gnu: Add lib2geom.

* gnu/packages/graphics.scm (lib2geom): New variable.
* gnu/packages/patches/lib2geom-enable-assertions.patch,
lib2geom-link-tests-against-glib.patch,
lib2geom-use-system-googletest.patch: New files.
* gnu/local.mk (dist_patch_DATA): Register new patches.

gnu/local.mk

@@ -1159,6 +1159,9 @@ dist_patch_DATA =						\
   %D%/packages/patches/ldc-disable-phobos-tests.patch		\
   %D%/packages/patches/leela-zero-gtest.patch			\
   %D%/packages/patches/less-hurd-path-max.patch			\
+  %D%/packages/patches/lib2geom-enable-assertions.patch		\
+  %D%/packages/patches/lib2geom-link-tests-against-glib.patch	\
+  %D%/packages/patches/lib2geom-use-system-googletest.patch	\
   %D%/packages/patches/liba52-enable-pic.patch			\
   %D%/packages/patches/liba52-link-with-libm.patch		\
   %D%/packages/patches/liba52-set-soname.patch			\

gnu/packages/graphics.scm

@@ -21,6 +21,7 @@
 ;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
 ;;; Copyright © 2020 Nicolas Goaziou <mail@nicolasgoaziou.fr>
 ;;; Copyright © 2020 Raghav Gururajan <raghavgururajan@disroot.org>
+;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -61,6 +62,7 @@
   #:use-module (gnu packages image)
   #:use-module (gnu packages imagemagick)
   #:use-module (gnu packages jemalloc)
+  #:use-module (gnu packages maths)
   #:use-module (gnu packages multiprecision)
   #:use-module (gnu packages pdf)
   #:use-module (gnu packages perl)
@@ -328,6 +330,81 @@ quaternions and other useful 2D and 3D math functions.  Iex is an
 exception-handling library.")
     (license license:bsd-3)))
 
+(define-public lib2geom
+  ;; Use the latest master commit, as the 1.0 release suffer build problems.
+  (let ((revision "1")
+        (commit "42e119d94934a9514c61571cfb6b4af503ece082"))
+    (package
+      (name "lib2geom")
+      (version (git-version "1.0" revision commit))
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference
+                      (url "https://gitlab.com/inkscape/lib2geom.git")
+                      (commit commit)))
+                (file-name (git-file-name name version))
+                (sha256
+                 (base32
+                  "195rs0kdbs8w62irha1nwy83bccz04wglmk578qrj1mky7fc4rjv"))
+                (patches
+                 ;; Patch submitted to upstream (see:
+                 ;; https://gitlab.com/inkscape/lib2geom/merge_requests/17).
+                 (search-patches "lib2geom-enable-assertions.patch"))
+                (modules '((guix build utils)))
+                (snippet
+                 '(begin
+                    ;; Fix py2geom module initialization (see:
+                    ;; https://gitlab.com/inkscape/lib2geom/merge_requests/18).
+                    (substitute* "src/py2geom/__init__.py"
+                      (("_py2geom") "py2geom._py2geom"))
+                    #t))))
+      (build-system cmake-build-system)
+      (arguments
+       `(#:imported-modules ((guix build python-build-system)
+                             ,@%cmake-build-system-modules)
+         #:configure-flags '("-D2GEOM_BUILD_SHARED=ON"
+                             "-D2GEOM_BOOST_PYTHON=ON"
+                             ;; Compiling the Cython bindings fail (see:
+                             ;; https://gitlab.com/inkscape/lib2geom/issues/21).
+                             "-D2GEOM_CYTHON_BINDINGS=OFF")
+         #:phases
+         (modify-phases %standard-phases
+           (add-after 'unpack 'patch-python-lib-install-path
+             (lambda* (#:key inputs outputs #:allow-other-keys)
+               (let* ((python-version (@ (guix build python-build-system)
+                                         python-version))
+                      (python-maj-min-version (python-version
+                                               (assoc-ref inputs "python")))
+                      (site-package (string-append
+                                     (assoc-ref outputs "out")
+                                     "/lib/python" python-maj-min-version
+                                     "/site-packages")))
+                 (substitute* '("src/cython/CMakeLists.txt"
+                                "src/py2geom/CMakeLists.txt")
+                   (("PYTHON_LIB_INSTALL \"[^\"]*\"")
+                    (format #f "PYTHON_LIB_INSTALL ~s" site-package))))
+               #t)))))
+      (native-inputs `(("python" ,python-wrapper)
+                       ("googletest" ,googletest)
+                       ("pkg-config" ,pkg-config)))
+      (inputs `(("cairo" ,cairo)
+                ("pycairo" ,python-pycairo)
+                ("double-conversion" ,double-conversion)
+                ("glib" ,glib)
+                ("gsl" ,gsl)))
+      (propagated-inputs
+       `(("boost" ,boost)))             ;referred to in 2geom/pathvector.h.
+      (home-page "https://gitlab.com/inkscape/lib2geom/")
+      (synopsis "C++ 2D graphics library")
+      (description "2geom is a C++ library of mathematics for paths, curves,
+and other geometric calculations.  Designed for vector graphics, it tackles
+Bézier curves, conic sections, paths, intersections, transformations, and
+basic geometries.")
+      ;; Because the library is linked with the GNU Scientific Library
+      ;; (GPLv3+), the combined work must be licensed as GPLv3+ (see:
+      ;; https://gitlab.com/inkscape/inkscape/issues/784).
+      (license license:gpl3+))))
+
 (define-public ogre
   (package
     (name "ogre")

