Can't get qwt_designer_plugin to load in Qt Creator

Question

My setup is:

• Visual Studio 2012
• Qt 5.2.0 from http://download.qt-project.org/official_releases/qt/5.2/5.2.0/qt-windows-opensource-5.2.0-msvc2012-x86_64-offline.exe

• Unzip Qwt from http://sourceforge.net/projects/qwt/files/qwt/6.1.0/qwt-6.1.0.zip/download to C:\qwt-6.1.0

• Opened Qt 5.2.0 64-bit for Desktop (MSVC 2012) and ran "qmake qwt.pro"

• Opened VS2012 x64 Native Tools Command Prompt and ran "nmake" and "nmake install"
• Set QWT_ROOT = C:\qwt-6.1.0
• Added C:\qwt-6.1.0\lib to PATH
• Copied C:\qwt-6.1.0\plugins\designer\qwt_designer_plugin.dll to C:\Qt\Qt5.2.0\Tools\QtCreator\bin\plugins\designer

When I open Qt Creator and edit the UI then go to Tools->Form Editor->About Qt Designer Plugins I see "Cannot load library qwt_designer_plugin.dll:" but no error or reason.

Answer 1

I used Dependency Walker to check the Dll, and QtCreator.exe and all its dependencies are 32-bit whereas my build of qwt_designer_plugin.dll is 64-bit. I wondered if this was causing the problem so I:

• Downloaded Qt5.2.0 from http://download.qt-project.org/official_releases/qt/5.2/5.2.0/qt-windows-opensource-5.2.0-msvc2012-x86-offline.exe and install into C:\Qt\Qt5.2.0-32
• Unzipped Qwt into C:\qwt-6.1.0-32bit to create a fresh copy.
• Opened Qt 5.2.0 32-bit for Desktop (MSVC 2012), cd into C:\qwt-6.1.0-32bit and "qmake qwt.pro"
• Opened VS2012 x86 Native Tools Command Prompt and ran "nmake" and "nmake install"
• Copied C:\qwt-6.1.0-32bit\designer\plugins\designer\qwt_designer_plugin.dll to C:\Qt\Qt5.2.0\Tools\QtCreator\bin\plugins\designer

This works fine and I can now see the plugin loaded correctly and add Qwt widgets in the UI designer.