# Objective
Make the output of this example repeatable so it can be utilized by
automated screenshot diffing.
## Solution
- Use a seeded RNG for the random colors
- Offset the meshes slightly in z so they don't intersect each other at
the extents of their animations.
# Objective
Fix these
```
-- rotate_cube and move_cube
conflict on: ["bevy_transform::components::transform::Transform", "transform::CubeState"]
-- rotate_cube and scale_down_sphere_proportional_to_cube_travel_distance
conflict on: ["bevy_transform::components::transform::Transform", "transform::CubeState"]
-- move_cube and scale_down_sphere_proportional_to_cube_travel_distance
conflict on: ["bevy_transform::components::transform::Transform", "transform::CubeState"]
```
The three systems in this example depend on the results of the others.
This leads to minor but detectable differences in output between runs by
automated screenshot diffing depending on the order of the schedule.
We don't necessarily need to be able to do this for **every** example,
but I think this is a case where fixing it is easy / maybe the right
thing to do anyway.
## Solution
Chain the three systems
# Objective
Replace instances of
```rust
for x in collection.iter{_mut}() {
```
with
```rust
for x in &{mut} collection {
```
This also changes CI to no longer suppress this lint. Note that since
this lint only shows up when using clippy in pedantic mode, it was
probably unnecessary to suppress this lint in the first place.
# Objective
- When reading API docs and seeing a reference to `ComponentId`, it
isn't immediately clear how to get one from your `Component`. It could
be made to be more clear.
## Solution
- Improve cross-linking of docs about `ComponentId`
# Objective
`no_archetype` benchmark group results were very noisy
## Solution
Use the `SingeThreaded` executor.
On my machine, this makes the `no_archetype` bench group 20 to 30 times
faster. Meaning that most of the runtime was accounted by the
multithreaded scheduler. ie: the benchmark was not testing system
archetype update, but the overhead of multithreaded scheduling.
With this change, the benchmark results are more meaningful.
The add_archetypes function is also simplified.
# Objective
The default division for a `usize` rounds down which means the batch
sizes were too small when the `max_size` isn't exactly divisible by the
batch count.
## Solution
Changing the division to round up fixes this which can dramatically
improve performance when using `par_iter`.
I created a small example to proof this out and measured some results. I
don't know if it's worth committing this permanently so I left it out of
the PR for now.
```rust
use std::{thread, time::Duration};
use bevy::{
prelude::*,
window::{PresentMode, WindowPlugin},
};
fn main() {
App::new()
.add_plugins((DefaultPlugins.set(WindowPlugin {
primary_window: Some(Window {
present_mode: PresentMode::AutoNoVsync,
..default()
}),
..default()
}),))
.add_systems(Startup, spawn)
.add_systems(Update, update_counts)
.run();
}
#[derive(Component, Default, Debug, Clone, Reflect)]
pub struct Count(u32);
fn spawn(mut commands: Commands) {
// Worst case
let tasks = bevy::tasks::available_parallelism() * 5 - 1;
// Best case
// let tasks = bevy::tasks::available_parallelism() * 5 + 1;
for _ in 0..tasks {
commands.spawn(Count(0));
}
}
// changing the bounds of the text will cause a recomputation
fn update_counts(mut count_query: Query<&mut Count>) {
count_query.par_iter_mut().for_each(|mut count| {
count.0 += 1;
thread::sleep(Duration::from_millis(10))
});
}
```
## Results
I ran this four times, with and without the change, with best case
(should favour the old maths) and worst case (should favour the new
maths) task numbers.
### Worst case
Before the change the batches were 9 on each thread, plus the 5
remainder ran on one of the threads in addition. With the change its 10
on each thread apart from one which has 9. The results show a decrease
from ~140ms to ~100ms which matches what you would expect from the maths
(`10 * 10ms` vs `(9 + 4) * 10ms`).
![Screenshot from 2023-09-14
20-24-36](https://github.com/bevyengine/bevy/assets/1353401/82099ee4-83a8-47f4-bb6b-944f1e87a818)
### Best case
Before the change the batches were 10 on each thread, plus the 1
remainder ran on one of the threads in addition. With the change its 11
on each thread apart from one which has 5. The results slightly favour
the new change but are basically identical as the total time is
determined by the worse case which is `11 * 10ms` for both tests.
