From 615b731783311af2564573a98e59739a281f8f91 Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Fri, 18 Nov 2022 09:10:22 +0100
Subject: CMake+Wayland: check for presence of required software  modules
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Also, remove hardcoded path to wayland-protocols when
CMake version ≥ 3.4
---
 CMake/options.cmake | 17 +++++++++++++++++
 src/CMakeLists.txt  | 14 +++++++++-----
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/CMake/options.cmake b/CMake/options.cmake
index b56ed77af..8805263c0 100644
--- a/CMake/options.cmake
+++ b/CMake/options.cmake
@@ -196,6 +196,16 @@ if (UNIX)
   list (APPEND FLTK_LDLIBS -lm)
   option (OPTION_USE_WAYLAND "support Wayland and X11 backends" OFF)
   if (OPTION_USE_WAYLAND)
+    pkg_check_modules(WLDCLIENT wayland-client)
+    pkg_check_modules(WLDCURSOR wayland-cursor)
+    pkg_check_modules(WLDPROTO wayland-protocols)
+    pkg_check_modules(XKBCOMMON xkbcommon)
+    pkg_check_modules(DBUS dbus-1)
+    if (NOT(DBUS_FOUND AND WLDCLIENT_FOUND AND WLDCURSOR_FOUND AND WLDPROTO_FOUND AND XKBCOMMON_FOUND))
+      message (STATUS "Not all software modules 'wayland-client wayland-cursor wayland-protocols xkbcommon dbus-1' are present")
+      message (STATUS "Consequently, building for the Wayland backend is not possible.")
+      message (FATAL_ERROR "*** Aborting ***")
+    endif (NOT(DBUS_FOUND AND WLDCLIENT_FOUND AND WLDCURSOR_FOUND AND WLDPROTO_FOUND AND XKBCOMMON_FOUND))
     option (OPTION_WAYLAND_ONLY "support Wayland backend only" OFF)
     set (FLTK_USE_WAYLAND 1)
     if (NOT OPTION_WAYLAND_ONLY)
@@ -409,6 +419,13 @@ if (HAVE_GL)
 endif (HAVE_GL)
 
 if (OPTION_USE_GL)
+  if (OPTION_USE_WAYLAND)
+    pkg_check_modules(WLDEGL wayland-egl)
+    if (NOT WLDEGL_FOUND)
+      message (STATUS "Module 'wayland-egl' is required to build for the Wayland backend.")
+      message (FATAL_ERROR "*** Aborting ***")
+    endif (NOT WLDEGL_FOUND)
+  endif (OPTION_USE_WAYLAND)
   if (OPTION_APPLE_X11)
     set (OPENGL_FOUND TRUE)
     find_library(OPENGL_LIB GL)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index edb3f54c0..b8b773d53 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -624,11 +624,15 @@ if (USE_XFT)
 endif (USE_XFT)
 
 if (UNIX AND OPTION_USE_WAYLAND)
-  if (${CMAKE_HOST_SYSTEM_NAME} STREQUAL "FreeBSD")
-    set(PROTOCOLS /usr/local/share/wayland-protocols)
-  else ()
-    set(PROTOCOLS /usr/share/wayland-protocols)
-  endif (${CMAKE_HOST_SYSTEM_NAME} STREQUAL "FreeBSD")
+  if (NOT (CMAKE_VERSION VERSION_LESS 3.4))
+    pkg_get_variable(PROTOCOLS wayland-protocols pkgdatadir) # requires cmake 3.4
+  else()
+    if (${CMAKE_HOST_SYSTEM_NAME} STREQUAL "FreeBSD")
+      set(PROTOCOLS /usr/local/share/wayland-protocols)
+    else ()
+      set(PROTOCOLS /usr/share/wayland-protocols)
+    endif (${CMAKE_HOST_SYSTEM_NAME} STREQUAL "FreeBSD")
+  endif (NOT (CMAKE_VERSION VERSION_LESS 3.4))
   add_custom_command(
     OUTPUT xdg-shell-protocol.c xdg-shell-client-protocol.h
     COMMAND wayland-scanner private-code ${PROTOCOLS}/stable/xdg-shell/xdg-shell.xml xdg-shell-protocol.c
-- 
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