feat(build): install/export rules, umbrella header, verified consumer

cmake/plot_options.cmake

@@ -16,6 +16,62 @@ option(PLOT_BUILD_GLFW "Build the GLFW adapter and demo" OFF)
 option(PLOT_BUILD_IMGUI "Build the Dear ImGui adapter and demo" OFF)
 option(PLOT_BUILD_QT6 "Build the Qt6 adapter and demo" OFF)
 option(PLOT_BUILD_GTK4 "Build the GTK4 adapter and demo" OFF)
+option(PLOT_INSTALL "Generate install and export rules (find_package(plot))" ON)
+set(PLOT_SANITIZE "" CACHE STRING
+    "Sanitizers to build with, as the list a -fsanitize= flag takes (e.g. address); empty for none")
+
+# Sanitizer flags go on every target in this project, fetched third-party sources
+# included: a partially instrumented build reports as loudly about the
+# instrumentation gap as about any real bug. The flags are one -fsanitize= list
+# (PLOT_SANITIZE) rather than a set of per-sanitizer options so the preset, the
+# tests' runtime environment and this file cannot disagree about what is on.
+if(PLOT_SANITIZE)
+  add_compile_options(-fsanitize=${PLOT_SANITIZE} -fno-omit-frame-pointer)
+  add_link_options(-fsanitize=${PLOT_SANITIZE})
+endif()
+
+# Read by tests/CMakeLists.txt, which points ASAN_OPTIONS at this project's
+# suppressions file when the address sanitizer is on.
+string(REPLACE "," ";" PLOT_SANITIZE_LIST "${PLOT_SANITIZE}")
+if("address" IN_LIST PLOT_SANITIZE_LIST)
+  set(PLOT_ASAN_ENABLED TRUE)
+endif()
+
+# --- install / export bookkeeping --------------------------------------------
+#
+# An adapter can only be installed and exported when its toolkit can be found
+# again on the consumer's machine. A dependency resolved by find_package() or
+# pkg-config can be: the installed config file re-finds it with the very same
+# call. A dependency that FetchContent supplied cannot -- there is nothing on the
+# consumer's machine to point at, and promising it would make every consumer
+# clone and build that toolkit at the same revision -- so those adapters stay out
+# of the export set and the configure log says why (see each adapter's
+# CMakeLists.txt for its own resolution order).
+#
+# The results are global properties, because the adapters decide inside their own
+# subdirectory while the install rules run at the top level. A property rather
+# than a cache entry: a cache value cannot hold the newlines a snippet of
+# find_dependency() calls needs, and nothing here has to survive the configure
+# pass that produced it.
+
+# Records one adapter's install/export decision and prints it. `dependency` is
+# the config-file snippet that re-creates the toolkit's imported target before
+# plotTargets.cmake is included; it is empty when the target is not exported.
+function(plot_record_adapter_export target exportable reason dependency)
+  if(NOT exportable)
+    message(STATUS "plot: not exporting ${target}: ${reason}")
+  elseif(NOT PLOT_INSTALL)
+    message(STATUS "plot: not exporting ${target}: PLOT_INSTALL is OFF")
+  else()
+    set_property(GLOBAL APPEND PROPERTY PLOT_ADAPTER_EXPORT_TARGETS "${target}")
+    # Read-modify-write, not APPEND: the snippets are one block of C++-style
+    # lines that must be substituted into one file, and a property read back is a
+    # list -- APPEND would join them with the separator ';' instead of a newline.
+    get_property(plot_dependencies GLOBAL PROPERTY PLOT_ADAPTER_DEPENDENCIES)
+    set_property(GLOBAL PROPERTY PLOT_ADAPTER_DEPENDENCIES "${plot_dependencies}${dependency}")
+    message(STATUS "plot: exporting ${target}: ${reason}")
+  endif()
+endfunction()
 
 # Apply the project warning set to a first-party target. Warnings are never
 # suppressed per file.
@@ -38,15 +94,22 @@ endfunction()
 # GLFW (the last resort, because it needs the network). The result is cached in
 # PLOT_GLFW_DEP, so a build with several adapters enabled discovers -- and at
 # worst fetches -- exactly one copy. Sets <out_var> to the target to link.
+#
+# PLOT_GLFW_DEP_ORIGIN records which of the three supplied it, because only the
+# first two can be promised to a consumer of an installed adapter (see
+# plot_record_adapter_export()).
 function(plot_find_glfw out_var)
   if(NOT DEFINED PLOT_GLFW_DEP)
     set(plot_glfw_dep "")
+    set(plot_glfw_origin "")
 
     find_package(glfw3 3.3 QUIET)
     if(TARGET glfw)
       set(plot_glfw_dep glfw)
+      set(plot_glfw_origin find_package)
     elseif(TARGET glfw3::glfw3)
       set(plot_glfw_dep glfw3::glfw3)
+      set(plot_glfw_origin find_package)
     endif()
 
     if(NOT plot_glfw_dep)
@@ -55,6 +118,7 @@ function(plot_find_glfw out_var)
         pkg_check_modules(GLFW_PC QUIET IMPORTED_TARGET glfw3)
         if(TARGET PkgConfig::GLFW_PC)
           set(plot_glfw_dep PkgConfig::GLFW_PC)
+          set(plot_glfw_origin pkg-config)
         endif()
       endif()
     endif()
@@ -72,12 +136,29 @@ function(plot_find_glfw out_var)
         GIT_SHALLOW TRUE)
       FetchContent_MakeAvailable(glfw)
       set(plot_glfw_dep glfw)
+      set(plot_glfw_origin FetchContent)
     endif()
 
     set(PLOT_GLFW_DEP "${plot_glfw_dep}" CACHE INTERNAL
         "GLFW target the plot adapters link against")
+    set(PLOT_GLFW_DEP_ORIGIN "${plot_glfw_origin}" CACHE INTERNAL
+        "How plot resolved GLFW: find_package, pkg-config or FetchContent")
     message(STATUS "plot: GLFW adapter dependency: ${plot_glfw_dep}")
   endif()
 
   set(${out_var} "${PLOT_GLFW_DEP}" PARENT_SCOPE)
 endfunction()
+
+# The find_dependency() snippet that re-creates an exported adapter's toolkit
+# target on a consumer's machine, for the toolkits a config file can re-find.
+# Adapters call these when they record their export decision; the snippets are
+# substituted into cmake/plotConfig.cmake.in.
+function(plot_glfw_dependency_snippet out_var)
+  if(PLOT_GLFW_DEP_ORIGIN STREQUAL "find_package")
+    set(${out_var} "find_dependency(glfw3 3.3)\n" PARENT_SCOPE)
+  else()
+    set(${out_var}
+        "find_dependency(PkgConfig)\npkg_check_modules(GLFW_PC REQUIRED IMPORTED_TARGET glfw3)\n"
+        PARENT_SCOPE)
+  endif()
+endfunction()