[rkward/frameworks] rkward/rbackend: Unify the "wait for security token" code a bit, also hoping it will fix the sporadic problems

[Thomas Friedrichsmeier]

Git commit 72af88de1bf0dda52f781275c84928c9368c29bc by Thomas Friedrichsmeier.
Committed on 27/05/2017 at 07:20.
Pushed by tfry into branch 'frameworks'.

Unify the "wait for security token" code a bit, also hoping it will fix the sporadic problems
when connecting on Windows.

M  +14   -16   rkward/rbackend/rkfrontendtransmitter.cpp
M  +4    -0    rkward/rbackend/rkfrontendtransmitter.h
M  +2    -3    rkward/rbackend/rkwarddevice/rkgraphicsdevice_frontendtransmitter.cpp

https://commits.kde.org/rkward/72af88de1bf0dda52f781275c84928c9368c29bc

diff --git a/rkward/rbackend/rkfrontendtransmitter.cpp b/rkward/rbackend/rkfrontendtransmitter.cpp
index 3ebdfc23..ffde284f 100644
--- a/rkward/rbackend/rkfrontendtransmitter.cpp
+++ b/rkward/rbackend/rkfrontendtransmitter.cpp
@@ -128,14 +128,7 @@ void RKFrontendTransmitter::run () {
 		handleTransmissionError (i18n ("The backend executable could not be started. Error message was: %1", backend->errorString ()));
 	}
 
-	// fetch security token
-	{
-		// NOTE: On Qt5+Windows, readyReady may actually come in char by char, so calling waitForReadyRead() does not guaranteed we will
-		//       see the full line, at all. But also, of course, we want to put some cap on trying. Using a time threshold for this.
-		QTime time;
-		time.start ();
-		while ((!backend->canReadLine ()) && (time.elapsed () < 3000)) backend->waitForReadyRead ();
-	}
+	waitForCanReadLine (backend, 3000);
 	token = QString::fromLocal8Bit (backend->readLine ()).trimmed ();
 	backend->closeReadChannel (QProcess::StandardError);
 	backend->closeReadChannel (QProcess::StandardOutput);
@@ -150,6 +143,16 @@ void RKFrontendTransmitter::run () {
 	}
 }
 
+void RKFrontendTransmitter::waitForCanReadLine (QIODevice* con, int msecs) {
+	RK_TRACE (RBACKEND);
+
+	// NOTE: On Qt5+Windows, readyReady may actually come in char by char, so calling waitForReadyRead() does not guarantee we will
+	//       see the full line, at all. But also, of course, we want to put some cap on trying. Using a time threshold for this.
+	QTime time;
+	time.start ();
+	while ((!con->canReadLine ()) && (time.elapsed () < msecs)) con->waitForReadyRead (500);
+}
+
 void RKFrontendTransmitter::connectAndEnterLoop () {
 	RK_TRACE (RBACKEND);
 	RK_ASSERT (server->hasPendingConnections ());
@@ -158,16 +161,11 @@ void RKFrontendTransmitter::connectAndEnterLoop () {
 	server->close ();
 
 	// handshake
-	if (!con->canReadLine ()) con->waitForReadyRead (1000);
-	QString token_c = QString::fromLocal8Bit (con->readLine ());
-	token_c = token_c.trimmed ();
+	waitForCanReadLine (con, 1000);
+	QString token_c = QString::fromLocal8Bit (con->readLine ()). trimmed ();
 	if (token_c != token) handleTransmissionError (i18n ("Error during handshake with backend process. Expected token '%1', received token '%2'", token, token_c));
-	if (!con->canReadLine ()) con->waitForReadyRead (1000);
+	waitForCanReadLine (con, 1000);
 	QString version_c = QString::fromLocal8Bit (con->readLine ().trimmed ());
-	if (version_c.isEmpty ()) {  // may happend on Windows, due to \r\n lines ends
-		if (!con->canReadLine ()) con->waitForReadyRead (1000);
-			version_c = QString::fromLocal8Bit (con->readLine ().trimmed ());
-	}
 	if (version_c != RKWARD_VERSION) handleTransmissionError (i18n ("Version mismatch during handshake with backend process. Frontend is version '%1' while backend is '%2'.\nPlease fix your installation.", QString (RKWARD_VERSION), version_c));
 
 	setConnection (con);
diff --git a/rkward/rbackend/rkfrontendtransmitter.h b/rkward/rbackend/rkfrontendtransmitter.h
index 6b4b263b..1e1a95af 100644
--- a/rkward/rbackend/rkfrontendtransmitter.h
+++ b/rkward/rbackend/rkfrontendtransmitter.h
@@ -21,6 +21,7 @@
 #include "rktransmitter.h"
 
 class QProcess;
+class QIODevice;
 class QLocalServer;
 class RKGraphicsDeviceFrontendTransmitter;
 
@@ -38,6 +39,9 @@ public:
 	};
 	void writeRequest (RBackendRequest *request) override;
 	void requestReceived (RBackendRequest *request) override;
+	/** Simple convenience function similar to QIODevice::waitForReadyRead(), but waiting for a full line to be available.
+	    In particular on Windows, we often receive _less_ than a full line per chunk. */
+	static void waitForCanReadLine (QIODevice *con, int msecs);
 private slots:
 	void connectAndEnterLoop ();
 	void backendExit (int exitcode);
diff --git a/rkward/rbackend/rkwarddevice/rkgraphicsdevice_frontendtransmitter.cpp b/rkward/rbackend/rkwarddevice/rkgraphicsdevice_frontendtransmitter.cpp
index f5c1f477..3de7c7b3 100644
--- a/rkward/rbackend/rkwarddevice/rkgraphicsdevice_frontendtransmitter.cpp
+++ b/rkward/rbackend/rkwarddevice/rkgraphicsdevice_frontendtransmitter.cpp
@@ -71,9 +71,8 @@ void RKGraphicsDeviceFrontendTransmitter::newConnection () {
 
 	// handshake
 	QString token = RKFrontendTransmitter::instance ()->connectionToken ();
-	if (!con->canReadLine ()) con->waitForReadyRead (1000);
-	QString token_c = QString::fromLocal8Bit (con->readLine ());
-	token_c.chop (1);
+	RKFrontendTransmitter::waitForCanReadLine (con, 2000);
+	QString token_c = QString::fromLocal8Bit (con->readLine ()).trimmed ();
 	if (token_c != token) {
 		KMessageBox::detailedError (0, QString ("<p>%1</p>").arg (i18n ("There has been an error while trying to connect the on-screen graphics backend. This means, on-screen graphics using the RKWard device will not work in this session.")), i18n ("Expected connection token %1, but read connection token %2", token, token_c), i18n ("Error while connection graphics backend"));
 		con->close ();