better links to GEO and API tutorials (cf. #795)

doc/texinfo/gmsh.texi

@@ -430,7 +430,7 @@ ways. Gmsh can display scalar, vector and tensor datasets, perform
 various operations on the resulting post-processing views
 (@pxref{Post-processing module}), can export plots in many different
 formats (@pxref{General options list}), and can generate complex
-animations (see @ref{General tools}, and @ref{t8.geo});
+animations (see @ref{General tools}, and @ref{t8});
 @item
 run on low end machines and/or machines with no graphical
 interface. Gmsh can be compiled with or without the GUI
@@ -669,8 +669,8 @@ contained in the files
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/view1.pos,view1.pos}
 and
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/view5.msh,view5.msh}
-together with the geometry of the first tutorial @ref{t1.geo}, you can
-type the following command:
+together with the geometry of the first tutorial @ref{t1}, you can type
+the following command:
 
 @example
 > gmsh t1.geo view1.pos view5.msh
@@ -1123,7 +1123,7 @@ this is followed by the various ONELAB options. See the
 ONELAB tutorial wiki} for more information.
 
 Character expressions are mostly used to specify non-numeric options and
-input/output file names. See @ref{t8.geo}, for an interesting usage of
+input/output file names. See @ref{t8}, for an interesting usage of
 @w{@var{char-expression}s} in an animation script.
 
 List of character expressions are defined as:
@@ -1167,7 +1167,7 @@ components as well as their alpha channel. The last case permits to use
 the value of a @var{color-option} as a @var{color-expression}. The
 various @w{@var{color-option}s} are listed in @ref{Options}.
 
-See @ref{t3.geo}, for an example of the use of color expressions.
+See @ref{t3}, for an example of the use of color expressions.
 
 @c -------------------------------------------------------------------------
 @c Operators
@@ -1413,7 +1413,7 @@ cannot be imbricated.
 Executes the body of a (previously defined) macro named @var{string}.
 @end ftable
 
-See @ref{t5.geo}, for an example of a user-defined macro. A
+See @ref{t5}, for an example of a user-defined macro. A
 shortcoming of Gmsh's scripting language is that all variables are
 ``public''. Variables defined inside the body of a macro will thus be
 available outside, too!
@@ -1484,7 +1484,7 @@ if none of the @var{expression} of the previous matching codes
 Ends a matching @code{If} command.
 @end ftable
 
-See @ref{t5.geo}, for an example of @code{For} and @code{If} commands. Gmsh
+See @ref{t5}, for an example of @code{For} and @code{If} commands. Gmsh
 does not provide any @code{Else} (or similar) command at the time of this
 writing.
 
@@ -1701,7 +1701,7 @@ terminal. @code{Printf} is equivalent to the @code{printf} C function:
 characters (@code{%f}, @code{%e}, etc.). Note that all @w{@var{expression}s}
 are evaluated as floating point values in Gmsh (@pxref{Expressions}), so
 that only valid floating point formatting characters make sense in
-@var{char-expression}. See @ref{t5.geo}, for an example of the use of
+@var{char-expression}. See @ref{t5}, for an example of the use of
 @code{Printf}.
 
 @item Printf ( @var{char-expression} , @var{expression-list} ) > @var{char-expression};
@@ -2825,7 +2825,7 @@ computed using other fields.
 @end itemize
 
 The list of available fields with their options is given below. An
-example is available in @ref{t10.geo}.
+example is available in @ref{t10}.
 @end enumerate
 
 The three aforementioned methods can be used simultaneously, in which
@@ -2910,7 +2910,7 @@ first @var{expression-list} defines how many elements should be created
 in each extruded layer, and the second @var{expression-list} gives the
 normalized height of each layer (the list should contain a sequence of
 @var{n} numbers 0 < @var{h1} < @var{h2} < @dots{} < @var{hn} <= 1). See
-@ref{t3.geo}, for an example.
+@ref{t3}, for an example.
 
 For curve extrusions, the @code{Recombine} option will recombine triangles
 into quadrangles when possible.  For surface extrusions, the
@@ -3362,8 +3362,8 @@ and the abscissa is the time step.
 Although visualization is usually mostly an interactive task, Gmsh
 exposes all the post-processing commands and options to the user in its
 scripting language and through the API to permit a complete automation
-of the post-processing process (see e.g., @ref{t8.geo}, and
-@ref{t9.geo}).
+of the post-processing process (see e.g., @ref{t8}, and
+@ref{t9}).
 
