| Value | Meaning |
|---|---|
| UNDEFINED0 | undefined merge mode |
| REPLACE_ALL1 | replace all tags (clear list and append) |
| REPLACE2 | replace tags |
| APPEND3 | append tags |
| PREPEND4 | prepend tags |
| KEEP5 | keep existing tags |
| KEEP_ALL6 | keep all existing tags |
| COUNT7 | the number of merge modes |
The different tag merging modes are basically replace, overwrite and append, but they can be seen from two directions. Given two taglists: (A) the tags already in the element and (B) the ones that are supplied to the element ( e.g. via Tag.setterMergeTags / Tag.setterAddTags or a GST_EVENT_TAG), how are these tags merged? In the table below this is shown for the cases that a tag exists in the list (A) or does not exists (!A) and combinations thereof.
<table frame="all" colsep="1" rowsep="1"> <title>merge mode</title> <tgroup cols='5' align='left'> <thead> <row> <entry>merge mode</entry> <entry>A + B</entry> <entry>A + !B</entry> <entry>!A + B</entry> <entry>!A + !B</entry> </row> </thead> <tbody> <row> <entry>REPLACE_ALL</entry> <entry>B</entry> <entry>-</entry> <entry>B</entry> <entry>-</entry> </row> <row> <entry>REPLACE</entry> <entry>B</entry> <entry>A</entry> <entry>B</entry> <entry>-</entry> </row> <row> <entry>APPEND</entry> <entry>A, B</entry> <entry>A</entry> <entry>B</entry> <entry>-</entry> </row> <row> <entry>PREPEND</entry> <entry>B, A</entry> <entry>A</entry> <entry>B</entry> <entry>-</entry> </row> <row> <entry>KEEP</entry> <entry>A</entry> <entry>A</entry> <entry>B</entry> <entry>-</entry> </row> <row> <entry>KEEP_ALL</entry> <entry>A</entry> <entry>A</entry> <entry>-</entry> <entry>-</entry> </row> </tbody> </tgroup> </table>