Previously we would write to class/style as strings `element.className` and `element.style.cssText`. Turns out that approach is good for initial render but not good for updates. Updates using this approach are problematic because we have to check to see if there was an out of bound write to style and than perform reconciliation. This also requires the browser to bring up CSS parser which is expensive.
Another problem with old approach is that we had to queue the DOM writes and flush them twice. Once on element advance instruction and once in `hostBindings`. The double flushing is expensive but it also means that a directive can observe that styles are not yet written (they are written after directive executes.)
The new approach uses `element.classList.add/remove` and `element.style.setProperty/removeProperty` API for updates only (it continues to use `element.className` and `element.style.cssText` for initial render as it is cheaper.) The other change is that the styling changes are applied immediately (no queueing). This means that it is the instruction which computes priority. In some circumstances it may result in intermediate writes which are than overwritten with new value. (This should be rare)
Overall this change deletes most of the previous code and replaces it with new simplified implement. The simplification results in code savings.
PR Close#34804
This change introduces class/style reconciliation algorithm for DOM elements.
NOTE: The code is not yet hooked up, it will be used by future style algorithm.
Background:
Styling algorithm currently has [two paths](https://hackmd.io/@5zDGNGArSxiHhgvxRGrg-g/rycZk3N5S)
when computing how the style should be rendered.
1. A direct path which concatenates styling and uses `elemnent.className`/`element.style.cssText` and
2. A merge path which uses internal data structures and uses `element.classList.add/remove`/`element.style[property]`.
The situation is confusing and hard to follow/maintain. So a future PR will remove the merge-path and do everything with
direct-path. This however breaks when some other code adds class or style to the element without Angular's knowledge.
If this happens instead of switching from direct-path to merge-path algorithm, this change provides a different mental model
whereby we always do `direct-path` but the code which writes to the DOM detects the situation and reconciles the out of bound write.
The reconciliation process is as follows:
1. Detect that no one has modified `className`/`cssText` and if so just write directly (fast path).
2. If out of bounds write did occur, switch from writing using `className`/`cssText` to `element.classList.add/remove`/`element.style[property]`.
This does require that the write function computes the difference between the previous Angular expected state and current Angular state.
(This requires a parser. The advantage of having a parser is that we can support `style="width: {{exp}}px" kind of bindings.`)
Compute the diff and apply it in non destructive way using `element.classList.add/remove`/`element.style[property]`
Properties of approach:
- If no out of bounds style modification:
- Very fast code path: Just concatenate string in right order and write them to DOM.
- Class list order is preserved
- If out of bounds style modification detected:
- Penalty for parsing
- Switch to non destructive modification: `element.classList.add/remove`/`element.style[property]`
- Switch to alphabetical way of setting classes.
PR Close#34004
Prior to this patch all the styling benchmarks only tested for
template map-based style/class bindings. Because of each of the bindings
being only present in the template, there was no possibility of
there being any duplicate map-based styling bindings.
This benchmark introduces benchmarking for map-based style/class bindings
that are evaluated from both template bindings as well as directives.
This benchmark can be executed by calling:
```
bazel build //packages/core/test/render3/perf:duplicate_map_based_style_and_class_bindings_lib.min_debug.es2015.js
node dist/bin/packages/core/test/render3/perf/duplicate_map_based_style_and_class_bindings_lib.min_debug.es2015.js
```
The benchmark is also run via the `profile_all.js` script (found in
`packages/core/test/render3/perf/`)
PR Close#33608
Prior to this patch all the styling benchmarks only tested for
template-based style/class bindings. Because of each of the bindings
being only present in the template, there was no possibility of
there being any duplicate bindings. This benchmark introduces
style/class bindings being evaluated from both a template and from
various directives.
This benchmark can be executed by calling:
```
bazel build //packages/core/test/render3/perf:duplicate_style_and_class_bindings_lib.min_debug.es2015.js
node dist/bin/packages/core/test/render3/perf/duplicate_style_and_class_bindings_lib.min_debug.es2015.js
```
The benchmark is also run via the `profile_all.js` script (found in
`packages/core/test/render3/perf/`)
PR Close#33600
this makes running and profiling tests much easier. Example usage:
```
yarn bazel run --define=compile=aot //packages/core/test/render3/perf:noop_change_detection
```
See README.md update for more info.
PS: I considered moving the ng_rollup bundle into the macro but I didn't want to make
too many changes in this PR. If we find running benchmarks in this way useful, we
should refactor the build file more, and move the ng_rollup_bundle targets into the
macro.
PR Close#33389
The styling algorithm requires that the `RNode` has a `className`
property in order to execute the fast-path. This changes adds the
emulation of this property.
PR Close#33392
This patch introduces a new micro benchmark that performance tests
against map-based style and class bindings in Ivy running together
on the same element.
PR Close#32401
This patch introduces a new micro benchmark that performance tests
against style and class bindings in Ivy running together on the same
element.
PR Close#32401
Miško Hevery
Pawel Kozlowski
Matias Niemelä
Igor Minar