 The two following sections summarize all available post-processing commands
 and options. Most options apply to both 2D and 3D plots (colormaps,
@@ -3469,7 +3469,7 @@ Executes the plugin @var{string}. The list of default plugins is given in
 
 @item Plugin (@var{string}) . @var{string} = @var{expression} | @var{char-expression};
 Sets an option for a given plugin. See @ref{Post-processing plugins}, for a
-list of default plugins and @ref{t9.geo}, for some examples.
+list of default plugins and @ref{t9}, for some examples.
 
 @item Save View[@var{expression}] @var{char-expression};
 Saves the @var{expression}-th post-processing view in a file named
@@ -3484,7 +3484,7 @@ with parameter name @var{char-expression}.
 Creates a new post-processing view, named @code{"@var{string}"}.  This
 is an easy and quite powerful way to import post-processing data: all
 the values are @var{expressions}, you can embed datasets directly into
-your geometrical descriptions (see, e.g., @ref{t4.geo}), the data can be
+your geometrical descriptions (see, e.g., @ref{t4}), the data can be
 easily generated ``on-the-fly'' (there is no header containing @emph{a
 priori} information on the size of the dataset). The syntax is also very
 permissive, which makes it ideal for testing purposes.
@@ -3704,8 +3704,8 @@ view take the form `@code{View[@var{n}].@var{string}}' (@var{n} = 0, 1, 2,
 @end enumerate
 
 The list of all post-processing and view options is given in
-@ref{Post-processing options list}.  See @ref{t8.geo}, and @ref{t9.geo},
-for some examples.
+@ref{Post-processing options list}.  See @ref{t8}, and @ref{t9}, for
+some examples.
 
 @c =========================================================================
 @c File Formats
@@ -5105,278 +5105,445 @@ the same for all other kinds of values.
 @cindex Examples
 @cindex Tutorial
 
-The following examples introduce new features gradually, starting with
-@ref{t1.geo}. The files corresponding to these examples are available in
-the
+The following tutorials introduce new features gradually, starting with
+@ref{t1}. The files corresponding to these examples are available in the
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial,tutorial}
-directory of the Gmsh distribution. C++, C, Python or Julia versions of
-several of these tutorials are also available in the
-@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c,tutorial/c},
-@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++,tutorial/c++},
-@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python,tutorial/python}
-and
-@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia,tutorial/julia}
-directories.
+directory of the Gmsh distribution.
 
 To learn how to run Gmsh on your computer, see @ref{Running Gmsh on your
 system}. Screencasts that show how to use the GUI are available on
-@uref{http://gmsh.info/screencasts/}.
+@uref{http://gmsh.info/screencasts/}. To learn how to run the C++, C,
+Python and Julia API examples, see the respective subdirectories in
+@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial,tutorial}.
 
 @menu
-* t1.geo:: Geometry basics, elementary entities, physical groups
-* t2.geo:: Transformations, extruded geometries, volumes
-* t3.geo:: Extruded meshes, parameters, options
-* t4.geo:: Built-in functions, holes in surfaces, annotations, entity colors
-* t5.geo:: Characteristic lengths, macros, loops, holes in volumes
-* t6.geo:: Transfinite meshes
-* t7.geo:: Background meshes
-* t8.geo:: Post-processing and animations
-* t9.geo:: Plugins
-* t10.geo:: Mesh size fields
-* t11.geo:: Unstructured quadrangular meshes
-* t12.geo:: Cross-patch meshing with compounds
-* t13.geo:: Remeshing an STL file without an underlying CAD model
-* t14.geo:: Homology and cohomology computation
-* t15.geo:: Embedded points, lines and surfaces
-* t16.geo:: Constructive Solid Geometry, OpenCASCADE geometry kernel
-* t17.geo:: Anisotropic background mesh
-* t18.geo:: Periodic meshes
-* t19.geo:: Thrusections, fillets, pipes, mesh size from curvature
-* t20.geo:: STEP import and manipulation, geometry partitioning
-* t21.geo:: Mesh partitioning
+* t1:: Geometry basics, elementary entities, physical groups
+* t2:: Transformations, extruded geometries, volumes
+* t3:: Extruded meshes, parameters, options
+* t4:: Built-in functions, holes in surfaces, annotations, entity colors
+* t5:: Characteristic lengths, macros, loops, holes in volumes
+* t6:: Transfinite meshes
+* t7:: Background meshes
+* t8:: Post-processing and animations
+* t9:: Plugins
+* t10:: Mesh size fields
+* t11:: Unstructured quadrangular meshes
+* t12:: Cross-patch meshing with compounds
+* t13:: Remeshing an STL file without an underlying CAD model
+* t14:: Homology and cohomology computation
+* t15:: Embedded points, lines and surfaces
+* t16:: Constructive Solid Geometry, OpenCASCADE geometry kernel
+* t17:: Anisotropic background mesh
+* t18:: Periodic meshes
+* t19:: Thrusections, fillets, pipes, mesh size from curvature
+* t20:: STEP import and manipulation, geometry partitioning
+* t21:: Mesh partitioning
+* x1:: Geometrical and mesh data access
+* x2:: Mesh import, discrete entities, hybrid models, terrain meshing
 @end menu
 