![Screenshot from 2023-09-14
20-48-51](https://github.com/bevyengine/bevy/assets/1353401/4532211d-ab36-435b-b864-56af3370d90e)
# Objective
according to
[khronos](https://github.com/KhronosGroup/glTF/issues/1697), gltf nodes
with inverted scales should invert the winding order of the mesh data.
this is to allow negative scale to be used for mirrored geometry.
## Solution
in the gltf loader, create a separate material with `cull_mode` set to
`Face::Front` when the node scale is negative.
note/alternatives:
this applies for nodes where the scale is negative at gltf import time.
that seems like enough for the mentioned use case of mirrored geometry.
it doesn't help when scales dynamically go negative at runtime, but you
can always set double sided in that case.
i don't think there's any practical difference between using front-face
culling and setting a clockwise winding order explicitly, but winding
order is supported by wgpu so we could add the field to
StandardMaterial/StandardMaterialKey and set it directly on the pipeline
descriptor if there's a reason to. it wouldn't help with dynamic scale
adjustments anyway, and would still require a separate material.
fixes#4738, probably fixes#7901.
---------
Co-authored-by: François <mockersf@gmail.com>
# Objective
The reasoning is similar to #8687.
I'm building a dynamic query. Currently, I store the ReflectFromPtr in
my dynamic `Fetch` type.
[See relevant
code](97ba68ae1e/src/fetches.rs (L14-L17))
However, `ReflectFromPtr` is:
- 16 bytes for TypeId
- 8 bytes for the non-mutable function pointer
- 8 bytes for the mutable function pointer
It's a lot, it adds 32 bytes to my base `Fetch` which is only
`ComponendId` (8 bytes) for a total of 40 bytes.
I only need one function per fetch, reducing the total dynamic fetch
size to 16 bytes.
Since I'm querying the components by the ComponendId associated with the
function pointer I'm using, I don't need the TypeId, it's a redundant
check.
In fact, I've difficulties coming up with situations where checking the
TypeId beforehand is relevant. So to me, if ReflectFromPtr makes sense
as a public API, exposing the function pointers also makes sense.
## Solution
- Make the fields public through methods.
---
## Changelog
- Add `from_ptr` and `from_ptr_mut` methods to `ReflectFromPtr` to
access the underlying function pointers
- `ReflectFromPtr::as_reflect_ptr` is now `ReflectFromPtr::as_reflect`
- `ReflectFromPtr::as_reflect_ptr_mut` is now
`ReflectFromPtr::as_reflect_mut`
## Migration guide
- `ReflectFromPtr::as_reflect_ptr` is now `ReflectFromPtr::as_reflect`
- `ReflectFromPtr::as_reflect_ptr_mut` is now
`ReflectFromPtr::as_reflect_mut`
# Objective
If you remove a `ContentSize` component from a Bevy UI entity and then
replace it `ui_layout_system` will remove the measure func from the
internal Taffy layout tree but no new measure func will be generated to
replace it since it's the widget systems that are responsible for
creating their respective measure funcs not `ui_layout_system`. The
widget systems only perform a measure func update on changes to a widget
entity's content. This means that until its content is changed in some
way, no content will be displayed by the node.
### Example
This example spawns a text node which disappears after a few moments
once its `ContentSize` component is replaced.
```rust
use bevy::prelude::*;
use bevy::ui::ContentSize;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, delayed_replacement)
.run();
}
fn setup(mut commands: Commands) {
commands.spawn(Camera2dBundle::default());
commands.spawn(
TextBundle::from_section(
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
TextStyle::default(),
)
);
}
// Waits a few frames to make sure the font is loaded and the text's glyph layout has been generated.
fn delayed_replacement(mut commands: Commands, mut count: Local<usize>, query: Query<Entity, With<Style>>) {
*count += 1;
if *count == 10 {
for item in query.iter() {
commands
.entity(item)
.remove::<ContentSize>()
.insert(ContentSize::default());
}
}
}
```
## Solution
Perform `ui_layout_system`'s `ContentSize` removal detection and
resolution first, before the measure func updates.
Then in the widget systems, generate a new `Measure` when a
`ContentSize` component is added to a widget entity.
