Documentation/Nightly/Developers/Tutorials/MigrationGuide/ObsoleteCodeRemoval

Obsolete Code Removal

This section documents suggested code changes after removing support for a particular features. Each category has a short description, code snippets, a suggested upgrade path, and references to relevant commits.

Qt>=5.0.0: Remove obsolete code supporting Qt4 plugin infrastructure (C++)

These changes apply to Qt loadable modules and designer plugins

qSlicerNAMEModuleWidgetsPlugin.h

Before:

#include "vtkSlicerConfigure.h" // For Slicer_HAVE_QT5

// Qt includes
#ifdef Slicer_HAVE_QT5
#include <QtUiPlugin/QDesignerCustomWidgetCollectionInterface>
#else
#include <QDesignerCustomWidgetCollectionInterface>
#endif

[...]

class Q_SLICER_MODULE_SUBJECTHIERARCHY_WIDGETS_PLUGINS_EXPORT qSlicerSubjectHierarchyModuleWidgetsPlugin
  : public QObject
  , public QDesignerCustomWidgetCollectionInterface
{
  Q_OBJECT
#ifdef Slicer_HAVE_QT5
  Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QDesignerCustomWidgetCollectionInterface")
#endif
  Q_INTERFACES(QDesignerCustomWidgetCollectionInterface);

After:

// Qt includes
#include <QtUiPlugin/QDesignerCustomWidgetCollectionInterface>

[...]

class Q_SLICER_MODULE_SUBJECTHIERARCHY_WIDGETS_PLUGINS_EXPORT qSlicerSubjectHierarchyModuleWidgetsPlugin
  : public QObject
  , public QDesignerCustomWidgetCollectionInterface
{
  Q_OBJECT
  Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QDesignerCustomWidgetCollectionInterface")
  Q_INTERFACES(QDesignerCustomWidgetCollectionInterface);

qSlicerNAMEModule.h

Before:

class Q_SLICER_QTMODULES_SUBJECTHIERARCHY_EXPORT qSlicerSubjectHierarchyModule :
  public qSlicerLoadableModule
{
  Q_OBJECT
#ifdef Slicer_HAVE_QT5
  Q_PLUGIN_METADATA(IID "org.slicer.modules.loadable.qSlicerLoadableModule/1.0");
#endif

After:

class Q_SLICER_QTMODULES_SUBJECTHIERARCHY_EXPORT qSlicerSubjectHierarchyModule :
  public qSlicerLoadableModule
{
  Q_OBJECT
  Q_PLUGIN_METADATA(IID "org.slicer.modules.loadable.qSlicerLoadableModule/1.0");

qSlicerNAMEModuleWidgetsAbstractPlugin.h

Before:

  #include <QtGlobal>
  #if(QT_VERSION < QT_VERSION_CHECKS(5, 0, 0))
  #include <QDesignerCustomWidgetInterface>
  #else
  #include <QtUiPlugin/QDesignerCustomWidgetInterface>
  #endif

  [...]

  class Q_SLICER_MODULE_SEGMENTATIONS_WIDGETS_PLUGINS_EXPORT qSlicerSegmentationsModuleWidgetsAbstractPlugin
      : public QDesignerCustomWidgetInterface
  {
  #if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QDesignerCustomWidgetInterface")
  #endif
    Q_INTERFACES(QDesignerCustomWidgetInterface);
  }

After:

  #include <QtUiPlugin/QDesignerCustomWidgetInterface>

  [...]

  class Q_SLICER_MODULE_SEGMENTATIONS_WIDGETS_PLUGINS_EXPORT qSlicerSegmentationsModuleWidgetsAbstractPlugin
      : public QDesignerCustomWidgetInterface
  {
    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QDesignerCustomWidgetInterface")
    Q_INTERFACES(QDesignerCustomWidgetInterface);
  }

qSlicerNAMEModule.cxx and qSlicerNAMEModuleWidgetsAbstractPlugin.cxx

Remove:

 #if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
 #include <QtPlugin>
 Q_EXPORT_PLUGIN2(customwidgetplugin, qSlicerSegmentationsModuleWidgetsPlugin);
 #endif

Qt>=5.0.0: Simpler use of QHeaderView::setSectionResizeMode

This migration guide entry is obsolete: Documentation/Nightly/Developers/Tutorials/MigrationGuide#Qt5:_Fix_error:_.E2.80.98class_QHeaderView.E2.80.99_has_no_member_named_.E2.80.98setResizeMode.E2.80.99

Solution for Cpp

Before:

 #if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
   this->SceneViewTableWidget->horizontalHeader()->setResizeMode(QHeaderView::Stretch);
   this->SceneViewTableWidget->horizontalHeader()->setResizeMode(QHeaderView::ResizeToContents);
   this->SceneViewTableWidget->horizontalHeader()->setResizeMode(SCENE_VIEW_DESCRIPTION_COLUMN, QHeaderView::Stretch);
 #else
   this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch);
   this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(QHeaderView::ResizeToContents);
   this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(SCENE_VIEW_DESCRIPTION_COLUMN, QHeaderView::Stretch);
 #endif