 @c -------------------------------------------------------------------------
-@c t1.geo
+@c t1
 @c -------------------------------------------------------------------------
 
-@node t1.geo, t2.geo, Tutorial, Tutorial
+@node t1, t2, Tutorial, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t1.geo,t1.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t1.cpp,t1.cpp}),
+C
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c/t1.c,t1.c}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t1.py,t1.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t1.jl,t1.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t1.geo
 @end smallformat
 
+
 @c -------------------------------------------------------------------------
-@c t2.geo
+@c t2
 @c -------------------------------------------------------------------------
 
-@node t2.geo, t3.geo, t1.geo, Tutorial
+@node t2, t3, t1, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t2.geo,t2.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t2.cpp,t2.cpp}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t2.py,t2.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t2.jl,t2.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t2.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t3.geo
+@c t3
 @c -------------------------------------------------------------------------
 
-@node t3.geo, t4.geo, t2.geo, Tutorial
+@node t3, t4, t2, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t3.geo,t3.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t3.cpp,t3.cpp}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t3.py,t3.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t3.jl,t3.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t3.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t4.geo
+@c t4
 @c -------------------------------------------------------------------------
 
-@node t4.geo, t5.geo, t3.geo, Tutorial
+@node t4, t5, t3, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t4.geo,t4.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t4.cpp,t4.cpp}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t4.py,t4.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t4.jl,t4.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t4.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t5.geo
+@c t5
 @c -------------------------------------------------------------------------
 
-@node t5.geo, t6.geo, t4.geo, Tutorial
+@node t5, t6, t4, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t5.geo,t5.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t5.cpp,t5.cpp}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t5.py,t5.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t5.jl,t5.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t5.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t6.geo
+@c t6
 @c -------------------------------------------------------------------------
 
-@node t6.geo, t7.geo, t5.geo, Tutorial
+@node t6, t7, t5, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t6.geo,t6.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t6.cpp,t6.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t6.py,t6.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t6.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t7.geo
+@c t7
 @c -------------------------------------------------------------------------
 
-@node t7.geo, t8.geo, t6.geo, Tutorial
+@node t7, t8, t6, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t7.geo,t7.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t7.cpp,t7.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t7.py,t7.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t7.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t8.geo
+@c t8
 @c -------------------------------------------------------------------------
 
-@node t8.geo, t9.geo, t7.geo, Tutorial
+@node t8, t9, t7, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t8.geo,t8.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t8.cpp,t8.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t8.py,t8.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t8.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t9.geo
+@c t9
 @c -------------------------------------------------------------------------
 
-@node t9.geo, t10.geo, t8.geo, Tutorial
+@node t9, t10, t8, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t9.geo,t9.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t9.cpp,t9.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t9.py,t9.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t9.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t10.geo
+@c t10
 @c -------------------------------------------------------------------------
 
-@node t10.geo, t11.geo, t9.geo, Tutorial
+@node t10, t11, t9, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t10.geo,t10.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t10.cpp,t10.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t10.py,t10.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t10.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t11.geo
+@c t11
 @c -------------------------------------------------------------------------
 
-@node t11.geo, t12.geo, t10.geo, Tutorial
+@node t11, t12, t10, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t11.geo,t11.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t11.cpp,t11.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t11.py,t11.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t11.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t12.geo
+@c t12
 @c -------------------------------------------------------------------------
 
-@node t12.geo, t13.geo, t11.geo, Tutorial
+@node t12, t13, t11, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t12.geo,t12.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t12.cpp,t12.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t12.py,t12.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t12.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t13.geo
+@c t13
 @c -------------------------------------------------------------------------
 
