Long live qHashMulti(Commutative)

Add a helper function so that we have a shortcut.
Instead of writing:

  QHashCombine hash;
  seed = hash(seed, fieldA);
  seed = hash(seed, fieldB);
  // etc.
  return seed;

one can now simply write:

  return qHashMulti(seed, fieldA, fieldB, fieldC);

Port a few usages inside qtbase as a demonstration.

[ChangeLog][QtCore][QHash] Added the qHashMulti and
qHashMultiCommutative functions as convenience helpers
to calculate a hash from multiple variables (typically,
data members of a class).

Change-Id: I881a9ad41168df20ceecc6588a94abe7ddc6a532
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 1 insertions, 6 deletions

diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index cbfc985eec..7a0ccca6a0 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -410,12 +410,7 @@ inline bool operator ==(const QFontEngine::FaceId &f1, const QFontEngine::FaceId
 inline size_t qHash(const QFontEngine::FaceId &f, size_t seed = 0)
     noexcept(noexcept(qHash(f.filename)))
 {
-    QtPrivate::QHashCombine hash;
-    seed = hash(seed, f.filename);
-    seed = hash(seed, f.uuid);
-    seed = hash(seed, f.index);
-    seed = hash(seed, f.encoding);
-    return seed;
+    return qHashMulti(seed, f.filename, f.uuid, f.index, f.encoding);
 }