Rich Text Format Line Spacing

Question

I try to convert a plain text in RTF-Format. Therefore, I use RichTextBox (WinForms).
The concerned method the RTF-Markup as string.

Now, I want to insert line spacing in the markup. I found that there are 2 parameters:

 - \slX (Space between lines in twips)
 - \slmultX (either 0 or 1)

If I set \slmult0, the line spacing is above the line of text.
When I set \slmult1, the line spacing is below the line of text.

I calculate the spacing in the following way:

(lineSpacing + fontSize)*20

When I switched from \slmult0 to \slmult1, I determined, that the line distance is little smaller than with \slmult0.

Does somebody know the reason for this behavior? Do I have to calculate with another formula?

Answer 1

If I set \slmult0, the line spacing is above the line of text. When I set \slmult1, the line spacing is below the line of text.

That is not what I read in the specs.

The way I understand it, it means that \slmult0 says that the value of \slN is to be used directly as a distance in some unit, whereas \slmult1 says the N in \slN is meant as a factor by which the regular line spacing is multiplied.

See the last post here for (some) more details! (But there is also a note about it taking effect one line too late..)

Also do note the importance of the sign of N in the \slN! (This was the reason of my comment above: The effect of, say \sl234, will depend on the size of the tallest character in the line..!)

Here is a nice discussion of some things RTF; a note about units:

Measurements in RTF are generally in twips. A twip is a twentieth of a point, i.e., a 1440th of an inch. That leads to some large numbers sometimes (like \li2160, to set the left indent to an inch and a half)

and a clear definition of extra spacing before and after paragraphs:

\sbN -- N twips of extra (vertical) space before this paragraph (default: 0)
\saN -- N twips of extra (vertical) space after this paragraph (default: 0)

Here are more direct instructions:

To double-space a paragraph, put the code \sl480\slmult1 right after the \pard. To triple-space it, use \sl720\slmult1. To have just 1.5-spacing, use \sl360\slmult1. A single-spaced paragraph is the default, and doesn’t need any particular code. (The magic numbers 480, 720, and 360 don’t depend on the point size of the text in the paragraph.)