What is Miklos hacking

Format-on-format change tracking in Collabora Online Writer

Miklos Vajna — Wed, 03 Jun 2026 15:41:57 +0200

Inter-dependent change tracking in Collabora Online was mostly a topic last year, see the post from November for more info about the feature in general: this is the case when you create a change on top of another change.

This post is meant to deal with the situation where you already have a recorded formatting and somebody else creates a new formatting on top of that.

Motivation¶

Writer supports insert-then-delete, insert-then-format and delete-then-format as combinations of changes with different types. So format-on-format is not supported at a file format level, DOCX can't represent it, either.

But instead of just losing the old format when we create a new format, we can do better: update the format redline to now track the formatting of the union of the old and new format change.

This still means that the metadata (e.g. author) will be only stored for the new change, but accept or reject on the format will result in the expected formatting.

Results so far¶

The document from the issue had BBB as bold by Alice:

Collabora Online Writer: a format redline

And now once a different editor marks the middle B as italic, additionally, then the formatting on this middle character is now attributed to the new editor:

Collabora Online Writer: format on top of format, different editors

Without the fix, rejection only removed the italics. With the fix, now reject correctly removes both the bold and the italic formatting. Accept is a little bit easier, since we don't need to touch the formatting in the model, just delete the change from the table of changes.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition.

Better pasting of markdown into Collabora Online Writer

Miklos Vajna — Mon, 04 May 2026 15:29:42 +0200

Writer has a markdown import/export filter in Collabora Online, see the post from December for more info about the filter in general.

This post is meant to detail a recent improvement when a markdown snippet is on the clipboard and it's pasted into an existing Writer document.

Motivation¶

Writer import filters operate in two modes: normally an empty model gets populated by reading user input from a file, in a certain format. You can also paste similar data from the clipboard, in which case the target model is not empty and this introduces some complexity.

The markdown import was missing some tweaks which were there already in the ODT and RTF paste code. Additionally, given that markdown only allows limited formatting, it makes sense to inherit more formatting from the paste position, so the pasted content's formatting is consistent with the formatting of the surrounding content.

Results so far¶

The document from the issue had bullets with text "A" and "B", the first problem was that pasting before "A" resulted in a mix of existing vs pasted content:

Collabora Online Writer markdown paste: before fixing paragraph splits

After fixing that, the problem was that the bullet format from markdown and in the existing document was different:

Collabora Online Writer markdown paste: paragraph splits are fixed, bullet formats are not

Once that got fixed, the paragraph style was still bad:

Collabora Online Writer markdown paste: bullet formats are fixed, paragraph style is not

Which lead to the correct paste result:

Collabora Online Writer markdown paste: paragraph style is fixed

As a bonus point, undo for the paste now works correctly, too.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition.

Comparing text documents in Collabora Online: improved UI

Miklos Vajna — Wed, 01 Apr 2026 08:55:11 +0200

The document compare view in Collabora Online Writer allows comparing documents side by side, see the first post for more info about the feature in general.

This second post is meant to give you an update on what happened in this area in the last month.

Motivation¶

Collabora Online core supports showing or hiding tracked changes in document content, we have a UI button for that, see the notebookbar's Review tab, the Tracking section's Show button.

Entering doc compare mode or leaving it works by clicking on the View Changes button, in the same section.

But this means that you can show/hide changes (modifies the document layout, affects everyone) and also view them (only affects your view), and they do quite different things. :-)

Results so far¶

The new UI has a button with a drop-down: the button is toggle that reflects if you compare change side-by-side or not. And if you click the drop-down next to the button, it's clear that show/hide is for inline rendering in the document layout while the other option is to render changes side-by-side:

Collabora Online: view changes inline or side-by-side

While this used to look like this:

Old UI: show or view changes?

There were also a number of other smaller improvements: now side-by-side rendering works nicely if you use IME to type characters, a missing invalidation is sorted out and side-by-side rendering is better with comments.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

tdf#171191 sw redline render mode: fix crash on IME input

COOL side:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition.

Comparing text documents in Collabora Online

Miklos Vajna — Tue, 03 Mar 2026 14:21:25 +0100

If you have two documents or two versions of a document to compare, then traditional tracked changes is too late, the untracked changes are already in the document.

