Merge #13458: gui: Drop qt4 support

af6ac3b677454644364fd24d0df0c02ac9b8c8db doc: Remove mention of Qt4 from build docs (Wladimir J. van der Laan)
462c71f71b5d753bc8327ab833dea23679450ca3 test: Update travis to not test Qt4 anymore (Wladimir J. van der Laan)
907f73bbc5b6c98b01d7c6088a294dea66634a3f gui: Remove QT_VERSION fallbacks for Qt < 5 (Wladimir J. van der Laan)
bad068ad9f4bc60bfc10e27d4ffaec92d7df8491 build: Build system changes to support only Qt5 (Wladimir J. van der Laan)

Pull request description:

  Implements #8263.

  Qt4.x has been EOL since 2015, and at least Gentoo has, or is going to drop support for it. I wouldn't be surprised if other Linux distributions follow.

  This removes Qt4 detection from the build system, as well as removes all Qt4 fallbacks from the code. Turns out there's more than I expected: this is going to make maintenance of the GUI code, as well as adding new features significantly easier.

  (I know there's still some references left to qt4 in RPM and Debian build script, but I don't have the knowledge how to fix them)

Tree-SHA512: d495924fd4dda6f6566ba44ee96be7cbe62e69ba1ca993b80a8449f78da852b7f1bd3e8200d57cfa1d72233c340eeff4596fb0032ecbddc715d99aea63817d3f

30 files changed, 110 insertions, 344 deletions

diff --git a/.travis.yml b/.travis.yml
index 75df290187..9332160926 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,8 +35,8 @@ env:
     - HOST=i686-pc-linux-gnu PACKAGES="g++-multilib python3-zmq" DEP_OPTS="NO_QT=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --enable-glibc-back-compat --enable-reduce-exports LDFLAGS=-static-libstdc++" CONFIG_SHELL="/bin/dash"
 # x86_64 Linux (uses qt5 dev package instead of depends Qt to speed up build and avoid timeout)
     - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools protobuf-compiler libdbus-1-dev libharfbuzz-dev libprotobuf-dev" DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports CPPFLAGS=-DDEBUG_LOCKORDER"
-# Qt4 & system libs
-    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qt4-dev-tools libssl1.0-dev libevent-dev bsdmainutils libboost-system-dev libboost-filesystem-dev libboost-chrono-dev libboost-program-options-dev libboost-test-dev libboost-thread-dev libdb5.3++-dev libminiupnpc-dev libzmq3-dev libprotobuf-dev protobuf-compiler libqrencode-dev xvfb libqt4-dev" NO_DEPENDS=1 NEED_XVFB=1 RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --enable-glibc-back-compat --enable-reduce-exports --with-gui=qt4 CPPFLAGS=-DDEBUG_LOCKORDER" DISPLAY=:99.0
+# x86_64 Linux (Qt5 & system libs)
+    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools libssl1.0-dev libevent-dev bsdmainutils libboost-system-dev libboost-filesystem-dev libboost-chrono-dev libboost-program-options-dev libboost-test-dev libboost-thread-dev libdb5.3++-dev libminiupnpc-dev libzmq3-dev libprotobuf-dev protobuf-compiler libqrencode-dev" NO_DEPENDS=1 RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --enable-glibc-back-compat --enable-reduce-exports --with-gui=qt5 CPPFLAGS=-DDEBUG_LOCKORDER"
 # x86_64 Linux, No wallet
     - HOST=x86_64-unknown-linux-gnu PACKAGES="python3" DEP_OPTS="NO_WALLET=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-glibc-back-compat --enable-reduce-exports"
 # Cross-Mac
@@ -45,7 +45,7 @@ env:
 before_install:
     - export PATH=$(echo $PATH | tr ':' "\n" | sed '/\/opt\/python/d' | tr "\n" ":" | sed "s|::|:|g")
 install:
-    - env | grep -E '^(CCACHE_|WINEDEBUG|DISPLAY|BOOST_TEST_RANDOM|CONFIG_SHELL)' | tee /tmp/env
+    - env | grep -E '^(CCACHE_|WINEDEBUG|BOOST_TEST_RANDOM|CONFIG_SHELL)' | tee /tmp/env
     - if [[ $HOST = *-mingw32 ]]; then DOCKER_ADMIN="--cap-add SYS_ADMIN"; fi
     - DOCKER_ID=$(docker run $DOCKER_ADMIN -idt --mount type=bind,src=$TRAVIS_BUILD_DIR,dst=$TRAVIS_BUILD_DIR --mount type=bind,src=$CCACHE_DIR,dst=$CCACHE_DIR -w $TRAVIS_BUILD_DIR --env-file /tmp/env ubuntu:18.04)
     - DOCKER_EXEC () { docker exec $DOCKER_ID bash -c "cd $PWD && $*"; }
@@ -58,8 +58,6 @@ before_script:
     - if [ -n "$OSX_SDK" -a -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then tar -C depends/SDKs -xf depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz; fi
     - if [[ $HOST = *-mingw32 ]]; then DOCKER_EXEC update-alternatives --set $HOST-g++ \$\(which $HOST-g++-posix\); fi
     - if [ -z "$NO_DEPENDS" ]; then DOCKER_EXEC CONFIG_SHELL= make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS; fi
-    # Start xvfb if needed, as documented at https://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-a-GUI
-    - if [ "$NEED_XVFB" = 1 ]; then DOCKER_EXEC /sbin/start-stop-daemon --start --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac; fi
 script:
     - export TRAVIS_COMMIT_LOG=`git log --format=fuller -1`
     - OUTDIR=$BASE_OUTDIR/$TRAVIS_PULL_REQUEST/$TRAVIS_JOB_NUMBER-$HOST
diff --git a/build-aux/m4/bitcoin_qt.m4 b/build-aux/m4/bitcoin_qt.m4
index f41508336c..fe0cc6c36d 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -53,8 +53,8 @@ dnl CAUTION: Do not use this inside of a conditional.
 AC_DEFUN([BITCOIN_QT_INIT],[
   dnl enable qt support
   AC_ARG_WITH([gui],
-    [AS_HELP_STRING([--with-gui@<:@=no|qt4|qt5|auto@:>@],
-    [build bitcoin-qt GUI (default=auto, qt5 tried first)])],
+    [AS_HELP_STRING([--with-gui@<:@=no|qt5|auto@:>@],
+    [build bitcoin-qt GUI (default=auto)])],
     [
      bitcoin_qt_want_version=$withval
      if test "x$bitcoin_qt_want_version" = xyes; then
@@ -94,18 +94,17 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   fi
 
   if test "x$use_pkgconfig" = xyes; then
-    BITCOIN_QT_CHECK([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG([$2])])
+    BITCOIN_QT_CHECK([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG])
   else
     BITCOIN_QT_CHECK([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG])
   fi
 
