More (mostly) documentation updates for FLTK 1.5.0

All files: remove autoconf/configure related stuff, update links.

- README.txt: describe prerequisites, provide generic instructions
  on how to use CMake to build FLTK
- test/demo.cxx: remove code used for configure/make build
- test/CMakeLists.txt: remove obsolete 'target_compile_definitions()'

1 files changed, 114 insertions, 32 deletions

diff --git a/README.txt b/README.txt
index e8bc87233..992b6661c 100644
--- a/README.txt
+++ b/README.txt
@@ -1,10 +1,10 @@
-README - Fast Light Tool Kit (FLTK) Version 1.5.0
--------------------------------------------------
+README - Fast Light Tool Kit (FLTK) Version 1.5
+------------------------------------------------
 
-WHAT IS FLTK?
+What is FLTK?
 
-    The Fast Light Tool Kit is a cross-platform C++ GUI toolkit for
-    UNIX®/Linux® (X11 or Wayland), Microsoft® Windows®, and macOS®.
+    The Fast Light Tool Kit (FLTK) is a cross-platform C++ GUI toolkit
+    for UNIX®/Linux® (X11 or Wayland), Microsoft® Windows®, and macOS®.
     FLTK provides modern GUI functionality without bloat and supports
     3D graphics via OpenGL® and its built-in GLUT emulation.
     It was originally developed by Mr. Bill Spitzak and is currently
@@ -15,7 +15,7 @@ WHAT IS FLTK?
         https://github.com/fltk/fltk/
 
 
-LICENSING
+Licensing
 
     FLTK comes with complete free source code.  FLTK is available
     under the terms of the GNU Library General Public License with
@@ -24,61 +24,142 @@ LICENSING
     software! (Even Bill Gates could use it.)
 
 
-ON-LINE DOCUMENTATION
+Online Documentation
 
     The documentation in HTML and PDF forms can be created by
     Doxygen from the source files. HTML and PDF versions of this
-    documentation is also available from the FLTK web site at:
+    documentation are also available from the FLTK web site at:
 
         https://www.fltk.org/documentation.php
 
 
-BUILDING AND INSTALLING FLTK UNDER UNIX AND macOS
+Prerequisites for Building FLTK
 
-    Since FLTK 1.5.0 the only available build system is CMake. CMake is a
+    To build FLTK 1.5 and higher you need:
+
+      - CMake
+      - a C++11 capable compiler, e.g. gcc, clang, Visual Studio, Xcode
+      - system specific build files (headers etc.)
+
+    CMake is used to generate the build environment on your system.
+    It can create build environments for a lot of different build tools,
+    please see the CMake documentation for more info. For details and the
+    required CMake version please see README.CMake.txt.
+
+    Since FLTK 1.5 we use C++11 features and you need at least a C++11 capable
+    compiler running in C++11 mode. The minimal C++ standard used for building
+    FLTK and your application *may* be raised in future versions.
+
+    The required header files etc. (build environment or SDK) vary across
+    platforms and are described in platform specific README.* files, e.g. on
+    Unix/Linux systems these are typically provided by the package manager.
+
+
+Building and Installing FLTK With CMake (Generic Instructions)
+
+    Since FLTK 1.5 the only available build system is CMake. CMake is a
     "build system generator" and can be used to create Makefile's, Ninja
     build files, Xcode (macOS), Visual Studio (Windows) IDE files, and
-    many more. Use `cmake --help` to display the available generators
-    on your platform.
+    many more. Use `cmake --help` or the CMake GUI tools (cmake-gui or
+    ccmake) to display the available generators on your platform.
 
     Please see also README.CMake.txt for further details. There are *many*
     options to configure the build as you need.
 
-    In a nutshell:
+    CMake comes in two flavors: a commandline utility and a GUI program.
+    On many platforms both can be used to generate the build files and
+    even to *build* the project (i.e. the FLTK library and programs).
+
+    The following paragraphs describe both tools in a nutshell.
+    For details please see README.CMake.txt.
+
+
+Building and Installing FLTK With CMake (Commandline)
+
+    On systems where a commandline `CMake` utility is available (this is
+    the case even on Windows), the commands to build FLTK using CMake can
+    be similar to:
 
       $ cd /path/to/fltk
-      $ cmake . -B build
+      $ cmake . -B build [ options ]
       $ cmake --build build
 
     These commands create the build folder 'build' inside your source tree,
-    build the library and all test programs. You may want to test the demo
-    programs by running `build/bin/test/demo`.
+    build the library and all test programs. Note that parameters in '[ ... ]'
+    are optional and '.' represents the current directory (the source folder).
+
+    You may want to test the demo programs by running `build/bin/test/demo`.
+
+    Instead of building FLTK with a CMake command you can also use the
+    build tool you generated in the first step and/or run CMake from the
+    build directory, for instance:
+
+      $ cd /path/to/fltk
+      $ mkdir build
+      $ cd build
+      $ cmake .. -G "Unix Makefiles" [ options ]
+      $ make [ -j N ]
+
+    You may want to test the demo programs by running `bin/test/demo`.
 
