[LyX/master] Rerun latex if necessary when generating previews

[Richard Kimberly Heck]

On 5/21/25 2:31 AM, Enrico Forestieri wrote:
> On Mon, May 19, 2025 at 09:34:54PM +0000, Enrico Forestieri wrote:
>>
>> commit 1888d50eb18277fd93aab2859233887ae5919ebf
>> Author: Enrico Forestieri <forenr at lyx.org>
>> Date:   Mon May 19 23:19:15 2025 +0200
>>
>>    Rerun latex if necessary when generating previews
>>
>>    Recent versions of dvipng may produce a last page whose content
>>    simply states that "LaTeX was unable to guess the total number
>>    of pages correctly. As there was some unprocessed data that
>>    should have been added to the final page this extra page has
>>    been added to receive it. If you rerun the document (without
>>    altering it) this surplus page will go away, because LaTeX now
>>    knows how many pages to expect for this document."
>>
>>    This confuses the lyxpreview2bitmap.py script, making it unable
>>    to distinguish pages that should follow the dvipng route or the
>>    legacy route. However, the presence of the extra page is reported
>>    in the log file and hence we know we have to rerun latex.
>
>
> Riki, this is also needed in stable.

Cherry-picked. Thanks.

I'll add a note about this to the ANNOUNCE file for 2.4.4.

Riki