-@node t13.geo, t14.geo, t12.geo, Tutorial
+@node t13, t14, t12, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t13.geo,t13.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t13.cpp,t13.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t13.py,t13.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t13.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t14.geo
+@c t14
 @c -------------------------------------------------------------------------
 
-@node t14.geo, t15.geo, t13.geo, Tutorial
+@node t14, t15, t13, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t14.geo,t14.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t14.cpp,t14.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t14.py,t14.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t14.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t15.geo
+@c t15
 @c -------------------------------------------------------------------------
 
-@node t15.geo, t16.geo, t14.geo, Tutorial
+@node t15, t16, t14, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t15.geo,t15.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t15.cpp,t15.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t15.py,t15.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t15.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t16.geo
+@c t16
 @c -------------------------------------------------------------------------
 
-@node t16.geo, t17.geo, t15.geo, Tutorial
+@node t16, t17, t15, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t16.geo,t16.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t16.cpp,t16.cpp}),
+Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t16.py,t16.py})
+and Julia
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia/t16.jl,t16.jl}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t16.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t17.geo
+@c t17
 @c -------------------------------------------------------------------------
 
-@node t17.geo, t18.geo, t16.geo, Tutorial
+@node t17, t18, t16, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t17.geo,t17.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t17.cpp,t17.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t17.py,t17.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t17.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t18.geo
+@c t18
 @c -------------------------------------------------------------------------
 
-@node t18.geo, t19.geo, t17.geo, Tutorial
+@node t18, t19, t17, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t18.geo,t18.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t18.cpp,t18.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t18.py,t18.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t18.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t19.geo
+@c t19
 @c -------------------------------------------------------------------------
 
-@node t19.geo, t20.geo, t18.geo, Tutorial
+@node t19, t20, t18, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t19.geo,t19.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t19.cpp,t19.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t19.py,t19.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t19.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t20.geo
+@c t20
 @c -------------------------------------------------------------------------
 
-@node t20.geo, t21.geo, t19.geo, Tutorial
+@node t20, t21, t19, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t20.geo,t20.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t20.cpp,t20.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t20.py,t20.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t20.geo
 @end smallformat
 
 @c -------------------------------------------------------------------------
-@c t21.geo
+@c t21
 @c -------------------------------------------------------------------------
 
-@node t21.geo,  , t20.geo, Tutorial
+@node t21, x1, t20, Tutorial
 @section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/t21.geo,t21.geo}
 
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/t21.cpp,t21.cpp})
+and Python
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/t21.py,t21.py}).
+@sp 1
+
 @smallformat
 @verbatiminclude ../../tutorial/t21.geo
 @end smallformat
 
+@c -------------------------------------------------------------------------
+@c x1
+@c -------------------------------------------------------------------------
+
+@node x1, x2, t21, Tutorial
+@section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/x1.py,x1.py}
+
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/x1.cpp,x1.cpp}).
+@sp 1
+
+@smallformat
+@verbatiminclude ../../tutorial/python/x1.py
+@end smallformat
+
+@c -------------------------------------------------------------------------
+@c x2
+@c -------------------------------------------------------------------------
+
+@node x2, , x1, Tutorial
+@section @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python/x2.py,x2.py}
+
+Also available in C++
+(@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++/x2.cpp,x2.cpp}).
+@sp 1
+
+@smallformat
+@verbatiminclude ../../tutorial/python/x2.py
+@end smallformat
+
 @c =========================================================================
 @c Options
 @c =========================================================================
@@ -5530,22 +5697,22 @@ the compilation of common dependencies.
 @cindex Programming, API
 
 The Gmsh Application Programming Interface (API) allows you to integrate
-the Gmsh library in your own application.  C++, C, Python and Julia
-versions of several of the @code{.geo} tutorials from @ref{Tutorial} are
-available in the
-@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c,tutorial/c},
+the Gmsh library in your own application. By design, the Gmsh API is
+purely functional, and only uses elementary types from the target
+language. Currently supported languages are C++, C, Python and Julia.
+See the
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c++,tutorial/c++},
+@url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/c,tutorial/c},
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/python,tutorial/python}
 and
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/tutorial/julia,tutorial/julia}
-directories.  Other API examples are available in the
+directories for the API @ref{Tutorial}. Other API examples are available
+in the
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/demos/api/,demos/api}
 directory.
 
