Add .labui file association — open by double-click, cross-platform

Windows/Linux self-register via core/file_association.py (winreg /
XDG .desktop+mime), triggered from a new Settings button since there's
no installer to do it at install time. macOS gets it at build time via
labui.spec's new BUNDLE() step (CFBundleDocumentTypes in Info.plist) —
that step also makes mac builds a real .app bundle for the first time,
not just a bare onedir folder. main.py gains a LabUIApplication
subclass to catch the macOS QFileOpenEvent (buffered if it arrives
before MainWindow exists) plus argv[1] handling for Windows/Linux.
ProfileButton.load_path() extracted so both paths share the same
load-and-apply logic as the existing file-dialog flow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

6 files changed, 295 insertions, 2 deletions

diff --git a/core/file_association.py b/core/file_association.py
new file mode 100644
index 0000000..047cdcc
--- /dev/null
+++ b/core/file_association.py
@@ -0,0 +1,199 @@
+"""
+core/file_association.py
+
+Self-registers LabUI as the handler for .labui files with the OS, so
+double-clicking one launches the app — Windows (registry) and Linux (XDG).
+User-scoped, no admin/root rights needed.
+
+macOS doesn't need any of this: labui.spec builds a real .app bundle with
+CFBundleDocumentTypes baked into Info.plist at build time, which is enough
+for Finder to associate .labui files with it automatically.
+
+Only meaningful for a packaged build (sys.frozen, set by PyInstaller) —
+registering the bare Python interpreter as the handler for "python.exe
+main.py" isn't useful, so callers should gate the UI action on that.
+"""
+
+from __future__ import annotations
+import os
+import sys
+import subprocess
+from typing import Optional
+
+_PROG_ID   = "LabUI.Profile"
+_EXT       = ".labui"
+_MIME_TYPE = "application/x-labui"
+
+
+def _exe_path() -> str:
+    return sys.executable
+
+
+def is_registered() -> bool:
+    if sys.platform.startswith("win"):
+        return _win_is_registered()
+    if sys.platform.startswith("linux"):
+        return _linux_is_registered()
+    return False
+
+
+def register() -> Optional[str]:
+    """Register .labui with this app. Returns an error string, or None on success."""
+    try:
+        if sys.platform.startswith("win"):
+            _win_register()
+        elif sys.platform.startswith("linux"):
+            _linux_register()
+        else:
+            return f"File association isn't needed on this platform ({sys.platform})."
+        return None
+    except Exception as e:
+        return str(e)
+
+
+def unregister() -> Optional[str]:
+    """Remove the association. Returns an error string, or None on success."""
+    try:
+        if sys.platform.startswith("win"):
+            _win_unregister()
+        elif sys.platform.startswith("linux"):
+            _linux_unregister()
+        return None
+    except Exception as e:
+        return str(e)
+
+
+# ── Windows ──────────────────────────────────────────────────────────────────
+
+def _win_is_registered() -> bool:
+    import winreg
+    try:
+        with winreg.OpenKey(winreg.HKEY_CURRENT_USER,
+                             f"Software\\Classes\\{_EXT}") as k:
+            value, _ = winreg.QueryValueEx(k, "")
+            return value == _PROG_ID
+    except FileNotFoundError:
+        return False
+
+
+def _win_register():
+    import winreg
+    exe = _exe_path()
+
+    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
+                           f"Software\\Classes\\{_EXT}") as k:
+        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, _PROG_ID)
+
+    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
+                           f"Software\\Classes\\{_PROG_ID}") as k:
+        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, "LabUI Profile")
+
+    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
+                           f"Software\\Classes\\{_PROG_ID}\\DefaultIcon") as k:
+        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, f'"{exe}",0')
+
+    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
+                           f"Software\\Classes\\{_PROG_ID}\\shell\\open\\command") as k:
+        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, f'"{exe}" "%1"')
+
+    _win_notify_shell()
+
+
+def _win_unregister():
+    import winreg
+    for path in (
+        f"Software\\Classes\\{_PROG_ID}\\shell\\open\\command",
+        f"Software\\Classes\\{_PROG_ID}\\shell\\open",
+        f"Software\\Classes\\{_PROG_ID}\\shell",
+        f"Software\\Classes\\{_PROG_ID}\\DefaultIcon",
