dev-qt/qtdeclarative: tentatively backport fix for musescore

~testing only for now, bit worried because:

1. upstream fix is recent and hasn't been reviewed/merged yet

2. it does not apply to 6.10.3 at all, and I needed to adapt it
   myself despite not really knowing C++

I can confirm that musescore works, but unsure if it could have
other negative effects.

Will wait a few days, and if nothing comes up will forward the
keywords to stable.

musescore users in stable may want to add to package.accept_keywords:

    =dev-qt/qtdeclarative-6.10.3-r1

Patching may be needed for 6.11.1 later as well, fix may not make it.

Closes: https://bugs.gentoo.org/973374
Signed-off-by: Ionen Wolkens <ionen@gentoo.org>

dev-qt/qtdeclarative/files/qtdeclarative-6.10.3-QTBUG-144701.patch

@@ -0,0 +1,33 @@
+Note that this is a non-official backport which required a bit
+of adaptation to work with 6.10.3, seems to work but possible
+overlooked something.
+
+https://bugs.gentoo.org/973374
+https://codereview.qt-project.org/c/qt%2Fqtdeclarative/+/733089
+--- a/src/qml/qml/qqmltypecompiler.cpp
++++ b/src/qml/qml/qqmltypecompiler.cpp
+@@ -5,4 +5,5 @@
+ #include "qqmltypecompiler_p.h"
+ 
++#include <iterator>
+ #include <private/qqmlobjectcreator_p.h>
+ #include <private/qqmlcustomparser_p.h>
+@@ -919,13 +920,12 @@
+     // Apply the ordering in the IR
+     obj->setFirstAlias(ordered[0]);
+-    if (ordered[0] == defaultPropertyAlias)
+-        obj->indexOfDefaultPropertyOrAlias = 0;
+-    for (qsizetype i = 0, end = ordered.size() - 1; i < end; ++i) {
++    for (qsizetype i = 0, end = ordered.size() - 1; i < end; ++i)
+         ordered[i]->next = ordered[i + 1];
+-        if (ordered[i] == defaultPropertyAlias)
+-            obj->indexOfDefaultPropertyOrAlias = i;
+-    }
+     ordered.last()->next = nullptr;
+ 
++    if (defaultPropertyAlias) {
++        auto it = std::find(ordered.constBegin(), ordered.constEnd(), defaultPropertyAlias);
++        obj->indexOfDefaultPropertyOrAlias = std::distance(ordered.constBegin(), it);
++    }
+     return true;
+ }

dev-qt/qtdeclarative/qtdeclarative-6.10.3-r1.ebuild

@@ -0,0 +1,65 @@
+# Copyright 2021-2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{11..14} )
+QT6_HAS_STATIC_LIBS=1
+# behaves very badly when qtdeclarative is not already installed, also
+# other more minor issues (installs junk, sandbox/offscreen issues)
+QT6_RESTRICT_TESTS=1
+inherit python-any-r1 qt6-build
+
+DESCRIPTION="Qt Declarative (Quick 2)"
+
+if [[ ${QT6_BUILD_TYPE} == release ]]; then
+	KEYWORDS="~amd64 ~arm ~arm64 ~hppa ~loong ~ppc ~ppc64 ~riscv ~x86"
+fi
+
+IUSE="accessibility +jit +network opengl qmlls +sql +ssl svg vulkan +widgets"
+
+RDEPEND="
+	~dev-qt/qtbase-${PV}:6[accessibility=,gui,network=,opengl=,sql?,ssl?,vulkan=,widgets=]
+	qmlls? ( ~dev-qt/qtlanguageserver-${PV}:6 )
+	svg? ( ~dev-qt/qtsvg-${PV}:6 )
+"
+DEPEND="
+	${RDEPEND}
+	vulkan? ( dev-util/vulkan-headers )
+"
+BDEPEND="
+	${PYTHON_DEPS}
+	~dev-qt/qtshadertools-${PV}:6
+"
+
+PATCHES=(
+	"${FILESDIR}"/${PN}-6.10.3-unity-build.patch
+	"${FILESDIR}"/${PN}-6.10.3-QTBUG-144701.patch
+)
+
+src_configure() {
+	local mycmakeargs=(
+		$(cmake_use_find_package qmlls Qt6LanguageServerPrivate)
+		$(cmake_use_find_package sql Qt6Sql)
+		$(cmake_use_find_package svg Qt6Svg)
+		$(qt_feature jit qml_jit)
+		$(qt_feature network qml_network)
+		$(qt_feature ssl qml_ssl)
+	)
+
+	qt6-build_src_configure
+}
+
+src_install() {
+	qt6-build_src_install
+
+	if [[ ! -e ${D}${QT6_LIBDIR}/libQt6QuickControls2.so.6 ]]; then #940675
+		eerror "${CATEGORY}/${PF} seems to have been improperly built and"
+		eerror "install was aborted to protect the system. Possibly(?) due"
+		eerror "to a rare portage ordering bug. If using portage, try:"
+		eerror "    emerge -1 qtshadertools:6 qtdeclarative:6"
+		eerror "If that did not resolve the issue, please provide build.log"
+		eerror "on https://bugs.gentoo.org/940675"
+		die "aborting due to incomplete/broken build (see above)"
+	fi
+}