-By design, the Gmsh API is purely functional, and only uses elementary
-types from the target language. Currently supported languages are C++,
-C, Python and Julia. The different versions of the API are generated
-automatically from the master API definition file
+The different versions of the API are generated automatically from the
+master API definition file
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/api/gen.py,api/gen.py}:
 
 @itemize @bullet
@@ -5567,8 +5734,8 @@ that this will lead to (slightly) reduced performance compared to using
 the native Gmsh C++ API, as it entails additional data copies between
 the C++ wrapper, the C API and the native C++ code.
 
-The structure of the API reflects the underlying Gmsh data model
-(see also @ref{Source code structure}):
+The structure of the API reflects the underlying Gmsh data model (see
+also @ref{Source code structure}):
 @itemize
 @item
 There are two main data containers: @emph{models} (which hold the
@@ -6000,7 +6167,7 @@ You can create simple MPEG animations by choosing MPEG as the format in
 post-processing data sets, or to change parameters according to
 @code{Print.Parameter}. To create fully customized animations or to use
 different output formats (AVI, MP4, etc.) you should write a
-script. Have a look at @ref{t8.geo} or
+script. Have a look at @ref{t8} or
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/demos/post_processing/anim.script,demos/post_processing/anim.script}
 for some examples.
 
@@ -6196,7 +6363,7 @@ elements, and it is up to the solver to interpret these tags as boundary
 conditions, materials, etc. Associating tags with elements in Gmsh is
 done by defining physical groups (Physical Points, Physical Curves,
 Physical Surfaces and Physical Volumes). See the reference manual as
-well as the tutorials (in particular @ref{t1.geo}) for a detailed
+well as the tutorials (in particular @ref{t1}) for a detailed
 description and some examples.
 
 @item How can I display only the mesh associated with selected geometrical entities?
@@ -6389,7 +6556,7 @@ Evaluate plugin.
 
 You can save simple MPEG animations directly from the `File->Export'
 menu. For other formats you should write a script. Have a look at
-@ref{t8.geo} or
+@ref{t8} or
 @url{https://gitlab.onelab.info/gmsh/gmsh/tree/master/demos/post_processing/anim.script,demos/post_processing/anim.script}
 for some examples.
 

tutorial/README.txt

@@ -11,17 +11,47 @@ the command line, run "gmsh t1.geo" (which will launch the GUI) or "gmsh t1.geo
    Gmsh app. See the top-level `README.txt' file in the Gmsh source code for
    instructions on how to compile the app from source.
 
-The `c++', `c', `python' and `julia' subdirectories contain C++, C, Python and
-Julia versions of (some of) these tutorials, written using the Gmsh Application
-Programming Interface (API): you will need the Gmsh dynamic library and the
-associated header files (for C++ and C) or modules (for Python and Julia) to run
-them. Each subdirectory also contains additional information on how to run the
-tutorials for each supported language, as well as extended tutorials (starting
-with `x') introducing features available through the API but not available in
-`.geo' files.
+The `c++', `c', `python' and `julia' subdirectories contain the C++, C, Python
+and Julia Gmsh tutorials, written using the Gmsh Application Programming
+Interface (API). You will need the Gmsh dynamic library and the associated
+header files (for C++ and C) or modules (for Python and Julia) to run them. Each
+subdirectory also contains additional information on how to run the tutorials
+for each supported language, as well as extended tutorials (starting with `x')
+introducing features available through the API but not available in `.geo'
+files.
 
  * A binary Software Development Kit (SDK) for Windows, Linux and macOS, that
    contains the dynamic Gmsh library and the associated header and module files,
    can be downloaded from http://gmsh.info. Several Linux distributions also
    ship the Gmsh SDK. See the top-level `README.txt' in the Gmsh source code for
    instructions on how to compile the dynamic Gmsh library from source.
+
+Table of contents
+=================
+
+* t1: Geometry basics, elementary entities, physical groups
+* t2: Transformations, extruded geometries, volumes
+* t3: Extruded meshes, parameters, options
+* t4: Built-in functions, holes in surfaces, annotations, entity colors
+* t5: Characteristic lengths, macros, loops, holes in volumes
+* t6: Transfinite meshes
+* t7: Background meshes
+* t8: Post-processing and animations
+* t9: Plugins
+* t10: Mesh size fields
+* t11: Unstructured quadrangular meshes
+* t12: Cross-patch meshing with compounds
+* t13: Remeshing an STL file without an underlying CAD model
+* t14: Homology and cohomology computation
+* t15: Embedded points, lines and surfaces
+* t16: Constructive Solid Geometry, OpenCASCADE geometry kernel
+* t17: Anisotropic background mesh
+* t18: Periodic meshes
+* t19: Thrusections, fillets, pipes, mesh size from curvature
+* t20: STEP import and manipulation, geometry partitioning
+* t21: Mesh partitioning
+
+Extended tutorials (API only):
+
+* x1: Geometrical and mesh data access
+* x2: Mesh import, discrete entities, hybrid models, terrain meshing

