JNI: treat enums as their underlying types

Android APIs use integer constants like enum values, so they are mapped
to one of the integeral types (jint, jshort, jlong etc) on the C++ side.
Enable C++ code to declare an equivalent enum (scoped or unscoped), and
to use that enum as a type in JNI calls by treating it as the underlying
type in the signature() generator.

Add a helper type trait that maps enums to their underlying type and
other integral types to themselves (we can't use std::underlying_type_t
on a non-enum type). Add tests.

Note: Java Enums are special classes with fields; this change does not
add any special support for those.

Change-Id: Iec430a1553152dcf7a24209aaebbeceb1c6e38a8
Reviewed-by: Petri Virkkunen <petri.virkkunen@qt.io>
Reviewed-by: Zoltan Gera <zoltan.gera@qt.io>
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
index b7685538f1..cbffb24ff8 100644
--- a/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
+++ b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
@@ -115,6 +115,23 @@ static_assert(!QtJniTypes::CTString("ABCDE").endsWith("ABCDEF"));
 static_assert(QtJniTypes::CTString("ABCDE").endsWith('E'));
 static_assert(!QtJniTypes::CTString("ABCDE").endsWith('F'));
 
+enum UnscopedEnum {};
+enum class ScopedEnum {};
+enum class IntEnum : int {};
+enum class UnsignedEnum : unsigned {};
+enum class Int8Enum : int8_t {};
+enum class ShortEnum : short {};
+enum class LongEnum : long {};
+enum class JIntEnum : jint {};
+
+static_assert(QtJniTypes::Traits<UnscopedEnum>::signature() == "I");
+static_assert(QtJniTypes::Traits<ScopedEnum>::signature() == "I");
+static_assert(QtJniTypes::Traits<IntEnum>::signature() == "I");
+static_assert(QtJniTypes::Traits<UnsignedEnum>::signature() == "I");
+static_assert(QtJniTypes::Traits<Int8Enum>::signature() == "B");
+static_assert(QtJniTypes::Traits<LongEnum>::signature() == "J");
+static_assert(QtJniTypes::Traits<JIntEnum>::signature() == "I");
+
 void tst_QJniTypes::initTestCase()
 {