Fixes for several rounding mistakes to achieve better precision, accuracy, and usability

[michaelcbrook]

First of all, really appreciate all your hard work on this library.

In the spirit of improving it and solving potentially many issues users could have with it (myself included), I've identified and fixed many instances of incorrect multiplication or rounding, which will resolve many common mistakes when passing decimal numbers into the API, and will actually increase the accuracy of the resulting PPTX to be perfectly consistent with the input style parameters.

The fixes:

1. Font sizes. Virtually all font sizes are using the following calculation: Math.round(fontSize) + "00". While this doesn't cause the resulting file to be corrupt, it removes a great deal of precision. If the font size input is 12.5, the output becomes 13. Alternatively, all of these should be Math.round(fontSize * 100). This will produce exactly the right result of 12.5.

2. lineSpacing. The above fix was applied partially to lineSpacing recently, however, lineSpacing was only multiplied by 100 but the result was not rounded. As a result, round-off errors could still occur. (i.e. 70.79 * 100 = 7079.000000000001 in JavaScript). Rounding additionally after the multiplication prevents this. This problem bit me a number of years ago. Unfortunately, if this fix isn't applied, there is no workaround for making this work.

3. Rotations. Similar to the above, the result was not being rounded, which made it susceptible to the round-off error. It also would fail if the input rotation was much more than four decimal places long.

4. Transparencies. Specifically, shapeFill alpha, shapeFill transparency, and chartColorsOpacity all were similar to # 1, simply being suffixed with "000" instead of properly being multiplied by 1000 and then rounded. Using decimals in these values would have simply not worked before, when they could completely be supported and produce a result with higher precision and accuracy.

Hopefully these changes will help prevent a lot of the hangups people first have when using it (not knowing which numbers accept decimals, which don't, how many decimals, etc.) and give everyone the ability to achieve near-perfect precision that was needlessly prevented before just because of the subpar multiplication logic.

Thanks again for the great library.

[michaelcbrook]

Just wanted to make a note on this additional commit. It contains:

1. Additional places where rounding was missed but should be performed (that I found later).

2. An unrelated bug fix from lines 2163 - 2166 that fixes a bug where, if a parent textbox is set to bold, italics, underline, or strike, words inside of the textbox can't be un-bolded, un-italicized, un-underlined, or un-striked by explicitly setting the word-level formatting to false. This is because the code only explicitly adds the associated attribute for the style if the value is truthy, but in cases where it's explicitly false, the attribute should be added with a negatory value in order to not just inherit the style from the parent textbox.

Thank you!

Edit: Flubbed on # 2. My changes didn't work for some reason. Will repost here when fixed, or feel free to jump in and see what I missed.

[michaelcbrook]

Fixed! 👍

[gitbrent]

Perfect

[gitbrent]

Thanks @michaelcbrook - great work!