Here’s my directory structure for my project (abbreviated):

Drawbox/
    Library/
        Drawbox.cpp
    APClass/
        smallAPstring.h

Here’s the top level CMakeLists.txt file:

cmake_minimum_required(VERSION 3.28)
project(my-project)

find_package(SDL2 REQUIRED)
link_directories(${SDL2_LIBRARY_DIRS})
include_directories(${SDL2_INCLUDE_DIRS} . Library APClass Library/jpeg)

add_library(Drawbox STATIC)

add_subdirectory(Library)
add_subdirectory(Tools)
add_subdirectory(APClass)

target_compile_features(Drawbox PUBLIC cxx_std_11)

And here’s the one for the Library directory:

target_sources(Drawbox
    PRIVATE
        Color.cpp  DrErrMessages.cpp DrEventQ.cpp 
        DrawboxWindow.cpp FinePoint.cpp Image.cpp 
        JpegReader.cpp 
        PVector.cpp Point.cpp Rect.cpp SpaceCalc.cpp Timer.cpp
        SDL/Drawbox.SDL.cpp  SDL/Keyboard.SDL.cpp
)

But I’m finding that a Drawbox.cpp located in the Library sub-directory doesn’t find smallAPstring.h when doing

#include “smallAPstring.h"

What I really want to say is, “All source files in all subdirectories should find include files in these directories.” Can that be said? Or should I be putting something in my sub-directory CMakeLists.txt files?