很遗憾，没有官方的FindQwt.cmake，Qwt 也没有提供QwtConfig.cmake。并且 cmake 不支持 qmake 的配置功能或者可以读取它的 mkspecs (.prf) 文件。
https://gitlab.kitware.com/cmake/community/-/wikis/contrib/modules/FindQwt 的脚本看起来不错，对我有用：
# Qt Widgets for Technical Applications
# available at http://www.http://qwt.sourceforge.net/
#
# The module defines the following variables:
# Qwt_FOUND - the system has Qwt
# QWT_INCLUDE_DIR - where to find qwt_plot.h
# QWT_INCLUDE_DIRS - qwt includes
# QWT_LIBRARY - where to find the Qwt library
# QWT_LIBRARIES - aditional libraries
# QWT_VERSION_STRING - version (ex. 5.2.1)
#
# It also defines this imported target:
# Qwt::Qwt
#=============================================================================
# Copyright 2010-2013, Julien Schueller
# Copyright 2018-2020, Rolf Eike Beer
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
# The views and conclusions contained in the software and documentation are those
# of the authors and should not be interpreted as representing official policies,
# either expressed or implied, of the FreeBSD Project.
#=============================================================================
if (Qt5Gui_FOUND)
get_target_property(QT_INCLUDE_DIR Qt5::Gui INTERFACE_INCLUDE_DIRECTORIES)
endif ()
find_path ( QWT_INCLUDE_DIR
NAMES qwt_plot.h
HINTS ${QT_INCLUDE_DIR}
PATH_SUFFIXES qwt qwt-qt5 qwt6
)
set ( QWT_INCLUDE_DIRS ${QWT_INCLUDE_DIR} )
# version
set ( _VERSION_FILE ${QWT_INCLUDE_DIR}/qwt_global.h )
if ( EXISTS ${_VERSION_FILE} )
file ( STRINGS ${_VERSION_FILE} _VERSION_LINE REGEX "define[ ]+QWT_VERSION_STR" )
if ( _VERSION_LINE )
string ( REGEX REPLACE ".*define[ ]+QWT_VERSION_STR[ ]+\"([^\"]*)\".*" "\\1" QWT_VERSION_STRING "${_VERSION_LINE}" )
endif ()
endif ()
unset ( _VERSION_FILE )
find_library ( QWT_LIBRARY
NAMES qwt qwt-qt5
HINTS ${QT_LIBRARY_DIR}
)
set ( QWT_LIBRARIES ${QWT_LIBRARY} )
include ( FindPackageHandleStandardArgs )
find_package_handle_standard_args( Qwt REQUIRED_VARS QWT_LIBRARY QWT_INCLUDE_DIR VERSION_VAR QWT_VERSION_STRING )
if (Qwt_FOUND AND NOT TARGET Qwt::Qwt)
add_library(Qwt::Qwt UNKNOWN IMPORTED)
set_target_properties(Qwt::Qwt PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "${QWT_INCLUDE_DIRS}"
IMPORTED_LOCATION "${QWT_LIBRARIES}")
endif ()
mark_as_advanced (
QWT_LIBRARY
QWT_INCLUDE_DIR
)
编辑：警告：这可能会返回错误的 Qwt 库！如果您同时安装了 Qt 4 和 Qt 5 版本，即使您使用 Qt 5，它也会返回 Qt 4 版本。这将导致您的应用程序同时链接到 Qt 4 和 Qt 5，从而立即崩溃。