+        f"Software\\Classes\\{_PROG_ID}",
+        f"Software\\Classes\\{_EXT}",
+    ):
+        try:
+            winreg.DeleteKey(winreg.HKEY_CURRENT_USER, path)
+        except FileNotFoundError:
+            pass
+    _win_notify_shell()
+
+
+def _win_notify_shell():
+    """Tell Explorer the file-type association changed — otherwise it keeps
+    showing the old icon/handler until logoff or reboot."""
+    try:
+        import ctypes
+        SHCNE_ASSOCCHANGED = 0x08000000
+        SHCNF_IDLIST = 0x0000
+        ctypes.windll.shell32.SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, None, None)
+    except Exception:
+        pass
+
+
+# ── Linux (XDG) ──────────────────────────────────────────────────────────────
+
+def _xdg_data_home() -> str:
+    return os.environ.get("XDG_DATA_HOME") or os.path.join(os.path.expanduser("~"), ".local", "share")
+
+
+def _desktop_file_path() -> str:
+    return os.path.join(_xdg_data_home(), "applications", "labui.desktop")
+
+
+def _mime_package_path() -> str:
+    return os.path.join(_xdg_data_home(), "mime", "packages", "labui-labui.xml")
+
+
+def _linux_is_registered() -> bool:
+    return os.path.isfile(_desktop_file_path())
+
+
+def _linux_register():
+    exe = _exe_path()
+
+    desktop_path = _desktop_file_path()
+    os.makedirs(os.path.dirname(desktop_path), exist_ok=True)
+    with open(desktop_path, "w") as f:
+        f.write(
+            "[Desktop Entry]\n"
+            "Type=Application\n"
+            "Name=LabUI\n"
+            f"Exec={exe} %f\n"
+            "Terminal=false\n"
+            f"MimeType={_MIME_TYPE};\n"
+            "NoDisplay=true\n"
+        )
+
+    mime_path = _mime_package_path()
+    os.makedirs(os.path.dirname(mime_path), exist_ok=True)
+    with open(mime_path, "w") as f:
+        f.write(
+            '<?xml version="1.0" encoding="UTF-8"?>\n'
+            '<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">\n'
+            f'  <mime-type type="{_MIME_TYPE}">\n'
+            '    <comment>LabUI Profile</comment>\n'
+            f'    <glob pattern="*{_EXT}"/>\n'
+            '  </mime-type>\n'
+            '</mime-info>\n'
+        )
+
+    # Best-effort — desktop-environment dependent, the glob-matched .desktop
+    # file alone is often enough even if these tools/steps are unavailable.
+    _run_best_effort(["update-desktop-database", os.path.join(_xdg_data_home(), "applications")])
+    _run_best_effort(["update-mime-database", os.path.join(_xdg_data_home(), "mime")])
+    _run_best_effort(["xdg-mime", "default", "labui.desktop", _MIME_TYPE])
+
+
+def _linux_unregister():
+    for path in (_desktop_file_path(), _mime_package_path()):
+        try:
+            os.remove(path)
+        except FileNotFoundError:
+            pass
+    _run_best_effort(["update-desktop-database", os.path.join(_xdg_data_home(), "applications")])
+    _run_best_effort(["update-mime-database", os.path.join(_xdg_data_home(), "mime")])
+
+
+def _run_best_effort(cmd: list):
+    try:
+        subprocess.run(cmd, check=False, capture_output=True, timeout=5)
+    except Exception:
+        pass
diff --git a/labui.spec b/labui.spec
index 71d50dd..0fdbedc 100644
--- a/labui.spec
+++ b/labui.spec
@@ -81,3 +81,24 @@ coll = COLLECT(
     upx_exclude=[],
     name="LabUI",
 )
+
+# macOS: wrap the onedir output in a real .app bundle. Required for both a
+# double-clickable Finder app AND file association — CFBundleDocumentTypes
+# here is what tells Finder/LaunchServices that LabUI opens .labui files
+# (core/file_association.py doesn't need to do anything at runtime on this
+# platform, unlike Windows/Linux, because of this).
+if sys.platform == "darwin":
+    app = BUNDLE(
+        coll,
+        name="LabUI.app",
+        bundle_identifier="org.labui.LabUI",  # placeholder — swap for a real reverse-DNS id
+        info_plist={
+            "CFBundleDocumentTypes": [{
+                "CFBundleTypeName": "LabUI Profile",
+                "CFBundleTypeExtensions": ["labui"],
+                "CFBundleTypeRole": "Editor",
+                "LSHandlerRank": "Owner",
+            }],
+            "NSHighResolutionCapable": True,
+        },
+    )
diff --git a/main.py b/main.py
index 26fcaaf..414d06f 100644
--- a/main.py
+++ b/main.py
@@ -12,10 +12,31 @@ import sys, os
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 
 from PyQt6.QtWidgets import QApplication
-from PyQt6.QtCore import qInstallMessageHandler, QtMsgType
+from PyQt6.QtCore import qInstallMessageHandler, QtMsgType, QEvent
 from ui.main_window import MainWindow
 