tutorial/c++/t10.cpp

@@ -116,7 +116,7 @@ int main(int argc, char **argv)
   // 2) if `Mesh.CharacteristicLengthFromPoints' is set, the mesh size specified
   //    at geometrical points;
   // 3) if `Mesh.CharacteristicLengthFromCurvature' is set, the mesh size based
-  //    on the curvature and `Mesh.MinimumCirclePoints';
+  //    on the curvature and `Mesh.MinimumElementsPerTwoPi';
   // 4) the background mesh field;
   // 5) any per-entity mesh size constraint.
   //

tutorial/c++/t13.cpp

@@ -39,7 +39,7 @@ int main(int argc, char **argv)
   // creation of patches that are amenable to reparametrization:
   bool forceParametrizablePatches = false;
 
-  // For open surfaces include the boundary edges in the classification process.
+  // For open surfaces include the boundary edges in the classification process:
   bool includeBoundary = true;
 
   // Force curves to be split on given angle:

tutorial/c++/t17.cpp

@@ -6,9 +6,9 @@
 //
 // -----------------------------------------------------------------------------
 
-// Characteristic lengths can be specified very accurately by providing a
-// background mesh, i.e., a post-processing view that contains the target mesh
-// sizes.
+// As seen in `t7.cpp', characteristic lengths can be specified very accurately
+// by providing a background mesh, i.e., a post-processing view that contains
+// the target mesh sizes.
 
 // Here, the background mesh is represented as a metric tensor field defined on
 // a square. One should use bamg as 2d mesh generator to enable anisotropic

tutorial/c++/t5.cpp

@@ -57,7 +57,8 @@ void cheeseHole(double x, double y, double z, double r, double lc,
   // With the OpenCASCADE kernel, `gmsh::model::occ::addSurfaceFilling()' uses a
   // much more general generic surface filling algorithm, creating a BSpline
   // surface passing through an arbitrary number of boundary curves. The
-  // `gmsh::model::geo::addThruSections()' allows to create ruled surfaces.
+  // `gmsh::model::geo::addThruSections()' allows to create ruled surfaces (see
+  // `t19.cpp').
 
   int s1 = factory::addSurfaceFilling({l1});
   int s2 = factory::addSurfaceFilling({l2});
@@ -103,6 +104,8 @@ int main(int argc, char **argv)
   // the mesh counts approximately 231,000 nodes and 1,360,000 tetrahedra. You
   // can check mesh statistics in the graphical user interface
   // (gmsh::fltk::run()) with the `Tools->Statistics' menu.
+  //
+  // See `t10.cpp' for more information about mesh sizes.
 
   // We proceed by defining some elementary entities describing a truncated cube:
 

tutorial/c++/t7.cpp

@@ -49,6 +49,9 @@ int main(int argc, char **argv)
   // Apply the view as the current background mesh
   gmsh::model::mesh::field::setAsBackgroundMesh(bg_field);
 
+  // Background meshes are one particular case of general mesh size fields: see
+  // `t10.cpp' for more mesh size field examples.
+
   gmsh::model::mesh::generate(2);
   gmsh::write("t7.msh");
 

tutorial/c++/x1.cpp

@@ -2,7 +2,7 @@
 //
 //  Gmsh C++ extended tutorial 1
 //
-//  Access basic geometrical and mesh data
+//  Geometrical and mesh data access
 //
 // -----------------------------------------------------------------------------
 

