Unsolved cannot find .h file from another directory

[tony67]

Hi All,
sorry this is almost certainly an easy answer but I can't work it out, I've done a search but with no luck. I'm used to c++ makefiles so using pro is a bit of a magic art.
What I've be done is add qcustomplot source directory to my project. It shows up in my project tree in source and headers inside it's directory. However when I try to use the .h file from my source I get an error, "qcustomplot.h no file or directory". My directory structure is as follows
master directory

-----------master directory-Desktop-Debug

-----------master directory-Qt_5_0_1_qt5-Debug

----------master directory

----------qcustomplot-source

looking up online I tried to add the directory to my projects via adding this to my .pro file "INCLUDEPATH += $$QT_PROJECT_DIR/qcustomplot-source/" and setting the path to the .h with #include "qcustomplot-source/qcustomplot.h" no luck. with just #include "qcustomplot.h" no luck either.
Can anyone advise what I need to do to get .pro to include paths to external headers?
Thanks in advance

[jsulm]

Where is the *.pro file located?
You can try to put absolute path to check whether it is working then:
INCLUDEPATH += c:/.../qcustomplot-source

What is QT_PROJECT_DIR ?

[dheerendra]

Add the following in your .pro file
INCLUDEPATH += DIR which contains the your .h file

e.g INCLUDEPATH += /Users/tony/qcustomplot.h

Clean, run the qmake and build it again.