QmlPreview: Tell users how to preview single files

In order to preview a specific (QML) file, a QML Preview process has to
have been started, before. The "Preview File" context menu action was
therefore disabled until at least one QML Preview was running. This
precondition is neither documented nor evident to users.

This change removes the disabling/enabling of the context menu action
and shows an explanatory message box for the case that no running QML
Preview is available.

Fixes: QTCREATORBUG-29300
Change-Id: I643c57cab15ef4893a8efa6ac8839a3c00e956fb
Reviewed-by: hjk <hjk@qt.io>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/plugins/qmlpreview/qmlpreviewplugin.cpp b/src/plugins/qmlpreview/qmlpreviewplugin.cpp
index 9d05d0ee398..2722ecb016e 100644
--- a/src/plugins/qmlpreview/qmlpreviewplugin.cpp
+++ b/src/plugins/qmlpreview/qmlpreviewplugin.cpp
@@ -44,6 +44,7 @@
 #include <android/androidconstants.h>
 
 #include <QAction>
+#include <QMessageBox>
 #include <QPointer>
 #include <QTimer>
 
@@ -174,11 +175,6 @@ QmlPreviewPluginPrivate::QmlPreviewPluginPrivate(QmlPreviewPlugin *parent)
 
     menu = Core::ActionManager::actionContainer(Constants::M_FILECONTEXT);
     action = new QAction(Tr::tr("Preview File"), this);
-    action->setEnabled(false);
-    connect(q, &QmlPreviewPlugin::runningPreviewsChanged,
-            action, [action](const QmlPreviewRunControlList &previews) {
-        action->setEnabled(!previews.isEmpty());
-    });
     connect(action, &QAction::triggered, q, &QmlPreviewPlugin::previewCurrentFile);
     menu->addAction(
         Core::ActionManager::registerAction(action, "QmlPreview.PreviewFile",  Core::Context(Constants::C_PROJECT_TREE)),
@@ -336,6 +332,11 @@ void QmlPreviewPlugin::previewCurrentFile()
             || currentNode->asFileNode()->fileType() != FileType::QML)
         return;
 
+    if (runningPreviews().isEmpty())
+        QMessageBox::warning(Core::ICore::dialogParent(), Tr::tr("QML Preview not running"),
+                             Tr::tr("Please start the QML Preview for the project before selecting "
+                                    "a specific file for preview."));
+
     const QString file = currentNode->filePath().toString();
     if (file != d->m_previewedFile)
         setPreviewedFile(file);