tutorial/python/t10.py

@@ -109,12 +109,12 @@ model.mesh.field.setAsBackgroundMesh(7)
 # 2) if `Mesh.CharacteristicLengthFromPoints' is set, the mesh size specified
 #    at geometrical points;
 # 3) if `Mesh.CharacteristicLengthFromCurvature' is set, the mesh size based
-#    on the curvature and `Mesh.MinimumCirclePoints';
+#    on the curvature and `Mesh.MinimumElementsPerTwoPi';
 # 4) the background mesh field;
 # 5) any per-entity mesh size constraint.
 #
 # This value is then constrained in the interval
-# [`Mesh.CharacteristicLengthMin', `MeshCharacteristicLengthMax'] and
+# [`Mesh.CharacteristicLengthMin', `Mesh.CharacteristicLengthMax'] and
 # multiplied by `Mesh.CharacteristicLengthFactor'.  In addition, boundary
 # mesh sizes (on curves or surfaces) are interpolated inside the enclosed
 # entity (surface or volume, respectively) if the option

tutorial/python/t13.py

@@ -29,7 +29,7 @@ angle = 40 # Angle for surface detection
 # patches that are amenable to reparametrization:
 forceParametrizablePatches = False
 
-# For open surfaces include the boundary edges in the classification process.
+# For open surfaces include the boundary edges in the classification process:
 includeBoundary = True
 
 # Force curves to be split on given angle:

tutorial/python/t17.py

@@ -6,9 +6,9 @@
 #
 # ------------------------------------------------------------------------------
 
-# Characteristic lengths can be specified very accurately by providing a
-# background mesh, i.e., a post-processing view that contains the target mesh
-# sizes.
+# As seen in `t7.py', characteristic lengths can be specified very accurately by
+# providing a background mesh, i.e., a post-processing view that contains the
+# target mesh sizes.
 
 # Here, the background mesh is represented as a metric tensor field defined on a
 # square. One should use bamg as 2d mesh generator to enable anisotropic meshes

tutorial/python/t5.py

@@ -40,6 +40,9 @@ lcar3 = .055
 # the mesh counts approximately 231,000 nodes and 1,360,000 tetrahedra. You can
 # check mesh statistics in the graphical user interface (gmsh.fltk.run()) with
 # the `Tools->Statistics' menu.
+#
+# See `t10.py' for more information about mesh sizes.
+
 
 # We proceed by defining some elementary entities describing a truncated cube:
 
@@ -137,7 +140,8 @@ def cheeseHole(x, y, z, r, lc, shells):
     # With the OpenCASCADE kernel, `gmsh.model.occ.addSurfaceFilling()' uses a
     # much more general generic surface filling algorithm, creating a BSpline
     # surface passing through an arbitrary number of boundary curves. The
-    # `gmsh.model.geo.addThruSections()' allows to create ruled surfaces.
+    # `gmsh.model.geo.addThruSections()' allows to create ruled surfaces (see
+    # `t19.py').
 
     s1 = factory.addSurfaceFilling([l1])
     s2 = factory.addSurfaceFilling([l2])

tutorial/python/t7.py

@@ -43,6 +43,9 @@ bg_field = model.mesh.field.add("PostView")
 # Apply the view as the current background mesh
 model.mesh.field.setAsBackgroundMesh(bg_field)
 
+# Background meshes are one particular case of general mesh size fields: see
+# `t10.py' for more mesh size field examples.
+
 gmsh.model.mesh.generate(2)
 gmsh.write("t7.msh")
 

tutorial/python/x1.py

@@ -2,7 +2,7 @@
 #
 #  Gmsh Python extended tutorial 1
 #
-#  Access basic geometrical and mesh data
+#  Geometrical and mesh data access
 #
 # -----------------------------------------------------------------------------
 

tutorial/t10.geo

@@ -89,12 +89,12 @@ Background Field = 7;
 // 2) if `Mesh.CharacteristicLengthFromPoints' is set, the mesh size specified
 //    at geometrical points;
 // 3) if `Mesh.CharacteristicLengthFromCurvature' is set, the mesh size based on
-//    the curvature and `Mesh.MinimumCirclePoints';
+//    the curvature and `Mesh.MinimumElementsPerTwoPi';
 // 4) the background mesh field;
 // 5) any per-entity mesh size constraint.
 //
 // This value is then constrained in the interval
-// [`Mesh.CharacteristicLengthMin', `MeshCharacteristicLengthMax'] and
+// [`Mesh.CharacteristicLengthMin', `Mesh.CharacteristicLengthMax'] and
 // multiplied by `Mesh.CharacteristicLengthFactor'.  In addition, boundary mesh
 // sizes (on curves or surfaces) are interpolated inside the enclosed entity
 // (surface or volume, respectively) if the option

tutorial/t11.geo

@@ -24,6 +24,7 @@ Field[1].F = "0.01*(1.0+30.*(y-x*x)*(y-x*x) + (1-x)*(1-x))";
 Background Field = 1;
 
