WIP: Add support for multi-source selection, and add a multi-source v…

…iew pane in the conversationview.

client/securedrop_client/gui/widgets.py

@@ -793,6 +793,7 @@ def __init__(
                 app_state.set_selected_conversation_for_source
             )
             self.source_list.source_selection_cleared.connect(app_state.clear_selected_conversation)
+            self.source_list.multi_select.connect(app_state.show_multi_select_view)
 
         # Create widgets
         self.view_holder = QWidget()
@@ -836,18 +837,24 @@ def show_sources(self, sources: list[Source]) -> None:
         """
         Update the sources list in the GUI with the supplied list of sources.
         """
-        # If no sources are supplied, display the EmptyConversationView with the no-sources message.
+        # If no sources are supplied, display the EmptyConversationView with the no-sources
+        # message.
         #
         # If there are sources but no source is selected in the GUI, display the
         # EmptyConversationView with the no-source-selected messaging.
         #
+        # If multiple sources are selected, show a variant of the view with the multi-select
+        # message.
+        #
         # Otherwise, hide the EmptyConversationView.
         if not sources:
             self.empty_conversation_view.show_no_sources_message()
             self.empty_conversation_view.show()
         elif not self.source_list.get_selected_source():
             self.empty_conversation_view.show_no_source_selected_message()
             self.empty_conversation_view.show()
+        elif len(self.source_list.selectedItems()) > 1:
+            self.empty_conversation_view.show_multi_select_message()
         else:
             self.empty_conversation_view.hide()
 
@@ -863,37 +870,41 @@ def show_sources(self, sources: list[Source]) -> None:
 
     def on_source_changed(self) -> None:
         """
-        Show conversation for the selected source.
+        Show conversation for the selected source, or, if multiple sources are selected,
+        show multi select view.
         """
-        try:
-            source = self.source_list.get_selected_source()
-            if not source:
-                return
-
-            self.controller.session.refresh(source)
-
-            # Immediately show the selected source as seen in the UI and then make a request to mark
-            # source as seen.
-            self.source_list.source_selected.emit(source.uuid)
-            self.controller.mark_seen(source)
-
-            # Get or create the SourceConversationWrapper
-            if source.uuid in self.source_conversations:
-                conversation_wrapper = self.source_conversations[source.uuid]
-                conversation_wrapper.conversation_view.update_conversation(  # type: ignore[has-type]
-                    source.collection
-                )
-            else:
-                conversation_wrapper = SourceConversationWrapper(
-                    source, self.controller, self._state
-                )
-                self.source_conversations[source.uuid] = conversation_wrapper
+        if len(self.source_list.selectedItems()) > 1:
+            self.empty_conversation_view.show_multi_select_message()
+        else:
+            try:
+                source = self.source_list.get_selected_source()
+                if not source:
+                    return
+
+                self.controller.session.refresh(source)
+
+                # Immediately show the selected source as seen in the UI and then make a request to mark
+                # source as seen.
+                self.source_list.source_selected.emit(source.uuid)
+                self.controller.mark_seen(source)
+
+                # Get or create the SourceConversationWrapper
+                if source.uuid in self.source_conversations:
+                    conversation_wrapper = self.source_conversations[source.uuid]
+                    conversation_wrapper.conversation_view.update_conversation(  # type: ignore[has-type]
+                        source.collection
+                    )
+                else:
+                    conversation_wrapper = SourceConversationWrapper(
+                        source, self.controller, self._state
+                    )
+                    self.source_conversations[source.uuid] = conversation_wrapper
 
-            self.set_conversation(conversation_wrapper)
-            logger.debug(f"Set conversation to the selected source with uuid: {source.uuid}")
+                self.set_conversation(conversation_wrapper)
+                logger.debug(f"Set conversation to the selected source with uuid: {source.uuid}")
 
-        except sqlalchemy.exc.InvalidRequestError as e:
-            logger.debug(e)
+            except sqlalchemy.exc.InvalidRequestError as e:
+                logger.debug(e)
 
     def refresh_source_conversations(self) -> None:
         """
@@ -1016,18 +1027,50 @@ def __init__(self) -> None:
         no_source_selected_layout.addWidget(bullet3)
         no_source_selected_layout.addSpacing(self.NEWLINE_HEIGHT_PX * 4)
 