This work for Collabora Online adds interactive a non-interactive document compare to create tracked changes after the fact, finally introduces a document compare view, to better understand these changes.

Motivation¶

Collabora Online's core already contained a document compare feature, but this was never integrated with the SDK (REST API) or with the browser UI.

Additionally, while some users took a training in understanding track changes (or: redlines), the usage of underlines for inserts and strike-throughs for deletions may not be obvious. An alternative of this is a side-by-side view, which is now available in Collabora Online for text documents.

Results so far¶

Non-interactive document compare¶

See the SDK, now you can convert e.g. an editable (new) docx file to PDF in a way that your request references your old docx file as a parameter, and the resulting PDF shows the differences:

curl -k -F "data=@new.docx" -F "compare=@old.docx" -F "format=pdf" -o out.pdf https://localhost:9980/cool/convert-to

Interactive document compare¶

Technically this is a bit similar to image insertion: once you open your new document, you can compare its content with an old local or remote document:

Collabora Online: interactive document compare for text documents

Just use the Compare button on the Review tab on the notebookbar.

Document compare view¶

We worked with Gokay to build this. The LOK API now provides "tile modes" for text documents, similar to how presentations already have tile modes for slide content, master pages and notes. The default tile mode is unchanged for text documents, but the Review tab of the notebookbar has a View Changes button and then the new left hand side, right hand side tile modes allow you to show the changes side by side:

Collabora Online: the new document compare view

Removed content is colored with a red-like color, added content is colored with a green-like color. The matching content on the other side is gray. This is not only for text, e.g. images have a frame with a similar color.

Now that the LOK API could provide tiles either left or right hand side mode, Gokay built a whole new tile layout on the browser side, so these are shown nicely side by side.

To better understand what you see on your screen, now there are also labels at the top of the first pages:

Collabora Online: the new document compare labels

This describes the purposes of the two sides, and in case you're right after a document compare action, also shows you the file names, modification dates and author names.

For integrators, it's possible to start in this mode by default, if you append &comparechanges=1 to COOL's iframe URL.

Finally if you hover over a tracked change with your mouse, now you get a highlight for that piece of text on both sides, to match the same parts of the old and new version better. A deletion looks like this:

Collabora Online: document compare view, highlight of a delete

This also works for inserts:

Collabora Online: document compare view, highlight of an insert

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

COOL side:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition.

Improving deleted commented text ranges in Writer's DOCX filter

Miklos Vajna — Wed, 04 Feb 2026 08:42:44 +0100

If you have a commented text range, which gets deleted while track changes is on and you later save and load this with Writer's DOCX filter, that works now correctly.

This work is primarily for Collabora Online, but the feature is available in desktop Writer as well.

Motivation¶

It was already possible to comment on text ranges. Comments were also supported inside deletes when track changes is enabled. These could be already exported to and imported from DOCX in Writer. But you could not combine these.

With the increasing popularity of commenting text ranges (rather than just inserting a comment with an anchor), not being able to combine these was annoying.

Results so far¶

Here is how a commented text range inside a delete from DOCX now looks like, note the semi-transparent comment hinting it's deleted:

Commented text range, inside a tracked delete, in DOCX, Collabora Online

As a side effect, this also fixes the behavior in desktop Writer, which crosses out deleted comments:

Commented text range, inside a tracked delete, in DOCX, desktop

In the past, the "is this deleted" property was not visible in the render result:

Commented text range, inside a tracked delete, in DOCX, Collabora Online, old bad state

And it was also bad in desktop Writer:

Commented text range, inside a tracked delete, in DOCX, desktop, old bad state

This required changes to both DOCX import and export: a comment could be deleted or could have an anchor which is a text range, but you couldn't have both.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition. Collabora intends to continue supporting and contributing to LibreOffice, the code is merged so we expect all of this work will be available in TDF's next release too (26.8).

Bullet improvements in Impress

Miklos Vajna — Mon, 05 Jan 2026 08:37:39 +0100

The bullet support in Impress got a couple of improvements recently, some of this is PPTX support and others are general UI improvements.

This work is primarily for Collabora Online, but the feature is available in desktop Impress as well.

Motivation¶

Probably the most simple presentations are just a couple of slides, each slide having a title shape and an outliner shape, containing some bullets, perhaps with some additional images. Images are just bitmaps, so let's focus on outliner shapes and their outliner / bullet styles.

