MobileRead Forums - View Single Post - Why is it so hard to preserve blank lines?

GeoffR · 04-30-2016, 04:42 PM

Using a single blank line to separate sections will not work in all situations, even if the ereader does respect the publisher's CSS styles.

For example, suppose that the reader has selected a font size and line spacing that results in a line height of 40px on their device, and has set the page margins to 30px. Because of things like superscripts, subscripts, images, headings, paragraph margins, etc. the position of the last line on the page is not always the same from page to page, resulting in a gap of 0px-39px in addition to the page margin, so during normal reading the reader could expect to see a gap at the bottom of the page of 30px-69px.

If you use a single blank line as a separator and that blank line happens to be the last line of the page, then the gap will be 40px + 0px-39px + 30px for a total of 70px-109px. That means in some situations the presence of the separator only results in a gap that is a few pixels larger than largest gap that can occur without a separator, and is likely to be invisible to the reader.

In a paper book or fixed-layout ebook the publisher knows in advance when a separator falls at the top or bottom of a page and can take special measures such as replacing it with a visible separator like an asterism, but in an ePub (ePub2 anyway) that is not possible. (Edit: I guess it is possible in a limited way using page-preak-after:avoid

So to ensure that the separator is visible in all situations you need to use at least two blank lines (not just 2em margin, that won't work because the margin can be supressed when it appears at the top or bottom of a page), or use a visible separator such as murg suggested, or else use a different style to start the new scene such as small-caps, italics, raised-cap, etc.

04-30-2016, 04:42 PM	#17
GeoffR Wizard Posts: 3,821 Karma: 19162882 Join Date: Nov 2012 Location: Te Riu-a-Māui Device: Kobo Glo	Using a single blank line to separate sections will not work in all situations, even if the ereader does respect the publisher's CSS styles. For example, suppose that the reader has selected a font size and line spacing that results in a line height of 40px on their device, and has set the page margins to 30px. Because of things like superscripts, subscripts, images, headings, paragraph margins, etc. the position of the last line on the page is not always the same from page to page, resulting in a gap of 0px-39px in addition to the page margin, so during normal reading the reader could expect to see a gap at the bottom of the page of 30px-69px. If you use a single blank line as a separator and that blank line happens to be the last line of the page, then the gap will be 40px + 0px-39px + 30px for a total of 70px-109px. That means in some situations the presence of the separator only results in a gap that is a few pixels larger than largest gap that can occur without a separator, and is likely to be invisible to the reader. In a paper book or fixed-layout ebook the publisher knows in advance when a separator falls at the top or bottom of a page and can take special measures such as replacing it with a visible separator like an asterism, but in an ePub (ePub2 anyway) that is not possible. (Edit: I guess it is possible in a limited way using page-preak-after:avoid So to ensure that the separator is visible in all situations you need to use at least two blank lines (not just 2em margin, that won't work because the margin can be supressed when it appears at the top or bottom of a page), or use a visible separator such as murg suggested, or else use a different style to start the new scene such as small-caps, italics, raised-cap, etc. Last edited by GeoffR; 04-30-2016 at 05:04 PM. Reason: ... possible in a limited way using page-preak-after:avoid;