   dnl This is ugly and complicated. Yuck. Works as follows:
-  dnl We can't discern whether Qt4 builds are static or not. For Qt5, we can
-  dnl check a header to find out. When Qt is built statically, some plugins must
-  dnl be linked into the final binary as well. These plugins have changed between
-  dnl Qt4 and Qt5. With Qt5, languages moved into core and the WindowsIntegration
-  dnl plugin was added. Since we can't tell if Qt4 is static or not, it is
-  dnl assumed for windows builds.
+  dnl For Qt5, we can check a header to find out whether Qt is build
+  dnl statically. When Qt is built statically, some plugins must be linked into
+  dnl the final binary as well.
+  dnl With Qt5, languages moved into core and the WindowsIntegration plugin was
+  dnl added.
   dnl _BITCOIN_QT_CHECK_STATIC_PLUGINS does a quick link-check and appends the
   dnl results to QT_LIBS.
   BITCOIN_QT_CHECK([
@@ -113,53 +112,40 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   TEMP_CXXFLAGS=$CXXFLAGS
   CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
   CXXFLAGS="$PIC_FLAGS $CXXFLAGS"
-  if test "x$bitcoin_qt_got_major_vers" = x5; then
-    _BITCOIN_QT_IS_STATIC
-    if test "x$bitcoin_cv_static_qt" = xyes; then
-      _BITCOIN_QT_FIND_STATIC_PLUGINS
-      AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol if qt plugins are static])
-      AC_CACHE_CHECK(for Qt < 5.4, bitcoin_cv_need_acc_widget,[
-        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-            #include <QtCore/qconfig.h>
-            #ifndef QT_VERSION
-            #  include <QtCore/qglobal.h>
-            #endif
-          ]],
-          [[
-            #if QT_VERSION >= 0x050400
-            choke
-            #endif
-          ]])],
-        [bitcoin_cv_need_acc_widget=yes],
-        [bitcoin_cv_need_acc_widget=no])
-      ])
-      if test "x$bitcoin_cv_need_acc_widget" = xyes; then
-        _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(AccessibleFactory)], [-lqtaccessiblewidgets])
-      fi
-      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QMinimalIntegrationPlugin)],[-lqminimal])
-      AC_DEFINE(QT_QPA_PLATFORM_MINIMAL, 1, [Define this symbol if the minimal qt platform exists])
-      if test "x$TARGET_OS" = xwindows; then
-        _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)],[-lqwindows])
-        AC_DEFINE(QT_QPA_PLATFORM_WINDOWS, 1, [Define this symbol if the qt platform is windows])
-      elif test "x$TARGET_OS" = xlinux; then
-        _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)],[-lqxcb -lxcb-static])
-        AC_DEFINE(QT_QPA_PLATFORM_XCB, 1, [Define this symbol if the qt platform is xcb])
-      elif test "x$TARGET_OS" = xdarwin; then
-        AX_CHECK_LINK_FLAG([[-framework IOKit]],[QT_LIBS="$QT_LIBS -framework IOKit"],[AC_MSG_ERROR(could not iokit framework)])
-        _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QCocoaIntegrationPlugin)],[-lqcocoa])
-        AC_DEFINE(QT_QPA_PLATFORM_COCOA, 1, [Define this symbol if the qt platform is cocoa])
-      fi
+  _BITCOIN_QT_IS_STATIC
+  if test "x$bitcoin_cv_static_qt" = xyes; then
+    _BITCOIN_QT_FIND_STATIC_PLUGINS
+    AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol if qt plugins are static])
+    AC_CACHE_CHECK(for Qt < 5.4, bitcoin_cv_need_acc_widget,[
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+          #include <QtCore/qconfig.h>
+          #ifndef QT_VERSION
+          #  include <QtCore/qglobal.h>
+          #endif
+        ]],
+        [[
+          #if QT_VERSION >= 0x050400
+          choke
+          #endif
+        ]])],
+      [bitcoin_cv_need_acc_widget=yes],
+      [bitcoin_cv_need_acc_widget=no])
+    ])
+    if test "x$bitcoin_cv_need_acc_widget" = xyes; then
+      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(AccessibleFactory)], [-lqtaccessiblewidgets])
     fi
-  else
+    _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QMinimalIntegrationPlugin)],[-lqminimal])
+    AC_DEFINE(QT_QPA_PLATFORM_MINIMAL, 1, [Define this symbol if the minimal qt platform exists])
     if test "x$TARGET_OS" = xwindows; then
-      AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol if qt plugins are static])
-      _BITCOIN_QT_CHECK_STATIC_PLUGINS([
-         Q_IMPORT_PLUGIN(qcncodecs)
-         Q_IMPORT_PLUGIN(qjpcodecs)
-         Q_IMPORT_PLUGIN(qtwcodecs)
-         Q_IMPORT_PLUGIN(qkrcodecs)
-         Q_IMPORT_PLUGIN(AccessibleFactory)],
-         [-lqcncodecs -lqjpcodecs -lqtwcodecs -lqkrcodecs -lqtaccessiblewidgets])
+      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)],[-lqwindows])
+      AC_DEFINE(QT_QPA_PLATFORM_WINDOWS, 1, [Define this symbol if the qt platform is windows])
+    elif test "x$TARGET_OS" = xlinux; then
+      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)],[-lqxcb -lxcb-static])
+      AC_DEFINE(QT_QPA_PLATFORM_XCB, 1, [Define this symbol if the qt platform is xcb])
+    elif test "x$TARGET_OS" = xdarwin; then
+      AX_CHECK_LINK_FLAG([[-framework IOKit]],[QT_LIBS="$QT_LIBS -framework IOKit"],[AC_MSG_ERROR(could not iokit framework)])
+      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QCocoaIntegrationPlugin)],[-lqcocoa])
+      AC_DEFINE(QT_QPA_PLATFORM_COCOA, 1, [Define this symbol if the qt platform is cocoa])
     fi
   fi
   CPPFLAGS=$TEMP_CPPFLAGS
@@ -167,9 +153,7 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   ])
 
   if test "x$use_pkgconfig$qt_bin_path" = xyes; then
-    if test "x$bitcoin_qt_got_major_vers" = x5; then
-      qt_bin_path="`$PKG_CONFIG --variable=host_bins Qt5Core 2>/dev/null`"
-    fi
+    qt_bin_path="`$PKG_CONFIG --variable=host_bins Qt5Core 2>/dev/null`"
   fi
 
   if test "x$use_hardening" != xno; then
@@ -219,11 +203,11 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
     ])
   fi
 
-  BITCOIN_QT_PATH_PROGS([MOC], [moc-qt${bitcoin_qt_got_major_vers} moc${bitcoin_qt_got_major_vers} moc], $qt_bin_path)
-  BITCOIN_QT_PATH_PROGS([UIC], [uic-qt${bitcoin_qt_got_major_vers} uic${bitcoin_qt_got_major_vers} uic], $qt_bin_path)
-  BITCOIN_QT_PATH_PROGS([RCC], [rcc-qt${bitcoin_qt_got_major_vers} rcc${bitcoin_qt_got_major_vers} rcc], $qt_bin_path)
-  BITCOIN_QT_PATH_PROGS([LRELEASE], [lrelease-qt${bitcoin_qt_got_major_vers} lrelease${bitcoin_qt_got_major_vers} lrelease], $qt_bin_path)
-  BITCOIN_QT_PATH_PROGS([LUPDATE], [lupdate-qt${bitcoin_qt_got_major_vers} lupdate${bitcoin_qt_got_major_vers} lupdate],$qt_bin_path, yes)
+  BITCOIN_QT_PATH_PROGS([MOC], [moc-qt5 moc5 moc], $qt_bin_path)
+  BITCOIN_QT_PATH_PROGS([UIC], [uic-qt5 uic5 uic], $qt_bin_path)
+  BITCOIN_QT_PATH_PROGS([RCC], [rcc-qt5 rcc5 rcc], $qt_bin_path)
+  BITCOIN_QT_PATH_PROGS([LRELEASE], [lrelease-qt5 lrelease5 lrelease], $qt_bin_path)
+  BITCOIN_QT_PATH_PROGS([LUPDATE], [lupdate-qt5 lupdate5 lupdate],$qt_bin_path, yes)
 
