build: Allow doc to build as its own project

We can now build the docs without having to have installed all
dependencies for polybar.

doc/.gitignore

@@ -0,0 +1 @@
+build

doc/CMakeLists.txt

@@ -1,3 +1,8 @@
+cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
+
+# Only used if documentation is built on its own
+project(polybar-doc NONE)
+
 find_program(SPHINX_EXECUTABLE
   NAMES sphinx-build
   DOC "Sphinx Documentation Builder")
@@ -6,14 +11,14 @@ if(NOT SPHINX_EXECUTABLE)
   message_colored(FATAL_ERROR "Failed to locate sphinx-build" 31)
 endif()
 
-# Configures conf.py in the current folder and puts it in the build folder
-configure_file(conf.py conf.py @ONLY)
-
 set(SPHINX_FLAGS "" CACHE STRING "Flags to pass to sphinx-build")
 separate_arguments(sphinx_flags UNIX_COMMAND "${SPHINX_FLAGS}")
 
 set(doc_path "${CMAKE_CURRENT_SOURCE_DIR}")
 
+# Configures conf.py in the current folder and puts it in the build folder
+configure_file(conf.py conf.py @ONLY)
+
 # We want to run `sphinx-build` with the following builders
 set(doc_builders "html" "man")
 
@@ -26,10 +31,13 @@ foreach(builder ${doc_builders})
   add_custom_target(${doc_target}
     COMMAND ${SPHINX_EXECUTABLE}
             -b ${builder}
+            # conf.py dir
             -c "${CMAKE_CURRENT_BINARY_DIR}"
             -d "${CMAKE_CURRENT_BINARY_DIR}/doctrees"
             ${sphinx_flags}
-            "${CMAKE_SOURCE_DIR}/doc"
+            # Documentation source file dir
+            "${CMAKE_CURRENT_SOURCE_DIR}"
+            # Output dir
             "${CMAKE_CURRENT_BINARY_DIR}/${builder}" > ${builder_log}
     COMMENT "sphinx-build ${builder}: see doc/${builder_log}")
 

doc/README.md

@@ -10,11 +10,13 @@ target `doc`).
 The documentation uses [Sphinx](http://www.sphinx-doc.org/en/stable/) to generate the documentation, so you will need to
 have that installed.
 
-To generate the documentation you first need to configure polybar the same as when you compile it (`cmake ..` in `build`
-folder).
-After that you can run `make doc` to generate all of the documentation or `make doc_html` or `make doc_man` to only
-generate the html documentation or the man pages.
+If you build polybar normally while having Sphinx installed during configuration, the documentation will be enabled and
+built as well. Building the documentation can be disabled by passing `-DBUILD_DOC=OFF` to `cmake`.
 
-Open `build/doc/html/index.html` to read the documentation in the browser.
+Alternatively the documentation can be built without the rest of polybar, for that run `cmake` only on the `doc`
+directory. For example, create a `build` directory in `doc` and then run `cmake ..` in there.
 
-The manual pages are placed in `build/doc/man`.
+Once configured, all of the documentation can be generated with `make doc` or use `make doc_html` or `make doc_man` to
+only generate the html documentation or the man pages respectively.
+
+The HTML documentation is in `doc/html/index.html` in your build directory and the man pages are in `doc/man`.