What happens if you save these to PPTX and load it back? Can you toggle between a numbering and a bullet? Can you return to an outliner style after you had direct formatting for your bullet?

Results so far¶

The first case was about bullet editing of this document:

Outliner shape with 3 outliner styles

If you pressed enter at the end of 'First level', then pressed <tab> to promote the current paragraph to the second level, nothing happened. The reason for this was that our PPTX export was missing the list styles of shapes, except for the very first list style. And the same was missing on the import side, too. With this, not only the rendering of the bullets are OK, but also adding new paragraphs and using promoting / demoting to change levels work as expected.

The second case was about this document, where the second level had a numbering, not a bullet:

Outliner shape with a numbering on the second level

We only had UI to first toggle off a numbering to no numbering, then you could toggle on bullets. Now it's possible to do this change in one step.

The last case was about styles. Imagine that you had a master page with an outline shape and some reasonably looking configuration for the first and second levels as outline styles:

Outliner shape with two outline styles

Notice how the last paragraph has a slightly inconsistent formatting, due to direct formatting. Let's fix this.

Go to the end of the last bullet, which is currently not connected to an outline style, toggle bullets off and then toggle it on again. Now we clear direct formatting when we turn off the bullet, so next time you turn bullets on, it'll be again connected to the outline style's bullet configuration and the content will look better.

Note how this even improves consistency: Writer was behaving the same way already, when toggling bullets off and then toggle on again resulted in getting rid of previously applied unwanted direct formatting.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition. Collabora intends to continue supporting and contributing to LibreOffice, the code is merged so we expect the core of this work will be available in TDF's next release too (26.2).

Markdown import in Writer: the new template option

Miklos Vajna — Wed, 03 Dec 2025 09:35:36 +0100

Writer recently got a new markdown import option to take styles from a template, leading to much prettier output when converting markdown to PDF, DOCX or ODT.

This work is primarily for Collabora Online, but the templating feature is available in desktop Writer as well.

Motivation¶

A previous post mentioned recent improvements to the markdown import/export in Writer.

But if you convert some markdown to e.g. PDF, all the headings just have the default look, wouldn't it be nice to take your organization template and add colors and other formatting there, automatically?

Also, wouldn't it be nice if you could paste as markdown in COOL or copy the current selection as markdown? Which would enable all sorts of interesting use-cases, like using an external API to turn the selection into a summary or translating it to a different language.

Results so far¶

Here is a sample input markdown:

# heading 1

body text

Here is how it looks like if you template it using the core.git sw/qa/filter/md/data/template.docx sample:

PDF result: templated

curl invocation for this:

curl -k -F "data=@/path/to/test.md" -F "template=@/path/to/template.docx" -F "format=pdf" -o out.pdf https://localhost:9980/cool/convert-to

Or example desktop command-line:

soffice --infilter='Markdown:{"TemplateURL":{"type":"string","value":"./template.ott"}}' test.md

While it would look like this by default:

PDF result: default

The other part is the PostMessage API of COOL, if you want to copy and paste as markdown. What's newly possible:

Copy the current selection: set MessageId to Action_Copy and the value to {"Mimetype": "text/markdown;charset=utf-8"}
Paste at the current cursor position: set MessageId to Action_Paste and the value to something like {"Mimetype": "text/markdown;charset=utf-8", "Data": "foo _bar_ baz"}

You can read more about the PostMessage API in the COOL SDK.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

Online side:

Want to start using this?¶

You can get a development edition of Collabora Online 25.04 and try it out yourself right now: try the development edition. Collabora intends to continue supporting and contributing to LibreOffice, the code is merged so we expect the core of this work will be available in TDF's next release too (26.2).

Interdependent tracked changes improvements in Writer, part 4: direct accept/reject

Miklos Vajna — Tue, 04 Nov 2025 08:11:48 +0100

Writer has some support for interdependent (or hierarchical) tracked changes: e.g. the case when you have a delete on top of an insert. See the third post for background.

This work is primarily for Collabora Online, but the feature is available in desktop Writer as well.

Motivation¶

Interdependent changes mean that the UI shows one type of change on top of another change, e.g. formatting on top of insert. Writer knows the priority of each type, so in case you have an insert or delete change and on top of that you have a formatting, then the UI will look "through" the formatting and work on the underlying insert or delete when you navigate with your cursor to a position with multiple changes and you press Accept on the Review tab of the notebookbar.

