Detach Library loading from render thread

In scenarios where the library takes a long amount of time, the
application would become locked up and unresponsive, as library loading
was blocking. By detaching library loading to its own thread, the
program remains responsive even while the library is loading.

tagstudio/src/qt/ts_qt.py

@@ -187,6 +187,7 @@ class QtDriver(QObject):
         self.thumb_cutoff: float = time.time()
         # self.selected: list[tuple[int,int]] = [] # (Thumb Index, Page Index)
         self.selected: list[tuple[ItemType, int]] = []  # (Item Type, Item ID)
+        self.loading_library = False
 
         self.SIGTERM.connect(self.handleSIGTERM)
 
@@ -588,6 +589,7 @@ class QtDriver(QObject):
         self.main_window.show()
         self.main_window.activateWindow()
         self.main_window.toggle_landing_page(True)
+        logging.info("Showing main window...")
 
         self.frame_dict = {}
         self.main_window.pagination.index.connect(
@@ -1439,26 +1441,41 @@ class QtDriver(QObject):
 
     def open_library(self, path: Path):
         """Opens a TagStudio library."""
+        # Prevents attemping to load a new library
+        # while another is already loading.
+        if self.loading_library:
+            return
+
         open_message: str = f'Opening Library "{str(path)}"...'
+        logging.info(open_message)
         self.main_window.landing_widget.set_status_label(open_message)
         self.main_window.statusbar.showMessage(open_message, 3)
         self.main_window.repaint()
 
+        self.loaded_library_path = path
+        self.loading_library = True
+
         if self.lib.library_dir:
             self.save_library()
             self.lib.clear_internal_vars()
 
-        return_code = self.lib.open_library(path)
+        r = CustomRunnable(lambda: self.lib.open_library(path))
+        r.done.connect(lambda return_code: self.library_load_callback(return_code))
+        QThreadPool.globalInstance().start(r)
+
+    def library_load_callback(self, return_code: int):
+        """Displays the newly loaded library."""
         if return_code == 1:
-            pass
+            logging.info(f"Succesfully loaded Library")
         else:
             logging.info(
-                f"{ERROR} No existing TagStudio library found at '{path}'. Creating one."
+                f"{ERROR} No existing TagStudio library found at '{self.loaded_library_path}'. Creating one."
             )
-            print(f"Library Creation Return Code: {self.lib.create_library(path)}")
+            result = self.lib.create_library(self.loaded_library_path)
+            logging.info(f"Library Creation Return Code: {result}")
             self.add_new_files_callback()
 
-        self.update_libs_list(path)
+        self.update_libs_list(self.loaded_library_path)
         title_text = f"{self.base_title} - Library '{self.lib.library_dir}'"
         self.main_window.setWindowTitle(title_text)
 
@@ -1469,6 +1486,7 @@ class QtDriver(QObject):
         self.preview_panel.update_widgets()
         self.filter_items()
         self.main_window.toggle_landing_page(False)
+        self.loading_library = False
 
     def create_collage(self) -> None:
         """Generates and saves an image collage based on Library Entries."""