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 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
- 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.
The experimental font family implementation for the base-14 fonts is quite buggy and is not an accurate solution. It is also not nicely structured and requires the proper implementation to write the streams and embed fonts into the PDF document and we need to create an in-memory Appearance with an in-memory Resource Dictionary, where the /Font entry points out to the on-disk Font Subdictionary inside AcroForm->DR. It would actually be good to save the in-memory appearance as /AP into the document (PDF 2.0 requires this, and a number of existing Okular issues arise from not saving AP). But that's unrelated to the font family issue.
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 have got a KDE developer account, set up a scratch repository to discuss the ideas and share experimental code 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:
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 solution and the support for the embedded fonts. This is how it works:
Branch where I'm working
- The beginning of GSoC 2018 with KDE
- FreeText typewriter annotation WYSIWYG implementation ideas
- GSoC Coding Period - Phase One (May 14th to June 12th): Initial implementation of typewriter annotation tool in Okular
- GSoC Coding Period - Phase Two (June 13th to July 7th): Font color implementation in Poppler and Okular
- I'm going to Akademy 2018 - Vienna, Austria
- FreeText Annotation :: Font family implementation in Poppler
- GSoC Coding Period - Phase Three (July 8th to August 6th): Create and parse DA string in Poppler Core and font family implementation
Patches / Published Code
- Add Typewriter Annotation Tool in Okular
- Add font color and create and parse DA string in the Poppler core
- (Experimental) Patch to display Base-14 font in typewriter annotations
Bug Reports where I'm working
Scratch GIT repos
Project presentation video at Akademy'18, Vienna