window: translate_selection: Only get clipboard when window is active

Fixes #407

dialect/window.blp

@@ -44,6 +44,8 @@ template $DialectWindow : Adw.ApplicationWindow {
   height-request: 320;
   focus-widget: src_text;
 
+  notify::is-active => $_on_is_active_changed();
+
   Adw.Breakpoint {
     condition ("max-width: 680px")
     setters {

dialect/window.py

@@ -105,6 +105,8 @@ class DialectWindow(Adw.ApplicationWindow):
     current_history = 0  # for history management
 
     # Translation-related variables
+    pending_trans_selection = False
+    trans_selection_langs: tuple[str | None, str | None] = (None, None)
     next_translation: TranslationRequest | None = None  # for ongoing translation
     translation_loading = False  # for ongoing translation
 
@@ -509,10 +511,16 @@ def translate(self, text: str, src_lang: str | None, dest_lang: str | None):
     @background_task
     async def translate_selection(self, src_lang: str | None, dest_lang: str | None):
         """Runs `translate` with the selection clipboard text"""
-        if display := Gdk.Display.get_default():
-            clipboard = display.get_primary_clipboard()
-            if text := await clipboard.read_text_async():  # type: ignore
-                self.translate(text, src_lang, dest_lang)
+        if self.props.is_active:
+            if display := Gdk.Display.get_default():
+                clipboard = display.get_primary_clipboard()
+                if text := await clipboard.read_text_async():  # type: ignore
+                    self.translate(text, src_lang, dest_lang)
+            self.pending_trans_selection = False
+            self.trans_selection_langs = (None, None)
+        else:
+            self.pending_trans_selection = True
+            self.trans_selection_langs = (src_lang, dest_lang)
 
     def save_settings(self, *args, **kwargs):
         if not self.is_maximized():
@@ -932,6 +940,12 @@ def _on_user_action_ended(self, _buffer):
         if Settings.get().live_translation:
             self._on_translation()
 
+    @Gtk.Template.Callback()
+    def _on_is_active_changed(self, *_args):
+        if self.pending_trans_selection and self.props.is_active:
+            src, dest = self.trans_selection_langs
+            self.translate_selection(src, dest)
+
     @Gtk.Template.Callback()
     def _on_retry_load_translator_clicked(self, *_args):
         self.reload_provider("translator")