Refactored the code base, separating scripts handling and introducing a help for script commands (which can be placed on the website too). At the moment it is:

Available commands are:
mesh <file> - Visualize the mesh.
solution <mesh> <solution> - Visualize the solution.
psolution <np> <mesh prefix> <keep attributes> <solution prefix> - Visualize the distributed solution.
quadrature <mesh> <quadrature> - Visualize the quadrature.
pquadrature <np> <mesh prefix> <keep attributes> <quadrature prefix> - Visualize the distributed quadrature.
data_coll_mesh <type> <data coll> - Visualize the mesh from data collection.
data_coll_field <type> <data coll> <field> - Visualize the field from data collection.
data_coll_quad <type> <data coll> <quad> - Visualize the Q-field from data collection.
data_coll_cycle <cycle> - Preset the cycle of the data collection.
data_coll_protocol <protocol> - Preset the protocol of the data collection.
screenshot <file> - Take a screenshot, saving it to the file.
viewcenter <x> <y> - Change the viewcenter.
perspective <on/off> - Turn on or off perspective projection.
light <on/off> - Turn on or off light.
view <theta> <phi> - Change the solid angle of view.
zoom <zoom> - Change the zoom factor.
shading <flat/smooth/cool> - Change the shading algorithm.
subdivisions <times> <dummy> - Change the refinement level.
valuerange <min> <max> - Change the value range.
autoscale <off/on/value/mesh> - Change the autoscale algorithm.
levellines <min> <max> <num> - Set the level lines.
axis_numberformat '<format>' - Set the axis number format.
colorbar_numberformat '<format>' - Set the colorbar number format.
window <x> <y> <w> <h> - Set the position and size of the window.
keys <key> - Send the control key sequence.
palette <index> - Set the palette index.
palette_repeat <times> - Set the repetition of the palette.
toggle_attributes <1/0> [[<1/0>] ...]; - Toggle visibility of the attributes.
rotmat <[0,0]> <[1,0]> ... <[3,3]> - Set the rotation matrix.
camera <cam[0]> ... <cam[2]> <dir[0]> ... <dir[2]> <up[0]> ... <up[2]> - Set the camera position, direction and upward vector.
scale <scale> - Set the scaling factor.
translate <x> <y> <z> - Set the translation coordinates.
plot_caption '<caption>' - Set the plot caption.

Similarly, handling of stream commands has been refactored, offering the following help:

Available commands are:
mesh <mesh> - Visualize the mesh.
solution <mesh> <solution> - Visualize the solution.
quadrature <mesh> <quadrature> - Visualize the quadrature.
fem2d_data <mesh> <data> - Visualize the 2D scalar data.
vfem2d_data <mesh> <data_x> <data_y> - Visualize the 2D vector data.
vfem2d_data_keys <mesh> <data_x> <data_y> <keys> - Visualize the 2D vector data and apply control keys.
fem3d_data <mesh> <data> - Visualize the 3D scalar data.
vfem3d_data <mesh> <data_x> <data_y> <data_z> - Visualize the 3D vector data.
vfem3d_data_keys <mesh> <data_x> <data_y> <data_z> <keys> - Visualize the 3D vector data and apply control keys.
fem2d_gf_data <mesh> <solution> - Visualize the 2D scalar grid function.
fem2d_gf_data_keys <mesh> <solution> <keys> - Visualize the 2D scalar grid function and apply control keys.
vfem2d_gf_data <mesh> <solution> - Visualize the 2D vector grid function.
vfem2d_gf_data_keys <mesh> <solution> <keys> - Visualize the 2D vector grid function and apply control keys.
fem3d_gf_data <mesh> <solution> - Visualize the 3D scalar grid function.
fem3d_gf_data_keys <mesh> <solution> <keys> - Visualize the 3D scalar grid function and apply control keys.
vfem3d_gf_data <mesh> <solution> - Visualize the 3D vector grid function.
vfem3d_gf_data_keys <mesh> <solution> <keys> - Visualize the 3D vector grid function and apply control keys.
raw_scalar_2d <data> - Visualize the 2D scalar data (see stream_reader.cpp).
parallel <num proc> <proc> - Prefix for distributed mesh/solution/quadrature.
screenshot <file> - Take a screenshot, saving it to the file.
viewcenter <x> <y> - Change the viewcenter.
view <theta> <phi> - Change the solid angle of view.
zoom <zoom> - Change the zoom factor.
shading <flat/smooth/cool> - Change the shading algorithm.
subdivisions <times> <dummy> - Change the refinement level.
valuerange <min> <max> - Change the value range.
autoscale <off/on/value/mesh> - Change the autoscale algorithm.
levellines <min> <max> <num> - Set the level lines.
axis_numberformat '<format>' - Set the axis number format.
colorbar_numberformat '<format>' - Set the colorbar number format.
window_size <w> <h> - Set the size of the window.
window_geometry <x> <y> <w> <h> - Set the position and size of the window.
window_title '<title>' - Set title of the window.
keys <keys> - Send the control key sequence.
palette <index> - Set the palette index.
palette_repeat <times> - Set the repetition of the palette.
camera <cam[0]> ... <cam[2]> <dir[0]> ... <dir[2]> <up[0]> ... <up[2]> - Set the camera position, direction and upward vector.
plot_caption '<caption>' - Set the plot caption.
axis_labels '<x label>' '<y label>' '<z label>' - Set labels of the axes.
pause - Stop the stream until space is pressed.
autopause <0/off/1/on> - Turns off or on autopause.

🌟 Besides there are multiple other improvements:

• Introduced Window structure bundling (some of) the shared objects, eliminating the global state. This is a lightweight version of Refactoring to remove global state #170 .
• Removed most of the references to GetAppWindow() (a global function for obtaining thread-local SdlWindow)
• Unified GLVisInitVis() and display() in aux_js.cpp.
• Unified handling of streams (through StreamReader) and improved DataState, so all data types can be animated 🎞️ .
• Fixed the flag for keeping of real attributes in the script command, which was broken since Parallel streams for web version #235 .
• Fixed the flag for keeping of real attributes in streams.
• Fixed the default padding digits for data collections.
• Fixed cycling of vector->scalar function in 2D to work with raw data
• Improved guarding of web-only source files.
• Fixed a typo in NOTICE.

✔️ Tests:

• some script
• serial stream
• parallel stream
• cmd-line file loading
• saved stream
• js