**Note**: This PR also contains content of previous Grid View PR. We decided to discard the previous, because this one did some refactoring of old one, and it's not a big addition.
Added a scrollable::GridView component, which just embeds the GridView in ScrollArea. Also, re-worked the idea of text layers.
https://user-images.githubusercontent.com/3919101/179020359-512ee127-c333-4f86-bff5-f1cb4154e03c.mp4
This PR contains all work for finishing integration of first Component List Panel in the IDE:
* It adds a stub for the whole Component Browser View. The documentation panel is re-used from the old searcher.
* It has the presenter implementation, integrating the view with Hierarchical Component List from the controller.
* It extends the View API, so the integration is possible, making use of Component Group Set wrapper.
* The selection integration was also merged into this PR, because it depended on the API extension mentioned above. However, we should avoid such practice in the future.
https://user-images.githubusercontent.com/3919101/177816427-8c4285b4-8941-4048-a400-52f4acf77a9f.mp4
# Important Notes
There are some known issues, to-be-fixed in the future.
* The performance is bad. It should be improved with new text::Area, and the decent one shall come with [GridView inside component browser](https://www.pivotaltracker.com/story/show/182561072)
* There is no keyboard navigation. It should also be delivered with [GridView](https://www.pivotaltracker.com/story/show/182561072).
* The Favorites section is not [filtered out by node source type](https://www.pivotaltracker.com/story/show/182661634).
implement simple variable assignments and function definitions.
This implements:
- https://www.pivotaltracker.com/story/show/182497122
- https://www.pivotaltracker.com/story/show/182497144 (the code blocks are not created yet, but the function declaration is recognized.)
# Important Notes
- Introduced S-expression-based tests, and pretty-printing-roundtrip testing.
- Started writing tests for TypeDef based on the examples in the issue. None of them parse successfully.
- Fixed Number tokenizing.
- Moved most contents of parser's `main.rs` to `lib.rs` (fixes a warning).
Implement generation of Java AST types from the Rust AST type definitions, with support for deserializing in Java syntax trees created in Rust.
### New Libraries
#### `enso-reflect`
Implements a `#[derive(Reflect)]` macro to enable runtime analysis of datatypes. Macro interface includes helper attributes; **the Rust types and the `reflect` attributes applied to them fully determine the Java types** ultimately produced (by `enso-metamodel`). This is the most important API, as it is used in the subject crates (`enso-parser`, and dependencies with types used in the AST). [Module docs](https://github.com/enso-org/enso/blob/wip/kw/parser/ast-transpiler/lib/rust/reflect/macros/src/lib.rs).
#### `enso-metamodel`
Provides data models for data models in Rust/Java/Meta (a highly-abstracted language-independent model--I have referred to it before as the "generic representation", but that was an overloaded term).
The high-level interface consists of operations on data models, and between them. For example, the only operations needed by [the binary that drives datatype transpilation](https://github.com/enso-org/enso/blob/wip/kw/parser/ast-transpiler/lib/rust/parser/generate-java/src/main.rs) are: `rust::to_meta`, `java::from_meta`, `java::transform::optional_to_null`, `java::to_syntax`.
The low-level interface consists of direct usage of the datatypes; this is used by [the module that implements some serialization overrides](https://github.com/enso-org/enso/blob/wip/kw/parser/ast-transpiler/lib/rust/parser/generate-java/src/serialization.rs) (so that the Java interface to `Code` references can produce `String`s on demand based on serialized offset/length pairs). The serialization override mechanism is based on customizing, not replacing, the generated deserialization methods, so as to be as robust as possible to changes in the Rust source or in the transpilation process.
### Important Notes
- Rust/Java serialization is exhaustively tested for structural compatibility. A function [`metamodel::meta::serialization::testcases`](https://github.com/enso-org/enso/blob/wip/kw/parser/ast-transpiler/lib/rust/metamodel/src/meta/serialization.rs) uses `reflect`-derived data to generate serialized representations of ASTs to use as test cases. Its should-accept cases cover every type a tree can contain; it also produces a representative set of should-reject cases. A Rust `#[test]` confirms that these cases are accepted/rejected as expected, and generated Java tests (see Binaries below) check the generated Java deserialization code against the same test cases.
