Show full program context when eye button is clicked in Hello World example by RowanTL · Pull Request #147 · godot-rust/book

RowanTL · 2026-08-02T23:00:52Z

Why

When I read through a rust book, I like to click on the little eye icon to see how a block of code fits into the entirety of the program. I found myself confused after reading through the Hello World example.

Problem

The current behavior of the eye button wraps the block of code in a main function call. This is not verbose enough and confusing in my opinion. Also, none of the playground examples compile.

Proposed Changes

Remove playground functionality
When the eye icon is pressed, show the rust block in relation to the entire lib.rs file

More details about the changes

The play button is removed by adding the block below to book.toml

[output.html.playground]
runnable = false

As for showing code when the eye icon is pressed, I created a file at src/intro/code/hello-world.rs that has anchors placed in it, controlling what code is shown. I removed the line fn init(base: Base<Sprite2D>) -> Self { /* as before */ } from being mentioned as the user could simply click the eye and see the implementation. Finally, I added an admonish tip to click the eye before the Rust entry point block.

AI Usage

I used Claude Opus 5 in this PR. Claude stitched together the code blocks and placed most of the anchor points in src/intro/code/hello-world.rs. I modified the anchor points to remain loyal to the original rust blocks.

Testing

Using Godot 4.7.1, I saw icon.svg moving in a circle from the code in src/intro/code/hello-world.rs when running the scene. I have not tested whether the Custom Rust APIs block functions.

Final Notes

If anything could be changed, let me know.

RowanTL · 2026-08-03T02:48:04Z

Here's a visual of what I changed:

New docs:

new_docs.mp4

Old docs:

old_docs.mp4

Yarwin · 2026-08-07T18:34:16Z

+# Snippets in this book are library code (cdylib entry points, #[godot_api] impls, ...) and
+# depend on the `godot` crate, so none of them can run on play.rust-lang.org. Without this,
+# mdbook silently wraps every Rust block in a hidden `fn main() { ... }`, which the "show
+# hidden lines" eye icon then reveals as if it were real code. Explicit `# ` hidden lines
+# still work as usual.


That's a lot of words used while shorter one-line sentence could do a job just fine.

Yarwin · 2026-08-07T18:36:41Z

+// Anchor names may be opened and closed more than once; mdbook concatenates the regions and
+// hides everything in between. That is how a block can show e.g. the `impl` header and one
+// method without the other methods.


why do you describe something which is included in mdbook documentation https://wofwca.github.io/mdBook/format/mdbook.html#including-portions-of-a-file?

Sometimes I leave slop in. Planning to remove.

Yarwin · 2026-08-07T18:37:12Z

+// Complete source for the Hello World tutorial. Every code block in
+// src/intro/hello-world.md includes one of the anchors below.


what does this comment is supposed to convey?

Yarwin · 2026-08-07T18:41:05Z

+        // ANCHOR_END: physics-process
+        // In GDScript, this would be:
+        // rotation += angular_speed * delta
+
+        // ANCHOR: physics-process
+        // GDScript code:
+        //
+        // rotation += angular_speed * delta
+        // var velocity = Vector2.UP.rotated(rotation) * speed
+        // position += velocity * delta
+
+        let radians = (self.angular_speed * delta) as f32;
+        self.base_mut().rotate(radians);
+        // The 'rotate' method requires a f32,
+        // therefore we convert 'self.angular_speed * delta' which is a f64 to a f32
+        // ANCHOR_END: rotate


these examples should be separate; while enlarged they are displayed as:

which is very confusing.

Seems like the best way around this is two have two separate Rust files or foregoing the hidden lines feature on one of the blocks. lmk what you think.

I think two files might be okay, people might want to copy-paste them

Yarwin · 2026-08-07T18:44:48Z

-        // therefore we convert 'self.angular_speed * delta' which is a f64 to a f32
-    }
-}
+{{#rustdoc_include code/hello-world.rs:rotate}}


Personally I would just inline this one example (or split existing one into two if somebody insists). Additionally, rotate section is misleading - the example showcases usage of virtual method physics_process.

and a small update can be made – for a long time one can use delta: f32 directly in *process methods.

Will change rotate to something else. If you're okay with losing the hidden context here, I'd be okay with inlining too (unless you want to copy and paste the entirety of hello-world.rs into the readme just for it).

New to godot and haven't really ever contributed to a large codebase personally or professionally before. Thanks for the review!

RowanTL · 2026-08-12T02:59:12Z

Created two new files. One with the updated physics function and one without. This inherently solves the rotate name problem as well.

I'm testing this on godot = "0.5.4" and am not seeing that physics_process's delta accepts an f32.

