unit testing and others

src/shared/flaresbasewidget.py

@@ -1877,7 +1877,8 @@ class InterGroupUIMixin:
 class ParticipantUIMixin:
     def setup_participant_ui(
         self, 
-        index_texts: Sequence[str]
+        index_texts: Sequence[str],
+        placeholder_text: str = ""
     ) -> None:
         
         # Create mappings: file_path -> participant label and dropdown display text
@@ -1890,9 +1891,9 @@ class ParticipantUIMixin:
             self.participant_map[file_path] = short_label
             self.participant_dropdown_items.append(display_label)
 
-        self.layout = QVBoxLayout(self)
+        self.main_layout = QVBoxLayout(self)
         self.top_bar = QHBoxLayout()
-        self.layout.addLayout(self.top_bar)
+        self.main_layout.addLayout(self.top_bar)
 
         self.participant_dropdown = self._create_multiselect_dropdown(self.participant_dropdown_items)
         self.participant_dropdown.currentIndexChanged.connect(self.update_participant_dropdown_label)
@@ -1917,12 +1918,16 @@ class ParticipantUIMixin:
         self.top_bar.addWidget(self.image_index_dropdown)
         self.top_bar.addWidget(self.submit_button)
 
-        self.scroll = QScrollArea()
-        self.scroll.setWidgetResizable(True)
+        self.scroll_area = QScrollArea()
+        self.scroll_area.setWidgetResizable(True)
         self.scroll_content = QWidget()
         self.grid_layout = QGridLayout(self.scroll_content)
-        self.scroll.setWidget(self.scroll_content)
-        self.layout.addWidget(self.scroll)
+        self.scroll_area.setWidget(self.scroll_content)
+        self.placeholder_label = QLabel(placeholder_text)
+        self.grid_layout.addWidget(self.placeholder_label, 0, 0)
+        self.placeholder_label.setWordWrap(True)
+        self.placeholder_label.setScaledContents(True)
+        self.main_layout.addWidget(self.scroll_area)
 
         self.thumb_size = QSize(280, 180)
         self.showMaximized()