 // To generate quadrangles instead of triangles, we can simply add
+//
 // Recombine Surface{100};
 
 // If we'd had several surfaces, we could have used `Recombine Surface {:};'.

tutorial/t13.geo

@@ -21,7 +21,7 @@ angle = DefineNumber[40, Min 20, Max 120, Step 1,
 forceParametrizablePatches = DefineNumber[0, Choices{0,1},
   Name "Parameters/Create surfaces guaranteed to be parametrizable"];
 
-// For open surfaces include the boundary edges in the classification process.
+// For open surfaces include the boundary edges in the classification process:
 includeBoundary = 1;
 
 // Force curves to be split on given angle:

tutorial/t17.geo

@@ -6,9 +6,9 @@
 //
 // -----------------------------------------------------------------------------
 
-// Characteristic lengths can be specified very accurately by providing a
-// background mesh, i.e., a post-processing view that contains the target mesh
-// sizes.
+// As seen in `t7.geo', characteristic lengths can be specified very accurately
+// by providing a background mesh, i.e., a post-processing view that contains
+// the target mesh sizes.
 
 // Here, the background mesh is represented as a metric tensor field defined on
 // a square. One should use bamg as 2d mesh generator to enable anisotropic

tutorial/t5.geo

@@ -27,6 +27,8 @@ lcar3 = .055;
 // the mesh counts approximately 231,000 nodes and 1,360,000 tetrahedra. You can
 // check mesh statistics in the graphical user interface with the
 // `Tools->Statistics' menu.
+//
+// See `t10.geo' for more information about mesh sizes.
 
 // We proceed by defining some elementary entities describing a truncated cube:
 
@@ -64,7 +66,7 @@ Macro CheeseHole
   // In the following commands we use the reserved variable name `newp', which
   // automatically selects a new point tag. Analogously to `newp', the special
   // variables `newl', `newll, `news', `newsl' and `newv' select new curve,
-  // curve loop, surface, surface loop and volume tag.
+  // curve loop, surface, surface loop and volume tags.
   //
   // If `Geometry.OldNewReg' is set to 0, the new tags are chosen as the highest
   // current tag for each category (points, curves, curve loops, ...), plus
@@ -95,7 +97,7 @@ Macro CheeseHole
   // With the OpenCASCADE kernel, `Surface' uses a much more general generic
   // surface filling algorithm, creating a BSpline surface passing through an
   // arbitrary number of boundary curves; and `ThruSections' allows to create
-  // ruled surfaces.
+  // ruled surfaces (see `t19.geo').
 
   l1 = newll; Curve Loop(l1) = {c5,c10,c4};
   l2 = newll; Curve Loop(l2) = {c9,-c5,c1};
@@ -115,8 +117,8 @@ Macro CheeseHole
   s7 = news; Surface(s7) = {l7};
   s8 = news; Surface(s8) = {l8};
 
-  // We then store the surface loops identification numbers in a list for later
-  // reference (we will need these to define the final volume):
+  // We then store the surface loops tags in a list for later reference (we will
+  // need these to define the final volume):
 
   theloops[t] = newsl;
   Surface Loop(theloops[t]) = {s1, s2, s3, s4, s5, s6, s7, s8};
@@ -144,9 +146,9 @@ For t In {1:5}
   Physical Volume (t) = thehole;
 
   // We also print some variables on the terminal (note that, since all
-  // variables are treated internally as floating point numbers, the format
-  // string should only contain valid floating point format specifiers like
-  // `%g', `%f', '%e', etc.):
+  // variables in `.geo' files are treated internally as floating point numbers,
+  // the format string should only contain valid floating point format
+  // specifiers like `%g', `%f', '%e', etc.):
 
   Printf("Hole %g (center = {%g,%g,%g}, radius = %g) has number %g!",
 	 t, x, y, z, r, thehole);

tutorial/t7.geo

@@ -17,3 +17,6 @@ Merge "t7_bgmesh.pos";
 
 // Apply the view as the current background mesh
 Background Mesh View[0];
+
+// Background meshes are actually a particular case of general mesh size
+// fields: see `t10.geo'.