Fix custom page size handling in the Unix print dialog

There were several problems that i've fixed in a single commit since they are very interwinded

 * The dialog used QPageSize::Custom for two things, the custom sizes coming from
   the printer and the "user can write whatever size they want" size. Now only
   the printer custom sizes use QPageSize::Custom and we use m_realCustomPageSizeIndex
   for the "user can write whatever size they want" one.

 * The dialog stored the QPageSize id as the combo userData, that doesn't work
   when the printer has multiple custom sizes since they all share QPageSize::Custom
   so now it stores the QPageSize itself

Task-number: QTBUG-58733
Change-Id: Ie640a07bb5e24b753db83c091c836e8af4ff126c
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/plugins/printsupport/cups/qcupsprintengine.cpp b/src/plugins/printsupport/cups/qcupsprintengine.cpp
index 287ab4b27a..763f676e41 100644
--- a/src/plugins/printsupport/cups/qcupsprintengine.cpp
+++ b/src/plugins/printsupport/cups/qcupsprintengine.cpp
@@ -104,10 +104,9 @@ void QCupsPrintEngine::setProperty(PrintEnginePropertyKey key, const QVariant &v
         break;
     case PPK_QPageLayout: {
         QPageLayout pageLayout = value.value<QPageLayout>();
-        if (pageLayout.isValid() && d->m_printDevice.isValidPageLayout(pageLayout, d->resolution)) {
+        if (pageLayout.isValid() && (d->m_printDevice.isValidPageLayout(pageLayout, d->resolution) || d->m_printDevice.supportsCustomPageSizes())) {
             d->m_pageLayout = pageLayout;
-            // Replace the page size with the CUPS page size
-            d->setPageSize(d->m_printDevice.supportedPageSize(pageLayout.pageSize()));
+            d->setPageSize(pageLayout.pageSize());
         }
         break;
     }