(WIP) Make PDF Print/Export work without having to use Print Preview first

[martinvanzijl]

Fixes #751.

Exporting/Printing PDF files now works without having to use Print Preview first. Tested on Ubuntu 18.04.

[lordofbikes]

Many thanks for this contribution!
Sadly, this is not the complete solution. PDF export would be limited to fit to page.
If one would generate a PDF with specified scale, via print preview, this will not work with this fix anymore.

[martinvanzijl]

@lordofbikes Thanks for your comment. I guess I should have tested more thoroughly!

I tried this since the call to graphic->fitToPage(); was the only difference I could see in the code for "print preview" vs. "print/export".

Anyway, I think I see the real problem. If you just use "print/export" without doing a print preview first, it will export the area around the center of the diagram. If there are no elements near the center, this exports an empty page.

I attached a demo below to explain this (zipped OGV), done with master branch without this fix:

export-problem-demo.zip

At least with print preview, it does a "fit to page" at the start, which means the diagram's elements will be included on page, regardless of whether they are near the center or not.

[martinvanzijl]

As for how to fix the issue properly, I can suggest either:

1. Use fit-to-page if the user has not done Print Preview yet. If the user has done Print Preview before, use the settings from there instead. OR
2. Always show print preview before printing/exporting.

Anyway, feel free to close this branch.

[lordofbikes]

Don't worry, this is a real issue indeed and your efforts are more than welcome.
I tend to your solution 1.
Then inexperienced users will have an output at least and often a fit to page print is enough.
Maybe a little hint message (about print preview) in the command history can help when fitToPage() was applied.
I think a missing drawing area is the cause for this issue. In slotFilePrint() we have access to RS_Graphic* graphic, I assume there is the drawing area and insertion point set from print preview.
So I think the solution is to check if graphic contains a valid area and if not, call fitToPage().

If you can have a look at this, you're welcome. Then simply push modifications to this branch.
But if you can't, no problem, I'll keep this open until someone has battled this issue down.

[dellus]

I have long since been of the opinion it would be better to always run printing and pdf/bitmap export via PrintPreview. I have recently discovered that QCAD does it this way, kind of. Maybe worth to have a look on it.

[fa201]

I agree with @dellus. The process would be smoother and easier for newcomers.
We could have one print menu in which we set up the print/export and then print/export.

[Salamek]

Still happening to me on 2.2.0... on Archlinux... i was getting white empty page when using File -> Export -> Export as PDF, when i did the same from print preview it worked ok...