   MOC_DEFS='-DHAVE_CONFIG_H -I$(srcdir)'
   case $host in
@@ -262,7 +246,7 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   ],[
     bitcoin_enable_qt=no
   ])
-  AC_MSG_RESULT([$bitcoin_enable_qt (Qt${bitcoin_qt_got_major_vers})])
+  AC_MSG_RESULT([$bitcoin_enable_qt (Qt5)])
 
   AC_SUBST(QT_PIE_FLAGS)
   AC_SUBST(QT_INCLUDES)
@@ -272,7 +256,7 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   AC_SUBST(QT_DBUS_LIBS)
   AC_SUBST(QT_TEST_INCLUDES)
   AC_SUBST(QT_TEST_LIBS)
-  AC_SUBST(QT_SELECT, qt${bitcoin_qt_got_major_vers})
+  AC_SUBST(QT_SELECT, qt5)
   AC_SUBST(MOC_DEFS)
 ])
 
@@ -301,7 +285,7 @@ AC_DEFUN([_BITCOIN_QT_CHECK_QT5],[
 ])])
 
 dnl Internal. Check if the linked version of Qt was built as static libs.
-dnl Requires: Qt5. This check cannot determine if Qt4 is static.
+dnl Requires: Qt5.
 dnl Requires: INCLUDES and LIBS must be populated as necessary.
 dnl Output: bitcoin_cv_static_qt=yes|no
 dnl Output: Defines QT_STATICPLUGIN if plugins are static.
@@ -346,58 +330,50 @@ AC_DEFUN([_BITCOIN_QT_CHECK_STATIC_PLUGINS],[
 ])
 
 dnl Internal. Find paths necessary for linking qt static plugins
-dnl Inputs: bitcoin_qt_got_major_vers. 4 or 5.
 dnl Inputs: qt_plugin_path. optional.
 dnl Outputs: QT_LIBS is appended
 AC_DEFUN([_BITCOIN_QT_FIND_STATIC_PLUGINS],[
-  if test "x$bitcoin_qt_got_major_vers" = x5; then
-      if test "x$qt_plugin_path" != x; then
-        QT_LIBS="$QT_LIBS -L$qt_plugin_path/platforms"
-        if test -d "$qt_plugin_path/accessible"; then
-          QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
-        fi
+    if test "x$qt_plugin_path" != x; then
+      QT_LIBS="$QT_LIBS -L$qt_plugin_path/platforms"
+      if test -d "$qt_plugin_path/accessible"; then
+        QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
       fi
-     if test "x$use_pkgconfig" = xyes; then
-     : dnl
-     m4_ifdef([PKG_CHECK_MODULES],[
-       PKG_CHECK_MODULES([QTPLATFORM], [Qt5PlatformSupport], [QT_LIBS="$QTPLATFORM_LIBS $QT_LIBS"])
-       if test "x$TARGET_OS" = xlinux; then
-         PKG_CHECK_MODULES([X11XCB], [x11-xcb], [QT_LIBS="$X11XCB_LIBS $QT_LIBS"])
-         if ${PKG_CONFIG} --exists "Qt5Core >= 5.5" 2>/dev/null; then
-           PKG_CHECK_MODULES([QTXCBQPA], [Qt5XcbQpa], [QT_LIBS="$QTXCBQPA_LIBS $QT_LIBS"])
-         fi
-       elif test "x$TARGET_OS" = xdarwin; then
-         PKG_CHECK_MODULES([QTPRINT], [Qt5PrintSupport], [QT_LIBS="$QTPRINT_LIBS $QT_LIBS"])
+    fi
+   if test "x$use_pkgconfig" = xyes; then
+   : dnl
+   m4_ifdef([PKG_CHECK_MODULES],[
+     PKG_CHECK_MODULES([QTPLATFORM], [Qt5PlatformSupport], [QT_LIBS="$QTPLATFORM_LIBS $QT_LIBS"])
+     if test "x$TARGET_OS" = xlinux; then
+       PKG_CHECK_MODULES([X11XCB], [x11-xcb], [QT_LIBS="$X11XCB_LIBS $QT_LIBS"])
+       if ${PKG_CONFIG} --exists "Qt5Core >= 5.5" 2>/dev/null; then
+         PKG_CHECK_MODULES([QTXCBQPA], [Qt5XcbQpa], [QT_LIBS="$QTXCBQPA_LIBS $QT_LIBS"])
        fi
-     ])
-     else
-       if test "x$TARGET_OS" = xwindows; then
-         AC_CACHE_CHECK(for Qt >= 5.6, bitcoin_cv_need_platformsupport,[
-           AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-               #include <QtCore/qconfig.h>
-               #ifndef QT_VERSION
-               #  include <QtCore/qglobal.h>
-               #endif
-             ]],
-             [[
-               #if QT_VERSION < 0x050600
-               choke
-               #endif
-             ]])],
-           [bitcoin_cv_need_platformsupport=yes],
-           [bitcoin_cv_need_platformsupport=no])
-         ])
-         if test "x$bitcoin_cv_need_platformsupport" = xyes; then
-           BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}PlatformSupport],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}PlatformSupport not found)))
-         fi
+     elif test "x$TARGET_OS" = xdarwin; then
+       PKG_CHECK_MODULES([QTPRINT], [Qt5PrintSupport], [QT_LIBS="$QTPRINT_LIBS $QT_LIBS"])
+     fi
+   ])
+   else
+     if test "x$TARGET_OS" = xwindows; then
+       AC_CACHE_CHECK(for Qt >= 5.6, bitcoin_cv_need_platformsupport,[
+         AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+             #include <QtCore/qconfig.h>
+             #ifndef QT_VERSION
+             #  include <QtCore/qglobal.h>
+             #endif
+           ]],
+           [[
+             #if QT_VERSION < 0x050600
+             choke
+             #endif
+           ]])],
+         [bitcoin_cv_need_platformsupport=yes],
+         [bitcoin_cv_need_platformsupport=no])
+       ])
+       if test "x$bitcoin_cv_need_platformsupport" = xyes; then
+         BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}PlatformSupport],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}PlatformSupport not found)))
        fi
      fi
-  else
-    if test "x$qt_plugin_path" != x; then
-      QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
-      QT_LIBS="$QT_LIBS -L$qt_plugin_path/codecs"
-    fi
-  fi
+   fi
 ])
 
 dnl Internal. Find Qt libraries using pkg-config.
@@ -406,38 +382,14 @@ dnl         first.
 dnl Inputs: $1: If bitcoin_qt_want_version is "auto", check for this version
 dnl         first.
 dnl Outputs: All necessary QT_* variables are set.
-dnl Outputs: bitcoin_qt_got_major_vers is set to "4" or "5".
 dnl Outputs: have_qt_test and have_qt_dbus are set (if applicable) to yes|no.
 AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
   m4_ifdef([PKG_CHECK_MODULES],[
-  auto_priority_version=$1
-  if test "x$auto_priority_version" = x; then
-    auto_priority_version=qt5
-  fi
-    if test "x$bitcoin_qt_want_version" = xqt5 ||  ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt5 ); then
-      QT_LIB_PREFIX=Qt5
-      bitcoin_qt_got_major_vers=5
-    else
-      QT_LIB_PREFIX=Qt
-      bitcoin_qt_got_major_vers=4
-    fi
+    QT_LIB_PREFIX=Qt5
     qt5_modules="Qt5Core Qt5Gui Qt5Network Qt5Widgets"
-    qt4_modules="QtCore QtGui QtNetwork"
     BITCOIN_QT_CHECK([
-      if test "x$bitcoin_qt_want_version" = xqt5 || ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt5 ); then
-        PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" have_qt=yes],[have_qt=no])
-      elif test "x$bitcoin_qt_want_version" = xqt4 || ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt4 ); then
-        PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes], [have_qt=no])
-      fi
+      PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" have_qt=yes],[have_qt=no])
 
