The Row Height Conondrum

[lordofscripts]

I think that burdening the end-user (users of the library) with having to specify a row height should actually be addressed in version 2 (latest release is 2.0.7) rather than 3. Currently the library works well for form-making rather than document-making.

I believe Maroto/V2 should address these 3 low-level) issues and not burden the end-developer with having to deal with these as it is currently (v2.0.7).

1st Problem: Row Height

There is a certain relation between font height and row height which is applicable in single line per row use cases.

In this case, in a first attempt, with curve fitting (regression), a simple cubic (3rd order polynomial) provides a good prediction of the single-line row height necessary for a given font height.

2nd Problem: How many rows in a page

My experiments revealed that for a Letter-sized page without header and a single-line footer (page nr.), a single page fits 240 rows, for example 60 rows of a row height of 4.

Obviously, that amount is slightly different for an A4 page.

3rd Problem: Multi-line rows

This issue is of extreme importance for using Maroto in regular document generation where text is composed of paragraphs (multiple lines).

In this situation we have several variables to predict the necessary row height for a given text of 1..n paragraphs:

• Font Height: bigger font, less character space available in a single line. Inversely proportional, big influence l.
• Font Family: some fonts (narrow) occupy less horizontal space than others. Medium influence.
• Font Style: Bold & Italic have a slight influence on how many characters fit in a single line.
• Horizontal space available: The column span in Maroto which is typically 1..12.

With that in mind there are methods to compute font metrics, knowing how a paragraph of a given font size, family & style would be split into several lines. Given those parameters and a mapping function, we could know how many row height units are needed to properly output a (series of) paragraphs.

Y: number of lines
X: Font metrics (family, size, style)
Z: Column Span (horizontal space)

y = f(x, z)

[lordofscripts]

May be of help: Go MeasureString provides font.MeasureString().

But at this moment the documentation here does not clarify the font size unit__, is it points, millimeters, pixels?

[lordofscripts]

Additionally, I noticed that Maroto has the GO pdfcpu library as an indirect dependency. It so happens that pdfcpu has a lot of built-in functionality to calculate these things we Maroto users need (and miss), and that it could be exposed by Maroto.

[Fernando-hub527]

I don't know if this is the right topic to discuss this issue, but...

I am implementing this feature to automatically calculate the line size, but I realized that the matrixcode component has its size calculated based on the available space (height and width). In this case I see two options:

• Calculate the size of the component only based on the available width and, based on the result, find the height necessary to accommodate the component.
• replace the percentage property with a fixed value, requiring the user to directly inform the size he expects the component to have and then find the required height.

I'm really unsure of the best way