Details
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Bug
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Resolution: Fixed
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P2: Important
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6.7.0
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None
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ed61e7c6d (dev)
Description
Applications built with QT_USE_QSTRINGBUILDER might behave erratic with qmlcachegen generated C++ code if string concatenation is required. The resulting type will then be a QStringBuilder instead of QString, which might cause problems.
The attached code illustrates such a problem. Here a QVariantMap with mimetype + data entries must be constructed for Drag&Drop. If the compiler is enabled and QT_USE_QSTRINGBUILDER is set, encoding of the string data will fail and this error is logged:
Don't know how to encode variant of type QMetaType(QStringBuilder<QString,QString>) as mime type "text/plain"
Workaround is to use an interim property for the concatination (coercing a string).
import QtQuick Window { width: 640 height: 480 visible: true title: qsTr("Hello World") Rectangle { id: dragSource width: 300 height: 100 property string modelData: "Drag Me" // workaround // readonly property string __modelData: "%" + modelData + "%" Text { id: parameterName anchors.centerIn: parent text: dragSource.modelData } Item { id: draggable Drag.active: dragArea.drag.active Drag.keys: [ "parameter" ] Drag.supportedActions: Qt.CopyAction Drag.proposedAction: Qt.CopyAction Drag.mimeData: { "text/plain": "%" + dragSource.modelData + "%" // "text/plain": dragSource.__modelData } Drag.dragType: Drag.Automatic } MouseArea { id: dragArea anchors.fill: parent hoverEnabled: true drag.target: draggable cursorShape: Qt.PointingHandCursor onPressed: dragSource.grabToImage(function(result) { draggable.Drag.imageSource = result.url }) } } Rectangle { id: dragTarget x: 300 width: 300 height: 100 Text { id: targetText anchors.centerIn: parent text: "Drop here" } DropArea { id: drop anchors.fill: parent keys: ["text/plain"] onDropped: function(drop) { console.log("DROP", drop, "hasTExt", drop.hasText, "Text", drop.text); if (drop.hasText) { targetText.text = drop.text; drop.accept(Qt.CopyAction); } } } } }
CMakeLists.txt:
target_compile_definitions(appuntitled12
PUBLIC
QT_USE_QSTRINGBUILDER
)