+        # Multi-source selection widget, same css properties as Empty view
+        self.multi_source_selected = QWidget()
+        self.multi_source_selected.setObjectName("EmptyConversationView_no_sources")
+        multi_sources_layout = QVBoxLayout()
+        self.multi_source_selected.setLayout(no_sources_layout)
+        multi_sources_instructions = QLabel(_("Multiple Sources Selected"))
+        multi_sources_instructions.setObjectName("EmptyConversationView_instructions")
+        multi_sources_instructions.setWordWrap(True)
+        multi_sources_instruction_details1 = QLabel(
+            _(
+                "Select or de-select sources using Ctrl+click, Shift+click, or by dragging the mouse."  # noqa: E501
+            )
+        )
+        multi_sources_instruction_details1.setWordWrap(True)
+        multi_sources_instruction_details2 = QLabel(
+            _("Use the top toolbar to delete multiple sources at once.")
+        )
+        multi_sources_instruction_details2.setWordWrap(True)
+        multi_sources_layout.addWidget(multi_sources_instructions)
+        multi_sources_layout.addSpacing(self.NEWLINE_HEIGHT_PX)
+        multi_sources_layout.addWidget(multi_sources_instruction_details1)
+        multi_sources_layout.addSpacing(self.NEWLINE_HEIGHT_PX)
+        multi_sources_layout.addWidget(multi_sources_instruction_details2)
+
         # Add widgets
         layout.addWidget(self.no_sources, alignment=Qt.AlignCenter)
         layout.addWidget(self.no_source_selected, alignment=Qt.AlignCenter)
+        layout.addWidget(self.multi_source_selected, alignment=Qt.AlignCenter)
 
     def show_no_sources_message(self) -> None:
         self.no_sources.show()
         self.no_source_selected.hide()
+        self.multi_source_selected.hide()
 
     def show_no_source_selected_message(self) -> None:
         self.no_sources.hide()
+        self.multi_source_selected.hide()
         self.no_source_selected.show()
 
+    def show_multi_select_message(self) -> None:
+        self.no_sources.hide()
+        self.no_source_selected.hide()
+        self.multi_source_selected.show()
+
 
 class SourceListWidgetItem(QListWidgetItem):
     def __lt__(self, other: SourceListWidgetItem) -> bool:
@@ -1053,6 +1096,7 @@ class SourceList(QListWidget):
 
     source_selection_changed = pyqtSignal(state.SourceId)
     source_selection_cleared = pyqtSignal()
+    multi_select = pyqtSignal()
     selected_sources = pyqtSignal(object)  # set[Source]
 
     NUM_SOURCES_TO_ADD_AT_A_TIME = 32
@@ -1267,11 +1311,20 @@ def set_snippet(self, source_uuid: str, collection_item_uuid: str, content: str)
 
     @pyqtSlot()
     def _on_item_selection_changed(self) -> None:
-        source = self.get_selected_source()
-        if source is not None:
-            self.source_selection_changed.emit(state.SourceId(source.uuid))
-        else:
+        """
+        One or more items may be selected. If multiple items are selected, to avoid confusion,
+        don't preview any individual source conversation, but instead show a contextual message.
+        """
+        count = self.selectedItems()
+        if count == 0:
             self.source_selection_cleared.emit()
+        elif count == 1:
+            source = self.get_selected_source()
+            if source:
+                self.source_selection_changed.emit(state.SourceId(source.uuid))
+        else:
+            # Multiple items, change the conversation view
+            self.multi_select.emit()
 
 
 class SourcePreview(SecureQLabel):

client/securedrop_client/state/state.py

@@ -107,3 +107,7 @@ def set_selected_conversation_for_source(self, source_id: SourceId) -> None:
     @pyqtSlot()
     def clear_selected_conversation(self) -> None:
         self.selected_conversation = None
+
+    @pyqtSlot()
+    def show_multi_select_view(self) -> None:
+        self.selected_conversation = None