     After successful tests you may install the library with the following
-    command, but please be aware that this will install FLTK in a system
-    directory for system-wide use. We don't recommend this unless you know
+    command or a similar one, but please be aware that this will install
+    FLTK in a system directory for system-wide use if you don't change the
+    default installation path. We don't recommend this unless you know
     what you're doing.
 
-      $ sudo cmake --install build  # default: to /usr/local/...
+      $ sudo cmake --install build  # from the source tree (with CMake)
+
+    or
+
+      $ sudo make install           # from the build folder (with make)
+
+    Other commands (e.g. `ninja`) may be used as well, depending on the
+    CMake generator you used.
+
+
+Building and Installing FLTK With CMake (GUI)
+
+    On most systems CMake comes with a GUI program called `cmake-gui`, on
+    Unix/Linux like systems also a "TUI" called `ccmake` (a "grapical" utility
+    for a terminal). The latter is out of scope for this README file.
 
+    If you want to use CMake's GUI program, execute it by running `cmake-gui`
+    and then follow the dialog on the screen.
 
-BUILDING FLTK UNDER MICROSOFT WINDOWS
+    You need to select the source folder and the build folder at the top
+    of the screen. After clicking on `Configure` CMake will prompt you to
+    select the build system or compilers of your choice. In many cases
+    you can select the default compilers, e.g Visual Studio on Windows.
+    For more details please see the CMake documentation.
+
+    Note: on Windows it may be necessary to run CMake from a "Visual Studio
+    Command Prompt" so CMake can find the existing Visual Studio compilers
+    and SDK's, but details are beyond the scope of this document.
+
+    After running `Configure` successfully (look for error messages in the
+    window) you need to click on `Generate` to create the actual build files,
+    for instance Makefiles, the Visual Studio IDE project files on Windows,
+    or the Xcode IDE project on macOS, etc..
+
+    With some CMake generators for IDE projects (VS, Xcode) you can finally
+    click on `Open Project` to launch the IDE tool of your choice. In other
+    cases you may execute the build system by running `make`, `ninja`, etc.
+    after leaving the GUI to build the library and FLTK (test) programs.
+
+
+Building FLTK under Microsoft Windows
 
     There are two ways to build FLTK under Microsoft Windows.
 
-    The first is to use CMake to create the Visual C++ project or NMake files
-    in your favorite development directory, then build FLTK with Visual Studio.
+    The first is to use CMake to create the Visual Studio IDE project or
+    NMake files as described above, then build FLTK with Visual Studio or
+    NMake.
 
     The second method is to use a GNU-based development tool. To build with
     the Cygwin, MinGW, or MSYS2 tools, use CMake to create the build files
-    as described above.
-
-    In most cases it's useful to install a binary CMake distribution from
-    https://cmake.org/download/ .
-
-    Then execute `cmake-gui` and generate Visual Studio project files or any
-    other build files of your choice, e.g. "Unix Makefiles" for MinGW, but
-    note that there are other options as well.
+    from the `cmake` commandline and build the library as described above.
+    On some of these systems you may also install and use `cmake-gui`.
 
     See README.Windows.txt and README.CMake.txt for more info.
 
@@ -86,7 +167,8 @@ BUILDING FLTK UNDER MICROSOFT WINDOWS
 BUILDING HTML DOCUMENTATION
 
     FLTK uses Doxygen for documentation, so you'll at least need doxygen
-    installed for creating html docs, and LaTeX for creating PDF docs.
+    installed for creating html docs, and additionally LaTeX for creating
+    PDF documentation.
 
     If you want to build the documentation, change directory to your build
     folder, for instance
@@ -100,7 +182,7 @@ BUILDING HTML DOCUMENTATION
 
     Note: instead of using the generic CMake commands above you can also
     use equivalent commands of your build system, e.g. `make html` or
-    `ninja pdf`.
+    `ninja pdf`, respectively.
 
 
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