Printing Problems, Koha, and Firefox

by Lucas Gass on Nov 10, 2020

Recently there have been some problems with various aspects of printing in Koha. Most of, but not all, these issues revolve around Firefox and some of the recent updates included in Firefox 81.0.0 through 82.0.2.

PROBLEM: Firefox prints look good when viewing the print preview but the actual print only spits out about 1 inch of paper with nothing on it.

SOLUTION: Turn on the new Chrome-like print preview window. Here is how it is done:

1. In the Firefox URL bar type ‘about:config’.
2. Accept the risk and continue.
3. Search for ‘print.tab_modal.enabled’ and set it to true.
4. Restart Firefox
5. Re-try your print, it should now print the entire contents.

PROBLEM: Prints look fine on the screen but when printed they come out very pixelated. This problem affects users in both Chrome and Firefox. Typically this affects thermal printers (like the TSP Star 100) more than it does other types of printers.

SOLUTION: Make sure Koha prints your notices/slips in ‘true black’ or the hex color #000000. Koha contains a print.css file which dictates how elements will look on the printed page. Print.css does not affect elements unless they are printed. In the Koha print.css the color of certain HTML elements like <h1> or <p> are being set to color other than ‘true black’. Sometimes print.css is using #333333 or #000066. Both of these colors seem to be problematic for thermal receipt printers. A bug has been filed on this issue:

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=26962

Luckily we can also fix this by adding a bit of CSS to the IntranetUSerCSS system preference:

@media print {
 body, p, h1, h2, h3, h4, h5, h6, a {
 color: black !important;
 }
}

By using the ‘@media print’ query we can ensure that this CSS will only affect printed HTML elements!