Add QT_IM_MODULES env to allows specify multi IM key

Like as QT_QPA_PLATFORM, supports specifying multiple keys, and can
perform fallback operations to prioritize the use of a certain plug-in.
This is useful when using Wayland and XWayland applications at the same
time. For an example, we can set "QT_IM_MODULES=wayland;fcitx", and the
wayland application will use the wayland input context plugin, the
xwayland application will use fcitx, which can't be done without adding
a new environment variable, if we specify "QT_IM_MODULE=wayland", the
XWayland applications may not be able to use the input method.

Fixes: QTBUG-120202
Change-Id: Iac408af241963147747a2fe685f1e27bf9d9ee64
Reviewed-by: Liang Qi <liang.qi@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: David Edmundson <davidedmundson@kde.org>

src/gui/kernel/qplatforminputcontextfactory.cpp

@@ -28,10 +28,33 @@ QStringList QPlatformInputContextFactory::keys()
 #endif
 }
 
-QString QPlatformInputContextFactory::requested()
+QStringList QPlatformInputContextFactory::requested()
 {
-    QByteArray env = qgetenv("QT_IM_MODULE");
-    return env.isNull() ? QString() : QString::fromLocal8Bit(env);
+    QStringList imList;
+    QByteArray env = qgetenv("QT_IM_MODULES");
+
+    if (!env.isEmpty())
+        imList = QString::fromLocal8Bit(env).split(QChar::fromLatin1(';'), Qt::SkipEmptyParts);
+
+    if (!imList.isEmpty())
+        return imList;
+
+    env = qgetenv("QT_IM_MODULE");
+    if (!env.isEmpty())
+        imList = {QString::fromLocal8Bit(env)};
+
+    return imList;
+}
+
+QPlatformInputContext *QPlatformInputContextFactory::create(const QStringList& keys)
+{
+    for (const QString &key : keys) {
+        auto plugin = create(key);
+        if (plugin)
+            return plugin;
+    }
+
+    return nullptr;
 }
 
 QPlatformInputContext *QPlatformInputContextFactory::create(const QString& key)

src/gui/kernel/qplatforminputcontextfactory_p.h

@@ -27,7 +27,8 @@ class Q_GUI_EXPORT QPlatformInputContextFactory
 {
 public:
     static QStringList keys();
-    static QString requested();
+    static QStringList requested();
+    static QPlatformInputContext *create(const QStringList &keys);
     static QPlatformInputContext *create(const QString &key);
     static QPlatformInputContext *create();
 };

src/plugins/platforms/android/qandroidplatformintegration.cpp

@@ -304,11 +304,11 @@ static bool needsBasicRenderloopWorkaround()
 
 void QAndroidPlatformIntegration::initialize()
 {
-    const QString icStr = QPlatformInputContextFactory::requested();
-    if (icStr.isNull())
+    const auto icStrs = QPlatformInputContextFactory::requested();
+    if (icStrs.isEmpty())
         m_inputContext.reset(new QAndroidInputContext);
     else
-        m_inputContext.reset(QPlatformInputContextFactory::create(icStr));
+        m_inputContext.reset(QPlatformInputContextFactory::create(icStrs));
 }
 
 bool QAndroidPlatformIntegration::hasCapability(Capability cap) const

src/plugins/platforms/cocoa/qcocoaintegration.mm

@@ -125,9 +125,9 @@ QCocoaIntegration::QCocoaIntegration(const QStringList &paramList)
 #endif
         mFontDb.reset(new QCoreTextFontDatabaseEngineFactory<QCoreTextFontEngine>);
 
