Some Native UI Widgets are not exported

[LabKlein]

Steps to reproduce:

• Create a Windows with button, label, text field, etc. from the Native UI Widgets set. This is, how it looks in Pencil:
• Export as PNG. This is how the export looks (not all elements were exported)

Bug is reproducable in 2.0.13. It worked in 2.0.3 (I have to use this old version, because of the issue #602)

[aleksandaratanasov]

I can confirm that on my Debian Jessie.

• Export to single web-page - some Native UI components are displayed, others - not
• Export as PDF - all pages are blank

[egroeper]

I can confirm, that this exists in 2.0.18 and works fine in 2.0.3 (just downloaded old version). Perhaps we should git bisect the root cause of this. I have read (somewhere -.-), that this issue exists at least since 2.0.5.

[egroeper]

I can't confirm the PNG export problem with 2.0.5. Just installed it in parallel to 2.0.3 an 2.0.18 on my VM and there were quirks when opening a page with native elements (similar to #638), but after touching each element (F2 + ENTER) everything looked fine again. After that PNG export of a test page went fine on 2.0.5.

[egroeper]

The issue exists in 2.0.8. So something between 2.0.5 and 2.0.8 causes the problem.