Options and the recent-file-list will be saved when you exit the program, and reloaded when you start it. (Menu Settings->Configure KDiff3 ...)
Select a fixed width font. (On some systems this dialog will also present variable width fonts, but you should not use them.)
If you select this, then text differences will be drawn with the italic version of the selected font. If the font doesn't support italic, then this does nothing.
Usually light gray.
Usually dark blue.
Usually dark green.
Usually dark magenta.
Usually light yellow.
Usually dark yellow.
Usually dark yellow.
Changing the colors for directory comparison will be effective only when starting the next directory comparison.
On systems with only 16 or 256 colors some colors are not available in pure form. On such systems the "Defaults"-button will choose a pure color.
If this is disabled and you press the tabulator key, a tab-character is inserted, otherwise the appropriate amount of characters is inserted.
Can be adjusted for your specific needs. Default is 8.
When pressing Enter or Return the indentation of the previous line is used for the new line.
Every selection is immediately copied to the clipboard when active and you needn't explicitely copy it.
When saving you can select what line end style you prefer. The default setting is the common choice for the used operating system.
When comparing files, KDiff3 first it tries to match lines that are equal in all input files. Only during this step it might ignore white space. The second step compares each line. In this step white space will not be ignored. Also during the merge white space will not be ignored.
Some editors (on some systems) save carriage return '\r' and linefeed '\n'-characters at the end of line, while others will only save the linefeed '\n'. Usually KDiff3 ignores the carriage return, but then files that don't have equal sizes, look equal in side by side comparison. When this option is on, then the carriage return characters are made visible but are treated as white space. This option must be off during a merge. Default is off.
Default is off. Number characters ('0'-'9', '.', '-') will be ignored in the first part of the analysis in which the line matching is done. In the result the differences will be shown nevertheless, but they are treated as white space.
Default is off. Changes in comments will be treated like changes in white space.
Default is off. Case-differences of characters (like 'A' vs. 'a') will be treated like changes in white space.
See next section.
See next section.
Try hard to find an even smaller delta. (Default is on.) This will probably be effective for complicated and big files. And slow for very big files.
When in auto-advance-mode this setting specifies how long to show the result of the selection before jumping to the next unsolved conflict.
Automatically solve all white-space conflict by choosing the specified file. (Default is manual choice.) Useful if white space really isn't important in many files. If you need this only occasionally better use "Choose A/B/C For All Unsolved Whitespace Conflicts" in the merge menu. Note that if you enable either "Ignore numbers" or "Ignore C/C++ comments" then this auto-choice also applies for conflicts in numbers or comments.
Regular expression for lines where KDiff3 should automatically choose one source. See also Automatic Merge ...
If activated KDiff3 runs the automatic merge using the "Auto merge regular expression" when a merge is started.
Regular expression for the start of the merge history entry. Usually this line contains the "$Log$"-keyword. Default value: ".*\$Log.*\$.*"
A merge history entry consists of several lines. Specify the regular expression to detect the first line (without the leading comment). Use parentheses to group the keys you want to use for sorting. If left empty, then KDiff3 assumes that empty lines separate history entries. See also Automatic Merge ...
Enable version control history sorting.
Each parentheses used in the regular expression for the history start entry groups a key that can be used for sorting. Specify the list of keys (that are numbered in order of occurrence starting with 1) using ',' as separator (e.g. "4,5,6,1,2,3,7"). If left empty, then no sorting will be done. See also Automatic Merge ...
If activated KDiff3 runs the automatic history merging using aforementioned options when a merge is started.
KDiff3 truncates the history list after the specified number of entries. Use -1 to avoid truncation. (Default is -1).
This button shows a dialog that allows you to improve and test the regular expressions above. Just copy the respective data from your files into the example lines. The "Match results" will immediately show whether the match succeeds or not. The "Sort key result" will display the key used for history merge sorting.
Specify a command of your own that should be called when KDiff3 detects that for a three file merge the file from B doesn't contribute any relevant data that isn't already contained in the file from C. The command is called with the three filenames as parameters. Data matched by the "Auto merge regular expression" or in the history isn't considered relevant.
These options are concerned with scanning the directory and handling the merge: See the Directory Comparison/Merge Docs for details.
Yet there is one option here that is also relevant for saving single files:
When a file is saved and an older version already exists, then the original version will be renamed with an ".orig" extension. If an old backup file with ".orig" extension already exists then this will be deleted without backup.
Adjust the language of the user interface. Changing this option doesn't affect the running program. You have to exit and restart KDiff3 so that the language is changed. (This option is not available in the KDE version of KDiff3 because the language is adjustable in the global KDE settings.)
The following encoding options can be adjusted separately for each item or if this option is true, all values will take the first value.
Above the codec-selectors appears a note that tells you what the local encoding is. (This is not adjustable but for your information just in case you don't know your local encoding, but need to select it.)
Adjust the file encoding for input files. This has an effect on how the special characters are interpreted. Since you can adjust each codec separately you can even compare and merge files that were saved using different codecs.
When you have edited a file, then you can adjust which encoding will be used when saving to disk.
When you define preprocessors then they might not be able to operate on your codec. (e.g.: Your files are 16-bit-unicode and your preprocessor can only take 8-bit-ascii.) With this option you can define the encoding of preprocessor output.
Some languages are written right to left. When this option is enabled, KDiff3 draws the text from right to left in the diff input windows and in the merge output window. Note that if you start KDiff3 with the command line option "--reverse" then all layouting will be done right to left too. (This is a feature provided by Qt.) This documentation was written assuming that "Right To Left Language" or reverse layout are disabled. So some references to "left" or "right" must be replaced by their respective counterpart if you use these options.
(These options and actions are available in menus or the buttonbar.)
You can select if line numbers should be shown for the input files.
Sometimes the visible spaces and tabs are disturbing. You can turn this off.
Turn this off to suppress any highlighting of white-space-only changes in the text or overview-columns. (Note that this also applies to changes in numbers or comments if the options "Ignore numbers" or "Ignore C/C++ comments" are active.)
These choices are only available when you compare three files. In normal mode all differences are shown in one color-coded overview-column. But sometimes you are especially interested in the differences between only two of these three files. Selecting "A vs. B", "A vs. C" or "B vs. C"-overview will show a second overview column with the required information next to the normal overview.
Wrap lines when their length would exceed the width of a window.
Sometimes you want to use the space on the screen better for long lines. Hide the windows that are not important. (In the Windows-menu.)
Switch between diff windows shown next to each other (A left of B left of C) or above each other (A above B above C). This should also help for long lines. (In the Windows-menu.)
Sometimes you are viewing the deltas and decide to merge. "Merge current file" in the Directory-menu also works if you only compare two files. A single click starts the merge and uses the filename of the last input-file as the default output filename. (When this is used to restart a merge, then the output filename will be preserved.)