FindTclStub: Do not require the Tk and ttk stub libraries

TclStub_FOUND also required TTK_STUB_LIBRARY, but Tk puts its ttk
stubs in the Tk stub library and has no separate one, so it was
false on standard installs. It now needs only TCL_STUB_LIBRARY,
which is what the docs say it reports.

Fixes: #28134

Modules/FindTclStub.cmake

@@ -32,6 +32,9 @@ This module defines the following variables:
 
   Boolean indicating whether the Tcl Stub Library was found.
 
+  .. versionchanged:: 4.5
+    This no longer depends on the Tk and ttk stub libraries being found.
+
 Cache Variables
 ^^^^^^^^^^^^^^^
 
@@ -40,9 +43,10 @@ The following cache variables may also be set:
 ``TCL_STUB_LIBRARY``
   The path to the Tcl stub library.
 ``TK_STUB_LIBRARY``
-  The path to the Tk stub library.
+  The path to the Tk stub library, needed by extensions that use the Tk API.
 ``TTK_STUB_LIBRARY``
-  The path to the ttk stub library.
+  The path to a separate ttk stub library, if any.  Standard Tk builds put
+  the ttk stubs in the Tk stub library.
 
 Examples
 ^^^^^^^^
@@ -161,7 +165,7 @@ mark_as_advanced(
   TK_STUB_LIBRARY
   )
 
-if(TCL_STUB_LIBRARY AND TK_STUB_LIBRARY AND TTK_STUB_LIBRARY)
+if(TCL_STUB_LIBRARY)
   set(TclStub_FOUND TRUE)
 else()
   set(TclStub_FOUND FALSE)

Tests/RunCMake/CMakeLists.txt

@@ -550,6 +550,7 @@ if(CMake_TEST_FindRuby)
     )
 endif()
 add_RunCMake_test(FindOpenGL)
+add_RunCMake_test(FindTclStub)
 add_RunCMake_test(InitialFlags)
 if(CMake_TEST_FindOpenSSL)
   add_RunCMake_test(FindOpenSSL)

Tests/RunCMake/FindTclStub/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 4.0)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/FindTclStub/FindTclStubTest.cmake

@@ -0,0 +1,82 @@
+# Ignore default and hard-coded paths to avoid finding a system Tcl
+set(CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH OFF)
+set(CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH OFF)
+set(CMAKE_FIND_USE_CMAKE_SYSTEM_PATH OFF)
+set(CMAKE_FIND_FRAMEWORK NEVER)
+set(CMAKE_IGNORE_PATH
+  "C:/Tcl/lib" "C:/Program Files/Tcl/lib" "$ENV{ProgramFiles}/Tcl/Lib")
+set(CMAKE_FIND_LIBRARY_PREFIXES "")
+set(CMAKE_FIND_LIBRARY_SUFFIXES .lib)
+
+function(check_layout name)
+  cmake_parse_arguments(PARSE_ARGV 1 arg ""
+    "FOUND;TCL_STUB_LIBRARY;TK_STUB_LIBRARY;TTK_STUB_LIBRARY" "FILES")
+
+  set(prefix "${CMAKE_CURRENT_BINARY_DIR}/${name}")
+  file(REMOVE_RECURSE "${prefix}")
+  foreach(f IN LISTS arg_FILES)
+    get_filename_component(dir "${prefix}/${f}" DIRECTORY)
+    file(MAKE_DIRECTORY "${dir}")
+    file(WRITE "${prefix}/${f}" "")
+  endforeach()
+
+  set(CMAKE_PREFIX_PATH "${prefix}")
+  # Empty skips the host tclsh/wish search, and FindTclsh running tclsh
+  set(TCL_TCLSH "")
+  set(TK_WISH "")
+
+  find_package(TclStub QUIET)
+
+  if(NOT TclStub_FOUND STREQUAL arg_FOUND)
+    message(SEND_ERROR "${name}: TclStub_FOUND is '${TclStub_FOUND}'"
+      " but expected '${arg_FOUND}'")
+  endif()
+  foreach(var IN ITEMS TCL_STUB_LIBRARY TK_STUB_LIBRARY TTK_STUB_LIBRARY)
+    if(arg_${var})
+      set(expect "${prefix}/${arg_${var}}")
+    else()
+      set(expect "${var}-NOTFOUND")
+    endif()
+    if(NOT "${${var}}" STREQUAL "${expect}")
+      message(SEND_ERROR "${name}: ${var} is\n  ${${var}}\n"
+        "but expected\n  ${expect}")
+    endif()
+  endforeach()
+  foreach(var IN ITEMS TCL_STUB_LIBRARY TK_STUB_LIBRARY TTK_STUB_LIBRARY
+                       TCL_LIBRARY TK_LIBRARY TCL_INCLUDE_PATH TK_INCLUDE_PATH)
+    unset(${var} CACHE)
+  endforeach()
+endfunction()
+
+check_layout(Stub86
+  FILES include/tcl.h include/tk.h lib/tcl86t.lib lib/tk86t.lib
+        lib/tclstub86.lib lib/tkstub86.lib
+  FOUND TRUE
+  TCL_STUB_LIBRARY lib/tclstub86.lib TK_STUB_LIBRARY lib/tkstub86.lib
+  )
+
+check_layout(Stub9
+  FILES include/tcl.h include/tk.h lib/tcl90.lib lib/tcl9tk90.lib
+        lib/tclstub.lib lib/tkstub.lib
+  FOUND TRUE
+  TCL_STUB_LIBRARY lib/tclstub.lib TK_STUB_LIBRARY lib/tkstub.lib
+  )
+
+check_layout(StubTclOnly
+  FILES include/tcl.h lib/tcl86t.lib lib/tclstub86.lib
+  FOUND TRUE
+  TCL_STUB_LIBRARY lib/tclstub86.lib
+  )
+
+check_layout(StubTtk
+  FILES include/tcl.h include/tk.h lib/tcl86t.lib lib/tk86t.lib
+        lib/tclstub86.lib lib/tkstub86.lib lib/ttkstub86.lib
+  FOUND TRUE
+  TCL_STUB_LIBRARY lib/tclstub86.lib TK_STUB_LIBRARY lib/tkstub86.lib
+  TTK_STUB_LIBRARY lib/ttkstub86.lib
+  )
+
+check_layout(NoStub
+  FILES include/tcl.h include/tk.h lib/tcl86t.lib lib/tk86t.lib
+  FOUND FALSE
+  )

Tests/RunCMake/FindTclStub/RunCMakeTest.cmake

@@ -0,0 +1,3 @@
+include(RunCMake)
+
+run_cmake(FindTclStubTest)