[Development] Proposal: Make QPen non-cosmetic by default
Uwe.Rathmann at tigertal.de
Thu Oct 11 22:59:46 CEST 2012
On Thu, 11 Oct 2012 14:33:30 +0000, Verbruggen Erik wrote:
>> I have personally never seen an actual use case where a cosmetic pen
>> makes sense, but I assume there are reasons for having i so anyone
>> creating an explicit QPen(Qt::black, 0.0) should get a 1.0 pixel thick
>> line regardless of scaling.
Think about a scatter plot with many points displayed as crosses. On a
large zoom level you only see a cloud but when zooming in you can see
each cross and its position in detail.
When the pen for the crosses would have been scaled you would end with
huge fat symbols - each probably larger than the plot widget itself.
Or think about a grid ( or ticks on an axis ), where each line indicates
a position according to scale. This line has to be one pixel regardless
of the scaling.
> PDF/PS define it this way, and is used when writing that kind of output.
The important part with PDF and cosmetic pens is when you zoom in the
generated document later in a PDF viewer. The cosmetic attribute used in
the Qt application code decided if the line gets scaled in the viewer or
Please note that when you change the default setting to non-cosmetic
almost all applications using Qwt for generating PDF documents will be
broken ( zooming itself is not a problem for Qwt as it is not implemented
using painter transformations, but I know other packages doing it ). And
as f.e curve pens are set in the application code I can't fix it with a
new version of the Qwt library.
I bet you will cause similar issues with any type of application that
implements zooming ( in the application itself or via PDF ).
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