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Implementing the FreeText annotation with FreeTextTypewriter behavior

Okular is a KDE universal document viewer. It allows reviewing and annotating the PDF documents and supports various text and graphic annotations. FreeText is one of them but the FreeTextTypewriter behavior is still missing to write directly on a PDF page. This project focus on implementing this missing FreeText annotation feature and adding a new ‘Typewriter’ entry in the annotation toolbar.

Mentor: Tobias Deiminger

Project Goals

  • Add a new typewriter icon and settings dialogue to the annotation toolbar.
  • Setting annotation background to transparent, and /IT set to FreeTextTypewriter.
  • Font color implementation in both Okular and Poppler for the FreeText Annotation.
  • Font family implementation in Poppler for the FreeText Annotation.

Work Report

Community Bonding Period

During the Community Bonding period, I've been in communication with my mentor, discussing various implementation ideas and learning more about the PDF format and the codebase of Okular and Poppler. In the meantime, I got a KDE developer account, set up a scratch repository to discuss the ideas and share experimental codes and explored pertinent bug reports on Bugzilla by taking part in the conversation. As I didn't mention any particular approach for click-to-type typewriter WYSIWYG editing in my GSoC proposal, we had to discuss, experiment and present a couple of ideas to the okular-devel list and would agree upon the community selected one. Further, I set up the working environment and built the project and I'm reading the Qt TextEdit and Poppler Qt5 frontend documentation while consulting with my mentor for the optimal approach to implement the proposed features.

Coding Period - Phase One (May 14th to June 12th)

Initial Implementation of Typewriter Annotation Tool in Okular

This phase was devoted to implementing the fully functional typewriter tool that creates the annotation with the transparent background in all the supported document formats and the text input UI in the current implementation is the popup QInputDialog window which is in accordance with the inline note. This is how it works:

A number of integration tests have also been written and the tasks for this phase are completed as planned. For the next phase, I'm aiming at fixing the minor bugs and implementing font color in Poppler where it should also respect the font family.

Coding Period - Phase Two (June 13th to July 7th)

Implementation of font color in Poppler and Okular

I have patched the poppler-qt5 with the font color by introducing the ‘rg’ operator in the GooString which formats the font color in the RGB color model. In Okular, the font color chooser is introduced in the typewriter annotation setting dialogue which sets both the text annotation’s color and the engine color and hence colorizes the typewriter icon color accordingly. The generator side and the doctype XML metadata for saving text color are also adapted. It is well supported in PagePainter too. This is how it works:


Bug Report:

Coding Period - Phase Three (July 8th to August 6th)

Create and parse DA string in Poppler Core and font family implementation

According to my blog post, I had to shift the creation and parsing of DA string in poppler-core and so the font color after the second evaluation. So in the final days of GSoC, I worked on font-family implementation in Poppler and came up with an experimental patch that shows the Base-14 fonts correctly for all the typewriter annotations in the same document. It is just a demo rather than an accurate solution and is very promising for the intuition of accurate solutions and the support for embedded fonts. This is how it works:

Bug Report:

Branch where I'm working

Important Links

Blog Posts

Patches / Published Code

Bug Reports where I'm working

Scratch GIT repos


Email: dileepsankhla.ds[at]gmail[dot]com