12.7.5. Troubleshoot Errors
It can be difficult to troubleshoot inputting errors, especially when you find them days or weeks after originally inputting that section of a score. The best way to fix errors is to input scores in a way that doesn't allow them in the first place. As they say, "an ounce of prevention is worth a pound of cure," which means "if you input your LilyPond files carefully, then you will encounter fewer problems." Such practices as proper spacing, and regular use of the octave- and bar-check features will deal with many common problems.
However, when searching for an error in your score, Frescobaldi does offer some features to help you find it:
If you have written something in the text-input window that is obviously incorrect, then Frescobaldi will sometimes catch your mistake and underline and highlight the erroneous code in red. This is most useful for catching typographical errors ("typos").
If LilyPond encounters a processing error, it will show up in the "LilyPond Log" window below the text-input window. You can click on the blue, underlined text to move the text-selection caret to the error.
If you can see an error in the PDF preview, but you can't find it in the source file, you can click on the problematic note or object in the PDF preview, and Frescobaldi will automatically move the text-selection caret to that object.