On 2019-05-21 13:03, Konstantin Ritt wrote:
вт, 21 мая 2019 г., 11:32 Mutz, Marc via Development
<[email protected]>:
And while the partially-formed
state can be extended to non-pimpled classes easily:
class QRect {
int x, y, w, h;
public:
QRect() = default;
};
QRect r; // partially-formed
r.x(); // compilers _already_ warn about this
QRect r = {}; // zero-initialized
That
should be modelled by optional<QRect>, not by QRect itself.
Whilst the statement feels reasonable, this will require tons of API
changes and double checks on the user side:
There are no double-checks. If the old code didn't check the rect before
using it, it was a bug.
optional<QRect> Item::childrenRect() const
{
if (hasChildren()) {
QRect r = {};
for (auto *child : children())
r.unite(child->boundingRect().value_or({});
for (auto *child : children())
if (auto rect = child->boundingRect())
r.unite(*rect);
return r;
}
return nullopt;
}
QRect r = item->boundingRect().value_or({});
if (!r.isEmpty())
~~~
if (auto r = item->boundingRect())
use(*r);
Note that I'm ok with that, but should we enforce such a huge efforts
all over Qt API just for making the default-constructible QRect a
no-op?
This is not proposed for Qt 6. Not by me, at least. But it's the logical
extension and once Qt can depend on C++17, iow: std::optional, it's the
correct way forward, IMNSHO.
Thanks,
Marc
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