Win10+VS2019+Qt5.15.2下编译QCAD
一：官方说法：
Windows
Download and install a C++ compiler, for example:
Visual Studio C++ Express or Visual Studio Community
Download and install Qt from qt.io (see supported platforms):
Download for example the online installer file
qt-opensource-windows-x86-5.13.2.exe
Install Qt by running the installer and following the instructions on screen
If available, download and extract Teigha (e.g. Kernel_vc14_amd64md.zip and Drawings_vc14_amd64md.zip) into qcadpro/src/io/dwg/opendesign and copy OdActivationInfo to qcadpro/src/io/dwg/opendesign/ThirdParty/activation.
Configure QCAD. Optional modules installed side-by-side with the qcad directory are configured automatically:
cd c:\Users\me\qcad\qcad
c:\Qt\Qt5.13.2\5.13\msvc2015_64\bin\qmake -r CONFIG+=ractivated
Compile QCAD. For example on cygwin:
nmake release
Alternatively, you may want to use jom, an nmake clone which speeds up compilation significantly by using all available CPU cores.
Launch QCAD. For example with:
release\qcad.exe
(Optional) For code signing, open certlm.msc, click on "Personal" folder, choose Action > All Tasks > Import and select P12 file to import.
但我按这做法不成功。
二：第二种网上说法：
与第一种说法的区别是构造visual studio 方案
qmake -r -spec win32-msvc2012 -tp vc
这个会报错，win32-msvc2012 改为2109 也一样，后来改为全路径，
qmake -r -spec C:\Qt\5.15.2\msvc2019\mkspecs\win32-msvc -tp vc
这样就可以产生工程了，并且可以编译链接成功。我想找64 位版本，应该是winrt-x64-msvc2019，可是不成功。
三：QT的下载和编译参考了这个链接：
https://www.cnblogs.com/fzu-Z9h/p/16587964.html
我不喜欢qt的下载器安装，想做点改变都不行，要重新来。我就下载了QT5.14, Qt5.13，发现没有vc2019 的项目，只好还是用下载器下了Qt5.15.2版本。
第一次装的Qt5.15.2 ，但是没有选择Qt Scripts(Deprecated),看了该文就做了这个选择。
主要的问题是
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.