very well.

- Resolve "Add Repository..." button in the dialog not closing the
  popup when pressed.
- Add a "Cancel" button while the remote resository data is
  downloading.
- Remove the hack to scale the UILayout to hide the existing
  confirm/cancel buttons.

Resolves #124098.

scripts/addons_core/bl_pkg/bl_extension_ops.py

@@ -258,26 +258,17 @@ class OperatorNonBlockingSyncHelper:
             self.completed = True
             return
 
-        layout = _operator_draw_hide_buttons_hack(op.layout)
+        layout = op.layout
         text, icon = update_ui_text()
         layout.label(text=text, icon=icon)
+        # Only show a "Cancel" button while the update is in progress.
+        layout.template_popup_confirm("", text="", cancel_text="Cancel")
 
 
 # -----------------------------------------------------------------------------
 # Internal Utilities
 #
 
-def _operator_draw_hide_buttons_hack(layout):
-    # EVIL! There is no good way to hide button on operator dialogs,
-    # so use a bad way (scale them to oblivion!)
-    # This could be supported by the internals, for now it's not though.
-    col = layout.column()
-    y = 1000.0
-    col.scale_y = y
-    layout.scale_y = 1.0 / y
-    return col
-
-
 def _sequence_split_with_job_limit(items, job_limit):
     # When only one job is allowed at a time, there is no advantage to splitting the sequence.
     if job_limit == 1:
@@ -2898,7 +2889,7 @@ class EXTENSIONS_OT_package_install(Operator, _ExtCmdMixIn):
             *,
             errors,
     ):
-        layout = _operator_draw_hide_buttons_hack(self.layout)
+        layout = self.layout
         icon = 'ERROR'
         for error in errors:
             if isinstance(error, str):
@@ -2906,6 +2897,9 @@ class EXTENSIONS_OT_package_install(Operator, _ExtCmdMixIn):
             else:
                 error(layout)
             icon = 'BLANK1'
+
+        # Only show a "Close" button since this is only showing a message.
+        layout.template_popup_confirm("", text="", cancel_text="Close")
         return True
 
     # Pass 3: add-repository (terminating).
@@ -2918,7 +2912,7 @@ class EXTENSIONS_OT_package_install(Operator, _ExtCmdMixIn):
         url_split = remote_url.partition("://")
         url_for_display = url_split[2] if url_split[2] else remote_url
 
-        layout = _operator_draw_hide_buttons_hack(self.layout)
+        layout = self.layout
         col = layout.column(align=True)
         col.label(text="The dropped extension comes from an unknown repository.")
         col.label(text="If you trust its source, add the repository and try again.")
@@ -2932,7 +2926,7 @@ class EXTENSIONS_OT_package_install(Operator, _ExtCmdMixIn):
             col.label(text="Alternatively download the extension to Install from Disk.")
 
         layout.operator_context = 'INVOKE_DEFAULT'
-        props = layout.operator("preferences.extension_repo_add", text="Add Repository...")
+        props = layout.template_popup_confirm("preferences.extension_repo_add", text="Add Repository...")
         props.remote_url = remote_url
         return True