qppdprintdevice: create temp queue to get ppd from IPP attributes

Call `cupsCopyDestInfo` to create temp queue.

CUPS will create ppd file from IPP attributes for temp queue.

Otherwise, when opening the Qt print dialog in the case
of an IPP printer, CUPS does not yet know its properties
(such as duplex), so all printer properties may not be displayed
in the print dialog.

Task-number: QTBUG-46093
Pick-to: 6.12
Change-Id: I8ce4e8ec1a12cadd9ebc1c8ce94207b4116a4571
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

Author: SgAkErRu

src/plugins/printsupport/cups/qppdprintdevice.cpp

@@ -37,6 +37,16 @@ QPpdPrintDevice::QPpdPrintDevice(const QString &id)
         m_cupsDest = cupsGetNamedDest(CUPS_HTTP_DEFAULT, m_cupsName, m_cupsInstance.isNull() ? nullptr : m_cupsInstance.constData());
         if (m_cupsDest) {
             const char *ppdFile = cupsGetPPD(m_cupsName);
+            if (ppdFile == nullptr) {
+                // For auto-discovered IPP printers without a local CUPS queue, CUPS doesn't have a PPD yet.
+                // Request supported values/capabilities, which could be used to read capabilities (IPP attributes) directly.
+                // But for now, we call it only for the useful side-effect that CUPS creates a temp queue
+                // and a PPD file from the IPP attributes for this queue that can be retrieved then.
+                if (cups_dinfo_t *destInfo = cupsCopyDestInfo(CUPS_HTTP_DEFAULT, m_cupsDest)) {
+                    cupsFreeDestInfo(destInfo);
+                    ppdFile = cupsGetPPD(m_cupsName);
+                }
+            }
             if (ppdFile) {
                 m_ppd = ppdOpenFile(ppdFile);
                 unlink(ppdFile);