[Spice-devel] [vdagent-win PATCH v12 3/6] Write code to decode PNG format

[Christophe de Dinechin]

> On 25 Jul 2017, at 20:01, Frediano Ziglio <fziglio at redhat.com> wrote:
> 
>> 
>> On Mon, Jul 24, 2017 at 01:39:35PM +0100, Frediano Ziglio wrote:
>>> +size_t PngCoder::convert_to_dib(uint8_t *out_buf, const uint8_t *data,
>>> size_t size)
>>> +{
>> [...]
>>> +    const unsigned int width = png_get_image_width(png, info);
>>> +    const unsigned int height = png_get_image_height(png, info);
>>> +    const size_t stride = compute_dib_stride(width, out_bits);
>>> +    const size_t image_size = stride * height;
>>> +    const int palette_colors = [=]() {
>> 
>> If you want to use a function, then give it a name, if you don't want to
>> use a function, then this can just go in convert_to_dib() body rather
>> than through a lambda (I know the latter means removing the 'const’).

Removing the ‘const’? Why?

> 
> Lambdas are functions.

I believe Christophe is objecting to using a lambda whereas all other
computations use named functions. But frankly, here, I would have
written:

    const int palette_colors =
          out_bits > 8  ? 0
        : bits == 2     ? 4
        : 1 << out_bits;

Not that I don’t like lambdas, but here, it’s a lot of additional syntactic noise.

Out of curiosity, I submitted both variants of the code to g++, and got
exactly the same generated code.

> I personally think the purpose of that code was clear even without
> a name.
> Using a "standard" function requires to declare parameters and pass
> them manually, something that lambda capture can do automatically.
> 
>> 
>> Christophe
>> 
> 
> By the way, got new version with more old style code.
> 
> Frediano
> _______________________________________________
> Spice-devel mailing list
> Spice-devel at lists.freedesktop.org <mailto:Spice-devel at lists.freedesktop.org>
> https://lists.freedesktop.org/mailman/listinfo/spice-devel <https://lists.freedesktop.org/mailman/listinfo/spice-devel>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/spice-devel/attachments/20170726/31254ab1/attachment.html>