## Changelog
* `measure_text_system`, `update_image_content_size_system` and
`update_atlas_content_size_system` generate a new `Measure` when a
`ContentSize` component is added.
# Objective
- There are errors when building for WebGPU, since Assets V2 PR
```
error[E0432]: unresolved import `file_id::get_file_id`
--> /Users/francoismockers/.cargo/registry/src/index.crates.io-6f17d22bba15001f/notify-debouncer-full-0.2.0/src/cache.rs:6:15
|
6 | use file_id::{get_file_id, FileId};
| ^^^^^^^^^^^ no `get_file_id` in the root
|
note: found an item that was configured out
--> /Users/francoismockers/.cargo/registry/src/index.crates.io-6f17d22bba15001f/file-id-0.1.0/src/lib.rs:41:8
|
41 | pub fn get_file_id(path: impl AsRef<Path>) -> io::Result<FileId> {
| ^^^^^^^^^^^
= note: the item is gated behind the `unix` feature
note: found an item that was configured out
--> /Users/francoismockers/.cargo/registry/src/index.crates.io-6f17d22bba15001f/file-id-0.1.0/src/lib.rs:54:8
|
54 | pub fn get_file_id(path: impl AsRef<Path>) -> io::Result<FileId> {
| ^^^^^^^^^^^
= note: the item is gated behind the `windows` feature
For more information about this error, try `rustc --explain E0432`.
error: could not compile `notify-debouncer-full` (lib) due to previous error
```
## Solution
- Don't enable feature `filesystem_watcher` in WebGPU as it can't work
anyway
# Objective
mikktspace tangent generation requires mesh indices, and currently fails
when they are not present. we can just generate them instead.
## Solution
generate the indices.
# Objective
`Val`'s natural place is in the `geometry` module with `UiRect`, not in
`ui_node` with the components.
## Solution
Move `Val` into `geometry`.
# Objective
Rename RemovedComponents::iter/iter_with_id to read/read_with_id to make
it clear that it consume the data
Fixes#9755.
(It's my first pull request, if i've made any mistake, please let me
know)
## Solution
Refactor RemovedComponents::iter/iter_with_id to read/read_with_id
## Changelog
Refactor RemovedComponents::iter/iter_with_id to read/read_with_id
Deprecate RemovedComponents::iter/iter_with_id
Remove IntoIterator implementation
Update removal_detection example accordingly
---
## Migration Guide
Rename calls of RemovedComponents::iter/iter_with_id to
read/read_with_id
Replace IntoIterator iteration (&mut <RemovedComponents>) with .read()
---------
Co-authored-by: denshi_ika <mojang2824@gmail.com>
# Objective
Fixes#9787
## Solution
~~"serialize" feature enables "bevy_asset" now~~
"serialize" feature no longer enables the optional "bevy_scene" feature
if it's not enabled from elsewhere (thanks to @mockersf)
# Objective
The rename is confusing. Each time I import `TypeRegistry` I have to
think at least 10 seconds about how to import it. And I've been working
a lot with bevy reflect, which multiplies the papercut.
In my crates, you can find lots of:
```rust
use bevy::reflect::{TypeRegistryInternal as TypeRegistry};
```
When I "go to definition" on `TypeRegistry` I get to `TypeRegistryArc`.
And when I mean `TypeRegistry` in my function signature, 100% of the
time I mean `TypeRegistry`, not the arc wrapper.
Rust has borrowing, and most use-cases of the TypeRegistry accepts
borrow of the registry, with no need to mutate it.
`TypeRegistryInternal` is also confusing. In bevy crates, it doesn't
exist. The bevy crate documentation often refers to `TypeRegistry` and
link to `TypeRegistryInternal`. It only exists in the bevy re-exports.
It makes it hard to understand which names qualifies which types.
## Solution
Remove the rename, keep the type names as they are in `bevy_reflect`
---
## Changelog
- Remove `TypeRegistry` and `TypeRegistryArc` renames from bevy
`bevy_reflect` re-exports.
## Migration Guide
- `TypeRegistry` as re-exported by the wrapper `bevy` crate is now
`TypeRegistryArc`
- `TypeRegistryInternal` as re-exported by the wrapper `bevy` crate is
now `TypeRegistry`
This should have been removed in
8a9f475edb when the rest of the references
to / usages of `clippy::manual-strip` were removed. It was originally
needed in the long ago past when supporting Rust 1.45 was a concern.
