Retry copying to clipboard if it fails as another application may have opened it

2 files changed, 28 insertions, 12 deletions

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 1c5f2f356..97c6d4f9f 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -539,7 +539,7 @@
 	IME target range displayed on Qt for OS X.
 	</li>
 	<li>
-	On Windows, make clipboard operations more robust by retrying OpenClipboard if it fails
+	On Qt and Windows, make clipboard operations more robust by retrying if they fail
 	as this may occur when another application has opened the clipboard.
 	</li>
     </ul>
diff --git a/qt/ScintillaEditBase/ScintillaQt.cpp b/qt/ScintillaEditBase/ScintillaQt.cpp
index 3b7db8002..e4bbb5c1d 100644
--- a/qt/ScintillaEditBase/ScintillaQt.cpp
+++ b/qt/ScintillaEditBase/ScintillaQt.cpp
@@ -25,6 +25,7 @@
 #include <QScrollBar>
 #include <QTimer>
 #include <QTextCodec>
+#include <QThread>
 
 #ifdef SCI_NAMESPACE
 using namespace Scintilla;
@@ -306,21 +307,36 @@ void ScintillaQt::ReconfigureScrollBars()
 	}
 }
 
+static bool clipboardAccessFailed;
+static void ClipboardMessageHandler(QtMsgType, const QMessageLogContext &, const QString &)
+{
+	clipboardAccessFailed = true;
+}
+
 void ScintillaQt::CopyToModeClipboard(const SelectionText &selectedText, QClipboard::Mode clipboardMode_)
 {
-	QClipboard *clipboard = QApplication::clipboard();
-	clipboard->clear(clipboardMode_);
-	QString su = StringFromSelectedText(selectedText);
-	QMimeData *mimeData = new QMimeData();
-	mimeData->setText(su);
-	if (selectedText.rectangular) {
-		AddRectangularToMime(mimeData, su);
-	}
+	// Try up to 8 times, with an initial delay of 1 ms and an exponential
+	// back off for a maximum total delay of 127 ms (1+2+4+8+16+32+64).
+	QString text = StringFromSelectedText(selectedText);
+	for (int attempt = 0; attempt < 8; attempt++) {
+		if (attempt > 0)
+			QThread::msleep(1 << (attempt-1));
+
+		QMimeData *mimeData = new QMimeData;
+		mimeData->setText(text);
+		if (selectedText.rectangular)
+			AddRectangularToMime(mimeData, text);
 
-	// Allow client code to add additional data (e.g rich text).
-	emit aboutToCopy(mimeData);
+		// Allow client code to add additional data (e.g rich text).
+		emit aboutToCopy(mimeData);
 
-	clipboard->setMimeData(mimeData, clipboardMode_);
+		clipboardAccessFailed = false;
+		QtMessageHandler handler = qInstallMessageHandler(ClipboardMessageHandler);
+		QApplication::clipboard()->setMimeData(mimeData, clipboardMode_);
+		qInstallMessageHandler(handler);
+		if (!clipboardAccessFailed)
+			return;
+	}
 }
 
 void ScintillaQt::Copy()