gnu/packages/patches/lib2geom-enable-assertions.patch

@@ -0,0 +1,36 @@
+From 4aa78f52232682b353eb15c219171e466987bac7 Mon Sep 17 00:00:00 2001
+From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
+Date: Thu, 16 Jan 2020 00:19:29 -0500
+Subject: [PATCH] build: Enable assertions for the RelWithDebugInfo build type.
+
+This fixes issue #5 (see:
+https://gitlab.com/inkscape/lib2geom/issues/5).
+
+* CMakeLists.txt: Remove the "-DNDEBUG" CXX flag from the default
+configuration for the RelWithDebugInfo build type.
+---
+ CMakeLists.txt | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index bfeb8f03..a663a1b0 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -19,6 +19,14 @@ enable_testing()
+ 
+ include(CheckCXXSourceCompiles)
+ 
++# Enable assertions for the RelWithDebugInfo build type.  This is
++# useful as some tests make use of it (see:
++# https://gitlab.com/inkscape/lib2geom/issues/5).
++if (CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
++  string(REPLACE "-DNDEBUG" ""
++    CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
++endif()
++
+ # Find dependencies
+ find_package(Boost 1.40 REQUIRED)
+ find_package(DoubleConversion REQUIRED)
+-- 
+2.24.1
+

gnu/packages/patches/lib2geom-link-tests-against-glib.patch

@@ -0,0 +1,34 @@
+From f95925afef451755fc1449e57fbfdc2e7277f4b4 Mon Sep 17 00:00:00 2001
+From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
+Date: Sat, 11 Jan 2020 00:44:55 -0500
+Subject: [PATCH 1/3] tests: Link against GLib.
+
+This resolves an error about not finding <glib.h> when linking the
+tests that make use of GLib.
+
+* src/tests/CMakeLists.txt[2GEOM_GTESTS_SRC]: Add the glib library to
+the link target libraries.
+---
+ src/tests/CMakeLists.txt | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
+index 5ddf7f9c..626cfd87 100644
+--- a/src/tests/CMakeLists.txt
++++ b/src/tests/CMakeLists.txt
+@@ -32,8 +32,10 @@ sbasis-test
+ 
+ foreach(source ${2GEOM_GTESTS_SRC})
+ 	add_executable(${source} ${source}.cpp)
+-	target_include_directories(${source} PRIVATE ${GSL_INCLUDE_DIRS} ${GTK3_INCLUDE_DIRS})
+-	target_link_libraries(${source} 2geom gtest_main gtest ${GSL_LIBRARIES} ${GTK3_LIBRARIES})
++	target_include_directories(${source} PRIVATE ${GSL_INCLUDE_DIRS}
++	  ${GTK3_INCLUDE_DIRS} ${GLIB_INCLUDE_DIRS})
++	target_link_libraries(${source} 2geom gtest_main gtest ${GSL_LIBRARIES}
++	  ${GTK3_LIBRARIES} ${GLIB_LIBRARIES})
+ 	add_test(NAME ${source} COMMAND ${source})
+ endforeach()
+ 
+-- 
+2.24.1
+

