Re: Text shadows

[Po Lu <luangruo@yahoo.com>]

Kai Ma <justksqsf@gmail.com> writes:

>> On Mar 12, 2023, at 15:12, Eli Zaretskii <eliz@gnu.org> wrote:
>> 
>>> From: Kai Ma <justksqsf@gmail.com>
>>> Date: Sun, 12 Mar 2023 12:06:28 +0800
>>> 
>>> Recently, I implemented the “text shadows” feature for Cairo-powered windowing systems, including X11 and Wayland.  See [1] if you wonder what that looks like.
>> 
>> Which parts of the feature implementation really require Cairo?  IOW,
>> why cannot this be available to non-Cairo builds as well?
>
> Theoretically, nothing.  I targeted Cairo because (I think) it is the most popular option on GNU/Linux.
>
> Speaking of this specific implementation, gaussian_blur() relies on a specific Cairo image format ARGB32, (this assumption could be easily removed), and then it is used by ftcrfont_draw() to generate shadows.
>
> I don’t know whether non-Cairo builds (non-cairo X, win32) can/should use gaussian_blur() though, since I’m not familiar with them.

Non-Cairo builds and Cairo builds alike should use the X Rendering
Extension, where an arbitrary blur kernel is a standard picture filter.
Cairo builds on X should as well.

P.S: the GNU project rejects the Unix convention that `foo()' refers to
the function `foo': `foo()' is a function declarator that returns int
and takes any number of arguments, or alternatively a function call to
`foo' with no arguments.