Usually this is what you mean, but what if you want to work on the formatting at the top, directly? You can now open the Manage Changes dialog using the Manage button on the Review tab of the notebookbar and if you go to the formatting change row of the dialog, then pressing Accept there will accept the formatting change, not the insert or delete change. This is possible, because the dialog gives you a way to precisely select which tracked change you want to work with, even if a specific cursor position has multiple tracked changes.

Results so far¶

Here is a sample ins-then-format.docx document from the core.git testcases, the baseline has an insertion, and part of that is covered by an additional formatting change on top:

Interdependent tracked change: baseline

If you just go in the middle of the document and press Accept, that will work with the more important insert change, so the result looks like this:

Interdependent tracked change: default accept result

But now you can also open the Manage Changes dialog, to be more specific by directly selecting the formatting change:

Interdependent tracked change: direct accept via the dialog

And when you accept the formatting change directly, the result will be just the insert change:

Interdependent tracked change: direct accept result

You can save and load the results in both DOCX and ODT, as usual.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

Want to start using this?¶

Markdown import/export in Writer

Miklos Vajna — Tue, 07 Oct 2025 08:13:55 +0200

Writer recently got a Markdown import & export filter and there were a number of improvements to that.

This work is primarily for Collabora Online, but the feature is available in desktop Writer as well.

Motivation¶

Ujjawal Kumar contributed a markdown import to Writer, as part of Google Summer of Code (GSoC) this summer. Mike Kaganski of Collabora also created a minimal markdown export in Writer. I looked at the feature differences between the two, and filled in various gaps in the markdown export. I also added a few general markdown import/export improvements relevant for normal Writer documents, like embedded image support.

Results so far¶

Here is a sample case of a document using inline code spans:

Code span: baseline

Exporting this to markdown & loading back to Writer, the code span was lost:

Code span: old result

And now it's preserved:

Code span: new result

This also works with code blocks.

Second, here is a document with lists:

Lists: baseline

Exporting this to markdown & loading back to Writer, the lists were lost:

Lists: old result

And now they are preserved:

Lists: new result

This also works with nested lists.

Third, here is a document with an image:

Image: baseline

Exporting this to markdown & loading back to Writer, the image was lost:

Image: old result

And now it's preserved:

Image: new result

This also works with embedded and anchored images.

Fourth, here is a document with a table:

Table: baseline

Exporting this to markdown & loading back to Writer, the table was lost:

Table: old result

And now it's preserved:

Table: new result

This also works with table alignments and nested tables (to the extent the markdown markup allows that).

Fifth, here is a document with a quote block:

Quote: baseline

Exporting this to markdown & loading back to Writer, the quote's paragraph indentation was lost:

Quote: old result

And now it's preserved:

Quote: new result

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side:

Want to start using this?¶

Interdependent tracked changes improvements in Writer, part 3

Miklos Vajna — Tue, 09 Sep 2025 08:23:48 +0200

Writer has some support for interdependent (or hierarchical) tracked changes: e.g. the case when you have a delete on top of an insert. See the second post for background.

This work is primarily for Collabora Online, but the feature is available in desktop Writer as well.

Motivation¶

With the already mentioned improvements in place, the area of format redlines with character style or direct formatting changes were still lacking: Writer's original model here was just marking a text range as "formatted" and then either accept the format redline as-is, or reject reverting back to the paragraph style (default formatting), losing the old character style or old direct formatting.

Results so far¶

Here is a sample case of a document where the old character style is Strong (~bold) and the font size is 24pt, while the new character style is Quote (~italic) and the font size is 36pt. The rest of the document uses no specific character styles and has the font size of 12pt:

Interdependent tracked change: improved format, after document load

Rejecting that format redline resulted in just the defaults, i.e. no character style and 12pt font size:

Interdependent tracked change: old reject, lost character style / direct format

But now we track the old character style & direct format:

Interdependent tracked change: new reject, handled character style / direct format

This required changes in the DOCX import, ODF import and ODF export, too.

How is this implemented?¶

If you would like to know a bit more about how this works, continue reading... :-)

As usual, the high-level problem was addressed by a series of small changes. Core side: