Re: [PATCH] Autocompletion list image scaling for HiDPI/Retina displays

Hi Neil,

> On May 11, 2025, at 11:31 PM, Neil Hodgson <[email protected]> wrote:
> 
> Hi Mitchell,
> 
>> Attached is a patch and zip against Scintilla 5.5.6 that implements ...
> 
> There are some warnings from compilers and linters so I made some more
> changes that silenced these.

Thanks. I’m not sure why my compiler didn’t catch some of those.

>> The only questionable bit in my opinion is the GTK implementation switches the list store image column type to CAIRO_GOBJECT_TYPE_SURFACE from GDK_TYPE_PIXBUF. Not only does this require the <cairo/cairo-gobject.h> header (which is included with my default libgtk-3-dev installation),
> 
> If this may be missing, there may be a need for a more complex check
> with a __has_include(<cairo/cairo-gobject.h>)

I figured if my libgtk-3-dev includes it, perhaps all or most distributions have it too. You know more about GTK than me though.

>> but it also performs a copy for each pixbuf to be included in the list. This copy is necessary because Cairo surfaces store device scale, not GDK Pixbufs[2]. The list store takes ownership of the surface (it’s a boxed pointer), and will free it when done[3]. I was not able to figure out how to create a Cairo surface from an incoming pixbuf, g_object_ref() it, and pass it to the list store directly (thus avoiding copies and a premature deallocation).
> 
> I was originally unconcerned but this is a new allocation for each row
> that shows an image. Probably not too bad in normal use.

In my testing with language servers that can return over 100 autocompletion items for me to show, I haven’t noticed any issues. I was initially concerned about the allocations and tried hard to avoid them, but I don’t know enough about GTK, Cairo, and GObject to keep a single copy of a Cairo surface around long enough; those surfaces were constantly being deallocated and my images were being drawn corrupted. I learned to live with the allocations and found that it wasn’t noticeable at all.

Cheers,
Mitchell

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