Bromeon · 2026-08-12T08:45:52Z

I'm testing this on godot = "0.5.4" and am not seeing that physics_process's delta accepts an f32.

It does 🙂 godot-rust/gdext#1110
We also have a test for it.

Yarwin · 2026-08-12T16:55:12Z

+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// Note: This code contains the updated version of the physics_process function.


firstly: it doesn't
secondly: why this note?

Honestly the top comment is comment slop. Removed. I wrote the note to orient myself in case I'm copy and pasting from the docs website directly into a file.

Edit: Seems like the top comment is needed for the CI. lmk if you think the note is appropriate. If not told anything, just gonna keep it in 🤷

this info should be over the edited physics_process function, so the context is obvious for reader (as something along the lines of "in physics_process both f32 or f64 can be used for delta")

I moved where the note is as well as added that little pointer in a comment.

RowanTL · 2026-08-13T07:16:18Z

I'm testing this on godot = "0.5.4" and am not seeing that physics_process's delta accepts an f32.

It does 🙂 godot-rust/gdext#1110 We also have a test for it.

I need to give my error messages a closer check!. Thanks :) I'll push a change in a little bit.

RowanTL · 2026-08-13T07:37:30Z

Any reason why angular_speed is a f64? I tried changing the type to f32 and it worked. I feel like this would make the code just a little nicer to read.

Bromeon · 2026-08-13T13:09:06Z

Not really, feel free to use f32 for both speed and angular_speed.

RowanTL · 2026-08-13T17:03:16Z

Not really, feel free to use f32 for both speed and angular_speed.

Also changed increase_speed's amount type to f32:

#[godot_api]
impl Player {
    #[func]
    fn increase_speed(&mut self, amount: f32) {
        self.speed += amount;
        self.signals().speed_increased().emit();
    }

    #[signal]
    fn speed_increased();
}

RowanTL · 2026-08-16T19:24:11Z

This looking good? Can condense the commits into one.

Bromeon · 2026-08-20T20:11:15Z

Why do you close this?

RowanTL · 2026-08-20T21:52:46Z

I felt like it wasn't going to get merged. No feedback in a week demoralized me.

Bromeon · 2026-08-20T22:22:51Z

I felt like it wasn't going to get merged. No feedback in a week demoralized me.

I don't even know what to answer here.

People have lives, this is a project made by volunteers in their free time, and the eye button in a book might not be on everyone's top priority 24/7. I appreciate your work but a bit of patience isn't unreasonable. It's not like this PR has been sitting for months or years, a very common thing in open-source btw. In fact, this PR has already gotten plenty of attention by two different maintainers.

Up to you how you'd like to proceed.

RowanTL · 2026-08-20T23:24:39Z

There is truth to your message. I appreciate even being able to program a game in Rust. I don't see why it can't stay open for a while.

documentation changes so eye button shows full file context

4eb4474

Yarwin reviewed Aug 7, 2026

View reviewed changes

physics_process examples into 2 files. Remove useless comments.

f297633

Yarwin reviewed Aug 12, 2026

View reviewed changes

physics_process(es) use delta: f32

ef96b99

RowanTL force-pushed the hello-world-change branch from 10a5309 to ef96b99 Compare August 13, 2026 07:33

Switch examples f32 -> f64 everywhere

25992ab

RowanTL closed this Aug 20, 2026

RowanTL reopened this Aug 20, 2026

		// Complete source for the Hello World tutorial. Every code block in
		// src/intro/hello-world.md includes one of the anchors below.

Conversation

RowanTL commented Aug 2, 2026

Why

Problem

Proposed Changes

More details about the changes

AI Usage

Testing

Final Notes

Uh oh!

RowanTL commented Aug 3, 2026

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Yarwin Aug 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

RowanTL commented Aug 12, 2026

Uh oh!

Bromeon commented Aug 12, 2026

Uh oh!

Choose a reason for hiding this comment

Uh oh!

RowanTL Aug 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

RowanTL commented Aug 13, 2026

Uh oh!

RowanTL commented Aug 13, 2026

Uh oh!

Bromeon commented Aug 13, 2026

Uh oh!

RowanTL commented Aug 13, 2026

Uh oh!

RowanTL commented Aug 16, 2026

Uh oh!

Bromeon commented Aug 20, 2026

Uh oh!

RowanTL commented Aug 20, 2026

Uh oh!

Bromeon commented Aug 20, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

RowanTL commented Aug 20, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Yarwin Aug 7, 2026 •

edited

Loading

RowanTL Aug 13, 2026 •

edited

Loading

Bromeon commented Aug 20, 2026 •

edited

Loading