From c92f992380704942825e6dcf4363ea45585ac6cd Mon Sep 17 00:00:00 2001
From: Albrecht Schlosser <albrechts.fltk@online.de>
Date: Tue, 12 Feb 2019 15:09:42 +0100
Subject: CMake: Cairo demo must also be built w/o Cairo

The Cairo demo program (test/cairo_test.cxx) can and should be built
even if Cairo is not configured with CMake as it is done with
autotools (configure/make).

The message window shown when Cairo support is not available has been
improved (is more explicit and has a window title).
---
 test/CMakeLists.txt | 10 ++++++----
 test/cairo_test.cxx | 17 ++++++++++-------
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 18772b1d2..1d1f98dbe 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -124,10 +124,12 @@ CREATE_EXAMPLE(gl_overlay gl_overlay.cxx "fltk;fltk_gl;${OPENGL_LIBRARIES}")
 CREATE_EXAMPLE(shape shape.cxx "fltk;fltk_gl;${OPENGL_LIBRARIES}")
 endif(OPENGL_FOUND)
 
-# Cairo demo
-if(FLTK_HAVE_CAIRO)
-   CREATE_EXAMPLE(cairo_test cairo_test.cxx "fltk;fltk_cairo")
-endif(FLTK_HAVE_CAIRO)
+# Cairo demo - must also be built w/o Cairo (displays a message box)
+if (FLTK_HAVE_CAIRO)
+  CREATE_EXAMPLE(cairo_test cairo_test.cxx "fltk;fltk_cairo")
+else ()
+  CREATE_EXAMPLE(cairo_test cairo_test.cxx fltk)
+endif (FLTK_HAVE_CAIRO)
 
 endif(NOT ANDROID)
 
diff --git a/test/cairo_test.cxx b/test/cairo_test.cxx
index 21a812be9..46348f23c 100644
--- a/test/cairo_test.cxx
+++ b/test/cairo_test.cxx
@@ -1,19 +1,19 @@
 //
 // "$Id$"
 //
-// Arc drawing test program for the Fast Light Tool Kit (FLTK).
+// Cairo drawing test program for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2018 by Bill Spitzak and others.
+// Copyright 1998-2019 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
 // file is missing or damaged, see the license at:
 //
-//     http://www.fltk.org/COPYING.php
+//     https://www.fltk.org/COPYING.php
 //
 // Please report all bugs and problems on the following page:
 //
-//     http://www.fltk.org/str.php
+//     https://www.fltk.org/str.php
 //
 
 #include <config.h>
@@ -27,7 +27,7 @@
 #include <FL/math.h>
 #define DEF_WIDTH 0.03
 
-// uncomment the following line to enable cairo context autolink feature:
+// uncomment the following line to enable Cairo context autolink feature:
 // #define AUTOLINK
 
 // put your drawing stuff here
@@ -116,7 +116,7 @@ static void round_button(cairo_t *cr, double x0, double y0,
   centered_text(cr, x0, y0, rect_width, rect_height, "FLTK loves Cairo!");
 }
 
-// The cairo rendering cb called during Fl_Cairo_Window::draw() :
+// The Cairo rendering cb called during Fl_Cairo_Window::draw() :
 static void my_cairo_draw_cb(Fl_Cairo_Window *window, cairo_t *cr) {
 
   int w = window->w(), h = window->h();
@@ -147,7 +147,10 @@ int main(int argc, char **argv) {
 #include <FL/fl_ask.H>
 
 int main(int argc, char **argv) {
-  fl_message("please configure fltk with CAIRO enabled (--enable-cairo or --enable-cairoext)"); 
+  fl_message_title("This program needs a Cairo enabled FLTK library");
+  fl_message(
+    "Please configure FLTK with Cairo enabled (--enable-cairo or --enable-cairoext)\n"
+    "or one of the CMake options OPTION_CAIRO or OPTION_CAIROEXT, respectively.");
   return 0;
 }
 #endif
-- 
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