405244fe30
std::optional<int> is the wrong datatype to use for compare.
First and foremost, it can't be used in the idiomatic form of
auto r = a.compare(b);
if (r < 0) ~~~ // a is less than b
if (r > 0) ~~~ // a is greater than b
which we *already* feature in Qt (QString, QByteArray).
Also, std::optional<int> (explicitly) converts to bool, which is
a trap, because the result of the comparison can be accidentally
tested as a bool:
if (a.compare(b)) ~~~ // oops! does NOT mean a<b
Not to mention extending this to algorithms:
auto lessThan = [](QVariant a, QVariant b) { return a.compare(b); }; // oops!
std::ranges::sort(vectorOfVariants, lessThan);
which thankfully doesn't compile as is -- std::optional has
an *explicit* operator bool, and the Compare concept requires an
implicit conversion. However, the error the user is going to face
will be "cannot convert to bool because the operator is explicit",
which is deceiving because the fix is NOT supposed to be:
auto lessThan = [](QVariant a, QVariant b) { return (bool)a.compare(b); }; // big oops!
Instead: backport to Qt the required subset of C++20's <compare>
API, and use that. This commits just adds the necessary parts
for compare() (i.e. partial ordering), the rest of <compare>
(classes, functions, conversions) can be added to 6.1.
Change-Id: I2b5522da47854da39f79993e1207fad033786f00
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 3e59c97c3453926fc66479d9ceca03901df55f90)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
|
||
|---|---|---|
| .. | ||
| auto | ||
| baselineserver | ||
| benchmarks | ||
| global | ||
| libfuzzer | ||
| manual | ||
| shared | ||
| testserver | ||
| .prev_CMakeLists.txt | ||
| CMakeLists.txt | ||
| README | ||
| tests.pro | ||
README
This directory contains autotests and benchmarks based on Qt Test. In order
to run the autotests reliably, you need to configure a desktop to match the
test environment that these tests are written for.
Linux X11:
* The user must be logged in to an active desktop; you can't run the
autotests without a valid DISPLAY that allows X11 connections.
* The tests are run against a KDE3 or KDE4 desktop.
* Window manager uses "click to focus", and not "focus follows mouse". Many
tests move the mouse cursor around and expect this to not affect focus
and activation.
* Disable "click to activate", i.e., when a window is opened, the window
manager should automatically activate it (give it input focus) and not
wait for the user to click the window.