* Add Support to Chart/Axis for Glow/SoftEdges
Chart is very under-covered in unit tests. I was hoping to just add some tests and be done with it, but that just won't suffice - many code changes are required. Adding Glow properties for Axis turned out to be a real mixed bag - no support in Xlsx/Reader at all, support in Xlsx/Writer ... for the X-axis only. So we'll just inch forward in many stages.
This change does not address other Axis properties (Fill, Shadow, Line, LineStyle, and maybe others, and their sub-properties). On my to-do list.
GridLines, and maybe other Chart objects, also should support these properties. This change does not address those. On my to-do list.
No support is added for spreadsheet formats other than Xlsx.
* Refactoring
This should make the code easier to follow, and I hope it will also be extensible to other object types (e.g. GridLines).
* More Refactoring
Make scheme/srgb easier to handle.
* Fix Typo
In a very rarely used function.
This is a leftover Scrutinizer change, but it needed more attention than most others. Chart/Title DocBlocks define caption as `null|string`. However, in the wild, Excel usually presents the caption as an array, and not an array of strings but rather of RichText items. I am not sure why an array is needed since a RichText item can contain many text runs, but things are what they are.
Reader/Xlsx/ChartTitleTest reads a spreadsheet with the captions stored as a RichText array. Since it performs array operations on something the DocBlock says cannot be an array, Scrutinizer objects, although not seriously enough to fail the module. Phpstan also objects; its objection is silenced with an annotation. Aside from this test, there are other tests which do set the caption to a string, and Excel seems to handle that without a problem. So, I have changed the DocBlock to specify `array|RichText|String`. I have dropped null as a possibility; nullstring will do equally well.
Because getCaption can now return multiple datatypes, I think a new function which can return the text portion of the entire caption as a single string is needed. I have added it. This simplifies the test named above, and some code in Writer/Html. The latter is not part of unit testing because the version of JpGraph found in Composer is too antiquated. I verified the Html change manually by running samples/Chart/32_Chart_read_write_HTML.php using a recent version of JpGraph. It was as a result of this test that I uncovered issue #2203. I did not see anything about Charts in docs, so did not add a description of the new function there.
Phpstan is happy with the changes. We'll see how Scrutinizer feels when I push it.
Because even if it doesn't make a difference in practice, it is
technically more correct to call static methods statically. It
also better advertise that those methods can be used from any context.
oleibman
Owen Leibman
Adrien Crivelli
Krzysztof Ruszczynski
Michael Bollman
Gabriel Caruso
Zharikov Viktor