- Deserializing `Code` is untested. The mechanism is in place (in Rust, we serialize only the offset/length of the `Cow`; in Java, during deserialization we obtain a context object holding a buffer for all string data; the accessor generated in Java uses the buffer and the offset/length to return `String`s), but it will be easier to test once we have implemented actually parsing something and instantiating the `Cow`s with source code.
- `#[tagged_enum]` [now supports](https://github.com/enso-org/enso/blob/wip/kw/parser/ast-transpiler/lib/rust/shapely/macros/src/tagged_enum.rs#L36-L51) control over what is done with container-level attributes; they can be applied to the container and variants (default), only to the container, or only to variants.
- Generation of `sealed` classes is supported, but currently disabled by `TARGET_VERSION` in `metamodel::java::syntax` so that tests don't require Java 15 to run. (The same logic is run either way; there is a shallow difference in output.)
### Binaries
The `enso-parser-generate-java` crate defines several binaries:
- `enso-parser-generate-java`: Performs the transpilation; after integration, this will be invoked by the build script.
- `java-tests`: Generates the Java code that tests format deserialization; after integration this command will be invoked by the build script, and its Java output compiled and run during testing.
- `graph-rust`/`graph-meta`/`graph-java`: Produce GraphViz representations of data models in different typesystems; these are for developing and understanding model transformations.
Until integration, a **script regenerates the Java and runs the format tests: `./tools/parser_generate_java.sh`**. The generated code can be browsed in `target/generated_java`.
* fixes a regression for watching ide in dev profile;
* add support for passing cargo-watch options;
* general improvements and cleanups around watch commands.
### Pull Request Description
Using the new tooling (#3491), I investigated the **performance / compile-time tradeoff** of different codegen options for release mode builds. By scripting the testing procedure, I was able to explore many possible combinations of options, which is important because their interactions (on both application performance and build time) are complex. I found **two candidate profiles** that offer specific advantages over the current `release` settings (`baseline`):
- `thin16`: Supports incremental compiles in 1/3 the time of `baseline` in common cases. Application runs about 2% slower than `baseline`.
- `fat1-O4`: Application performs 13% better than `baseline`. Compile time is almost 3x `baseline`, and non-incremental.
(See key in first chart for the settings defining these profiles.)
We can build faster or run faster, though not in the same build. Because the effect sizes are large enough to be impactful to developer and user experience, respectively, I think we should consider having it both ways. We could **split the `release` profile** into two profiles to serve different purposes:
- `release`: A profile that supports fast developer iteration, while offering realistic performance.
- `production`: A maximally-optimized profile, for nightly builds and actual releases.
Since `wasm-pack` doesn't currently support custom profiles (rustwasm/wasm-pack#1111), we can't use a Cargo profile for `production`; however, we can implement our own profile by overriding rustc flags.
### Performance details
As you can see, `thin16` is slightly slower than `baseline`; `fat1-O4` is dramatically faster.
<details>
<summary>Methodology (click to show)</summary>
I developed a procedure for benchmarking "whole application" performance, using the new "open project" workflow (which opens the IDE and loads a complex project), and some statistical analysis to account for variance. To gather this data:
Build the application with profiling:
`./run.sh ide build --profiling-level=debug`
Run the `open_project` workflow repeatedly:
`for i in $(seq 0 9); do dist/ide/linux-unpacked/enso --entry-point profile --workflow open_project --save-profile open_project_thin16_${i}.json; done`
For each profile recorded, take the new `total_self_time` output of the `intervals` tool; gather into CSV:
`echo $(for i in $(seq 0 9); do target/rust/debug/intervals < open_project_thin16_${i}.json | tail -n1 | awk '{print $2}'; do`
(Note that the output of intervals should not be considered stable; this command may need modification in the future. Eventually it would be nice to support formatted outputs...)
The data is ready to graph. I used the `boxplot` method of the [seaborn](https://seaborn.pydata.org/index.html) package, in order to show the distribution of data.
</details>
#### Build times
In the case of changing a file in `enso-prelude`, with the current `baseline` settings rebuilding takes over 3 minutes. With the `thin16` settings, the same rebuild completes in 40 seconds.
(To gather this data on different hardware or in the future, just run the new `bench-build.sh` script for each case to be measured.)
Define some workflows for batch-mode profiling.