After:

 this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch);
 this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(QHeaderView::ResizeToContents);
 this->SceneViewTableWidget->horizontalHeader()->setSectionResizeMode(SCENE_VIEW_DESCRIPTION_COLUMN, QHeaderView::Stretch);

Solution for Python

Before:

  def _setSectionResizeMode(header, *args, **kwargs):
    if version.parse(qt.Qt.qVersion()) < version.parse("5.0.0"):
      header.setResizeMode(*args, **kwargs)
    else:
      header.setSectionResizeMode(*args, **kwargs)

    [...]
   
  _setSectionResizeMode(self.horizontalHeader(), 0, qt.QHeaderView.Stretch)

After:

 self.horizontalHeader().setSectionResizeMode(0, qt.QHeaderView.Stretch)

C++11: Update source code to use nullptr

C++11 introduced the keyword nullptr allowing to explicitly identify a pointer of type std::nullptr_t. It avoids ambiguous function overloads. See also https://stackoverflow.com/questions/20509734/null-vs-nullptr-why-was-it-replaced

Prior to supporting only C++11, 0 and NULL integral type were used to check for pointer value, and macro like Q_NULLPTR and ITK_NULLPTR macros were used to ensure usage of nullptr when C++11 support was enabled.

Updating the code base to use nullptr is a 2-step process:

• use clang-tidy for updating source code being explicitly compiled in the project.
• directly update source code not being compiled: conditionally compiled code, templated headers, comments, ...

Automatic update: Using clang-tidy

This will iteratively check files for updates. It takes a while. The sources are only modified at the end of the process, so you could cancel anytime before with no consequences.

1. Compile Slicer with the CMake option -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON to generate the file compile_commands.json at configuration time.
2. Run clang-tidy on the generated compile_commands.json (in the build folder: Slicer-build)

 run-clang-tidy.py -header-filter='.*' -checks='-*,modernize-use-nullptr' -fix

clang-tidy is a tool from clang. In Archlinux: sudo pacman -S clang, in other distros might be clang-extra-tools or similar.

clang-tidy will substitute NULL and 0 for nullptr when appropiate. It is an iterative process, so it may take time. Also, it replaces all the compiled code, including external dependencies. It is recommended to do a fresh build with the modified code, for testing it without modifications in any external repo.

Direct update: Using shell script

After clang-tidy has modified the compiled code with the help of compile_commands.json, there will still be ignored instances of NULL and 0 in some headers, and comments.

Manually replace with the following regex to change those.

1) Change NULL to nullptr except when there is a quote or an underscore in front of it. And there is not a quote after.

 ack --cpp "NULL" -l --print0 | xargs -0 -n 1 sed -i 's/\([^\"\_]\)NULL\([^\"\_]\)/\1nullptr\2/g'

2) The same than before but match end of line NULL

 ack --cpp "NULL" -l --print0 | xargs -0 -n 1 sed -i 's/\([^\"\_]\)NULL$/\1nullptr/g'

Replace ITK_NULLPTR

It was adapted from the ITK script in ReplaceITK_NULLPTRMacroNames.sh

 git grep -l "ITK_NULLPTR" | fgrep -v CMakeLists.txt |fgrep -v .cmake | xargs sed -i  -e "s/ITK_NULLPTR/nullptr/g"

C++11: Update source code to use override

From: https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-override.html

Adds override (introduced in C++11) to overridden virtual functions and removes virtual from those functions as it is not required.

virtual on non base class implementations was used to help indicate to the user that a function was virtual. C++ compilers did not use the presence of this to signify an overriden function.

In C++ 11 override and final keywords were introduced to allow overridden functions to be marked appropriately. Their presence allows compilers to verify that an overridden function correctly overrides a base class implementation.

This can be useful as compilers can generate a compile time error when:

1. The base class implementation function signature changes.
2. The user has not created the override with the correct signature.

First we replace ITK_OVERRIDE and VTK_OVERRIDE for override:

Replace ITK_OVERRIDE

The regexp involving ITK were extracted from the ReplaceITK_OVERRIDEMacroNames.sh script in ITK.

 git grep -l "ITK_OVERRIDE" | fgrep -v CMakeLists.txt |fgrep -v .cmake | xargs sed -i  -e "s/ITK_OVERRIDE/override/g"

Replace VTK_OVERRIDE

 git grep -l "VTK_OVERRIDE" | fgrep -v CMakeLists.txt |fgrep -v .cmake | xargs sed -i  -e "s/VTK_OVERRIDE/override/g"