cxx-qt-lib: ensure correct sizes for wasm 32bit

Related to #414

Author: ahayzen-kdab

crates/cxx-qt-lib/src/core/qmodelindex.cpp

@@ -15,6 +15,7 @@
 // https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.h?h=v6.2.4#n195
 assert_alignment_and_size(QModelIndex,
                           alignof(::std::size_t),
-                          sizeof(::std::size_t[3]));
+                          (sizeof(::std::int32_t) * 2) + sizeof(::std::size_t) +
+                            sizeof(::std::size_t));
 
 static_assert(::std::is_trivially_copyable<QModelIndex>::value);

crates/cxx-qt-lib/src/core/qmodelindex.rs

@@ -56,7 +56,10 @@ mod ffi {
 #[derive(Clone)]
 #[repr(C)]
 pub struct QModelIndex {
-    _space: MaybeUninit<[usize; 3]>,
+    _r: MaybeUninit<i32>,
+    _c: MaybeUninit<i32>,
+    _i: MaybeUninit<usize>,
+    _m: MaybeUninit<usize>,
 }
 
 impl Default for QModelIndex {

crates/cxx-qt-lib/src/core/qvariant/mod.rs

@@ -51,10 +51,21 @@ pub struct QVariant {
     ///
     /// Qt5 QVariant has one member, which contains three uints (but they are optimised to a size of 8) and a union
     /// Qt6 QVariant has one member, which contains three pointers and a union (pointer largest)
+    _data: MaybeUninit<usize>,
+
+    #[cfg(qt_version_major = "5")]
+    _type: MaybeUninit<u32>,
+    #[cfg(qt_version_major = "5")]
+    _is_shared: MaybeUninit<u32>,
     #[cfg(qt_version_major = "5")]
-    _space: MaybeUninit<[usize; 2]>,
+    _is_null: MaybeUninit<u32>,
+
+    #[cfg(qt_version_major = "6")]
+    _is_shared: MaybeUninit<usize>,
+    #[cfg(qt_version_major = "6")]
+    _is_null: MaybeUninit<usize>,
     #[cfg(qt_version_major = "6")]
-    _space: MaybeUninit<[usize; 4]>,
+    _packed_type: MaybeUninit<usize>,
 }
 
 impl Clone for QVariant {

crates/cxx-qt-lib/src/core/qvariant/qvariant.cpp

@@ -24,13 +24,24 @@
 // https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/kernel/qvariant.h?h=v6.2.4#n540
 // https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/kernel/qvariant.h?h=v6.2.4#n474
 #if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+
+#if (QT_POINTER_SIZE == 4)
+// 32bit is 3 * 32bit ptr (12) + union with double (8) + 4 bytes padding
+// alignment is 8 byte on 32bit systems as well due to the double
+assert_alignment_and_size(QVariant,
+                          alignof(double),
+                          (sizeof(::std::size_t) * 3) + sizeof(double) + 4);
+#else
+// 64bit is 3 * 64ptr ptr (16) + union with double (8)
 assert_alignment_and_size(QVariant,
                           alignof(::std::size_t),
-                          sizeof(::std::size_t[4]));
+                          (sizeof(::std::size_t) * 3) + sizeof(double));
+#endif
+
 #else
 assert_alignment_and_size(QVariant,
                           alignof(::std::size_t),
-                          sizeof(::std::size_t[2]));
+                          (sizeof(::std::uint32_t) * 3) + sizeof(::std::size_t)));
 #endif
 
 static_assert(!::std::is_trivially_copy_assignable<QVariant>::value);

crates/cxx-qt-lib/src/gui/qcolor.cpp

@@ -18,7 +18,9 @@
 // https://code.qt.io/cgit/qt/qtbase.git/tree/src/gui/painting/qcolor.h?h=v6.2.4#n237
 assert_alignment_and_size(QColor,
                           alignof(::std::size_t),
-                          sizeof(::std::size_t[2]));
+                          sizeof(::std::size_t) +
+                            (sizeof(::std::uint16_t) * 5) +
+                            2 /* compiler padding */);
 
 // QColor still had copy & move constructors in Qt 5 but they were basically
 // trivial.

crates/cxx-qt-lib/src/gui/qcolor.rs

@@ -58,7 +58,9 @@ mod ffi {
 #[derive(Clone)]
 #[repr(C)]
 pub struct QColor {
-    _space: MaybeUninit<[usize; 2]>,
+    _cspec: MaybeUninit<usize>,
+    _ct: MaybeUninit<[u16; 5]>,
+    _padding: MaybeUninit<u16>,
 }
 
 impl QColor {