Rename README files to README.txt (and several similar files).

Files without '.txt' suffix can't be handled well by Windows (users),
hence renaming such text files to *.txt makes FLTK more "Windows-friendly".

There are a few exceptions (this is intentional): README and other files
in bundled libraries (maintained upstream) are not changed.

1 files changed, 112 insertions, 0 deletions

diff --git a/documentation/README.txt b/documentation/README.txt
new file mode 100644
index 000000000..6b7e39980
--- /dev/null
+++ b/documentation/README.txt
@@ -0,0 +1,112 @@
+README.txt (documentation)
+---------------------------
+FLTK 1.3 (and higher) documentation is available in HTML and PDF format.
+The documentation must be generated in a separate step or downloaded
+from FLTK's software download pages. The documentation can also
+be accessed online.
+
+To read the docs after downloading or generating them, open the files:
+
+    documentation/html/index.html
+    documentation/fltk.pdf
+
+with your browser or PDF viewer, respectively.
+
+
+Online Documentation:
+---------------------
+A documentation version is available online at the FLTK web site,
+along with the PDF version of the manual. The docs on the web site
+are usually somewhat older (latest release). Use this URL to find
+the current online documentation:
+
+    https://www.fltk.org/documentation.php
+
+
+Documentation Download:
+-----------------------
+To download pre-generated docs, go to
+
+    https://www.fltk.org/software.php
+
+and look for the files
+
+    fltk-<version>-docs-html.tar.gz
+    fltk-<version>-docs-pdf.tar.gz
+
+Extract the documentation tarballs into the same directory as you
+did with the source tarball.
+
+
+Generation of Documentation (common part):
+------------------------------------------
+To generate the documentation yourself, you should have Doxygen
+version 1.8 or later (recommended version is 1.8.13 or later).
+Older Doxygen versions than 1.8 may or may not work.
+
+To generate the PDF version you also need a current version of LaTeX.
+You can use the packages tetex (older) or texlive (current) if your
+distribution provides them. You may need to install additional fonts
+and other sub-packages for the PDF version to be generated correctly.
+
+Note: packages known to work under Ubuntu 18.04:
+
+  texlive texlive-extra-utils texlive-latex-extra texlive-font-utils
+
+
+Generation of Documentation with autoconf (configure) + make:
+-------------------------------------------------------------
+Use "make html" in the documentation directory to generate the HTML
+documentation, or "make pdf" to generate the PDF version. "make docs"
+generates both versions in one step (as would do "make clean html pdf").
+
+To read the HTML or PDF docs, see above.
+
+
+Generation of Documentation with CMake + make:
+----------------------------------------------
+We assume that you use an out-of-source build as recommended.
+Documentation is not generated in a default build. You must set one or
+more CMake options using cmake-gui, ccmake, or cmake -DOPTION...
+
+These options are predefined to OFF and can be switched ON:
+
+  - OPTION_BUILD_HTML_DOCUMENTATION:BOOL=OFF	target:	html
+  - OPTION_BUILD_PDF_DOCUMENTATION:BOOL=OFF	target:	pdf
+
+  - OPTION_INSTALL_HTML_DOCUMENTATION:BOOL=OFF
+  - OPTION_INSTALL_PDF_DOCUMENTATION:BOOL=OFF
+
+If you switch one or both of the first two options ON, then the
+targets 'html' and/or 'pdf' are generated, respectively. Target 'docs'
+is added to generate both 'html' and 'pdf'. As said above, you need
+installed Doxygen and LaTeX software for this to work.
+
+Use "make html" in the root or documentation directory of the build tree
+to generate the HTML documentation, or "make pdf" to generate the PDF
+version. "make docs" generates both versions in one step (as would do
+"make clean html pdf").
+
+To read the HTML or PDF docs, see above, but use the build directory.
+
+Note: if you enable one or more of the "*INSTALL*" options, then
+`make install' will install the docs, but you must still build them
+manually, because the generation is not included in the standard ('all')
+target. This may be changed in the future.
+
+
+FLTK Developer Snapshots or Git Usage:
+--------------------------------------
+There is no pre-generated documentation available if you use a current
+developer snapshot or git. You must generate the documentation
+yourself or access the online documentation.
+
+
+Bugs and Feature Requests:
+--------------------------
+If you find any typos, things that are unclear, or would like to
+contribute an example, section, or chapter to the FLTK manual, please
+post a question in the fltk newsgroup fltk.general or post a bug
+report or feature request at:
+
+    https://www.fltk.org/str.php