Implemented:
- collapse nodes
- create node
- enter collapsed node
- new project
- open visualization
They can currently be built and run with a command like:
`./run.sh ide build --profiling-level=debug && dist/ide/linux-unpacked/enso --entry-point profile --workflow create_node --save-profile out.json`
And the data can be displayed with:
`dist/ide/linux-unpacked/enso --entry-point profiling_run_graph --load-profile out.json`
Demo of recording and viewing a profile with a command-line one-liner:
https://user-images.githubusercontent.com/1047859/169954795-2d9520ca-84f9-45d2-b83a-5063ebe6f718.mp4
See: https://www.pivotaltracker.com/story/show/182195399.
# Important Notes
- When defining workflows, two helpers are enough to allow us to tell when the action is really done: `Fixture::compile_new_shaders`, and `Fixture::backend_execution`. Often, it is appropriate to await both, but it depends on the task.
- The shader compiler is now driven by a `Controller`; while the `Compiler` is reset if context is lost, the `Controller`'s state survives context loss.
- A new `--load-profile` option supports specifying a profile by path when running `profiling_run_graph`.
- Drop the `with_same_start` profiler interface; we ended up preferring a child profiler convention, and this interface was not implemented compatibly with the stricter data model we've had since the introduction of `profiler::data`.
- Fix the noisy `rustfmt` output.
* The bash entry point was renamed `run.sh` -> `run`. Thanks to that `./run` works both on Linux and Windows with PowerShell (sadly not on CMD).
* Everyone's favorite checks for WASM size and program versions are back. These can be disabled through `--wasm-size-limit=0` and `--skip-version-check` respectively. WASM size limit is stored in `build-config.yaml`.
* Improved diagnostics for case when downloaded CI run artifact archive cannot be extracted.
* Added GH API authentication to the build script calls on CI. This should fix the macOS build failures that were occurring from time to time. (Actually they were due to runner being GitHub-hosted, not really an OS-specific issue by itself.)
* If the GH API Personal Access Token is provided, it will be validated. Later on it is difficult to say, whether fail was caused by wrong PAT or other issue.
* Renamed `clean` to `git-clean` as per suggestion to reduce risk of user accidently deleting unstaged work.
* Whitelisting dependabot from changelog checks, so PRs created by it are mergeable.
* Fixing issue where wasm-pack-action (third party) randomly failed to recognize the latest version of wasm-pack (macOS runners), leading to failed builds.
* Build logs can be filtered using `ENSO_BUILD_LOG` environment variable. See https://docs.rs/tracing-subscriber/0.3.11/tracing_subscriber/struct.EnvFilter.html#directives for the supported syntax.
* Improve help for ci-run source, to make clear that PAT token is required and what scope is expected there.
Also, JS parts were updated with some cleanups and fixes following the changes made when introducing the build script.
This PR contains minimal integration with new engine's method and an integration test printing the method's return value. It was written as a part of https://www.pivotaltracker.com/story/show/181743571
# Important Notes
The test requires 2022.1.1-nightly.2022-04-26 engine version or later.
This PR extends the Component Group Entry with icon and option to highlight the text. Here the convert has highlighted "con".
https://user-images.githubusercontent.com/3919101/169046537-4f8b823c-322e-40dc-8abb-24d1d7092341.mp4
### Important Notes
Although this PR includes effort for adjusting Component Group style to better reflect the design, it is not entirely finished: the selection still works badly and will be fixed in another PR.
[ci no changelog needed]
[Task link](https://www.pivotaltracker.com/story/show/181725003)
This PR implements a fully visible component group header while scrolling the group (using the ScrollArea).
The header moves in sync with scrolling movements (using new `set_header_pos` FRP input), so it looks like the component group is scrolled. ScrollArea masks the "scrolled" entries above the header. This design allows a fully visible header even though our renderer doesn't support nested layers masking yet.
The screencast:
https://user-images.githubusercontent.com/6566674/168320360-2c2017b2-0ef5-42ce-9c79-82b9641c1d73.mp4
The most recent one, with the updated demo scene from develop:
https://user-images.githubusercontent.com/6566674/168555268-8552c4b0-f887-4388-89a1-e65ddf668be6.mp4
# Important Notes
- I fixed the API of the list view so now it supports non-hardcoded scene layers (previously it did not). I also believe it was implemented incorrectly.
- I've found a [pretty weird bug](https://www.pivotaltracker.com/story/show/182193824): the component group inside the ScrollArea is invisible unless I add some arbitrary shape to the scroll area content. I use a `transparent_circle` for this purpose in the demo scene. The bug is probably related to masking the sublayers, though I wasn't able to reproduce it properly on a simpler example.
