From dcc5ed93775b66339c14f297e35c91f1cf3dd43a Mon Sep 17 00:00:00 2001
From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Tue, 14 Sep 2021 17:46:30 -0700
Subject: [PATCH] fix inability to include and use gvc.h from a parent CMake
 project

When attempting to declare a dependency on gvc when using Graphviz as a CMake
subproject, the include path necessary to compile gvc headers would not be
propagated to dependent targets. The result would be a compilation error when
the transitive includes of gvc.h could not be found.

To validate this change, create an empty directory and add the following
CMakeLists.txt:

  project(foo)
  add_subdirectory(graphviz)
  add_executable(bar main.c)
  target_link_libraries(bar gvc)

Add the following main.c:

  #include <gvc/gvc.h>
  int main(void) { return 0; }

Clone Graphviz into the subdirectory 'graphviz'. Then the standard CMake steps:

  mkdir build
  cd build
  cmake ..
  make

Note that Graphviz dependencies and then 'bar' are correctly built.

I am not a CMake expert; this was written based on my best guess of what
Graphviz should be doing according to the CMake docs. Assuming this is correct,
other Graphviz targets probably need similar fixes.

Fixes #1477, #2109.
---
 CHANGELOG.md           |  4 ++++
 lib/gvc/CMakeLists.txt | 17 ++++++++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c6571020..5898e90ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - the CMake build system installs gzipped man pages if `gzip` is available #1883
+- CMake projects using Graphviz as a subproject (`add_subdirectory`) can now
+  link against and use `gvc`.
 
 ### Fixed
 
@@ -18,6 +20,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   projects #2119
 - compile failures with a C++20-compatible toolchain #2122
 - compile errors on macOS when using Bison 3.8 #2127
+- Make Graphviz buildable as a cmake subproject/subdirectory #1477
+- Header not found in Cmake project #2109
 
 ## [2.49.0] – 2021-08-28
 
diff --git a/lib/gvc/CMakeLists.txt b/lib/gvc/CMakeLists.txt
index 038636469..745841176 100644
--- a/lib/gvc/CMakeLists.txt
+++ b/lib/gvc/CMakeLists.txt
@@ -36,14 +36,17 @@ add_library(gvc SHARED
     gvc.def
 )
 
-target_include_directories(gvc PRIVATE
-    ${GRAPHVIZ_LIB_DIR}
-    ${CMAKE_CURRENT_SOURCE_DIR}
+target_include_directories(gvc
+  PUBLIC
+    $<BUILD_INTERFACE:${GRAPHVIZ_LIB_DIR}>
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+    $<BUILD_INTERFACE:${GRAPHVIZ_LIB_DIR}/cdt>
+    $<BUILD_INTERFACE:${GRAPHVIZ_LIB_DIR}/cgraph>
+    $<BUILD_INTERFACE:${GRAPHVIZ_LIB_DIR}/common>
+    $<BUILD_INTERFACE:${GRAPHVIZ_LIB_DIR}/pathplan>
+    $<INSTALL_INTERFACE:include/graphviz>
+  PRIVATE
     ${TOP_SOURCE_DIR}
-    ${GRAPHVIZ_LIB_DIR}/cdt
-    ${GRAPHVIZ_LIB_DIR}/cgraph
-    ${GRAPHVIZ_LIB_DIR}/common
-    ${GRAPHVIZ_LIB_DIR}/pathplan
 )
 
 target_link_libraries(gvc PRIVATE
-- 
2.40.0