Change const T&& parameters to T&& to enable proper move semantics

[Sea-n]

Replace const T&& parameters with correct T&& (non-const rvalue references) so that move() semantics actually take effect.

Problem

const T&& disables moves

Move constructors/operators are declared as widget(T&&) / widget& operator=(T&&). When a parameter is const T&&, the argument becomes an immutable rvalue, so the move constructor cannot be called, only the copy constructor is viable.

std::move() is pointless on const rvalues

std::move merely casts to exactly the same reference type it receives; if the variable is const, the result is still const T&&.

Unnecessary copies & misleading code

Large objects are copied instead of moved, wasting memory/CPU and hiding the real cost from programmers.

Fix

Drop the const qualifier on all rvalue-reference parameters:

 ItemImage::ItemImage(
- const QPixmap &&pixmap,
+ QPixmap &&pixmap,
  ItemBase::Data data)
 : ItemBase(std::move(data))
 , _pixmap(std::move(pixmap)) {
 }

Impact

• Restores true move semantics, eliminating extra deep/shallow copies.
• Reduces temporary allocations when loading images or constructing message items.
• Aligns code intent with behavior, improving maintainability and readability.

References

• I found this improvement by reading "Effective Modern C++" book, please refer to page 160.
• StackOverflow: Why can we use std::move on a const object?
• PVS Code Analyzer: V833. Using 'std::move' function's with const object disables move semantics

[john-preston]

Last one changes const lvalue reference to non const lvalue reference 🤔

[john-preston]

And it even broke the build as you can see here:

https://github.com/telegramdesktop/tdesktop/actions/runs/15718851021/job/44295293711?pr=29464

[Sea-n]

Oh, thanks for pointing out rpl::start_with_next() takes const lvalue reference, which is different thing with this one. 😅