- The selection box is removed from the demo scene as agreed with @farmaazon . The correct implementation has proven to be much harder than I expected, and we will implement another approach in a separate PR.
- I also modified the `shadow::Parameters` so that it uses `Var`s instead of plain values.
* Extends the instrumentation of the code base and upgrades some FRPs to the newer API macro.
* Extends the run-graph demo scene to specify a profile via URL without recompilation.
* Fixes labels in the flame graph demo scene.
* Fixes an issue with loading profiles that contains escaped characters.
# Important Notes
* no longer contains the upgrade of the `text::View` to `define_endpoints_2`. This should be fixed as part of the text rendering rewrite.
[ci no changelog needed]
* Extends the instrumentation of the code base and upgrades some FRPs to the newer API macro.
* Extends the run-graph demo scene to specify a profile via URL without recompilation.
* Fixes labels in the flame graph demo scene.
* Fixes an issue with loading profiles that contains escaped characters.
# Important Notes
[ci no changelog needed]
Implement a command that launches the application, runs a series of steps (a "workflow"), writes a profile to a file, and exits.
See: [#181775808](https://www.pivotaltracker.com/story/show/181775808)
# Important Notes
- The command to capture run and profile is used like: `./run profile --workflow=new_project --save-profile=out.json`. Defining some more workflows (collapse nodes, create node and edit value) comes next; they are implemented with the same infrastructure as the integration-tests.
- The `--save-profile` option can also be used when profiling interactively; when the option is provided, capturing a profile with the hotkey will write a file instead of dumping the data to the devtools console.
- If the IDE panics, the error message is now printed to the console that invoked the process, as well as the devtools console. (If a batch workflow fails, this allows us to see why.)
- New functionality (writing profile files, quitting on command, logging to console) relies on Electron APIs. These APIs are implemented in `index.js`, bridged to the render process in `preload.js`, and wrapped for use in Rust in a `debug_api` crate.
* New JSON profile format.
* Use string-table optimization for labels in JSON format.
* Use TimeOffset header to render beanpoles
* Log RPC messages sent to the backend.
* Display RPC requests on graph
* Simplify metadata-logging interface.
Implements a visualization that is integrated with our GUI profiling visualization for the multiprocess data implemented in #3395https://user-images.githubusercontent.com/1428930/165915395-c850c7b2-1cc5-4eb0-8f21-37565d113b1e.mp4
The visualization shows a horizontal line for Engine, Language Server and GUI and renders arrows for each message passed between them. Information about the message is revealed on hover.
# Important Notes
* this PR refactors the tooltip mechanism. Note that this has not been in active use anywhere else, as tooltips for node received a custom implementation and the tooltip that was previously implemented was used nowhere else yet.
[ci no changelog needed]
* The List View component was refactored: it allows for hiding the internal selection widget, and exposes information where the widget should be placed. This allows us to create selection widget in component list panel, so it can be animated between component groups and sections.
* Fixed some warnings when checking WASM code.
* Adjusted the style of Component Group View a little, so it better reflects the design doc. Still not ideal, because the list_view has some weird design regarding padding, but I don't want to stuck in some bigger refactoring.
I will add a video in a few minutes.
# Important Notes
https://user-images.githubusercontent.com/3919101/165507826-60329f9e-7de3-4eb2-9271-292e45568cb2.mov
See: [#181837344](https://www.pivotaltracker.com/story/show/181837344).
I've separated this PR from some deeper changes I'm making to the profile format, because the changeset was getting too complex. The new APIs and tools in this PR are fully-implemented, except the profile format is too simplistic--it doesn't currently support headers that are needed to determine the relative timings of events from different processes.
- Adds basic support for profile files containing data collected by multiple processes.
- Implements `api_events_to_profile`, a tool for converting backend message logs (#3392) to the `profiler` format so they can be merged with frontend profiles (currently they can be merged with `cat`, but the next PR will introduce a merge tool).
- Introduces `message_beanpoles`, a simple tool that diagrams timing relationships between frontend and backend messages.
### Important Notes
- All TODOs introduced here will be addressed in the next PR that defines the new format.
- Introduced a new crate, `enso_profiler_enso_data`, to be used by profile consumers that need to refer to Enso application datatypes to interpret metadata.
