@asemke, Could you verify, that this commit don't breaks vector output for you? My system use mime application/x-extension-html for html, so I can't check, that after this commit R expression still can work with mime text/html.

In D12998#265385, @sirgienko wrote:

@asemke, Could you verify, that this commit don't breaks vector output for you? My system use mime application/x-extension-html for html, so I can't check, that after this commit R expression still can work with mime text/html.

No, this breaks the output for me:

What is the mime type for the generated files on your system? What does 'file' shows for the generated html files? For me it is:

alex@notebook:~/Projekte/cantor/build_debug (arcpatch-D12998 $%)>file /tmp/cantor_rserver-8561/Rtable0.html 
/tmp/cantor_rserver-8561/Rtable0.html: HTML document, ASCII text, with no line terminators

In D12998#265407, @asemke wrote:

No, this breaks the output for me:

Could you add log from console for this entry?

What is the mime type for the generated files on your system? What does 'file' shows for the generated html files? For me it is:

alex@notebook:~/Projekte/cantor/build_debug (arcpatch-D12998 $%)>file /tmp/cantor_rserver-8561/Rtable0.html 
/tmp/cantor_rserver-8561/Rtable0.html: HTML document, ASCII text, with no line terminators

mmmm1998:/tmp/cantor_rserver-19234
[16:19:25]$ file Rtable3.html 
Rtable3.html: HTML document, ASCII text, with no line terminators

Very intresting:

[16:25:08]$ mimetype /tmp/cantor_rserver-19234/Rtable3.html
/tmp/cantor_rserver-19234/Rtable3.html: text/html

but in log there is another mimetype

showing files:  ("/tmp/cantor_rserver-19234/Rtable3.html")
MimeType:  "application/x-extension-html"

@asemke, which Qt version do you have? My version is 5.9.5.

In D12998#265410, @sirgienko wrote:

In D12998#265407, @asemke wrote:

No, this breaks the output for me:

Could you add log from console for this entry?

showing files:  ("/tmp/cantor_rserver-8561/Rtable1.html")
MimeType:  "text/html" its a HTML document
content:  "<table border=\"1\" align=\"center\" valign=\"center\"><tr><td bgcolor=\"#AAAAAA\">[1]</td><td>1</td><td>2</td><td>3</td></tr><table>"
settting result to a type  1
result update Entry

In D12998#265412, @sirgienko wrote:

Very intresting:

[16:25:08]$ mimetype /tmp/cantor_rserver-19234/Rtable3.html
/tmp/cantor_rserver-19234/Rtable3.html: text/html

but in log there is another mimetype

showing files:  ("/tmp/cantor_rserver-19234/Rtable3.html")
MimeType:  "application/x-extension-html"

@asemke, which Qt version do you have? My version is 5.9.5.

I have

alex@notebook:~/Projekte/cantor/build_debug (arcpatch-D12998 $%)>file --mime-type /tmp/cantor_rserver-8561/Rtable1.html 
/tmp/cantor_rserver-8561/Rtable1.html: text/html

and

showing files:  ("/tmp/cantor_rserver-8561/Rtable1.html")
MimeType:  "text/html"

with Qt 5.10.

In D12998#265474, @sirgienko wrote:

@asemke, Could you test R backend with this update?

yes, this works.

For me it is also sufficient to check in rexpression.cpp:106 for type.inherits(QLatin1String("text/plain")) only - application/x-extension-html inherits apparently from text/plain.

In D12998#265482, @asemke wrote:

For me it is also sufficient to check in rexpression.cpp:106 for type.inherits(QLatin1String("text/plain")) only - application/x-extension-html inherits apparently from text/plain.

Your system, as I see, doesn't use application/x_extension-html (uses text/html instead), so you can remove condition for this mimetype without problem.
But removing this condition for me gives:
cannot open file /tmp/cantor_rserver-14014/Rtable1.html: Unknown MimeType