-      dnl qt version is set to 'auto' and the preferred version wasn't found. Now try the other.
-      if test "x$have_qt" = xno && test "x$bitcoin_qt_want_version" = xauto; then
-        if test "x$auto_priority_version" = xqt5; then
-          PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt; bitcoin_qt_got_major_vers=4], [have_qt=no])
-        else
-          PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt5; bitcoin_qt_got_major_vers=5], [have_qt=no])
-        fi
-      fi
       if test "x$have_qt" != xyes; then
         have_qt=no
         BITCOIN_QT_FAIL([Qt dependencies not found])
@@ -458,7 +410,6 @@ dnl from the discovered headers.
 dnl Inputs: bitcoin_qt_want_version (from --with-gui=). The version to use.
 dnl         If "auto", the version will be discovered by _BITCOIN_QT_CHECK_QT5.
 dnl Outputs: All necessary QT_* variables are set.
-dnl Outputs: bitcoin_qt_got_major_vers is set to "4" or "5".
 dnl Outputs: have_qt_test and have_qt_dbus are set (if applicable) to yes|no.
 AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   TEMP_CPPFLAGS="$CPPFLAGS"
@@ -480,13 +431,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
     if test "x$bitcoin_qt_want_version" = xauto; then
       _BITCOIN_QT_CHECK_QT5
     fi
-    if test "x$bitcoin_cv_qt5" = xyes || test "x$bitcoin_qt_want_version" = xqt5; then
-      QT_LIB_PREFIX=Qt5
-      bitcoin_qt_got_major_vers=5
-    else
-      QT_LIB_PREFIX=Qt
-      bitcoin_qt_got_major_vers=4
-    fi
+    QT_LIB_PREFIX=Qt5
   ])
 
   BITCOIN_QT_CHECK([
@@ -508,9 +453,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Core]   ,[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Core not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Gui]    ,[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Gui not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Network],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Network not found)))
-  if test "x$bitcoin_qt_got_major_vers" = x5; then
-    BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Widgets],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Widgets not found)))
-  fi
+  BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Widgets],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Widgets not found)))
   QT_LIBS="$LIBS"
   LIBS="$TEMP_LIBS"
 
diff --git a/configure.ac b/configure.ac
index 926d0b8d00..027e429140 100644
--- a/configure.ac
+++ b/configure.ac
@@ -837,7 +837,7 @@ fi
 BITCOIN_QT_INIT
 
 dnl sets $bitcoin_enable_qt, $bitcoin_enable_qt_test, $bitcoin_enable_qt_dbus
-BITCOIN_QT_CONFIGURE([$use_pkgconfig], [qt5])
+BITCOIN_QT_CONFIGURE([$use_pkgconfig])
 
 if test x$build_bitcoin_utils$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench = xnonononono; then
     use_boost=no
@@ -1422,7 +1422,6 @@ echo "Options used to compile and link:"
 echo "  with wallet   = $enable_wallet"
 echo "  with gui / qt = $bitcoin_enable_qt"
 if test x$bitcoin_enable_qt != xno; then
-    echo "    qt version  = $bitcoin_qt_got_major_vers"
     echo "    with qr     = $use_qr"
 fi
 echo "  with zmq      = $use_zmq"
diff --git a/doc/build-osx.md b/doc/build-osx.md
index abd305cf9a..a07dbd1e1d 100644
--- a/doc/build-osx.md
+++ b/doc/build-osx.md
@@ -24,8 +24,6 @@ If you want to build the disk image with `make deploy` (.dmg / optional), you ne
 
     brew install librsvg
 
-NOTE: Building with Qt4 is still supported, however, could result in a broken UI. Building with Qt5 is recommended.
-
 Berkeley DB
 -----------
 It is recommended to use Berkeley DB 4.8. If you have to build it yourself,
diff --git a/doc/build-unix.md b/doc/build-unix.md
index 1ab5659511..e884c0ab67 100644
--- a/doc/build-unix.md
+++ b/doc/build-unix.md
@@ -100,18 +100,13 @@ ZMQ dependencies (provides ZMQ API 4.x):
 #### Dependencies for the GUI
 
 If you want to build Bitcoin-Qt, make sure that the required packages for Qt development
-are installed. Either Qt 5 or Qt 4 are necessary to build the GUI.
-If both Qt 4 and Qt 5 are installed, Qt 5 will be used. Pass `--with-gui=qt4` to configure to choose Qt4.
+are installed. Qt 5 is necessary to build the GUI.
 To build without GUI pass `--without-gui`.
 
-To build with Qt 5 (recommended) you need the following:
+To build with Qt 5 you need the following:
 
     sudo apt-get install libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools libprotobuf-dev protobuf-compiler
 
-Alternatively, to build with Qt 4 you need the following:
-
-    sudo apt-get install libqt4-dev libprotobuf-dev protobuf-compiler
-
 libqrencode (optional) can be installed with:
 
     sudo apt-get install libqrencode-dev
@@ -132,7 +127,7 @@ Optional:
 
     sudo dnf install miniupnpc-devel
 
-To build with Qt 5 (recommended) you need the following:
+To build with Qt 5 you need the following:
 
     sudo dnf install qt5-qttools-devel qt5-qtbase-devel protobuf-devel
 
diff --git a/doc/dependencies.md b/doc/dependencies.md
index 7aa96c4c9b..793c659419 100644
--- a/doc/dependencies.md
+++ b/doc/dependencies.md
@@ -23,7 +23,7 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | protobuf | [2.6.3](https://github.com/google/protobuf/releases) |  | No |  |  |
 | Python (tests) |  | [3.4](https://www.python.org/downloads) |  |  |  |
 | qrencode | [3.4.4](https://fukuchi.org/works/qrencode) |  | No |  |  |
-| Qt | [5.7.1](https://download.qt.io/official_releases/qt/) | 4.7+ | No |  |  |
+| Qt | [5.7.1](https://download.qt.io/official_releases/qt/) | 5.x | No |  |  |
 | XCB |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L94) (Linux only) |
 | xkbcommon |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L93) (Linux only) |
 | ZeroMQ | [4.2.3](https://github.com/zeromq/libzmq/releases) |  | No |  |  |
diff --git a/src/qt/README.md b/src/qt/README.md
index bf8139666c..3ec538b4f4 100644
--- a/src/qt/README.md
+++ b/src/qt/README.md
@@ -1,6 +1,6 @@
 This directory contains the BitcoinQT graphical user interface (GUI). It uses the cross-platform framework [Qt](https://www1.qt.io/developers/).
 
-The current precise version for Qt 5 is specified in [qt.mk](/depends/packages/qt.mk). Qt 4 is also supported (see [#8263](https://github.com/bitcoin/bitcoin/issues/8263)).
+The current precise version for Qt 5 is specified in [qt.mk](/depends/packages/qt.mk).
 
