Qt4: Add module dependencies to the IMPORTED targets

This means for example, that consumers can use:

 target_link_libraries(foo ${QT_QTGUI_LIBRARIES})

instead of also needing to specify all 'public' dependencies:

 target_link_libraries(foo ${QT_QTGUI_LIBRARIES} ${QT_QTCORE_LIBRARIES} )

when using the IMPORTED targets.  Also populate the
IMPORTED_LINK_DEPENDENT_LIBRARIES property so CMake can help the linker
find shared library dependencies.

Modules/FindQt4.cmake

@@ -942,12 +942,36 @@ if (QT_QMAKE_EXECUTABLE AND QTVERSION)
   ############################################
 
 
+  macro(_qt4_add_target_depends_internal _QT_MODULE _PROPERTY)
+    if (TARGET Qt4::${_QT_MODULE})
+      foreach(_DEPEND ${ARGN})
+        if (NOT TARGET Qt4::Qt${_DEPEND})
+          message(FATAL_ERROR "_qt4_add_target_depends invoked with invalid arguments")
+        endif()
+        set_property(TARGET Qt4::${_QT_MODULE} APPEND PROPERTY
+          ${_PROPERTY}
+          "Qt4::Qt${_DEPEND}"
+        )
+      endforeach()
+    endif()
+  endmacro()
+
+  macro(_qt4_add_target_depends _QT_MODULE)
+    _qt4_add_target_depends_internal(${_QT_MODULE} IMPORTED_LINK_INTERFACE_LIBRARIES ${ARGN})
+  endmacro()
+
+  macro(_qt4_add_target_private_depends _QT_MODULE)
+    _qt4_add_target_depends_internal(${_QT_MODULE} IMPORTED_LINK_DEPENDENT_LIBRARIES ${ARGN})
+  endmacro()
+
+
   # Set QT_xyz_LIBRARY variable and add
   # library include path to QT_INCLUDES
   _QT4_ADJUST_LIB_VARS(QtCore)
 
   foreach(QT_MODULE ${QT_MODULES})
     _QT4_ADJUST_LIB_VARS(${QT_MODULE})
+    _qt4_add_target_depends(${QT_MODULE} Core)
   endforeach()
 
   _QT4_ADJUST_LIB_VARS(QtAssistant)
@@ -962,6 +986,37 @@ if (QT_QMAKE_EXECUTABLE AND QTVERSION)
     _QT4_ADJUST_LIB_VARS(QAxContainer)
   endif()
 
+  # Only public dependencies are listed here.
+  # Eg, QtDBus links to QtXml, but users of QtDBus do not need to
+  # link to QtXml because QtDBus only uses it internally, not in public
+  # headers.
+  # Everything depends on QtCore, but that is covered above already
+  _qt4_add_target_depends(Qt3Support Sql Gui Network)
+  _qt4_add_target_depends(QtDeclarative Script Gui)
+  _qt4_add_target_depends(QtDesigner Gui)
+  _qt4_add_target_depends(QtHelp Gui)
+  _qt4_add_target_depends(QtMultimedia Gui)
+  _qt4_add_target_depends(QtOpenGL Gui)
+  _qt4_add_target_depends(QtSvg Gui)
+  _qt4_add_target_depends(QtWebKit Gui Network)
+
+  _qt4_add_target_private_depends(Qt3Support Xml)
+  _qt4_add_target_private_depends(QtSvg Xml)
+  _qt4_add_target_private_depends(QtDBus Xml)
+  _qt4_add_target_private_depends(QtUiTools Xml Gui)
+  _qt4_add_target_private_depends(QtHelp Sql Xml Network)
+  _qt4_add_target_private_depends(QtXmlPatterns Network)
+  _qt4_add_target_private_depends(QtScriptTools Gui)
+  _qt4_add_target_private_depends(QtWebKit XmlPatterns)
+  _qt4_add_target_private_depends(QtDeclarative XmlPatterns Svg Sql Gui)
+  _qt4_add_target_private_depends(QtMultimedia Gui)
+  _qt4_add_target_private_depends(QtOpenGL Gui)
+  _qt4_add_target_private_depends(QAxServer Gui)
+  _qt4_add_target_private_depends(QAxContainer Gui)
+  _qt4_add_target_private_depends(phonon Gui)
+  if(QT_QTDBUS_FOUND)
+    _qt4_add_target_private_depends(phonon DBus)
+  endif()
 
   #######################################
   #

Tests/CMakeLists.txt

@@ -989,6 +989,21 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
       )
     list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/QtAutomoc")
   endif()
+  if(QT4_WORKS AND QT_QTGUI_FOUND)
+    add_test(Qt4Targets ${CMAKE_CTEST_COMMAND}
+      --build-and-test
+      "${CMake_SOURCE_DIR}/Tests/Qt4Targets"
+      "${CMake_BINARY_DIR}/Tests/Qt4Targets"
+      --build-generator ${CMAKE_TEST_GENERATOR}
+      --build-project Qt4Targets
+      --build-makeprogram ${CMAKE_TEST_MAKEPROGRAM}
+      --build-exe-dir "${CMake_BINARY_DIR}/Tests/Qt4Targets"
+      --force-new-ctest-process
+      --build-options -DQT_QMAKE_EXECUTABLE:FILEPATH=${QT_QMAKE_EXECUTABLE}
+      --test-command ${CMAKE_CTEST_COMMAND} -V
+      )
+    list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/Qt4Targets")
+  endif()
 
   add_test(ExternalProject ${CMAKE_CTEST_COMMAND}
     --build-and-test

Tests/Qt4Targets/CMakeLists.txt

@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 2.8)
+
+project(Qt4Targets)
+
+find_package(Qt4 REQUIRED)
+
+include_directories(${QT_INCLUDES})
+
+add_executable(Qt4Targets WIN32 main.cpp)
+target_link_libraries(Qt4Targets Qt4::QtGui)
+
+if (WIN32)
+  target_link_libraries(Qt4Targets Qt4::qtmain)
+endif()

Tests/Qt4Targets/main.cpp

@@ -0,0 +1,16 @@
+
+#include <QApplication>
+#include <QWidget>
+
+#include <QString>
+
+int main(int argc, char **argv)
+{
+  QApplication app(argc, argv);
+
+  QWidget w;
+  w.setWindowTitle(QString::fromLatin1("SomeTitle"));
+  w.show();
+
+  return 0;
+}