--- a/configure.in
+++ b/configure.in
@@ -4703,49 +4703,75 @@ dnl = QT support
 dnl ========================================================
 if test "$MOZ_ENABLE_QT"
 then
     MOZ_ARG_WITH_STRING(qtdir,
     [  --with-qtdir=\$dir       Specify Qt directory ],
     [ QTDIR=$withval])
 
     if test -z "$QTDIR"; then
-        PKG_CHECK_MODULES(MOZ_QT, QtGui QtNetwork QtCore QtOpenGL)
-        PKG_CHECK_MODULES(MOZ_QT5, Qt5Widgets Qt5Multimedia Qt5PrintSupport,
-                      MOZ_ENABLE_QT5=1,
-                      MOZ_ENABLE_QT5=)
-        if test "$MOZ_ENABLE_QT5"; then
-            echo "Using qt5"
-            MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS $MOZ_QT5_CFLAGS"
-            MOZ_QT_LIBS="$MOZ_QT_LIBS $MOZ_QT5_LIBS"
-        fi
+        AC_CHECK_PROGS(HOST_QMAKE, $HOST_QMAKE qmake, "")
+    else
+        HOST_QMAKE="$QTDIR/bin/qmake"
+    fi
+    QT_VERSION=`$HOST_QMAKE -v | grep 'Using Qt version' | grep -oP '\d+\.\d+\.\d+'`
+
+    if test -z "$QTDIR"; then
+        case $QT_VERSION in
+        5.*)
+            AC_MSG_RESULT("Using qt5: $QT_VERSION")
+            PKG_CHECK_MODULES(MOZ_QT, Qt5Gui Qt5Network Qt5Core Qt5OpenGL Qt5Widgets Qt5PrintSupport, ,
+            [
+              AC_MSG_ERROR([$MOZ_QT_PKG_ERRORS Need qtbase development packages, (On Ubuntu, you might try installing the packages qtbase5-dev libqt5opengl5-dev.)])
+            ])
+            QT5INCDIR=`pkg-config --variable=includedir Qt5Gui`
+            MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QT5INCDIR/QtGui/$QT_VERSION/QtGui"
+            ;;
+        4.*)
+            AC_MSG_RESULT("Using qt4: $QT_VERSION")
+            PKG_CHECK_MODULES(MOZ_QT, QtGui QtNetwork QtCore QtOpenGL, ,
+            [
+              AC_MSG_ERROR([$MOZ_QT_PKG_ERRORS Need qt4 development package, (On Ubuntu, you might try installing the packages libqt4-dev libqt4-opengl-dev.)])
+            ])
+            ;;
+        *)
+            AC_MSG_ERROR([* * * Unsupported Qt Version: $QT_VERSION])
+            ;;
+        esac
 
         AC_CHECK_PROGS(HOST_MOC, $MOC moc, "")
         AC_CHECK_PROGS(HOST_RCC, $RCC rcc, "")
     else
         MOZ_QT_CFLAGS="-DQT_SHARED"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtGui"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtCore"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtNetwork"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtXml"
         MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtDeclarative"
 
-        # QtWidgets was introduced only in Qt5
-        if test -d $QTDIR/include/QtWidgets; then
-            echo "Using qt5"
+        case $QT_VERSION in
+        5.*)
+            AC_MSG_RESULT("Using qt5: $QT_VERSION")
             MOZ_QT_LIBS="-L$QTDIR/lib/ -lQt5Gui -lQt5Network -lQt5Core -lQt5Xml -lQt5OpenGL"
-            MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtGui/5.0.1/QtGui"
+            MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtGui/$QT_VERSION/QtGui"
             MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtWidgets"
             MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/QtPrintSupport"
             MOZ_QT_LIBS="$MOZ_QT_LIBS -lQt5Widgets -lQt5PrintSupport"
-        else
+            ;;
+        4.*)
+            AC_MSG_RESULT("Using qt4: $QT_VERSION")
             MOZ_QT_LIBS="-L$QTDIR/lib/ -lQtGui -lQtNetwork -lQtCore -lQtXml -lQtOpenGL"
             MOZ_QT_CFLAGS="$MOZ_QT_CFLAGS -I$QTDIR/include/Qt"
-        fi
+            ;;
+        *)
+            AC_MSG_ERROR([* * * Unsupported Qt Version: $QT_VERSION])
+            ;;
+        esac
+
         HOST_MOC="$QTDIR/bin/moc"
         HOST_RCC="$QTDIR/bin/rcc"
     fi
     if test -z "$HOST_MOC"; then
         AC_MSG_ERROR([No acceptable moc preprocessor found. Qt SDK is not installed or --with-qt is
 incorrect])
     fi
     if test -z "$HOST_RCC"; then

--- a/gfx/thebes/gfxQtPlatform.cpp
+++ b/gfx/thebes/gfxQtPlatform.cpp
@@ -197,17 +197,17 @@ gfxQtPlatform::GetXScreen(QWidget* aWind
 #if (QT_VERSION < QT_VERSION_CHECK(5,0,0))
 #ifdef Q_WS_X11
   return ScreenOfDisplay(GetXDisplay(aWindow), aWindow ? aWindow->x11Info().screen() : QX11Info().screen());
 #else
   return nullptr;
 #endif
 #else
   return ScreenOfDisplay(GetXDisplay(aWindow),
-                         (int)qApp->platformNativeInterface()->
+                         (int)(intptr_t)qApp->platformNativeInterface()->
                            nativeResourceForWindow("screen",
                              aWindow ? aWindow->windowHandle() : nullptr));
 #endif
 }
 #endif
 
 already_AddRefed<gfxASurface>
 gfxQtPlatform::CreateOffscreenSurface(const gfxIntSize& size,

--- a/widget/qt/nsQtKeyUtils.cpp
+++ b/widget/qt/nsQtKeyUtils.cpp
@@ -362,17 +362,16 @@ QtKeyCodeToDOMKeyNameIndex(int aKeysym)
         case Qt::Key_Yacute:
         case Qt::Key_THORN:
         case Qt::Key_ssharp:
         case Qt::Key_division:
         case Qt::Key_ydiaeresis:
             return KEY_NAME_INDEX_PrintableKey;
 
         case Qt::Key_Backtab:
-        case Qt::Key_Print:
         case Qt::Key_Direction_L:
         case Qt::Key_Direction_R:
         case Qt::Key_SingleCandidate:
         case Qt::Key_Hiragana_Katakana:
         case Qt::Key_Zenkaku_Hankaku:
         case Qt::Key_Touroku:
         case Qt::Key_Massyo:
         case Qt::Key_Hangul:

--- a/widget/qt/nsWindow.cpp
+++ b/widget/qt/nsWindow.cpp
@@ -3259,20 +3259,20 @@ nsWindow::SetInputContext(const InputCon
 }
 
 NS_IMETHODIMP_(InputContext)
 nsWindow::GetInputContext()
 {
     mInputContext.mIMEState.mOpen = IMEState::OPEN_STATE_NOT_SUPPORTED;
     // Our qt widget looks like using only one context per process.
     // However, it's better to set the context's pointer.
-#if (QT_VERSION <= QT_VERSION_CHECK(5, 0, 0))
+#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
     mInputContext.mNativeIMEContext = qApp->inputContext();
 #else
-    mInputContext.mNativeIMEContext = nullptr;
+    mInputContext.mNativeIMEContext = qApp->inputMethod();
 #endif
     return mInputContext;
 }
 
 void
 nsWindow::SetSoftwareKeyboardState(bool aOpen,
                                    const InputContextAction& aAction)
 {