 ## Compile and run
 
@@ -16,7 +16,7 @@ To run:
 
 ### forms
 
-Contains [Designer UI](http://doc.qt.io/qt-5.9/designer-using-a-ui-file.html) files. They are created with [Qt Creator](#using-qt-creator-as-ide), but can be edited using any text editor.
+Contains [Designer UI](https://doc.qt.io/qt-5.9/designer-using-a-ui-file.html) files. They are created with [Qt Creator](#using-qt-creator-as-ide), but can be edited using any text editor.
 
 ### locale
 
@@ -36,7 +36,7 @@ Represents the main window of the Bitcoin UI.
 
 ### \*model.(h/cpp)
 
-The model. When it has a corresponding controller, it generally inherits from  [QAbstractTableModel](http://doc.qt.io/qt-5/qabstracttablemodel.html). Models that are used by controllers as helpers inherit from other Qt classes like [QValidator](http://doc.qt.io/qt-5/qvalidator.html).
+The model. When it has a corresponding controller, it generally inherits from  [QAbstractTableModel](https://doc.qt.io/qt-5/qabstracttablemodel.html). Models that are used by controllers as helpers inherit from other Qt classes like [QValidator](https://doc.qt.io/qt-5/qvalidator.html).
 
 ClientModel is used by the main application `bitcoingui` and several models like `peertablemodel`.
 
@@ -46,7 +46,7 @@ A controller. `:NAMEpage.cpp` generally includes `:NAMEmodel.h` and `forms/:NAME
 
 ### \*dialog.(h/cpp)
 
-Various dialogs, e.g. to open a URL. Inherit from [QDialog](http://doc.qt.io/qt-4.8/qdialog.html).
+Various dialogs, e.g. to open a URL. Inherit from [QDialog](https://doc.qt.io/qt-5/qdialog.html).
 
 ### paymentserver.(h/cpp)
 
diff --git a/src/qt/addressbookpage.cpp b/src/qt/addressbookpage.cpp
index f2ddbf259b..d51069d922 100644
--- a/src/qt/addressbookpage.cpp
+++ b/src/qt/addressbookpage.cpp
@@ -160,13 +160,8 @@ void AddressBookPage::setModel(AddressTableModel *_model)
     ui->tableView->sortByColumn(0, Qt::AscendingOrder);
 
     // Set column widths
-#if QT_VERSION < 0x050000
-    ui->tableView->horizontalHeader()->setResizeMode(AddressTableModel::Label, QHeaderView::Stretch);
-    ui->tableView->horizontalHeader()->setResizeMode(AddressTableModel::Address, QHeaderView::ResizeToContents);
-#else
     ui->tableView->horizontalHeader()->setSectionResizeMode(AddressTableModel::Label, QHeaderView::Stretch);
     ui->tableView->horizontalHeader()->setSectionResizeMode(AddressTableModel::Address, QHeaderView::ResizeToContents);
-#endif
 
     connect(ui->tableView->selectionModel(), SIGNAL(selectionChanged(QItemSelection,QItemSelection)),
         this, SLOT(selectionChanged()));
diff --git a/src/qt/bantablemodel.cpp b/src/qt/bantablemodel.cpp
index 26cb03c2c7..aa0d4a31d3 100644
--- a/src/qt/bantablemodel.cpp
+++ b/src/qt/bantablemodel.cpp
@@ -52,9 +52,7 @@ public:
         node.getBanned(banMap);
 
         cachedBanlist.clear();
-#if QT_VERSION >= 0x040700
         cachedBanlist.reserve(banMap.size());
-#endif
         for (const auto& entry : banMap)
         {
             CCombinedBan banEntry;
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index 6ddc819113..e3d1c746b1 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -55,13 +55,6 @@
 
 #if defined(QT_STATICPLUGIN)
 #include <QtPlugin>
-#if QT_VERSION < 0x050000
-Q_IMPORT_PLUGIN(qcncodecs)
-Q_IMPORT_PLUGIN(qjpcodecs)
-Q_IMPORT_PLUGIN(qtwcodecs)
-Q_IMPORT_PLUGIN(qkrcodecs)
-Q_IMPORT_PLUGIN(qtaccessiblewidgets)
-#else
 #if QT_VERSION < 0x050400
 Q_IMPORT_PLUGIN(AccessibleFactory)
 #endif
@@ -73,11 +66,6 @@ Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin);
 Q_IMPORT_PLUGIN(QCocoaIntegrationPlugin);
 #endif
 #endif
-#endif
-
-#if QT_VERSION < 0x050000
-#include <QTextCodec>
-#endif
 
 // Declare meta types used for QMetaObject::invokeMethod
 Q_DECLARE_METATYPE(bool*)
@@ -151,16 +139,6 @@ static void initTranslations(QTranslator &qtTranslatorBase, QTranslator &qtTrans
 }
 
 /* qDebug() message handler --> debug.log */
-#if QT_VERSION < 0x050000
-void DebugMessageHandler(QtMsgType type, const char *msg)
-{
-    if (type == QtDebugMsg) {
-        LogPrint(BCLog::QT, "GUI: %s\n", msg);
-    } else {
-        LogPrintf("GUI: %s\n", msg);
-    }
-}
-#else
 void DebugMessageHandler(QtMsgType type, const QMessageLogContext& context, const QString &msg)
 {
     Q_UNUSED(context);
@@ -170,7 +148,6 @@ void DebugMessageHandler(QtMsgType type, const QMessageLogContext& context, cons
         LogPrintf("GUI: %s\n", msg.toStdString());
     }
 }
-#endif
 
 /** Class encapsulating Bitcoin Core startup and shutdown.
  * Allows running startup and shutdown in a different thread from the UI thread.
@@ -586,12 +563,6 @@ int main(int argc, char *argv[])
     // Do not refer to data directory yet, this can be overridden by Intro::pickDataDirectory
 
     /// 1. Basic Qt initialization (not dependent on parameters or configuration)
-#if QT_VERSION < 0x050000
-    // Internal string conversion is all UTF-8
-    QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
-    QTextCodec::setCodecForCStrings(QTextCodec::codecForTr());
-#endif
-
     Q_INIT_RESOURCE(bitcoin);
     Q_INIT_RESOURCE(bitcoin_locale);
 
@@ -722,17 +693,12 @@ int main(int argc, char *argv[])
     /// 9. Main GUI initialization
     // Install global event filter that makes sure that long tooltips can be word-wrapped
     app.installEventFilter(new GUIUtil::ToolTipToRichTextFilter(TOOLTIP_WRAP_THRESHOLD, &app));
-#if QT_VERSION < 0x050000
-    // Install qDebug() message handler to route to debug.log
-    qInstallMsgHandler(DebugMessageHandler);
-#else
 #if defined(Q_OS_WIN)
     // Install global event filter for processing Windows session related Windows messages (WM_QUERYENDSESSION and WM_ENDSESSION)
     qApp->installNativeEventFilter(new WinShutdownMonitor());
 #endif
     // Install qDebug() message handler to route to debug.log
     qInstallMessageHandler(DebugMessageHandler);
-#endif
     // Allow parameter interaction before we create the options model
     app.parameterSetup();
     // Load GUI settings from QSettings
@@ -753,7 +719,7 @@ int main(int argc, char *argv[])
         // so the GUI thread won't be held up.
         if (node->baseInitialize()) {
             app.requestInitialize();
-#if defined(Q_OS_WIN) && QT_VERSION >= 0x050000
+#if defined(Q_OS_WIN)
             WinShutdownMonitor::registerShutdownBlockReason(QObject::tr("%1 didn't yet exit safely...").arg(QObject::tr(PACKAGE_NAME)), (HWND)app.getMainWinId());
 #endif
             app.exec();
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index c6cc631201..b3c8f57deb 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -55,14 +55,8 @@
 #include <QStyle>
 #include <QTimer>
 #include <QToolBar>
-#include <QVBoxLayout>
-
-#if QT_VERSION < 0x050000
-#include <QTextDocument>
-#include <QUrl>
-#else
 #include <QUrlQuery>
-#endif
+#include <QVBoxLayout>
 
 const std::string BitcoinGUI::DEFAULT_UIPLATFORM =
 #if defined(Q_OS_MAC)
@@ -148,12 +142,6 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
 #endif
     setWindowTitle(windowTitle);
 