- Introduced a `ProfileBuilder` abstraction for writing the JSON profile format; partially decouples the runtime event log structures from the format definition.
- Introducing the conversion performed for `ProfilerBuilder` uncovered that the `.._with_same_start!` low-level `profiler` APIs don't currently work; they return `Started<_>` profilers, but that is inconsistent with the stricter data model that I introduced when I implemented `profiler_data`; they need to return profilers in a created, unstarted state. Low-level async profilers have not been a priority, but once #3382 merges we'll have a way to render their data, which will be really useful because async profilers capture *why* we're doing things. I'll bring up scheduling this in the next performance meeting.
Add logging of EnsoGL performance stats to the profiling framework. Also extends the visualization in the debug scene to show an overview of the performance stats. We now render a timeline of blocks that indicate by their colour the rough FPS range we are in:
https://user-images.githubusercontent.com/1428930/162433094-57fbb61a-b502-43bb-8815-b7fc992d3862.mp4
# Important Notes
[ci no changelog needed]
Needs to be merged after https://github.com/enso-org/enso/pull/3382 as it requires some changes about metadata logging from there. That is why this PR is currently still in draft mode and based on that branch.
* Profiling: intervals tool
* devtools profile generator
* docs
* ignore open intervals, because devtools does
* intervals tool: show interval counts
* Re-add a doc comment. Was accidentally deleted.
* Implement review.
* DURATION_FLOOR_MS
* Rename methods that apply a profile's contents to self
* Description of chrome format
* Link to profile.json format documentation is design doc
* Implement profiling-level switch described in design doc
* lint
In this branch:
* The workaround for cursor-not-being-updated-after-closing-searcher bug (discovered while testing #3278) is reverted.
* The proper fix was introduced: created an abstraction for EnsoGL component, which, when dropping, will not immediately drop the FRP network and model, but instead put it into the Garbage Collector. The Collector ensures, that all "component hiding" effects and events will be handled, and drops FRP network and model only after that.
* I run clippy for wasm32 target out of curiosity. There was one warning, and I fixed it on this branch.
* Profiling application details
Add enough profiling to account for every missed frame during startup.
See https://www.pivotaltracker.com/story/show/181499507
* Build ActiveInterval hierarchy in profiler_data
* update doctests / await_!
* docs/formatting/naming
* more graph modes
* increase WASM size
Due to new render-profile-flamegraph scene. We should remove these from the main release WASM blob one way or another.
* lint
* fix a test
* Organization (feedback)
* Add @wdanilo to Cargo.lock CODEOWNERS
As discussed after my previous PR got stuck waiting for Cargo.lock review.
* fix doctests
* Update docs. Removed a limitation.
* Creating a new node with the (+) button (#3278)
[The Task](https://www.pivotaltracker.com/story/show/180887253)
A new (+) button on the left-bottom corner appeared. It may be clicked to open searcher in the middle of the scene, as an alternative to tab key.
https://user-images.githubusercontent.com/3919101/154514279-7972ed6a-0203-47cb-9a09-82dba948cf2f.mp4
* The window_control_buttons::common was extracted to separate crate `ensogl-component-button` almost without change.
* This includes a severe refactoring of adding nodes in general in the Graph Editor. The whole responsibility of adding new nodes (and starting their editing) was moved to Graph Editor - the Project View only reacts for GE events to show searcher properly.
* The status bar was moved from the bottom-left corner to the middle-top of the scene. It does not collide with (+) button, and plays "notification" role anyway.
* The `interface` debug scene was buggy. The problem was with one expression's span-tree. When I replaced it, the scene works.
* I've removed "new searcher" API, as it is completely outdated.
* I've changed code owners of integration tests to GUI team, as it is the team writing mostly the integration tests (int rust)
* Fix regression #181528359
* Add docs & remove unused function
* Fix & enable native Rust tests
* Fix formatting
Co-authored-by: Adam Obuchowicz <adam.obuchowicz@enso.org>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
[ci no changelog needed]
This PR reverts commit [0836ce741d](0836ce741d) because of the spotted regression:
To reproduce:
1. Open a default project.
2. Without doing anything else, cmd + click on any node to edit it.
3. Abort editing by pressing escape.
4. Top-most node disappears (it is actually removed from scene)
If you start editing the bottom node - you will also see a visible regression in node searcher's position.
See thread https://discord.com/channels/401396655599124480/950730235719065620/950731247909478410 for details.
