feat: support OpenGL dependencies with config

Author: aminya

Matplot++Config.cmake.in

@@ -16,6 +16,11 @@ if(NOT ${MATPLOT_BUILT_SHARED})
     list(APPEND CMAKE_MODULE_PATH ${MATPLOT_CONFIG_INSTALL_DIR})
     list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
     find_dependency(Filesystem COMPONENTS Experimental Final)
+    # OpenGL backend
+    if (@MATPLOTPP_BUILD_EXPERIMENTAL_OPENGL_BACKEND@)
+        find_dependency(glad CONFIG)
+        find_dependency(glfw3 CONFIG)
+    endif()
     list(POP_BACK CMAKE_MODULE_PATH)
 endif()
 

source/matplot/CMakeLists.txt

@@ -214,40 +214,49 @@ if (MATPLOTPP_BUILD_EXPERIMENTAL_OPENGL_BACKEND)
     # The biggest con of the OpenGL backend is that it cannot open a window
     #     in another thread. All it can do is get in the middle of the render
     #     loop and draw the plot.
-    find_package(OpenGL REQUIRED)
+    find_package(OpenGL)
 
     # https://github.com/Dav1dde/glad
-    find_package(GLAD QUIET)
-    if (NOT GLAD_FOUND AND NOT TARGET glad)
-        # Use CPM only if not found, to avoid ODR violations
-        # find_package(GLAD REQUIRE) would suffice if it worked well
-        FetchContent_Declare(glad GIT_REPOSITORY https://github.com/Dav1dde/glad.git GIT_TAG df8e9e16110b305479a875399cee13daa0ccadd9)
-        FetchContent_MakeAvailable(glad)
-    else ()
-        # FindGLAD does not usually create a target, so we create an interface target
-        if (NOT TARGET glad)
-            add_library(glad INTERFACE)
-            target_include_directories(glad INTERFACE ${GLAD_INCLUDE_PATH})
-            target_link_libraries(glad INTERFACE ${GLAD_LIBRARIES})
-        endif ()
-    endif ()
+    find_package(glad CONFIG)
+    if (NOT glad_FOUND)
+        find_package(GLAD QUIET)
+        if (NOT GLAD_FOUND AND NOT TARGET glad)
+            # Use CPM only if not found, to avoid ODR violations
+            # find_package(GLAD REQUIRE) would suffice if it worked well
+            FetchContent_Declare(glad GIT_REPOSITORY https://github.com/Dav1dde/glad.git GIT_TAG df8e9e16110b305479a875399cee13daa0ccadd9)
+            FetchContent_MakeAvailable(glad)
+        else ()
+            if(TARGET glad)
+                add_library(glad::glad ALIAS glad)
+                endif()
+            if(NOT TARGET glad::glad)
+                # FindGLAD does not usually create a target, so we create an interface target
+                add_library(glad::glad INTERFACE)
+                target_include_directories(glad::glad INTERFACE ${GLAD_INCLUDE_PATH})
+                target_link_libraries(glad::glad INTERFACE ${GLAD_LIBRARIES})
+            endif()
+        endif()
+    endif()
 
     # https://github.com/glfw/glfw
-    find_package(glfw3 QUIET)
-    if (NOT GLFW3_FOUND AND NOT TARGET glfw)
-        # Use CPM only if not found, to avoid ODR violations
-        # find_package(glfw3 REQUIRE) would suffice if it worked well
-        FetchContent_Declare(glfw3 GIT_REPOSITORY https://github.com/glfw/glfw.git GIT_TAG 3.3.2)
-        FetchContent_MakeAvailable(glfw3)
-    endif ()
+    find_package(glfw3 CONFIG)
+    if (NOT glfw3_FOUND)
+        find_package(glfw3 QUIET)
+        if (NOT GLFW3_FOUND AND NOT TARGET glfw)
+            # Use CPM only if not found, to avoid ODR violations
+            # find_package(glfw3 REQUIRE) would suffice if it worked well
+            FetchContent_Declare(glfw3 GIT_REPOSITORY https://github.com/glfw/glfw.git GIT_TAG 3.3.2)
+            FetchContent_MakeAvailable(glfw3)
+        endif ()
+    endif()
 
     add_library(matplot_opengl
             backend/opengl_embed.h
             backend/opengl_embed.cpp
             backend/opengl.h
             backend/opengl.cpp
             )
-    target_link_libraries(matplot_opengl PUBLIC matplot glad glfw ${CMAKE_DL_LIBS})
+    target_link_libraries(matplot_opengl PUBLIC matplot glad::glad glfw ${CMAKE_DL_LIBS})
 
     list(APPEND TARGETS matplot_opengl)
 endif()