Question & Answer
Question
IBM i Access Client Solutions 5250 Display sessions have a Font Preference available for Font Scaling that when turned on will resize the font horizontally and vertically to match the session window. Why does the screen data not line up as expected even when fixed width fonts like Monospaced or PCommSession are used?
Answer
When the IBM i Access Client Solutions (IBM i ACS) 5250 Font Scaling option is enabled the font will be resized both horizontally and vertically to match the dimensions of the 5250 session window. This allows the display area to fill nearly all of the window.
There are a series of calculations that are made between Java and the client Operating System to take the session window size and then divide that horizontal and vertical space to know what dimensions each character should fill. The problem is that there can be calculation errors introduced between how the Operating System and Java handle their calculations, particularly with rounding differences. So, because of this, even when using a fixed width font like Monospaced or PCommSession the column and row alignment may be off.
IBM i ACS 5250 basically has no control over these calculations, so in these environments where alignment gets off, we recommend setting font scaling to no. With font scaling disabled, and the fixed font set to no the font will be resized based on the session window size, but the font's original aspect ratio is maintained so it resizes in steps.
Note: There have been reports of more font scaling alignment issues with Java 17.
There are a series of calculations that are made between Java and the client Operating System to take the session window size and then divide that horizontal and vertical space to know what dimensions each character should fill. The problem is that there can be calculation errors introduced between how the Operating System and Java handle their calculations, particularly with rounding differences. So, because of this, even when using a fixed width font like Monospaced or PCommSession the column and row alignment may be off.
IBM i ACS 5250 basically has no control over these calculations, so in these environments where alignment gets off, we recommend setting font scaling to no. With font scaling disabled, and the fixed font set to no the font will be resized based on the session window size, but the font's original aspect ratio is maintained so it resizes in steps.
Note: There have been reports of more font scaling alignment issues with Java 17.
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Document Information
Modified date:
24 February 2022
UID
ibm16559318