# Objective
- Docs on linting should match the actual current practice.
- Docs currently mention `-A clippy::manual-strip` which hasn't been
needed in a long time.
## Solution
- Remove reference to `-A clippy::manual-strip`.
# Objective
When using `set_if_neq`, sometimes you'd like to know if the new value
was different from the old value so that you can perform some additional
branching.
## Solution
Return a bool from this function, which indicates whether or not the
value was overwritten.
---
## Changelog
* `DetectChangesMut::set_if_neq` now returns a boolean indicating
whether or not the value was changed.
## Migration Guide
The trait method `DetectChangesMut::set_if_neq` now returns a boolean
value indicating whether or not the value was changed. If you were
implementing this function manually, you must now return `true` if the
value was overwritten and `false` if the value was not.
# Objective
I noticed this while testing #9733.
It's not causing any problems, but we shouldn't teach users to scale 2d
stuff in z.
## Solution
Only scale in x and y.
# Objective
- Compile all targets without warnings about unused doc comments.
## Solution
- Turn unused doc comments into regular comments. Doc comments aren't
supported on expressions, so they can just be regular comments.
# Objective
Fix#9747
## Solution
Linkers don't like what we're doing with CowArc (I'm guessing it has
something to do with `?Sized`). Weirdly the `Reflect` derive on
`AssetPath` doesn't fail, despite `CowArc` not implementing `Reflect`.
To resolve this, we manually implement "reflect value" for
`AssetPath<'static>`. It sadly cannot use `impl_reflect_value` because
that macro doesn't support static lifetimes.
---------
Co-authored-by: Martin Dickopp <martin@zero-based.org>
# Objective
Add tests for `ui_layout_system` and `UiSurface` to the
`bevy_ui::Layout` module.
## Solution
Spawn a dummy window entity with `Window` and `PrimaryWindow` components
so that `ui_layout_system` can run in a test without a window present.
---
## Changelog
Added tests to the `bevy_ui::layout` module.
# Objective
- I want to associate `TypeData` with `Mesh`, to make it
editable/inspectable in my reflection-based editor. `Mesh` has to
implement `Reflect` for that. The precise reflection behavior does not
matter.
## Solution
- `#[derive(Reflect)]`, ignore fields whose types aren't reflectable.
- Call `App::register_asset_reflect` in the `MeshPlugin`.
---
## Changelog
- `Mesh` now implements `Reflect`.
Comment references non existent `FromResources` instead of `FromWorld`
---------
Co-authored-by: Nicola Papale <nicopap@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François <mockersf@gmail.com>
# Objective
- The tick access methods mention "ticks" (as in: plural). Yet, most of
them only access a single tick.
## Solution
- Rename those methods and fix docs to reflect the singular aspect of
the return values
---
## Migration Guide
The following method names were renamed, from `foo_ticks_bar` to
`foo_tick_bar` (`ticks` is now singular, `tick`):
- `ComponentSparseSet::get_added_ticks` → `get_added_tick`
- `ComponentSparseSet::get_changed_ticks` → `get_changed_tick`
- `Column::get_added_ticks` → `get_added_tick`
- `Column::get_changed_ticks` → `get_changed_tick`
- `Column::get_added_ticks_unchecked` → `get_added_tick_unchecked`
- `Column::get_changed_ticks_unchecked` → `get_changed_tick_unchecked`
# Objective
- Make it possible to snapshot/save states
- Useful for re-using parts of the state system for rollback safe states
- Or to save states with scenes/savegames
## Solution
- Conditionally add the derive if the `bevy_reflect` is enabled
---
## Changelog
- `NextState<S>` and `State<S>` now implement `Reflect` as long as `S`
does.
