Seeking Guidance on Modularizing Calibre's Ebook Viewer and Organizing Source Code

suprezg · 05-31-2025, 09:11 AM

I am currently working on a fork of Calibre and want to separate all code and files related solely to the ebook viewer into a dedicated directory. My goal is to make the viewer runnable as a standalone application by executing main.py from src/calibre/gui2/viewer.

If this separation is not feasible, I would like to know how I can write my own viewer that leverages Calibre’s ebook viewer features, such as read aloud, search, highlights, and bookmarks. Which classes or modules should I study so I can invoke these functionalities from my own code?

Additionally, I have noticed that running python -m src.calibre.gui2.viewer.main results in errors like "polyglot module not found," and even after fixing that, other errors appear. However, running calibre-debug -c "from calibre.gui2.viewer.main import main; main()" works fine and launches the viewer. What does calibre-debug do in the backend to make this work, and how can I replicate this behavior in my own setup?

Are there any tips or sources available for organizing the Calibre source code?

Any guidance or insights would be helpful!!!

kovidgoyal · 05-31-2025, 10:27 AM

You cannot use calibre's viewer code in isolation. It's not designed for that and its not going to ever work like that.

suprezg · 05-31-2025, 11:14 PM

Hi Kovid, thank you for your reply.

Is there a way to use the bypy utility to create an ebook-viewer.exe without packaging the entire calibre application? Alternatively, can I develop a new viewer that utilizes existing calibre features such as Read Aloud and Search?

Additionally, I’ve noticed that when I try to run certain main.py files using Python directly, they do not work, but when I run them using calibre-debug, they execute successfully. Why does this happen?

Ultimately, my goal is to create a stripped-down version of calibre that consists solely of the ebook viewer.

Any guidance would be greatly appreciated. Thank you!

kovidgoyal · 06-01-2025, 12:21 AM

There is no way to do that. The viewer is not separable in any form from the rest of calibre.

suprezg · 06-02-2025, 08:08 AM

Hi Kovid,
Thank you for your reply. I really need your help with this. While studying the repository, I noticed that there are many files related to ebook conversion to various formats, the ebook metadata editor, news fetcher, and other features.

I want to create a small app that I can integrate into my project, focusing solely on the ebook viewer. It would be very helpful if you could list the folders that are not related to the ebook viewer and can be safely removed.

Even if the viewer cannot be made completely standalone, I am looking for a stripped-down version without any additional functionalities.

I also noticed that there is an ebook-viewer.exe file. How can I build an executable like this with only ebook viewing capability?

Additionally, please guide me on how to test the application after removing unnecessary files from the source code.

Thank you!

05-31-2025, 09:11 AM	#1
suprezg Junior Member Posts: 4 Karma: 10 Join Date: May 2025 Device: none	Seeking Guidance on Modularizing Calibre's Ebook Viewer and Organizing Source Code I am currently working on a fork of Calibre and want to separate all code and files related solely to the ebook viewer into a dedicated directory. My goal is to make the viewer runnable as a standalone application by executing main.py from src/calibre/gui2/viewer. If this separation is not feasible, I would like to know how I can write my own viewer that leverages Calibre’s ebook viewer features, such as read aloud, search, highlights, and bookmarks. Which classes or modules should I study so I can invoke these functionalities from my own code? Additionally, I have noticed that running python -m src.calibre.gui2.viewer.main results in errors like "polyglot module not found," and even after fixing that, other errors appear. However, running calibre-debug -c "from calibre.gui2.viewer.main import main; main()" works fine and launches the viewer. What does calibre-debug do in the backend to make this work, and how can I replicate this behavior in my own setup? Are there any tips or sources available for organizing the Calibre source code? Any guidance or insights would be helpful!!!

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05-31-2025, 10:27 AM	#2
kovidgoyal creator of calibre Posts: 45,250 Karma: 27110894 Join Date: Oct 2006 Location: Mumbai, India Device: Various	You cannot use calibre's viewer code in isolation. It's not designed for that and its not going to ever work like that.

05-31-2025, 11:14 PM	#3
suprezg Junior Member Posts: 4 Karma: 10 Join Date: May 2025 Device: none	Hi Kovid, thank you for your reply. Is there a way to use the bypy utility to create an ebook-viewer.exe without packaging the entire calibre application? Alternatively, can I develop a new viewer that utilizes existing calibre features such as Read Aloud and Search? Additionally, I’ve noticed that when I try to run certain main.py files using Python directly, they do not work, but when I run them using calibre-debug, they execute successfully. Why does this happen? Ultimately, my goal is to create a stripped-down version of calibre that consists solely of the ebook viewer. Any guidance would be greatly appreciated. Thank you!

06-01-2025, 12:21 AM	#4
kovidgoyal creator of calibre Posts: 45,250 Karma: 27110894 Join Date: Oct 2006 Location: Mumbai, India Device: Various	There is no way to do that. The viewer is not separable in any form from the rest of calibre.

06-02-2025, 08:08 AM	#5
suprezg Junior Member Posts: 4 Karma: 10 Join Date: May 2025 Device: none	Hi Kovid, Thank you for your reply. I really need your help with this. While studying the repository, I noticed that there are many files related to ebook conversion to various formats, the ebook metadata editor, news fetcher, and other features. I want to create a small app that I can integrate into my project, focusing solely on the ebook viewer. It would be very helpful if you could list the folders that are not related to the ebook viewer and can be safely removed. Even if the viewer cannot be made completely standalone, I am looking for a stripped-down version without any additional functionalities. I also noticed that there is an ebook-viewer.exe file. How can I build an executable like this with only ebook viewing capability? Additionally, please guide me on how to test the application after removing unnecessary files from the source code. Thank you!