Qt QPluginLoader Architecture Migration

Table of Contents

Problem

The initial plugin extraction (Steps 3–8 of the Qt plugin refactor) produced six STATIC domain library plugins wired by direct std::unique_ptr<XxxPlugin> members in MainWindow. This is Option 3 from the architecture analysis (explicit factory / registry) and does NOT achieve the isolation goal:

  • Host must be relinked for every plugin change.
  • MainWindow has compile-time dependencies on all domain headers.
  • Each plugin class duplicated identical signals and connect_controller_signals.

Solution

Implement Option 1 (QPluginLoader + SHARED libraries) from the analysis document.

Implementation (completed 2026-04-08)

Phase 1 — ores.qt.api framework changes

ores.qt.api was already a SHARED library (add_library(SHARED ...) with ORES_QT_API_LIBRARY compile definition and BOOST_SYMBOL_EXPORT macros).

Changes made:

  1. IPlugin.hpp — added Q_DECLARE_INTERFACE(ores::qt::IPlugin, "ores.qt.IPlugin/1.0") and #include <QtPlugin>. This registers the interface IID used by QPluginLoader for ABI version checking.
  2. New PluginBase class (include/ores.qt/PluginBase.hpp + src/PluginBase.cpp). Inherits public QObject, public IPlugin with Q_OBJECT. Provides:
    • Signals: statusMessage(const QString&), windowCreated(DetachableMdiSubWindow*), windowDestroyed(DetachableMdiSubWindow*).
    • Protected method: connectControllerSignals(EntityController* ctrl) — wires the four EntityController signals using modern functor syntax, eliminating the 6× per-plugin duplication.
  3. PluginRegistry redesign (include/ores.qt/PluginRegistry.hpp + src/PluginRegistry.cpp).
    • Removed register_plugin(std::unique_ptr<IPlugin>).
    • Added load_from_directory(const QString& plugin_dir) — scans directory for shared libraries, loads each IPlugin via QPluginLoader, sorts by load_order().
    • Holds QVector<QPluginLoader*> loaders_ to keep plugins alive for the process lifetime.

Phase 2 — Six domain plugins: STATIC → SHARED

For each of ores.qt.admin, ores.qt.compute, ores.qt.refdata, ores.qt.party, ores.qt.mktdata, ores.qt.trading:

CMakeLists.txt

  • add_library(STATIC ...) → add_library(SHARED ...)
  • Added LIBRARY_OUTPUT_DIRECTORY pointing to ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/plugins so plugin .so files land in publish/lib/plugins/ during development builds.
  • Added INSTALL_RPATH "$ORIGIN/.." (plugins/ → lib/ where ores.qt.api.so lives).
  • Changed install target to LIBRARY DESTINATION lib/plugins.

Plugin header

  • Base changed from public QObject, public IPlugin → public PluginBase.
  • Added Q_PLUGIN_METADATA(IID "ores.qt.IPlugin/1.0") and Q_INTERFACES(ores::qt::IPlugin).
  • Removed per-plugin signals: block (status_message, window_created, window_destroyed).
  • Removed per-plugin private forwarding slots and connect_controller_signals declaration.

Plugin source

  • Constructor changed from : QObject(parent) to : PluginBase(parent).
  • Removed void XxxPlugin::connect_controller_signals(QObject*) implementation.
  • Replaced all connect_controller_signals(ctrl) calls with connectControllerSignals(ctrl).
  • Replaced any remaining emit status_message(msg) / &XxxPlugin::status_message with emit statusMessage(msg) / &PluginBase::statusMessage.

Phase 3 — MainWindow decoupled from domain plugins

MainWindow.hpp: removed six typed plugin forward declarations and std::unique_ptr<XxxPlugin> member variables.

MainWindow.cpp:

  • Removed six plugin #include directives; added #include "ores.qt/PluginBase.hpp" and #include "ores.qt/PluginRegistry.hpp".
  • Constructor: replaced 18 individual signal connects (3 per plugin × 6) with a single loop over PluginRegistry::instance().plugins().
  • onLoginSuccess: replaced six explicit on_login() + six create_menus() calls with a single loop.
  • performDisconnectCleanup: replaced six explicit on_logout() calls with a reverse loop (last-loaded plugin logs out first).

Phase 4 — Plugin discovery in main.cpp

Added PluginRegistry::instance().load_from_directory(plugin_dir) before MainWindow construction, where plugin_dir = applicationDirPath() + "/../lib/plugins". At runtime (development build): publish/bin/../lib/plugins = publish/lib/plugins/.

Phase 5 — ores.qt CMakeLists cleanup

Removed ores.qt.admin.lib, ores.qt.compute.lib, ores.qt.refdata.lib, ores.qt.party.lib, ores.qt.mktdata.lib, ores.qt.trading.lib from ores.qt.lib link dependencies. These are now loaded at runtime by QPluginLoader — no compile-time link required.

Known issues / future work

  • Inter-plugin compile-time dependencies: ores.qt.compute links ores.qt.admin (SessionHistoryDialog), ores.qt.mktdata links ores.qt.refdata, and ores.qt.trading links ores.qt.party for types not yet moved to ores.qt.api. These should be resolved by moving shared types to ores.qt.api in a follow-up.
  • OrgExplorer null BusinessUnitController: TradingPlugin passes nullptr for businessUnitController to OrgExplorerMdiWindow because this cross-plugin reference requires a different approach (e.g., a service interface on IPlugin).
  • ores.qt.app rename: the architecture analysis proposes renaming the host static library to ores.qt.app. Not done yet.