# Objective
- Fixes#6662
- Wireframe crash for skinned meshes:
```
wgpu error: Validation Error
Caused by:
In Device::create_render_pipeline
note: label = `opaque_mesh_pipeline`
Error matching ShaderStages(VERTEX) shader requirements against the pipeline
Location[4] Uint32x4 interpolated as Some(Flat) with sampling None is not provided by the previous stage outputs
Input is not provided by the earlier stage in the pipeline
```
- Wireframe crash for morphed meshes:
```
wgpu error: Validation Error
Caused by:
In a RenderPass
note: encoder = `<CommandBuffer-(0, 14, Metal)>`
In a draw command, indexed:true indirect:false
note: render pipeline = `opaque_mesh_pipeline`
The pipeline layout, associated with the current render pipeline, contains a bind group layout at index 1 which is incompatible with the bind group layout associated with the bind group at 1
```
## Solution
- Fix the locations for skinned meshes in the wireframe shader
- Add the morph key to the wireframe specialisation key
- Morph the vertex in the wireframe shader
https://github.com/bevyengine/bevy/assets/8672791/ce0a9584-bd28-4d74-9c3f-256602e6fac5
# Objective
In `extract_text2d_sprite` the scaling by the scale factor should be
only be applied to the x and y axes but it's also applied to the z axis.
# Solution
Remove the scaling in the z axis
# Objective
- Fixes#9683
## Solution
- Moved `get_component` from `Query` to `QueryState`.
- Moved `get_component_unchecked_mut` from `Query` to `QueryState`.
- Moved `QueryComponentError` from `bevy_ecs::system` to
`bevy_ecs::query`. Minor Breaking Change.
- Narrowed scope of `unsafe` blocks in `Query` methods.
---
## Migration Guide
- `use bevy_ecs::system::QueryComponentError;` -> `use
bevy_ecs::query::QueryComponentError;`
## Notes
I am not very familiar with unsafe Rust nor its use within Bevy, so I
may have committed a Rust faux pas during the migration.
---------
Co-authored-by: Zac Harrold <zharrold@c5prosolutions.com>
Co-authored-by: Tristan Guichaoua <33934311+tguichaoua@users.noreply.github.com>
# Objective
Implement `From<String>` and `From<&str>` for `TextSection`
Example from something I was working on earlier:
```rust
parent.spawn(TextBundle::from_sections([
TextSection::new("press ".to_string(), TextStyle::default()),
TextSection::new("space".to_string(), TextStyle { color: Color::YELLOW, ..default() }),
TextSection::new(" to advance frames".to_string(), TextStyle::default()),
]));
```
After an `impl From<&str> for TextSection` :
```rust
parent.spawn(TextBundle::from_sections([
"press ".into(),
TextSection::new("space".to_string(), TextStyle { color: Color::YELLOW, ..default() }),
" to advance frames".into(),
]));
```
* Potentially unhelpful without a default font, so behind the
`default_font` feature.
Co-authored-by: [hate](https://github.com/hate)
---------
Co-authored-by: hate <15314665+hate@users.noreply.github.com>
# Objective
`TextLayoutInfo::size` isn't the drawn size of the text, but a scaled
value. This is fragile, counter-intuitive and makes it awkward to
retrieve the correct value.
## Solution
Multiply `TextLayoutInfo::size` by the reciprocal of the window's scale
factor after generating the text layout in `update_text2d_layout` and
`bevy_ui::widget::text_system`.
---
fixes: #7787
## Changelog
* Multiply `TextLayoutInfo::size` by the reciprocal of the scale factor
after text computation to reflect the actual size of the text as drawn.
* Reorder the operations in `extract_text2d_sprite` to apply the
alignment offset before the scale factor scaling.
## Migration Guide
The `size` value of `TextLayoutInfo` is stored in logical pixels and has
been renamed to `logical_size`. There is no longer any need to divide by
the window's scale factor to get the logical size.
This needs to be much higher to avoid failures in CI. I don't love the
"loop until" test methodology generally, but this is testing internal
state and making this event driven would change the nature of the test.
# Objective
The `AssetServer` and `AssetProcessor` do a lot of `AssetPath` cloning
(across many threads). To store the path on the handle, to store paths
in dependency lists, to pass an owned path to the offloaded thread, to
pass a path to the LoadContext, etc , etc. Cloning multiple string
allocations multiple times like this will add up. It is worth optimizing
this.
Referenced in #9714
## Solution
Added a new `CowArc<T>` type to `bevy_util`, which behaves a lot like
`Cow<T>`, but the Owned variant is an `Arc<T>`. Use this in place of
`Cow<str>` and `Cow<Path>` on `AssetPath`.