-#if defined(Q_OS_MAC) && QT_VERSION < 0x050000
-    // This property is not implemented in Qt 5. Setting it has no effect.
-    // A replacement API (QtMacUnifiedToolBar) is available in QtMacExtras.
-    setUnifiedTitleAndToolBarOnMac(true);
-#endif
-
     rpcConsole = new RPCConsole(node, _platformStyle, 0);
     helpMessageDialog = new HelpMessageDialog(node, this, false);
 #ifdef ENABLE_WALLET
@@ -230,7 +218,7 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
 
     // Override style sheet for progress bar for styles that have a segmented progress bar,
     // as they make the text unreadable (workaround for issue #1071)
-    // See https://qt-project.org/doc/qt-4.8/gallery.html
+    // See https://doc.qt.io/qt-5/gallery.html
     QString curStyle = QApplication::style()->metaObject()->className();
     if(curStyle == "QWindowsStyle" || curStyle == "QWindowsXPStyle")
     {
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index b08de27041..222ed6f65f 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -109,11 +109,7 @@ CoinControlDialog::CoinControlDialog(const PlatformStyle *_platformStyle, QWidge
     connect(ui->treeWidget, SIGNAL(itemChanged(QTreeWidgetItem*, int)), this, SLOT(viewItemChanged(QTreeWidgetItem*, int)));
 
     // click on header
-#if QT_VERSION < 0x050000
-    ui->treeWidget->header()->setClickable(true);
-#else
     ui->treeWidget->header()->setSectionsClickable(true);
-#endif
     connect(ui->treeWidget->header(), SIGNAL(sectionClicked(int)), this, SLOT(headerSectionClicked(int)));
 
     // ok button
@@ -392,13 +388,11 @@ void CoinControlDialog::viewItemChanged(QTreeWidgetItem* item, int column)
 
     // TODO: Remove this temporary qt5 fix after Qt5.3 and Qt5.4 are no longer used.
     //       Fixed in Qt5.5 and above: https://bugreports.qt.io/browse/QTBUG-43473
-#if QT_VERSION >= 0x050000
     else if (column == COLUMN_CHECKBOX && item->childCount() > 0)
     {
         if (item->checkState(COLUMN_CHECKBOX) == Qt::PartiallyChecked && item->child(0)->checkState(COLUMN_CHECKBOX) == Qt::PartiallyChecked)
             item->setCheckState(COLUMN_CHECKBOX, Qt::Checked);
     }
-#endif
 }
 
 // shows count of locked unspent outputs
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index 563f930dec..acd9f7b35c 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -53,13 +53,9 @@
 #include <QSettings>
 #include <QTextDocument> // for Qt::mightBeRichText
 #include <QThread>
+#include <QUrlQuery>
 #include <QMouseEvent>
 
-#if QT_VERSION < 0x050000
-#include <QUrl>
-#else
-#include <QUrlQuery>
-#endif
 
 #if QT_VERSION >= 0x50200
 #include <QFontDatabase>
@@ -95,11 +91,7 @@ QFont fixedPitchFont()
     return QFontDatabase::systemFont(QFontDatabase::FixedFont);
 #else
     QFont font("Monospace");
-#if QT_VERSION >= 0x040800
     font.setStyleHint(QFont::Monospace);
-#else
-    font.setStyleHint(QFont::TypeWriter);
-#endif
     return font;
 #endif
 }
@@ -127,12 +119,10 @@ void setupAddressWidget(QValidatedLineEdit *widget, QWidget *parent)
     parent->setFocusProxy(widget);
 
     widget->setFont(fixedPitchFont());
-#if QT_VERSION >= 0x040700
     // We don't want translators to use own addresses in translations
     // and this is the only place, where this address is supplied.
     widget->setPlaceholderText(QObject::tr("Enter a Bitcoin address (e.g. %1)").arg(
         QString::fromStdString(DummyAddress(Params()))));
-#endif
     widget->setValidator(new BitcoinAddressEntryValidator(parent));
     widget->setCheckValidator(new BitcoinAddressCheckValidator(parent));
 }
@@ -151,12 +141,8 @@ bool parseBitcoinURI(const QUrl &uri, SendCoinsRecipient *out)
     }
     rv.amount = 0;
 
-#if QT_VERSION < 0x050000
-    QList<QPair<QString, QString> > items = uri.queryItems();
-#else
     QUrlQuery uriQuery(uri);
     QList<QPair<QString, QString> > items = uriQuery.queryItems();
-#endif
     for (QList<QPair<QString, QString> >::iterator i = items.begin(); i != items.end(); i++)
     {
         bool fShouldReturnFalse = false;
@@ -242,11 +228,7 @@ bool isDust(interfaces::Node& node, const QString& address, const CAmount& amoun
 
 QString HtmlEscape(const QString& str, bool fMultiLine)
 {
-#if QT_VERSION < 0x050000
-    QString escaped = Qt::escape(str);
-#else
     QString escaped = str.toHtmlEscaped();
-#endif
     if(fMultiLine)
     {
         escaped = escaped.replace("\n", "<br>\n");
@@ -287,11 +269,7 @@ QString getSaveFileName(QWidget *parent, const QString &caption, const QString &
     QString myDir;
     if(dir.isEmpty()) // Default to user documents location
     {
-#if QT_VERSION < 0x050000
-        myDir = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
-#else
         myDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
-#endif
     }
     else
     {
@@ -337,11 +315,7 @@ QString getOpenFileName(QWidget *parent, const QString &caption, const QString &
     QString myDir;
     if(dir.isEmpty()) // Default to user documents location
     {
-#if QT_VERSION < 0x050000
-        myDir = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
-#else
         myDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
-#endif
     }
     else
     {
@@ -495,11 +469,7 @@ void TableViewLastColumnResizingFixer::disconnectViewHeadersSignals()
 // Refactored here for readability.
 void TableViewLastColumnResizingFixer::setViewHeaderResizeMode(int logicalIndex, QHeaderView::ResizeMode resizeMode)
 {
-#if QT_VERSION < 0x050000
-    tableView->horizontalHeader()->setResizeMode(logicalIndex, resizeMode);
-#else
     tableView->horizontalHeader()->setSectionResizeMode(logicalIndex, resizeMode);
-#endif
 }
 
 void TableViewLastColumnResizingFixer::resizeColumn(int nColumnIndex, int width)
diff --git a/src/qt/guiutil.h b/src/qt/guiutil.h
index 4a26964098..e965a91d18 100644
--- a/src/qt/guiutil.h
+++ b/src/qt/guiutil.h
@@ -233,7 +233,7 @@ namespace GUIUtil
         void mouseReleaseEvent(QMouseEvent *event);
     };
 
