Two Problems with Html Chart Rendering - Minor Break

[oleibman]

Several problems are noted in #3783. This PR addresses those problems which make the rendering unsatisfactory (see following paragraphs). It does not address some items where the rendering is IMO satisfactory although it doesn't match Excel. In particular, the use of a different color palette and the rotation of charts are not addressed. I will leave the issue open for now because of those.

As for the items which are addressed, in some cases the Html was omitting a chart altogether. This is because it had been extending the column range for charts only when it decided that extending the row range was needed. The code is changed to now extend the column range whenever the chart begins beyond the current column range of the sheet.

Also, the rendering always produced a fixed-size image, so saving as Html could result in charts overlaying each other or other parts of the spreadsheet. New properties renderedWidth and renderedHeight are added to Chart, along with setters and getters. Writer/Html is changed to set these values using the chart's top left and bottom right cells to try to determine the actual size that is needed. Users can also set these properties outside of Writer/Html if they wish. Thanks to @f1mishutka for determining the source of this problem and suggesting an approach to resolving it.

Because the size of the rendered image in Html/Pdf is changed, this could be considered a breaking change. To restore the prior behavior, do the following for all charts before saving as Html:

$chart->setRenderedWidth(640.0);
$chart->setRenderedHeight(480.0);

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New sample been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.