 
+class LabUIApplication(QApplication):
+    """Catches the macOS "open with" launch event (QFileOpenEvent) for a
+    double-clicked .labui file — delivered via this event, not argv, and
+    can arrive before or after MainWindow exists, so it's buffered."""
+
+    def __init__(self, argv):
+        super().__init__(argv)
+        self.file_to_open: str | None = None
+        self.main_window = None
+
+    def event(self, e):
+        if e.type() == QEvent.Type.FileOpen:
+            path = e.file()
+            if self.main_window is not None:
+                self.main_window.load_profile_path(path)
+            else:
+                self.file_to_open = path
+            return True
+        return super().event(e)
+
+
 def _qt_message_handler(msg_type, context, message):
     """Silence one specific, harmless Qt warning: the native windowsvista
     style's combo-box/menu popup code calls QFont::setPointSize() on a
@@ -36,7 +57,7 @@ def _qt_message_handler(msg_type, context, message):
 
 def main():
     qInstallMessageHandler(_qt_message_handler)
-    app = QApplication(sys.argv)
+    app = LabUIApplication(sys.argv)
     app.setApplicationName("LabUI")
 
     qss = os.path.join(os.path.dirname(os.path.abspath(__file__)), "ui", "style_dark.qss")
@@ -45,7 +66,15 @@ def main():
             app.setStyleSheet(f.read())
 
     win = MainWindow()
+    app.main_window = win
     win.show()
+
+    # Opened via double-click / CLI argv (Windows, Linux) or the buffered
+    # macOS FileOpen event (see LabUIApplication.event above).
+    path = app.file_to_open or (sys.argv[1] if len(sys.argv) > 1 else None)
+    if path and path.lower().endswith(".labui") and os.path.isfile(path):
+        win.load_profile_path(path)
+
     sys.exit(app.exec())
 
 
diff --git a/ui/main_window.py b/ui/main_window.py
index 012d6f5..b632535 100644
--- a/ui/main_window.py
+++ b/ui/main_window.py
@@ -601,6 +601,11 @@ class MainWindow(QMainWindow):
 
     # ── Profile callbacks ─────────────────────────────────────────────────
 
+    def load_profile_path(self, path: str) -> bool:
+        """Load a .labui file from an explicit path — used when one is
+        opened from the OS (double-click / CLI argv), see main.py."""
+        return self._file_btn.load_path(path)
+
     def _profile_new(self):
         """Reset to a blank slate."""
         # Clear devices
diff --git a/ui/profile_manager_ui.py b/ui/profile_manager_ui.py
index 446e867..79f333e 100644
--- a/ui/profile_manager_ui.py
+++ b/ui/profile_manager_ui.py
@@ -85,13 +85,21 @@ class ProfileButton(QPushButton):
         )
         if not path:
             return
+        self.load_path(path)
+
+    def load_path(self, path: str) -> bool:
+        """Load a profile from an explicit path — shared by the file dialog
+        above and by opening a .labui file from the OS (double-click / CLI
+        argv), see main.py."""
         try:
             profile = Profile.load(path)
             self._apply_profile(profile)
             self._current_path = path
             self._update_title(profile.name)
+            return True
         except Exception as e:
             QMessageBox.critical(self, "Load Failed", str(e))
+            return False
 
     def _do_save(self):
         if not self._current_path:
diff --git a/ui/windows/settings_window.py b/ui/windows/settings_window.py
index cea7e5c..ae44c31 100644
--- a/ui/windows/settings_window.py
+++ b/ui/windows/settings_window.py
@@ -137,6 +137,24 @@ class SettingsWindow(QWidget):
         self._update_status_lbl.setWordWrap(True)
         lay.addRow("", self._update_status_lbl)
 
+        import sys as _sys
+        if _sys.platform.startswith(("win", "linux")):
+            assoc_row = QHBoxLayout()
+            self._assoc_btn = QPushButton("Register .labui Files")
+            self._assoc_btn.setObjectName("configButton")
+            self._assoc_btn.setToolTip(
+                "Associates .labui files with LabUI so double-clicking one\n"
+                "in the OS file browser opens it here."
+            )
+            self._assoc_btn.clicked.connect(self._register_file_association)
+            assoc_row.addWidget(self._assoc_btn)
+            assoc_row.addStretch()
+            lay.addRow("File Associations:", assoc_row)
+            self._assoc_status_lbl = QLabel("")
+            self._assoc_status_lbl.setObjectName("traceSource")
+            self._assoc_status_lbl.setWordWrap(True)
+            lay.addRow("", self._assoc_status_lbl)
+
         rst = QPushButton("Reset to Defaults"); rst.setObjectName("configButton")
         rst.clicked.connect(self._reset_to_defaults)
         lay.addRow("", rst)
@@ -390,6 +408,19 @@ class SettingsWindow(QWidget):
             except Exception as e:
                 QMessageBox.critical(self, "Update Failed", str(e))
 
+    def _register_file_association(self):
+        from core.updater import is_frozen
+        if not is_frozen():
+            self._assoc_status_lbl.setText("Not available outside the packaged app (dev mode).")
+            return
+
+        from core.file_association import register
+        err = register()
+        if err:
+            self._assoc_status_lbl.setText(f"Failed: {err}")
+        else:
+            self._assoc_status_lbl.setText("✓ .labui files now open with LabUI.")
+
     def _reset_to_defaults(self):
         reply = QMessageBox.question(
             self, "Reset Settings",