* WIP Namespacing Phase 2 - Styles
This is part 2 of a several-phase process to permit PhpSpreadsheet to handle input Xlsx files which use unexpected namespacing. The first phase, introduced as part of release 1.19.0, essentially handled the reading of data. This phase handles the reading of styles. More phases are planned.
It is my intention to leave this in draft status for at least a month. This will give time for additional testing, by me and, I hope, others who might be interested.
This fixes the same problem addressed by PR #2458, if it reaches mergeable status before I am ready to take this out of draft status. I do not anticipate any difficult merge conflicts if the other change is merged first.
This change is more difficult than I'd hoped. I can't get xpath to work properly with the namespaced style file, even though I don't have difficulties with others. Normally we expect:
```xml
<stylesheet xmlns="http://whatever" ...
```
In the namespaced files, we typically see:
```xml
<x:stylesheet xmlns:x="http://whatever" ...
```
Simplexml_load_file specifying a namespace handles the two situations the same, as expected. But, for some reason that I cannot figure out, there are significant differences when xpath processes the result. However, I can manipulate the xml if necessary; I'm not proud of doing that, and will gladly accept any suggestions. In the meantime, it seems to work.
My major non-standard unit test file had disabled any style-related tests when phase 1 was installed. These are now all enabled.
* Scrutinizer
Its analysis is wrong, but the "errors" it pointed out are easy to fix.
* Eliminate XML Source Manipulation
Original solution required XML manipulation to overcome what appears to be an xpath problem. This version replaces xpath with iteration, eliminating the need to manipulate the XML.
* Handle Some Edge Cases
For example, Style file without a Fills section.
* Restore RGB/ARGB Interchangeability
Fix#2494. Apparently EPPlus outputs fill colors as `<fgColor rgb="BFBFBF">` while most output fill colors as `<fgColor rgb="FFBFBFBF">`. EPPlus actually makes more sense. Regardless, validating length of rgb/argb is a recent development for PhpSpreadsheet, under the assumption that an incorrect length is a user error. This development invalidates that assumption, so restore the previous behavior.
In addition, a comment in Colors.php says that the supplied color is "the ARGB value for the colour, or named colour". However, although named colors are accepted, nothing sensible is done with them - they are passed unchanged to the ARGB value, where Excel treats them as black. The routine should either reject the named color, or convert it to the appropriate ARGB value. This change implements the latter.
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