How to use CreateFont API function in Qt5

Uncle Kris · wrote on 20 May 2016, 16:58

Hi. Beginner's question. I try to port my application to Qt. I need call to Windows' CreateFont function. Header files are ok, compiler is happy. But linker complains : "undefined reference to '_imp__CreateFontW". Code is not changed and used to work.
I found info that I need "" so I added @win32:LIBS += c:/Windows/System32/Kernel32
C:/Windows/System32/Gdi32@
Same error. Any idea what else I can try?

SGaist · wrote on 20 May 2016, 22:36

Hi and welcome to devnet,

It would rather be LIBS += -lGdi32.

Out of curiosity, why not use Qt's QFont class ?

[edit: Fixed casing SGaist]

Uncle Kris · 21 May 2016, 13:39

The program was written using APIs originally. I like to compile and link it before I start to make changes.

I have tried your solution. Same error.

kshegunov · wrote on 21 May 2016, 13:39

@Uncle-Kris
Do you have the windows SDKs installed? Did you make sure that the -L switch points to the correct path containing the import library files (.lib) and that you have -lgdi32 in your pro (that's a typo on part of @SGaist as the library is specified with a lowercase letter)?

Uncle Kris · wrote on 21 May 2016, 16:41

I see your point. No, SDK is not installed. I used to work in BCB 4 and all basic libraries were part of installation. I will look for them now.

Uncle Kris · 21 May 2016, 19:48

I have installed SDK, updated path in .pro file. Same error.

kshegunov · wrote on 21 May 2016, 19:48

@Uncle-Kris
Okay, what libraries does the SDK provide (for which compilers), do they match the compiler you're using? Can we see the line from the project where you set the link flags (i.e. LIBS += ...)?

Uncle Kris · 21 May 2016, 19:57

The line is:
LIBS += -L"H:\Windows Kits\8.1\Lib\winv6.3\um\x86/gdi32"\

There is no info on compiler dependency. Just folder full of libraries. How I can check?

kshegunov · 22 May 2016, 10:23

@Uncle-Kris
LIBS += -L"H:\Windows Kits\8.1\Lib\winv6.3\um\x86/gdi32"\

This is incomplete. The backslash at the end means it continues on to the next line. Also, when giving paths, use the forward slash instead of the a backwards. It is recognized on windows and you'll work around a ton of problems with escaping in the long run.

There is no info on compiler dependency. Just folder full of libraries. How I can check?

It should be noted somewhere on the MS's site, however I have no windows on hand to check. What compiler are you using currently? The 8.1 SDK should work with MSVC 2012/2013 if I recall correctly.

SGaist · 21 May 2016, 22:19

@kshegunov Not a typo ;) See here

kshegunov · S SGaist 21 May 2016, 22:08

@SGaist said:

It would rather be LIBS += -LGdi32.

I know, I know. Still looks like you typed -L instead of -l ;)

SGaist · 22 May 2016, 10:28

Haaaaaaa that typo ! Good catch ! Then indeed, there was ! :)

Uncle Kris · wrote on 22 May 2016, 10:23

@kshegunov There was a next line. I have removed it for test time. Also changes to shash/backslash do not make any difference for now. Linker is not happy.

Uncle Kris · 22 May 2016, 11:16

@SGaist What typo? Can you be more specific, please? Compiler has no problem with that line. And it used to work in another IDE.

Also: "It would rather be LIBS += -LGdi32." No. Without full path there is a message that file is not found. -L and -l makes no difference so far.

kshegunov · wrote on 22 May 2016, 11:16

@Uncle-Kris
A library is passed to qmake (respectively make) with the following syntax:

LIBS += -L/path/to/library -llibraryname

The typo was that @SGaist used the switch for library path -L to specify the library name. It should've been -lgdi32. So in your case it'd look something like this:

LIBS += -L"H:/Windows Kits/8.1/Lib/winv6.3/um/x86" -lgdi32

SGaist · 22 May 2016, 17:20

Yes the typo was the L vs l but still the library name is Gdi32

kshegunov · S SGaist 22 May 2016, 15:12

@SGaist said:

but still the library name is Gdi32

The windows linker isn't case sensitive. :)

SGaist · 22 May 2016, 20:48

@kshegunov said:

@SGaist said:

but still the library name is Gdi32

The windows linker isn't case sensitive. :)

Indeed, but I wouldn't be surprised if that changed at some point :D

kshegunov · S SGaist 22 May 2016, 20:42

@SGaist said:

Indeed, but I wouldn't be surprised if that changed at some point :D

Perhaps, perhaps. Although, judging from the time it took MS to introduce the x64 compiler, if it were to change, it'd take decades. And since it hasn't changed for over 30 years, I really doubt that it ever will. :D