Re: Text shadows

[Kai Ma <justksqsf@gmail.com>]

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> On Mar 12, 2023, at 16:46, Po Lu <luangruo@yahoo.com> wrote:
>> 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.


I agree XRender should be used for non-Cairo X builds (when XRender is available).

But it’s probably not a good idea to use XRender on X+Cairo.  In this setting, cairo_show_glyphs is used to draw glyphs, but Cairo does not expose any interface to the underlying Picture object.  So it would require additional memory copies between X and Cairo just for blurring.  I guess it would be slower as the image to blur is usually small.  I will do the benchmarks once I get XRender blurring working.

> 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.


Point taken.


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