Joining views with storages

[TerensTare]

Views are pretty much a core utility of EnTT already and there is good support for many common operations. One of them is joining with other views, especially useful when one view might have named pools. However, the syntax becomes a little noisy when you need to join a view with one storage, which most often is a named void storage or a storage out of the registry (from my experience). To do this, we currently have to do something like:

entt::storage_for_t<void> dirty_entities;
// ...
auto view = registry.view<C1, const C2>() | entt::basic_view{dirty_entities};
for (auto id : view) {
    // ...
}

To address this, I propose to add a join function to basic_view, which works similarly to the existing operator|, except that it only accepts a storage as a parameter instead of a view. So the example before would now look like this:

entt::storage_for_t<void> dirty_entities;
// ...
auto view = registry.view<C1, const C2>().join(dirty_entities);
for (auto id : view)
{
    // ...
}

Now the function returns a new view, so you can chain .join() calls one after another. This is something of preference but I would advise to use operator| in that case.

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[skypjack]

Out of curiosity, why not:

auto view = registry.view<C1, const C2>() | dirty_entities;

It seems more on the line of the already existing functionality. Any particular reasons for using a dedicate function instead?

[TerensTare]

Any particular reasons for using a dedicate function instead?

Purely a matter of semantics, since storages are a different type from views. Nothing against operator| except that. Also, I just realized that the implementation does not support joining a view with a const-storages,I will have to add that too.

[skypjack]

Ehy, sorry for the late reply. I've been busy recently.
I think you can have OGet &other and remove the is_lvalue_reference_v check as a consequence, no? remove_reference_t below is also useless then.
Same for the other join. Am I missing something? 👍

[TerensTare]

Huh I'd swear I had a problem with the const not propagating from storage to view earlier, I probably did something wrong... Anyway I just reverted the changes, let me know if you need anything else.

[skypjack]

Looks like my playing with branches other than master messed up here. I'll merge the PR to a yet another branch and clean it up. 👍