gnu/packages/patches/lib2geom-use-system-googletest.patch

@@ -0,0 +1,94 @@
+From 6693b9c8ff1ae1ec02c9002c0a8f5f416f0c88f0 Mon Sep 17 00:00:00 2001
+From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
+Date: Sun, 12 Jan 2020 23:23:33 -0500
+Subject: [PATCH 3/3] build: Prefer googletest from the system.
+
+Fixes issue #4.
+
+The build system now look for a system installed googletest or falls
+back to the bundled copy of googletest otherwise.
+
+* CMakeLists.txt: Add call to find_package(GTest).
+(include_directories): Remove "src/googletest/googletest/include" from
+arg.
+* src/CMakeLists.txt[NOT GTEST_FOUND]: Define the gtest and gtest_main
+libraries when GTEST_FOUND is false.  Globally include the googletest
+headers here.  Define aliases for the gtest and gtest_main libraries
+that match those defined by the FindGTest module.
+* src/tests/CMakeLists.txt: Replace references to gtest_main and gtest
+by GTest::Main and GTest::GTest, respectively.
+---
+ CMakeLists.txt           |  3 ++-
+ src/CMakeLists.txt       | 15 +++++++++++----
+ src/tests/CMakeLists.txt |  6 +++---
+ 3 files changed, 16 insertions(+), 8 deletions(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index bfeb8f03..96fbd58c 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -25,13 +25,14 @@ find_package(DoubleConversion REQUIRED)
+ find_package(PkgConfig REQUIRED)
+ find_package(Cython)
+ find_package(Threads)
++find_package(GTest)
+ pkg_check_modules(GTK3 gtk+-3.0)
+ pkg_check_modules(GLIB glib-2.0)
+ pkg_check_modules(CAIRO cairo)
+ pkg_check_modules(GSL gsl)
+ 
+ # Add global include and link directories
+-include_directories(src src/googletest/googletest/include ${CMAKE_CURRENT_BINARY_DIR})
++include_directories(src ${CMAKE_CURRENT_BINARY_DIR})
+ link_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/2geom)
+ 
+ check_cxx_source_compiles("#include <math.h>\nint main() { double a=0.5,b=0.5,c=0.5; sincos(a, &b, &c); return 0; }" HAVE_SINCOS)
+diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
+index eefb3ac5..941dc4c7 100644
+--- a/src/CMakeLists.txt
++++ b/src/CMakeLists.txt
+@@ -1,7 +1,14 @@
+-add_library(gtest SHARED googletest/googletest/src/gtest-all.cc)
+-target_include_directories(gtest PRIVATE googletest/googletest)
+-target_link_libraries(gtest Threads::Threads)
+-add_library(gtest_main STATIC googletest/googletest/src/gtest_main.cc)
++if(NOT GTEST_FOUND)
++  message("No system googletest library: using bundled copy.")
++  add_library(gtest SHARED googletest/googletest/src/gtest-all.cc)
++  add_library(gtest_main STATIC googletest/googletest/src/gtest_main.cc)
++  target_include_directories(gtest PRIVATE googletest/googletest)
++  target_link_libraries(gtest Threads::Threads)
++  include_directories(SYSTEM googletest/googletest/include)
++  # Aliases to share the same nomenclature with FindGTest.
++  add_library(GTest::GTest ALIAS gtest)
++  add_library(GTest::Main ALIAS gtest_main)
++endif()
+ 
+ add_subdirectory(2geom)
+ add_subdirectory(tests)
+diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
+index 626cfd87..3538f8cf 100644
+--- a/src/tests/CMakeLists.txt
++++ b/src/tests/CMakeLists.txt
+@@ -34,15 +34,15 @@ foreach(source ${2GEOM_GTESTS_SRC})
+ 	add_executable(${source} ${source}.cpp)
+ 	target_include_directories(${source} PRIVATE ${GSL_INCLUDE_DIRS}
+ 	  ${GTK3_INCLUDE_DIRS} ${GLIB_INCLUDE_DIRS})
+-	target_link_libraries(${source} 2geom gtest_main gtest ${GSL_LIBRARIES}
+-	  ${GTK3_LIBRARIES} ${GLIB_LIBRARIES})
++	target_link_libraries(${source} 2geom GTest::Main GTest::GTest
++	  ${GSL_LIBRARIES} ${GTK3_LIBRARIES} ${GLIB_LIBRARIES})
+ 	add_test(NAME ${source} COMMAND ${source})
+ endforeach()
+ 
+ foreach(source ${2GEOM_TESTS_SRC})
+     add_executable(${source} ${source}.cpp)
+     target_include_directories(${source} PRIVATE ${GSL_INCLUDE_DIRS} ${GTK3_INCLUDE_DIRS})
+-    target_link_libraries(${source} 2geom gtest ${GSL_LIBRARIES} ${GTK3_LIBRARIES})
++    target_link_libraries(${source} 2geom GTest::GTest ${GSL_LIBRARIES} ${GTK3_LIBRARIES})
+     add_test(NAME ${source} COMMAND ${source})
+ endforeach(source)
+ 
+-- 
+2.24.1
+