QUiLoader, QAbstractFormBuilder: Introduce errorString().

Introduce errorString() to be able to obtain load errors
in Qt Designer. Remove automatic Qt 3 form conversion
from Qt Designer (since uic3 no longer exists) and move
all form load error checking logic including language
check into QAbstractFormBuilder.
Make language accessible in FormBuilderExtra in case
Jambi is revived.

Reviewed-by: hjk

1 files changed, 89 insertions, 23 deletions

diff --git a/tools/uilib/abstractformbuilder.cpp b/tools/uilib/abstractformbuilder.cpp
index 4d142bd09f..1d44ad5ee6 100644
--- a/tools/uilib/abstractformbuilder.cpp
+++ b/tools/uilib/abstractformbuilder.cpp
@@ -52,6 +52,7 @@
 #include <QtCore/QDir>
 #include <QtCore/QQueue>
 #include <QtCore/QHash>
+#include <QtCore/QPair>
 #include <QtCore/qdebug.h>
 #include <QtCore/QCoreApplication>
 
@@ -177,44 +178,97 @@ QAbstractFormBuilder::~QAbstractFormBuilder()
 {
 }
 
+// Return UI file version from attribute 'version="4.0"'
+static QPair<int, int> uiVersion(const QString &attr)
+{
+    const QStringList versions = attr.split(QLatin1Char('.'), QString::SkipEmptyParts);
+    if (versions.size() >= 2) {
+        bool okMajor, okMinor;
+        const int majorVersion = versions.at(0).toInt(&okMajor);
+        const int minorVersion = versions.at(1).toInt(&okMinor);
+        if (okMajor &&  okMinor)
+            return QPair<int, int>(majorVersion, minorVersion);
+    }
+    return QPair<int, int>(-1, -1);
+}
+
+static inline QString msgXmlError(const QXmlStreamReader &reader)
+{
+    return QCoreApplication::translate("QAbstractFormBuilder", "An error has occurred while reading the UI file at line %1, column %2: %3")
+                                       .arg(reader.lineNumber()).arg(reader.columnNumber()).arg(reader.errorString());
+}
+
+// Read and check the  version and the (optional) language attribute
+// of an <ui> element and leave reader positioned at <ui>.
+static bool inline readUiAttributes(QXmlStreamReader &reader, const QString &language, QString *errorMessage)
+{
+    const QString uiElement = QLatin1String("ui");
+    // Read up to first element
+    while (!reader.atEnd()) {
+        switch (reader.readNext()) {
+        case QXmlStreamReader::Invalid:
+            *errorMessage = msgXmlError(reader);
+            return false;
+        case QXmlStreamReader::StartElement:
+            if (reader.name().compare(uiElement, Qt::CaseInsensitive) == 0) {
+                const QString versionAttribute = QLatin1String("version");
+                const QString languageAttribute = QLatin1String("language");
+                const QXmlStreamAttributes attributes = reader.attributes();
+                if (attributes.hasAttribute(versionAttribute)) {
+                    const QString versionString = attributes.value(versionAttribute).toString();
+                    if (uiVersion(versionString).first < 4) {
+                        *errorMessage = QCoreApplication::translate("QAbstractFormBuilder", "This file was created using Designer from Qt-%1 and cannot be read.")
+                                .arg(versionString);
+                        return false;
+                    } // version error
+                }     // has version
+                if (attributes.hasAttribute(languageAttribute)) {
+                    // Check on optional language (Jambi)
+                    const QString formLanguage = attributes.value(languageAttribute).toString();
+                    if (!formLanguage.isEmpty() && formLanguage.compare(language, Qt::CaseInsensitive)) {
+                        *errorMessage = QCoreApplication::translate("QAbstractFormBuilder", "This file cannot be read because it was created using %1.").arg(formLanguage);
+                        return false;
+                    } // language error
+                }    // has language
+                return true;
+            }  // <ui> matched
+            break;
+        default:
+            break;
+        }
+    }
+    // No <ui> found.
+    *errorMessage = QCoreApplication::translate("QAbstractFormBuilder",  "Invalid UI file: The root element <ui> is missing.");
+    return false;
+}
+
 /*!
     \fn QWidget *QAbstractFormBuilder::load(QIODevice *device, QWidget *parent)
 
     Loads an XML representation of a widget from the given \a device,
     and constructs a new widget with the specified \a parent.
 
-    \sa save()
+    \sa save(), errorString()
 */
 QWidget *QAbstractFormBuilder::load(QIODevice *dev, QWidget *parentWidget)
 {
-    QXmlStreamReader reader;
-    reader.setDevice(dev);
-    DomUI ui;
-    bool initialized = false;
-
-    const QString uiElement = QLatin1String("ui");
-    while (!reader.atEnd()) {
-        if (reader.readNext() == QXmlStreamReader::StartElement) {
-            if (reader.name().compare(uiElement, Qt::CaseInsensitive) == 0) {
-                ui.read(reader);
-                initialized = true;
-            } else {
-                reader.raiseError(QCoreApplication::translate("QAbstractFormBuilder", "Unexpected element <%1>").arg(reader.name().toString()));
-            }
-        }
+    QXmlStreamReader reader(dev);
+    d->m_errorString.clear();
+    if (!readUiAttributes(reader, d->m_language, &d->m_errorString)) {
+        uiLibWarning(d->m_errorString);
+        return false;
     }
+    DomUI ui;
+    ui.read(reader);
     if (reader.hasError()) {
-        uiLibWarning(QCoreApplication::translate("QAbstractFormBuilder", "An error has occurred while reading the UI file at line %1, column %2: %3")
-                                .arg(reader.lineNumber()).arg(reader.columnNumber())
-                                .arg(reader.errorString()));
-        return 0;
-    }
-    if (!initialized) {
-        uiLibWarning(QCoreApplication::translate("QAbstractFormBuilder", "Invalid UI file: The root element <ui> is missing."));
+        d->m_errorString = msgXmlError(reader);
+        uiLibWarning(d->m_errorString);
         return 0;
     }
 
     QWidget *widget = create(&ui, parentWidget);
+    if (!widget && d->m_errorString.isEmpty())
+        d->m_errorString = QCoreApplication::translate("QAbstractFormBuilder", "Invalid UI file");
     return widget;
 }
 
@@ -3119,4 +3173,16 @@ bool QAbstractFormBuilder::isScriptingEnabled() const
 #endif
 }
 
+/*!
+    Returns a human-readable description of the last error occurred in load().
+
+    \since 5.0
+    \sa load()
+*/
+
+QString QAbstractFormBuilder::errorString() const
+{
+    return d->m_errorString;
+}
+
 QT_END_NAMESPACE