Enable UNICODE for all Qt targets and Qt consumers by default

After discussion we decided to opt-out the UNICODE definintion
behavior. To disable UNICODE in user projects the
qt6_disable_unicode_defines function could be used.

Amends 5b64e5950c

[ChangeLog][CMake] Enables the UNICODE and _UNICODE definitions on
WIN32 platforms by default for all cmake projects to reflect the
qmake behavior. Use qt6_disable_unicode_defines function to disable
the default unicode definitions.

Pick-to: 6.1
Fixes: QTBUG-93895
Change-Id: Id70ff7dcf8c74f660ec851f8b950e1e3b94d9fb4
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtFlagHandlingHelpers.cmake

@@ -256,6 +256,15 @@ function(qt_enable_utf8_sources target)
     endif()
 endfunction()
 
+function(qt_internal_enable_unicode_defines)
+    if(WIN32)
+        set(no_unicode_condition
+            "$<NOT:$<BOOL:$<TARGET_PROPERTY:QT_NO_UNICODE_DEFINES>>>")
+        target_compile_definitions(Platform
+            INTERFACE "$<${no_unicode_condition}:UNICODE;_UNICODE>")
+    endif()
+endfunction()
+
 # Saves the list of known optimization flags for the current compiler in out_var.
 #
 # Mostly used for removing them before adding new ones.

cmake/QtInternalTargets.cmake

@@ -148,14 +148,11 @@ elseif(UIKIT)
     target_compile_definitions(PlatformCommonInternal INTERFACE GLES_SILENCE_DEPRECATION)
 endif()
 
-if(WIN32)
-    target_compile_definitions(PlatformCommonInternal INTERFACE "UNICODE;_UNICODE")
-    if(MSVC)
-        target_compile_definitions(PlatformCommonInternal INTERFACE
-            "_CRT_SECURE_NO_WARNINGS"
-            "$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:_WINDLL>"
-        )
-    endif()
+if(MSVC)
+    target_compile_definitions(PlatformCommonInternal INTERFACE
+        "_CRT_SECURE_NO_WARNINGS"
+        "$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:_WINDLL>"
+    )
 endif()
 
 if(UIKIT)

cmake/QtPlatformTargetHelpers.cmake

@@ -30,4 +30,6 @@ function(qt_internal_setup_public_platform_target)
     # By default enable utf8 sources for both Qt and Qt consumers. Can be opted out.
     qt_enable_utf8_sources(Platform)
 
+    # By default enable unicode on WIN32 platforms for both Qt and Qt consumers. Can be opted out.
+    qt_internal_enable_unicode_defines(Platform)
 endfunction()

src/corelib/Qt6CoreMacros.cmake

@@ -1884,3 +1884,14 @@ properties of both types."
         )
     endforeach()
 endfunction()
+
+# Disables the default unicode definitions for the target
+function(qt6_disable_unicode_defines target)
+    set_target_properties(${target} PROPERTIES QT_NO_UNICODE_DEFINES TRUE)
+endfunction()
+
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_disable_unicode_defines)
+        qt6_disable_unicode_defines(${ARGV})
+    endfunction()
+endif()