Prevented View from firing the render event if there were no changes since the last view.render() call

[ma2ciek]

Suggested merge commit message (convention)

Fix: Prevented View from firing the render event if there were no changes since the last rendering. Closes ckeditor/ckeditor5#4473. Closes ckeditor/ckeditor5#4475.

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Additional information

• BREAKING CHANGE: The editing.view.render() method was renamed to editing.view.forceRender(). It should be used with caution as it will re-render editing view and repaint the UI.

[ma2ciek]

I see that there's one test failing in the ckeditor5-image (image caption placeholder). I'll need to fix it, but it shouldn't block reviewing.

[pjasiun]

Looks promising.

I checked all usage of the render method and all of them uses render with the force flag (except the one in the editing controller). It makes sense, render with no force flag should not be needed since all view changes cause rendering. This is why I propose such additional change: https://github.com/ckeditor/ckeditor5-engine/compare/t/1653-b...t/1653-b2?expand=1

It makes a huge number of tests fail, but mostly because of the missing view.render method. When I've added alias:

	render() {
		this.forceRender();
	}

Only 8 tests are failing (4 in FocusObserver, 2 integration test, 1 SelectionObserver and one view.focus()). Could you check such change?

[ma2ciek]

Could you clarify then how the view.change() / view.render() should be called in the EditingController?

[oleq]

I checked this branch in the context of ckeditor/ckeditor5#479 constellation and it seems to be working.

[pjasiun]

Could you clarify then how the view.change() / view.render() should be called in the EditingController?

I pushed one more commit to my POC.

[ma2ciek]

I've just merged your proposal @pjasiun to that branch.

[pjasiun]

I think you should add to this docs that this method does not need to be used after changes in the view - they will cause rendering anyway. This method is dedicated to special cases when view does not change be need to be rendered anyway (for instance for some observers which overwrites DOM changes if they were not handled).

[pjasiun]

Only a view docs improvements needed.

[ma2ciek]

I've fixed the placeholder implementation (wrapped initial changes in the view.change() block) and its tests so all tests (especially the one failing in the ckeditor5-image) are green now.