---
## Changelog
- `AssetPath` now internally uses `CowArc`, making clone operations much
cheaper
- `AssetPath` now serializes as `AssetPath("some_path.extension#Label")`
instead of as `AssetPath { path: "some_path.extension", label:
Some("Label) }`
## Migration Guide
```rust
// Old
AssetPath::new("logo.png", None);
// New
AssetPath::new("logo.png");
// Old
AssetPath::new("scene.gltf", Some("Mesh0");
// New
AssetPath::new("scene.gltf").with_label("Mesh0");
```
`AssetPath` now serializes as `AssetPath("some_path.extension#Label")`
instead of as `AssetPath { path: "some_path.extension", label:
Some("Label) }`
---------
Co-authored-by: Pascal Hertleif <killercup@gmail.com>
# Objective
- Fix these warnings
```rust
warning: unused doc comment
--> /bevy/crates/bevy_pbr/src/light.rs:62:13
|
62 | /// Luminous power in lumens
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
63 | intensity: 800.0, // Roughly a 60W non-halogen incandescent bulb
| ---------------- rustdoc does not generate documentation for expression fields
|
= help: use `//` for a plain comment
= note: `#[warn(unused_doc_comments)]` on by default
```
```rust
warning: `&` without an explicit lifetime name cannot be used here
--> /bevy/crates/bevy_asset/src/lib.rs:89:32
|
89 | const DEFAULT_FILE_SOURCE: &str = "assets";
| ^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
= note: `#[warn(elided_lifetimes_in_associated_constant)]` on by default
help: use the `'static` lifetime
|
89 | const DEFAULT_FILE_SOURCE: &'static str = "assets";
|
```
# Objective
`TextureAtlas` supports pregenerated texture atlases with padding, but
`TextureAtlasBuilder` can't add padding when it creates a new atlas.
fixes#8150
## Solution
Add a method `padding` to `TextureAtlasBuilder` that sets the amount of
padding to add around each texture.
When queueing the textures to be copied, add the padding value to the
size of each source texture. Then when copying the source textures to
the output atlas texture subtract the same padding value from the sizes
of the target rects.
unpadded:
<img width="961" alt="texture_atlas_example"
src="https://github.com/bevyengine/bevy/assets/27962798/8cf02442-dc3e-4429-90f1-543bc9270d8b">
padded:
<img width="961" alt="texture_atlas_example_with_padding"
src="https://github.com/bevyengine/bevy/assets/27962798/da347bcc-b083-4650-ba0c-86883853764f">
---
## Changelog
`TextureAtlasBuilder`
* Added support for building texture atlases with padding.
* Adds a `padding` method to `TextureAtlasBuilder` that can be used to
set an amount of padding to add between the sprites of the generated
texture atlas.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
`many_buttons` enhancements:
* use `argh` to manage the commandline arguments like the other stress
tests
* add an option to set the number of buttons
* add a grid layout option
* centre the grid properly
* use viewport coords for the layout's style constraints
* replace use of absolute positioning
includes the changes from #9636
Displaying an image isn't actually about stress testing image rendering.
Without a second texture (the first is used by the text) the entire grid
will be drawn in a single batch. The extra texture used by the image
forces the renderer to break up the batches at every button displaying
an image, where it has to switch between the font atlas texture and the
image texture.
## Solution
<img width="401" alt="many_buttons_new"
src="https://github.com/bevyengine/bevy/assets/27962798/82140c6d-d72c-4e4f-b9b6-dd204176e51d">
---
## Changelog
`many_buttons` stress test example enhancements:
* uses `argh` to the manage the commandline arguments.
* New commandline args:
- `--help` display info & list all commandline options
- `--buttons` set the number of buttons.
- `--image-freq` set the frequency of buttons displaying images
- `--grid` use a grid layout
* style constraints are specified in viewport coords insead of
percentage values
* margins and nested bundles are used to construct the layout, instead
of absolute positioning
* the button grid centered in the window, the empty gap along the bottom
and right is removed
* an image is drawn as the background to every Nth button where N is set
using the `--image-freq` commandline option.
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Co-authored-by: Rob Parrett <robparrett@gmail.com>