An extended error message (e.g. with Overwrite option) for Browse Mode needs a bit of rework, since the renaming is done by the model (not Gwenview) here.

In D13754#284182, @rkflx wrote:

The only thing I'm not sure about is showErrorMessage(): Why did it work in KDE 4, but does not work anymore? Your new code is fine, but maybe we also have a problem in KF5, which obviously we should try to fix (or we might run into it again and again… – e.g. did you check GVPart::showJobError?).

I think it just works like stated in the api docu now and the previous use was incorrect (but worked nevertheless). Calling showErrorMessage() from inside a result slot is ok and the error message shows up, e.g. using this code instead of enabling AutoErrorHandling works too:

KIO::SimpleJob* job = KIO::rename(oldUrl, newUrl, KIO::HideProgressInfo);
QObject::connect(job, &KJob::result, [=](KJob* job) {
    job->uiDelegate()->showErrorMessage();
});

(GVPart::saveAs() / GVPart::showJobError should work fine but no idea how to test this.)

In D13754#284275, @muhlenpfordt wrote:

KIO::SimpleJob* job = KIO::rename(oldUrl, newUrl, KIO::HideProgressInfo);
QObject::connect(job, &KJob::result, [=](KJob* job) {
    job->uiDelegate()->showErrorMessage();
});

Okay, at least it's still working in that case. Thanks for the sample code ;)

The following change in R288 KJobWidgets makes it work for me, so this seems to be related to event handling:

@@ -102,7 +104,7 @@ void KDialogJobUiDelegate::Private::queuedMessageBox(QWidget *widget, KMessageBo
 
     if (!running) {
         running = true;
-        QMetaObject::invokeMethod(this, "next", Qt::QueuedConnection);
+        next();
     }
 }

Looks like some of the porting work to KF5 caused this: efbf655b7ab5. Anyway, probably better to keep this as is.

(GVPart::saveAs() / GVPart::showJobError should work fine but no idea how to test this.)

You are right, I could now confirm it works fine: Using Gwenview's KPart, Save As in Konqueror to a read-only directory and compare w/ and w/o the call to showErrorMessage (the rename case is already caught by the file dialog).

In D13754#284307, @rkflx wrote:

The following change in R288 KJobWidgets makes it work for me, so this seems to be related to event handling:

@@ -102,7 +104,7 @@ void KDialogJobUiDelegate::Private::queuedMessageBox(QWidget *widget, KMessageBo
 
     if (!running) {
         running = true;
-        QMetaObject::invokeMethod(this, "next", Qt::QueuedConnection);
+        next();
     }
 }

Looks like some of the porting work to KF5 caused this: efbf655b7ab5. Anyway, probably better to keep this as is.

BTW, this also works:

job->uiDelegate()->showErrorMessage();
qApp->processEvents();

(Might be useful in cases where setAutoErrorHandlingEnabled(true) is inappropriate.)