-#if defined(Q_OS_MAC) && QT_VERSION >= 0x050000
+#if defined(Q_OS_MAC)
     // workaround for Qt OSX Bug:
     // https://bugreports.qt-project.org/browse/QTBUG-15631
     // QProgressBar uses around 10% CPU even when app is in background
diff --git a/src/qt/macdockiconhandler.mm b/src/qt/macdockiconhandler.mm
index 9e7de0f98f..a0b62ae000 100644
--- a/src/qt/macdockiconhandler.mm
+++ b/src/qt/macdockiconhandler.mm
@@ -14,10 +14,6 @@
 #include <objc/objc.h>
 #include <objc/message.h>
 
-#if QT_VERSION < 0x050000
-extern void qt_mac_set_dock_menu(QMenu *);
-#endif
-
 static MacDockIconHandler *s_instance = nullptr;
 
 bool dockClickHandler(id self,SEL _cmd,...) {
@@ -54,9 +50,7 @@ MacDockIconHandler::MacDockIconHandler() : QObject()
     this->m_dummyWidget = new QWidget();
     this->m_dockMenu = new QMenu(this->m_dummyWidget);
     this->setMainWindow(nullptr);
-#if QT_VERSION < 0x050000
-    qt_mac_set_dock_menu(this->m_dockMenu);
-#elif QT_VERSION >= 0x050200
+#if QT_VERSION >= 0x050200
     this->m_dockMenu->setAsDockMenu();
 #endif
     [pool release];
diff --git a/src/qt/networkstyle.cpp b/src/qt/networkstyle.cpp
index 2816633b0f..c4b732e3e0 100644
--- a/src/qt/networkstyle.cpp
+++ b/src/qt/networkstyle.cpp
@@ -68,11 +68,7 @@ NetworkStyle::NetworkStyle(const QString &_appName, const int iconColorHueShift,
         }
 
         //convert back to QPixmap
-#if QT_VERSION >= 0x040700
         pixmap.convertFromImage(img);
-#else
-        pixmap = QPixmap::fromImage(img);
-#endif
     }
 
     appIcon             = QIcon(pixmap);
diff --git a/src/qt/openuridialog.cpp b/src/qt/openuridialog.cpp
index 751cfa8b43..d211f908c8 100644
--- a/src/qt/openuridialog.cpp
+++ b/src/qt/openuridialog.cpp
@@ -15,9 +15,7 @@ OpenURIDialog::OpenURIDialog(QWidget *parent) :
     ui(new Ui::OpenURIDialog)
 {
     ui->setupUi(this);
-#if QT_VERSION >= 0x040700
     ui->uriEdit->setPlaceholderText("bitcoin:");
-#endif
 }
 
 OpenURIDialog::~OpenURIDialog()
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index 108aa4f99c..3ff6f59c25 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -97,28 +97,16 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
         /** check if the locale name consists of 2 parts (language_country) */
         if(langStr.contains("_"))
         {
-#if QT_VERSION >= 0x040800
             /** display language strings as "native language - native country (locale name)", e.g. "Deutsch - Deutschland (de)" */
             ui->lang->addItem(locale.nativeLanguageName() + QString(" - ") + locale.nativeCountryName() + QString(" (") + langStr + QString(")"), QVariant(langStr));
-#else
-            /** display language strings as "language - country (locale name)", e.g. "German - Germany (de)" */
-            ui->lang->addItem(QLocale::languageToString(locale.language()) + QString(" - ") + QLocale::countryToString(locale.country()) + QString(" (") + langStr + QString(")"), QVariant(langStr));
-#endif
         }
         else
         {
-#if QT_VERSION >= 0x040800
             /** display language strings as "native language (locale name)", e.g. "Deutsch (de)" */
             ui->lang->addItem(locale.nativeLanguageName() + QString(" (") + langStr + QString(")"), QVariant(langStr));
-#else
-            /** display language strings as "language (locale name)", e.g. "German (de)" */
-            ui->lang->addItem(QLocale::languageToString(locale.language()) + QString(" (") + langStr + QString(")"), QVariant(langStr));
-#endif
         }
     }
-#if QT_VERSION >= 0x040700
     ui->thirdPartyTxUrls->setPlaceholderText("https://example.com/tx/%s");
-#endif
 
     ui->unit->setModel(new BitcoinUnits(this));
 
diff --git a/src/qt/paymentrequestplus.cpp b/src/qt/paymentrequestplus.cpp
index b0ef475b35..dfeb70d669 100644
--- a/src/qt/paymentrequestplus.cpp
+++ b/src/qt/paymentrequestplus.cpp
@@ -97,12 +97,10 @@ bool PaymentRequestPlus::getMerchant(X509_STORE* certStore, QString& merchant) c
             qWarning() << "PaymentRequestPlus::getMerchant: Payment request: certificate expired or not yet active: " << qCert;
             return false;
         }
-#if QT_VERSION >= 0x050000
         if (qCert.isBlacklisted()) {
             qWarning() << "PaymentRequestPlus::getMerchant: Payment request: certificate blacklisted: " << qCert;
             return false;
         }
-#endif
         const unsigned char *data = (const unsigned char *)certChain.certificate(i).data();
         X509 *cert = d2i_X509(nullptr, &data, certChain.certificate(i).size());
         if (cert)
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 59bb5d5bb6..e5e6430959 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -41,12 +41,7 @@
 #include <QSslSocket>
 #include <QStringList>
 #include <QTextDocument>
-
-#if QT_VERSION < 0x050000
-#include <QUrl>
-#else
 #include <QUrlQuery>
-#endif
 
 const int BITCOIN_IPC_CONNECT_TIMEOUT = 1000; // milliseconds
 const QString BITCOIN_IPC_PREFIX("bitcoin:");
@@ -100,11 +95,7 @@ static QList<QString> savedPaymentRequests;
 
 static void ReportInvalidCertificate(const QSslCertificate& cert)
 {
-#if QT_VERSION < 0x050000
-    qDebug() << QString("%1: Payment server found an invalid certificate: ").arg(__func__) << cert.serialNumber() << cert.subjectInfo(QSslCertificate::CommonName) << cert.subjectInfo(QSslCertificate::OrganizationalUnitName);
-#else
     qDebug() << QString("%1: Payment server found an invalid certificate: ").arg(__func__) << cert.serialNumber() << cert.subjectInfo(QSslCertificate::CommonName) << cert.subjectInfo(QSslCertificate::DistinguishedNameQualifier) << cert.subjectInfo(QSslCertificate::OrganizationalUnitName);
-#endif
 }
 
 //
@@ -157,13 +148,11 @@ void PaymentServer::LoadRootCAs(X509_STORE* _store)
             continue;
         }
 
-#if QT_VERSION >= 0x050000
         // Blacklisted certificate
         if (cert.isBlacklisted()) {
             ReportInvalidCertificate(cert);
             continue;
         }
-#endif
         QByteArray certData = cert.toDer();
         const unsigned char *data = (const unsigned char *)certData.data();
 
