GTKD Cairo get pixel color

[TheDGuy via Digitalmars-d-learn]

On Friday, 1 January 2016 at 22:00:04 UTC, TheDGuy wrote:
> On Friday, 1 January 2016 at 19:32:40 UTC, Basile B. wrote:
>> On Wednesday, 30 December 2015 at 23:20:23 UTC, Basile B. 
>> wrote:
>>> On Wednesday, 30 December 2015 at 20:44:44 UTC, TheDGuy wrote:
>>>> Hello,
>>>>
>>>> is there any way to get the pixel color of a single pixel by 
>>>> x and y coordinates of a context?
>>>
>>> render to a png back buffer.
>>>
>>> see cairo_image_surface_create_for_data
>>>
>>> then you'll be able to access the data and, at the same time, 
>>> to blit your buffer to screen.
>>
>>
>> Actually I was thinking to a user defined buffer type:
>>
>> struct SurfaceBuffer
>> {
>>     void* data; // used as param to create the surface
>>     Rgba[] opIndex(size_t index);
>>     Rgba[][] scanline();
>> }
>>
>> that you would pass as data in 
>> cairo_image_surface_create_for_data().
>>
>> But gtk certainly has pitcure classes with the typical 
>> scanline method and that you could use in 
>> cairo_image_surface_create_for_data.
>
> Ahm, i am not quite sure if you and [Mike Wey] talk about the 
> same thing. And i posted the error message in my last post when 
> i try to call "cairo_image_surface_create_for_data". I still 
> don't know where i am able to call the function?

I took a look into the source code of cairo and in the 
"ImageSurface.d"-file there is a function called "createForData" 
but if i try to use it like this:

cairo.ImageSurface.createForData(c,cairo.FORMAT_ARGB32,256,256,256*4);

i get: "undefined identifier 'createForData' in module 
'cairo.ImageSurface'

That is just one example of my experience using D:

some things are easy to understand but in other cases: even if 
you think it should work and you can proof it, it just doesn't or 
you have to do it in a really inconvenient way. I am getting 
frustrated