Jetpack Compose internals 📖

Do you wonder how Jetpack Compose works internally, or how the compiler or the runtime work together? Are you curious about other use cases for Compose? Did you ever think about how Composable functions communicate with the compiler and the runtime?

It's your lucky day 🙌 Jetpack Compose internals is your chance to go one step further and learn the guts of what will become the new standard of Android UI.

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Companies supporting the book

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How to sponsor this book

Any company can become a sponsor. There are different sponsorship levels, but all of them will make the company appear in the book attributions page and in any existing book sites like Leanpub and this page you are reading now. The company will provide a paragraph that will be advertised along with the company name and logo.

Any sponsorships will have a frequent prominent position on any relevant updates about the book shared in social media.

Sponsorship levels

Diamond 💎

A Diamond sponsor makes the book completely free for a month, so it becomes effectively accessible to every developer in the world. A Diamond sponsor has total exclusivity, if there is a diamond sponsor, no more sponsors will be accepted.


Platinum sponsors reduce the book price a 75% during a month. If there is more than one platinum sponsor, the book becomes completely free.

Gold 🥇

Gold sponsors reduce the book price a 50% during a month. If there are three or more gold sponsors, the book becomes completely free.

Silver 🥈

Silver sponsors reduce the book price a 25% during a month. If there are 4 silver sponsors or more, the book becomes completely free.

Copper 🥉

Copper sponsors reduce the book price a 10% during a month.

Previous sponsors

The book content

The book covers following topics among many others.

1. Composable functions

1. The nature of Composable functions
2. Composable function properties
3. Calling context
4. Idempotent
5. Free of side effects
6. Restartable
7. Fast execution
8. Positional memoization
9. Similarities with suspend functions
10. Composable functions are colored
11. Composable function types

2. The Compose Compiler

1. A Kotlin compiler plugin
2. Compose annotations
3. Registering compiler extensions
4. Static analysis and static checkers
5. Call, type, and declaration checks
6. Diagnostic suppression
7. Kotlin and runtime version checks
8. Code generation (IR) and lowering
9. Inferring class stability
10. Enabling live literals
11. Compose lambda memoization
12. Injecting the Composer
13. Comparison propagation
14. Default parameters
15. Control flow group generation
16. Klib and decoy generation

3. The Compose Runtime

1. The Slot table and the list of changes
2. Modeling the changes
3. The Composer and how it is fed
4. Writing and reading groups
5. Remembering values
6. Recompose scopes for recomposition
7. Side effects in the Composer
8. Storing CompositionLocals & source info
9. Linking Compositions as a tree
10. The current State snapshot
11. Navigating the tree nodes
12. Performance when building the tree
13. Applying the changes
14. Attaching and drawing the nodes
15. Composition
16. Creating a Composition
17. The initial Composition process
18. Applying changes after Composition
19. The Recomposer
20. Recomposition process
21. Concurrent Recomposition

4. Compose UI

1. Integrating UI with the Compose runtime
2. Mapping scheduled changes to actual changes to the tree
3. Composition from the point of view of Compose UI
4. Subcomposition from the point of view of Compose UI
5. Reflecting changes in the UI
6. Different types of Appliers
7. Materializing a new LayoutNode
8. Materializing a change to remove nodes
9. Materializing a change to move nodes
10. Materializing a change to clear all the nodes
11. setContent as the integration point to close the circle
12. Measuring in Compose UI
13. Measuring policies
14. Intrinsic measurements
15. Layout Constraints
16. Modeling modifier chains
17. Setting modifiers to the LayoutNode
18. How LayoutNode ingests new modifiers
19. Drawing the node tree
20. Semantics in Jetpack Compose
21. Notifying about semantic changes
22. Merged and unmerged semantic trees

5. The State snapshot system

1. What snapshost state is
2. Concurrency control systems
3. Multiversion concurrency control (MVCC)
4. The Snapshot
5. The snapshot tree
6. Snapshots and threading
7. Observing reads and writes
8. MutableSnapshots
9. GlobalSnapshot and nested snapshots
10. StateObjects and StateRecords
11. Reading and writing state
12. Removing or reusing obsolete records
13. Change propagation
14. Merging write conflicts

6. Smart recomposition

1. To be written
2. To be written
3. To be written
4. To be written
5. To be written
6. To be written
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8. To be written
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14. To be written

7. Effects and effect handlers

1. Introducing side effects
2. Side effects in Compose
3. What we need
4. Effect handlers
5. Non suspended effects
6. Suspended effects
7. Third party library adapters

8. The Composable lifecycle

1. To be written
2. To be written
3. To be written
4. To be written
5. To be written
6. To be written
7. To be written

9. Advanced Compose use cases

1. Compose runtime vs Compose UI
2. Composition of vector graphics
3. Building vector image tree
4. Integrating vector composition into Compose UI
5. Managing DOM with Compose
6. Standalone composition in the browser
7. Conclusion

The authors and the project

This book is being written by me (Jorge Castillo) and Andrei Shikov.

I started writing this book around a year ago, and it helped me to escape a bit from the events happening around and focus on something interesting. It started as a series of posts and suddenly became a book. It is a chance to challenge myself and learn more about a new technology. A great consequence is to be able to share all the gathered knowledge with others 🥳

To write this book we explored the Jetpack Compose sources via and sources included in Android Studio. We also had to built our own side projects.

This book aims to gather all the relevant knowledge about Jetpack Compose internals so it works as a reference for the years to come. Jetpack Compose is the future of Android UI, but it will also gain relevance in other platforms given its multiplatform nature.

Support me by buying the book

By buying the book you are not only rewarding the countless hours of effort invested, but also boosting my motivation to keep working on it 🙏

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Manuel Vivo

“Certainly one of the best resources to learn about the internals of Jetpack Compose. The details in which everything is explained in the book are mind-blowing. 100% recommended for any developer interested in what Jetpack Compose does under the hood. Disclaimer: it does a lot!”

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Joe Birch

“Being clearly explained and easily consumable, Jorge’s Jetpack Compose content has been a great learning resource. I’m really looking forward to picking up this book and soaking up all of the knowledge around these Compose topics!”

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Antonio Leiva

“Jorge is able to explain hard concepts in the simplest possible way. This book is another proof of his teaching abilities.”

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Enrique López-Mañas

“Jorge has done an astonishing job at presenting Compose and its internal to the masses. I can absolutely endorse his book for any developer interested in the peculiarities of Compose and eager to learn more about it.”

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Andrei Shikov

“Jorge did an amazing job explaining how Compose works in smallest detail, and there’s so much more to it than only displaying UI. I thoroughly enjoyed hacking different things based on it, and I hope you will too!”

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Jorge Castillo

“This book is one of the hardest challenges I’ve faced as a developer. I’ve put all my love and effort on creating a consciously crafted piece of knowledge.”

Support me by buying the book

By buying the book you are not only rewarding the countless hours of effort invested, but also boosting my motivation to keep working on it 🙏