Using an MFC custom control from Qt

[Perdrix]

Until I can re-implement a complex MFC custom control in native Qt, I need to be able to continue to use it.

The usage of the control is to either take over a CStatic control in a dialog by invoking it's

BOOL CreateFromStatic(CWnd * static)

member function,

or as is probably more appropriate here to invoke this mf:

BOOL Create(RECT const & r, CWnd * parent, UINT id,
DWORD dwStyle = WS_CHILD | WS_VISIBLE);

I can extract a RECT from the widget that I wish to take over (a QLabel), but I'm not clear how I can create a CWND that I can use to refer to the "this" QWidget as its parent. I can readily extract my own hwnd by calling winId() but can I use CWND::Attach() against a just created CWND to do create a useable CWND for this purpose?

Thanks
David

[JKSH]

@Perdrix said in Using an MFC custom control from Qt:

can I use CWND::Attach() against a just created CWND to do create a useable CWND for this purpose?

What happens if you try it?

Note: This is not officially supported by Qt, so I won't be surprised if you encounter strange behaviours.

[Perdrix]

Well I didn't want to "just try it" as that could be the "wrong" way to proceed.

What's the recommended approach for hosting an MFC CWND derived window with a QWidget? Surely this must have come up before?

[JonB]

@Perdrix
https://forum.qt.io/topic/76525/cwnd-to-qwidget

Separately, I don't know whether it's relevant but you may wish to look through https://docs.huihoo.com/qt/solutions/4/qtwinmigrate/winmigrate-walkthrough.html

[JKSH]

@Perdrix said in Using an MFC custom control from Qt:

What's the recommended approach for hosting an MFC CWND derived window with a QWidget? Surely this must have come up before?

MFC and Qt are quite different frameworks and combining them is challenging. I don't have the experience to do it "correctly"; I'm not sure if anyone in this forum has that experience.

Thank you @JonB for providing links to what others have tried before. The source code for the Qt/MFC Migration Framework used by the walkthrough can be found at https://github.com/qtproject/qt-solutions/tree/master/qtwinmigrate . Unfortunately, it is no longer maintained so there is currently no officially-supported way to merge CWND and QWidget.

[Perdrix]

I'm using qmfcapp and qwinwidget as they seem to be the only way to go.

I'm frankly quite shocked that you don't support those anymore - this must be a very common requirement for everyone who's converting their code to Qt!

I'm also a bit surprised that there's no expertise on porting to Qt here either ...

David

[hskoglund]

Just want to add to what @JKSH said above (.. they are quite different frameworks):

I used MFC and Visual C++ for almost 20 years before waking up to Qt and initially tried to port some code over, however all the MFC macros like message maps etc I could just toss and same for MVC stuff, so the only type of code that I did port was CString juggling (CString and QString are probably the most similar in vein parts of their respective frameworks).

[mrjj]

Hi
What does this complex MFC custom control do ?
Mixing MFC and Qt might end up being a bigger job than to recreate
this control in Qt.

[Perdrix]

One of them is a class derived from this: https://www.codeproject.com/articles/555/wndimage-control.

It adds mouse tracking, hit-testing, wheel zooming and "4-corners" mode that zooms into the four corners of the image.

With four corners not enabled:

https://www.codeproject.com/articles/555/wndimage-control

With four corners enabled:

The image is populated from an internally calculated windows bitmap (BITMAPINFO) derived from a 32bit floating point representation of an image. We'd obviously need to have a non-Windows in storage bitmap representation (maybe a Pixmap?) that could be built dynamically from our internal representation.

David

[mrjj]

Hi
The https://doc.qt.io/qt-5/graphicsview.html
would give panning / zooming and and mouse tracking for (almost) free.

is the 4 zoom area like a lens effect that zoom the area while you can pan the image around or is it more static ?

[Perdrix]

The four corner stuff is static ...

I'll take another look at the graphicsview control. I thought that was for managing lots of items within a scene, not for handling a single image.

Thanks
David

[mrjj]

@Perdrix
Hi
Well its also good to have many items but can also be
used for a single item like an image

https://doc.qt.io/qt-5/qgraphicspixmapitem.html