Add an API to create a flame graph from profiling data. Also adds a demo scene showcasing the functionality that generates some profiling data by measuring dummy function calls and rendering a flame graph for the dummy data (see video for the result).
Not that the functionality is not yet exposed user-facing in the GUI itself, but only as API and demo scene, therefore [ci no changelog needed]
https://user-images.githubusercontent.com/1428930/155118977-ecac0628-777c-48bd-9aa7-30ee6aef1976.mp4
# Important Notes
* Change from the initial design: labels are shown on the flame graph instead of as a tooltip. This is because tooltips are currently only implemented in the graph editor and would require some additional refactoring (probably taking the better part of a day).
* re-instated the behaviour that logs are shown in the JS console if development mode is active.
API for storing metadata.
See: https://www.pivotaltracker.com/story/show/181149277
# Important Notes
**New APIs**:
- Storing metadata is implemented with `profiler::MetadataLogger`.
- A full metadata storage/retrieval example is in [the top-level doctests](https://github.com/enso-org/enso/blob/wip/kw/profiling-metadata-api/lib/rust/profiler/data/src/lib.rs) for profiler::data, a crate which implements an API for profiling data consumers (it abstracts away the low-level details of the event log, and checks its invariants in the process) [after review of this new API here I'll open a PR to add it to the design doc].
**Implementation**:
- `profiler::Event` is parameterized by a metadata type, so that different types of metadata can be dependency-injected into it.
- A data consumer defines its metadata type as an enum of all the kinds of metadata it is interested in.
- Producing the metadata enum is accomplished without defining its type (which would require dependencies from around the app): A `MetadataLogger` internally use a serialization helper `Variant` to serialize its variant of the metadata enum without knowledge of the other possible variants.
**Performance impact**: still in the low ns/measurement range, comparable to pushing to a vec.
*Note*: `LocalVecBuilder` is currently present under the name `Log`, which is accurate but probably too overloaded. I'd like to find the right name for it, document it with examples, and move it to its own crate under data-structures, but I don't want doing that to hold up this PR.
[The Task](https://www.pivotaltracker.com/story/show/180887253)
A new (+) button on the left-bottom corner appeared. It may be clicked to open searcher in the middle of the scene, as an alternative to tab key.
https://user-images.githubusercontent.com/3919101/154514279-7972ed6a-0203-47cb-9a09-82dba948cf2f.mp4
# Important Notes
* The window_control_buttons::common was extracted to separate crate `ensogl-component-button` almost without change.
* This includes a severe refactoring of adding nodes in general in the Graph Editor. The whole responsibility of adding new nodes (and starting their editing) was moved to Graph Editor - the Project View only reacts for GE events to show searcher properly.
* The status bar was moved from the bottom-left corner to the middle-top of the scene. It does not collide with (+) button, and plays "notification" role anyway.
* The `interface` debug scene was buggy. The problem was with one expression's span-tree. When I replaced it, the scene works.
* I've removed "new searcher" API, as it is completely outdated.
* I've changed code owners of integration tests to GUI team, as it is the team writing mostly the integration tests (int rust)
This reverts commit e69e8078c3.
The removed code (stats aggregation and `stats` demo scene) will not be needed by the profiling framework, as discussed on chat.
(reverts changes introduced as part of https://www.pivotaltracker.com/story/show/181093920)
* profiling instrumentation
* Support native testing with mock impl of `mod js`
* Add benchmarks
* Wrapper: support methods.
* `#[profile]`: work in any context
* feature-gate lineno info that breaks IDE
* Support async; more docs; add perf analysis
* docs & formatting
This change adds utility code for calculating summaries from multiple samples (snapshots) of EnsoGL runtime stats values.
This internal feature is expected to be used by Enso IDE performance profiling tools, which are planned to be added in the near future.
https://www.pivotaltracker.com/story/show/181093920
A demo scene named `stats` was added, showcasing how to perform calculations using the new tools. Currently, the summary calculations in the scene work only when the EnsoGL stats Monitor Panel is visible; this is planned to be improved in a future task (https://www.pivotaltracker.com/story/show/181093601).
- Note: the stats aggregation code is intended to be later used in Enso IDE's main rendering loop, so it needs to have very good performance characteristics.
- Due to that, `Accumulator` was designed to only use simple addition arithmetic, and be constant-memory once created.
