e07fc849e4
Some browsers (Chrome, Firefox) are now using non-integer font widths for the fixed width text display from CM3. Chrome on Mac OS X is now measuring 7.2 pixels per character. Unfortunately this can only be discovered by measuring the width of an element with more than 1 character in it. CM3's defaultCharWidth() function measures the width of a single "x" and assumes this is going to be accurate. Except the browser rounds down and returns 7.0, which is 0.2 short for longer runs of text. Measure a 100 character string in a span and take the average width of these 100 characters to identify the real character width used for text in a CM3 instance. This is now coming in around 7.2 px, which can be multipled out with the integral columns to get the margin bar positioned at the desired location in source files. The string length needs to be long enough that most browsers will show evidence of fractional character widths. 100 is a good guess as some coding standard conventions limit lines to 100 (or even 80), suggesting no conforming code would even reach this length of 100. If the margin was set at 100, and the measurement was taken for 100 but is still flawed, at worst the margin bar should position correctly at 100. It also gives about 2 decimal places of precision on the char width, assuming fractional widths are being used by the browser. This may be fine for 100 character wide line lengths, any residual error should be small enough to go unnoticed. Issue: 2918 Change-Id: I37f328f1c5475f4aaa2ad1c90b6339fdc2c6ef5c |
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