Re: create-image and find-image consistency

[Clément Pit-Claudel]

On 30/04/2020 05.24, David Ponce wrote:
> On 30/04/2020 07:08, Lars Ingebrigtsen wrote:
>>
>> I think it conceptually makes sense to have find-image use create-image,
>> but looking at the code, and where find-image is used, it looks like the
>> use case it for creating toolbars and the like, where you want to pick
>> out one of the (built-in) image formats that Emacs supports...
>>
>> Looking at your patch, you remove the (image-type-available-p type), and
>> instead rely on create-image not bugging out instead?  That feels like a
>> less obvious way to do the test (and more breakable; there may be other
>> reasons create-image fails).
>>
>> And I'm not 100% sure that we want to auto-scale toolbars and the like.
>> I'm pretty sure we do, but perhaps somebody else has an opinion here?
>>
>> Anyway, I think you should file this as a bug report so that the patch
>> doesn't get lost, because I think you're basically correct that the
>> find-image behaviour should be changed.
>>
> 
> Hi Lars,
> 
> I created bug report #40978 as suggested.
> 
> My idea was to better separate the role of find-image from
> create-image:
> 
> - create-image to actually make a new image based on given specs, and
>   maybe some common options and device capabilities (for example, auto
>   scaling based on screen resolution).
>   - find-image to lookup for an image in the file system or in raw data,
>   but delegating to create-image the actual creation of the image.
> 
> Currently find-image & create-image can return a different image from
> the same spec, which is not consistent. My patch proposes to fix such
> potential inconsistencies.
> When you don't need auto-scaling for example, you can pass :scale 1.0
> to find-image, like you would have done with create-image :-)
> IMHO, auto-scaling is particularly useful with graphics elements like
> tool bars, tab bars, and widgets ;-)

One problem is that SVG scaling is broken at the moment, so auto-scaling SVGs 
yields blurry results, so it's not clear that scaling is in fact desirable for 
tool bars.
Additionally, the scaling that create-image does is based on font size, right?  
Do we expect font size changes to change the size of tab bar icons?