Second release candidate for gnuplot 6

[Ethan A M. <me...@uw...>]

The "testing" directory on SourceForge now has a tarball for gnuplot-6-0-rc2

   https://sourceforge.net/projects/gnuplot/files/gnuplot/testing/gnuplot-6.0.rc2.tar.gz

This is a second release candidate for version 6.0.


	Gnuplot Version 6.0 rc2 Release Notes
	=====================================

Version 6.0 is the start of a new stable release series.
Work on gnuplot 6 has proceeded in parallel with the incremental updates to
version 5.4 over the past three years.  The new version introduces extensions
to the gnuplot command language, support for new output protocols, and
additional plotting styles.  Backwards compatibility is given high priority
in gnuplot development, so users should find no significant changes required
for techniques or code they are currently using with gnuplot 5.

Your feedback from testing of this release candidate will contribute to
the success of a full 6.0 release expected later in 2023.

Release Notes date:  18-Sep-2023

	Features introduced in version 6
	================================
For a detailed list of new features, with illustrations, see
  http://gnuplot.info/docs_6.0/NewFeatures.html

For more example plots see
  http://gnuplot.info/demo_6.0/

  - Function blocks and scoped variables
  - Larger collection of special and complex-valued functions
  - New plot styles
	o 2D plot style `with surface` works in 2D polar coordinates to produce a
	  solid-fill gridded representation of the plane. This is analogous to the
	  use of dgrid3d and pm3d to produce a 3D gridded surface.
	o 2D plot style `with sectors` renders one annular segment ("sector") for
	  each line of input data. This style can generate pie and donut charts,
	  windrose charts, and a polar equivalent to sparse-matrix heatmaps.
	o 2D plot style `with lines` now has a filter option `sharpen`.
	  This filter detects spikes in a function plot that would be missed or
	  under-represented due to coarse sampling.  It adds an additional
	  sampling point at the location of each such peak.
	o 3D plot style `with contourfill` produces 2D or 3D surfaces with
	  distinct z-ranges indicated by solid color fill.
  - Hulls, masks, and smoothing
	o A cluster of 2D points can be replaced by a bounding polygon ("hull").
	  Both convex hulls and concave hulls (χ-shapes) are supported.
	o Any hull or other closed path can be used as a mask to display only
	  selected regions of a pm3d surface or image plot.
	o New smoothing option "smooth path" can be used on 2D and 3D curves
	  that are not monotonic on x or y.  This allows smoothing of hulls.
  - Named palettes
	o The current palette can be saved to a named colormap for future us.
	o A predefined palette named "viridis" is provided.
	o Plots can specify a previously saved palette by name.
	  This permits the use of multiple palettes in a single plot command.
	o Named palettes can be edited to contain an alpha channel.
  - New built-in functions and array operations
	o palette(z) returns the current RGB palette color mapping for z.
	o rgbcolor("name") returns the 32bit ARGB value for a named color.
	o index(Array, element) returns the first index i for which Array[i]
	  is equal to element.
	o split("string", "separator") unpacks the fields in a string into
	  an array of strings.
	o join(array, "separator") is the complement to split().
	  It concatenates the elements of a string array into a single string.
	o `stats <non-existent file>` yields a testable value with no error;
	  useful to avoid errors or warnings in scripts.
  - Program control flow
	o New syntax if {...} else if {...} else {...}
	o XDG base directory conventions for configuration files are supported.
	o `unset warnings` suppresses output of warning messages to the console.
	o The `fit` command is protected by exception handling. Control always
	  returns to the next line of input even in the case of fit errors.
	  On return FIT_ERROR is non-zero if an error occurred.
	o "Watchpoints"  are target values associated with individual plots
	  in a graph. As that plot is drawn, each component line segment is
	  monitored to see if its endpoints bracket the target value of a
	  watchpoint coordinate (x, y, or z) or function f(x,y).
	  If a match is found, the [x,y] coordinates of the match point are
	  saved for later use.  Possible uses include
		- find the intersection points of two curves
		- find zeros of a function
		- find and notate where a dependent variable or function f(x,y)
		  crosses a threshold value
		- use the mouse to track values along multiple plots simultaneously
  - New terminals and terminal options
	o Terminals that display graphics in the same window as text entry now
	  support pseudo-mousing; i.e. they respond to arrow keys and other
	  hot-key bindings during "pause mouse".
	o New terminals kittygd and kittycairo provide in-window graphics for
	  terminal emulators that support the kitty protocol.
	o New terminal webp generates a single frame or an animation sequence
	  using webp encoding. Frames are generated using pngcairo,
	  then encoded through the WebPAnimEncoder API.
	o New terminal block for text-mode pseudo-graphics uses Unicode block
	  or Braille characters to offer improved resolution compared to the
	  dumb or caca terminals.
	o latex terminals standalone mode updated to work with texlive2023
  - Miscellaneous other new features
	o Time unit settings for major and minor axis tics.  For example,
	  minor tic marks can be placed at exactly one month intervals.
	o The character sequence $# in a using specifier evaluates to the total
	  number of columns available in the current line of data.
	  "plot FOO using 0:(column($# - 1))" plots the last-but-one field of each row.
	o keyword binvalue=avg plots the average, rather than the sum, of binned data.
	o "set colorbox bottom" places the color box underneath the plot.
	o "set pm3d spotlight" adds a user-controlled spotlight to the lighting model.
	o New key layout options to force specific width or number of columns.
	  Automatic positioning of the key on the page can be manually tweaked
	  by giving an offset.
	o "set isotropic" adjusts the axis scaling in both 2D and 3D plots such
	  that x, y, and z axes all have the same scale.
	o Text rotation angles are not limited to integral degree values.
	o Data-driven color assignments in plot style "histograms".


	Changes between 6.0 -rc1 and -rc2
	=================================
* New plot style "with contourfill" generates 2D and 3D contour plots with
  solid fill areas rather than lines.
* Support building against Qt6
	- ./configure falls back to Qt5 if the Qt6 libraries are not found
* Japanese documentation updated
	- added missing file title-ja.tex, build dependencies for mingw
* New configure option --enable-stable-sort
	- Use mergesort rather than qsort if the system provides it.
	- If neither mergesort nor glibc stable qsort is available,
	  modify internal gnuplot structures to contain a secondary sort key
* Render color gradient in colorbox as a pixel array
	- cairo, qt terminals
* "reset session" restores initial state of all linetype properties
	- previously only the colors were restored
	- now it also reinitializes linewidth, point and dash properties
* postscript terminal now handles pixmaps
* svg terminal now correctly tracks pattern-fill color

---------

happy gnuplotting

    Ethan