@@ -413,11 +402,7 @@ void PaymentServer::handleURIOrFile(const QString& s)
     }
     else if (s.startsWith(BITCOIN_IPC_PREFIX, Qt::CaseInsensitive)) // bitcoin: URI
     {
-#if QT_VERSION < 0x050000
-        QUrl uri(s);
-#else
         QUrlQuery uri((QUrl(s)));
-#endif
         if (uri.hasQueryItem("r")) // payment request URI
         {
             QByteArray temp;
diff --git a/src/qt/peertablemodel.cpp b/src/qt/peertablemodel.cpp
index 7e318e3035..0ca9d48bf6 100644
--- a/src/qt/peertablemodel.cpp
+++ b/src/qt/peertablemodel.cpp
@@ -64,9 +64,7 @@ public:
 
             interfaces::Node::NodesStats nodes_stats;
             node.getNodesStats(nodes_stats);
-#if QT_VERSION >= 0x040700
             cachedNodeStats.reserve(nodes_stats.size());
-#endif
             for (auto& node_stats : nodes_stats)
             {
                 CNodeCombinedStats stats;
diff --git a/src/qt/receiverequestdialog.cpp b/src/qt/receiverequestdialog.cpp
index 75146e2214..f9610f2d3b 100644
--- a/src/qt/receiverequestdialog.cpp
+++ b/src/qt/receiverequestdialog.cpp
@@ -16,9 +16,6 @@
 #include <QMimeData>
 #include <QMouseEvent>
 #include <QPixmap>
-#if QT_VERSION < 0x050000
-#include <QUrl>
-#endif
 
 #if defined(HAVE_CONFIG_H)
 #include <config/bitcoin-config.h> /* for USE_QRCODE */
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
index e4e8d3535a..f222357f27 100644
--- a/src/qt/rpcconsole.cpp
+++ b/src/qt/rpcconsole.cpp
@@ -40,10 +40,6 @@
 #include <QTimer>
 #include <QStringList>
 
-#if QT_VERSION < 0x050000
-#include <QUrl>
-#endif
-
 // TODO: add a scrollback limit, as there is currently none
 // TODO: make it possible to filter out categories (esp debug messages when implemented)
 // TODO: receive errors and debug messages through ClientModel
diff --git a/src/qt/sendcoinsentry.cpp b/src/qt/sendcoinsentry.cpp
index 977425f7e3..e8c85bc2a1 100644
--- a/src/qt/sendcoinsentry.cpp
+++ b/src/qt/sendcoinsentry.cpp
@@ -32,9 +32,7 @@ SendCoinsEntry::SendCoinsEntry(const PlatformStyle *_platformStyle, QWidget *par
 
     if (platformStyle->getUseExtraSpacing())
         ui->payToLayout->setSpacing(4);
-#if QT_VERSION >= 0x040700
     ui->addAsLabel->setPlaceholderText(tr("Enter a label for this address to add it to your address book"));
-#endif
 
     // normal bitcoin address field
     GUIUtil::setupAddressWidget(ui->payTo, this);
diff --git a/src/qt/signverifymessagedialog.cpp b/src/qt/signverifymessagedialog.cpp
index 94a3ad7987..c8e694e658 100644
--- a/src/qt/signverifymessagedialog.cpp
+++ b/src/qt/signverifymessagedialog.cpp
@@ -37,9 +37,7 @@ SignVerifyMessageDialog::SignVerifyMessageDialog(const PlatformStyle *_platformS
     ui->verifyMessageButton_VM->setIcon(platformStyle->SingleColorIcon(":/icons/transaction_0"));
     ui->clearButton_VM->setIcon(platformStyle->SingleColorIcon(":/icons/remove"));
 
-#if QT_VERSION >= 0x040700
     ui->signatureOut_SM->setPlaceholderText(tr("Click \"Sign Message\" to generate signature"));
-#endif
 
     GUIUtil::setupAddressWidget(ui->addressIn_SM, this);
     GUIUtil::setupAddressWidget(ui->addressIn_VM, this);
diff --git a/src/qt/test/test_main.cpp b/src/qt/test/test_main.cpp
index 56d4d3e457..f0ac43a58c 100644
--- a/src/qt/test/test_main.cpp
+++ b/src/qt/test/test_main.cpp
@@ -26,12 +26,6 @@
 
 #if defined(QT_STATICPLUGIN)
 #include <QtPlugin>
-#if QT_VERSION < 0x050000
-Q_IMPORT_PLUGIN(qcncodecs)
-Q_IMPORT_PLUGIN(qjpcodecs)
-Q_IMPORT_PLUGIN(qtwcodecs)
-Q_IMPORT_PLUGIN(qkrcodecs)
-#else
 #if defined(QT_QPA_PLATFORM_MINIMAL)
 Q_IMPORT_PLUGIN(QMinimalIntegrationPlugin);
 #endif
@@ -43,7 +37,6 @@ Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin);
 Q_IMPORT_PLUGIN(QCocoaIntegrationPlugin);
 #endif
 #endif
-#endif
 
 extern void noui_connect();
 
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index 33c49dc7cb..c314dadde4 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -87,17 +87,6 @@ QModelIndex FindTx(const QAbstractItemModel& model, const uint256& txid)
     return {};
 }
 
-//! Request context menu (call method that is public in qt5, but protected in qt4).
-void RequestContextMenu(QWidget* widget)
-{
-    class Qt4Hack : public QWidget
-    {
-    public:
-        using QWidget::customContextMenuRequested;
-    };
-    static_cast<Qt4Hack*>(widget)->customContextMenuRequested({});
-}
-
 //! Invoke bumpfee on txid and check results.
 void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, std::string expectError, bool cancel)
 {
@@ -110,7 +99,7 @@ void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, st
     QAction* action = view.findChild<QAction*>("bumpFeeAction");
     table->selectionModel()->select(index, QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
     action->setEnabled(expectDisabled);
-    RequestContextMenu(table);
+    table->customContextMenuRequested({});
     QCOMPARE(action->isEnabled(), !expectDisabled);
 
     action->setEnabled(true);
diff --git a/src/qt/transactionview.cpp b/src/qt/transactionview.cpp
index aa6444245a..e60a387934 100644
--- a/src/qt/transactionview.cpp
+++ b/src/qt/transactionview.cpp
@@ -95,15 +95,11 @@ TransactionView::TransactionView(const PlatformStyle *platformStyle, QWidget *pa
     hlayout->addWidget(typeWidget);
 
     search_widget = new QLineEdit(this);
-#if QT_VERSION >= 0x040700
     search_widget->setPlaceholderText(tr("Enter address, transaction id, or label to search"));
-#endif
     hlayout->addWidget(search_widget);
 
     amountWidget = new QLineEdit(this);
-#if QT_VERSION >= 0x040700
     amountWidget->setPlaceholderText(tr("Min amount"));
-#endif
     if (platformStyle->getUseExtraSpacing()) {
         amountWidget->setFixedWidth(97);
     } else {
diff --git a/src/qt/winshutdownmonitor.cpp b/src/qt/winshutdownmonitor.cpp
index 1e7a76efc0..6190a74598 100644
--- a/src/qt/winshutdownmonitor.cpp
+++ b/src/qt/winshutdownmonitor.cpp
@@ -4,7 +4,7 @@
 
 #include <qt/winshutdownmonitor.h>
 
-#if defined(Q_OS_WIN) && QT_VERSION >= 0x050000
+#if defined(Q_OS_WIN)
 #include <init.h>
 #include <util.h>
 
diff --git a/src/qt/winshutdownmonitor.h b/src/qt/winshutdownmonitor.h
index 0bed55a2c6..c8a523a538 100644
--- a/src/qt/winshutdownmonitor.h
+++ b/src/qt/winshutdownmonitor.h
@@ -9,7 +9,6 @@
 #include <QByteArray>
 #include <QString>
 
-#if QT_VERSION >= 0x050000
 #include <windef.h> // for HWND
 
 #include <QAbstractNativeEventFilter>
@@ -24,6 +23,5 @@ public:
     static void registerShutdownBlockReason(const QString& strReason, const HWND& mainWinId);
 };
 #endif
-#endif
 
 #endif // BITCOIN_QT_WINSHUTDOWNMONITOR_H