-    QString icStr = QPlatformInputContextFactory::requested();
-    icStr.isNull() ? mInputContext.reset(new QCocoaInputContext)
-                   : mInputContext.reset(QPlatformInputContextFactory::create(icStr));
+    auto icStrs = QPlatformInputContextFactory::requested();
+    icStrs.isEmpty() ? mInputContext.reset(new QCocoaInputContext)
+                     : mInputContext.reset(QPlatformInputContextFactory::create(icStrs));
 
     initResources();
     QMacAutoReleasePool pool;

src/plugins/platforms/wasm/qwasmintegration.cpp

@@ -222,12 +222,12 @@ QPlatformOpenGLContext *QWasmIntegration::createPlatformOpenGLContext(QOpenGLCon
 
 void QWasmIntegration::initialize()
 {
-    if (qgetenv("QT_IM_MODULE").isEmpty() && touchPoints < 1)
+    auto icStrs = QPlatformInputContextFactory::requested();
+    if (icStrs.isEmpty() && touchPoints < 1)
         return;
 
-    QString icStr = QPlatformInputContextFactory::requested();
-    if (!icStr.isNull())
-        m_inputContext.reset(QPlatformInputContextFactory::create(icStr));
+    if (!icStrs.isEmpty())
+        m_inputContext.reset(QPlatformInputContextFactory::create(icStrs));
     else
         m_inputContext.reset(new QWasmInputContext());
 }

src/plugins/platforms/windows/qwindowsintegration.cpp

@@ -256,9 +256,9 @@ QWindowsIntegration::~QWindowsIntegration()
 
 void QWindowsIntegration::initialize()
 {
-    QString icStr = QPlatformInputContextFactory::requested();
-    icStr.isNull() ? d->m_inputContext.reset(new QWindowsInputContext)
-                   : d->m_inputContext.reset(QPlatformInputContextFactory::create(icStr));
+    auto icStrs = QPlatformInputContextFactory::requested();
+    icStrs.isEmpty() ? d->m_inputContext.reset(new QWindowsInputContext)
+                     : d->m_inputContext.reset(QPlatformInputContextFactory::create(icStrs));
 }
 
 bool QWindowsIntegration::hasCapability(QPlatformIntegration::Capability cap) const

src/plugins/platforms/windows/uiautomation/qwindowsuiamainprovider.cpp

@@ -27,6 +27,7 @@
 #include <QtGui/qaccessible.h>
 #include <QtGui/qguiapplication.h>
 #include <QtGui/qwindow.h>
+#include <qpa/qplatforminputcontextfactory_p.h>
 
 #if !defined(Q_CC_BOR) && !defined (Q_CC_GNU)
 #include <comdef.h>
@@ -434,7 +435,7 @@ HRESULT QWindowsUiaMainProvider::GetPropertyValue(PROPERTYID idProp, VARIANT *pR
 
             // The native OSK should be disabled if the Qt OSK is in use,
             // or if disabled via application attribute.
-            static bool imModuleEmpty = qEnvironmentVariableIsEmpty("QT_IM_MODULE");
+            static bool imModuleEmpty = QPlatformInputContextFactory::requested().isEmpty();
             bool nativeVKDisabled = QCoreApplication::testAttribute(Qt::AA_DisableNativeVirtualKeyboard);
 
             // If we want to disable the native OSK auto-showing

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -344,11 +344,12 @@ void QXcbIntegration::initialize()
     const auto defaultInputContext = "compose"_L1;
     // Perform everything that may potentially need the event dispatcher (timers, socket
     // notifiers) here instead of the constructor.
-    QString icStr = QPlatformInputContextFactory::requested();
-    if (icStr.isNull())
-        icStr = defaultInputContext;
-    m_inputContext.reset(QPlatformInputContextFactory::create(icStr));
-    if (!m_inputContext && icStr != defaultInputContext && icStr != "none"_L1)
+    auto icStrs = QPlatformInputContextFactory::requested();
+    if (icStrs.isEmpty())
+        icStrs = { defaultInputContext };
+    m_inputContext.reset(QPlatformInputContextFactory::create(icStrs));
+    if (!m_inputContext && !icStrs.contains(defaultInputContext)
+        && icStrs != QStringList{"none"_L1})
         m_inputContext.reset(QPlatformInputContextFactory::create(defaultInputContext));
 
     connection()->keyboard()->initialize();