Thomas, in your opinion, would this problem be worth a patch? What is the
status of editor framework regarding GWT 3?
If editors should be evolved further, I could propose a patch for this. I
don't like exposing ListEditorWrapper in getList method signature, so that
would call for a bit more thinking, but over all, patch would be rather
small.
On Friday, March 10, 2017 at 10:56:49 AM UTC+1, Thomas Broyer wrote:
>
>
>
> On Friday, March 10, 2017 at 10:13:44 AM UTC+1, Gordan Krešić wrote:
>>
>> I'm editing List of ValueProxies and I'm trying to implement reordering
>> of items (move to front, move to back, move up, move down the list). Since
>> ListEditors work by reflecting change in underlying List and List
>> interface does not support atomic "move" operation for item reordering, my
>> only option is to first remove item from List and then add elements at
>> desired index. So far so good, but in ListEditor, underlying List
>> contains *unflushed* values so when I reinsert them, newely created
>> editors get old values and I loose changes made before reordering took
>> place.
>>
>> Since flushing ListEditor before remove/add didn't seem as a good idea
>> (breaks editor contract and I would have to propagate Driver down the
>> editors hierarchy) I've ended up cloning ListEditor and its underlying
>> ListEditorWrapper to my own DynamicListEditor and
>> DynamicListEditorWrapper (couldn't even extend them, because relevant
>> members are private).
>>
>> In DynamicListEditorWrapper I've added one additional method to reorder
>> both elements in underlying list and their corresponding editors in-place:
>>
>> public void move(int fromIndex, int toIndex) {
>> workingCopy.add(toIndex, workingCopy.remove(fromIndex));
>> editors.add(toIndex, editors.remove(fromIndex));
>> for (int i = Math.min(fromIndex, toIndex), j = Math.max(fromIndex,
>> toIndex); i <= j; i++)
>> editorSource.setIndex(editors.get(i), i);
>> }
>>
>> In DynamicListEditor I've used that new wrapper and exposed it in getList
>> method:
>>
>> public DynamicListEditorWrapper<T, E> getList() {
>> return list;
>> }
>>
>> Now I'm able to move item one place up the list by calling:
>>
>> int currIndex = /* get current index, easy */;
>> if (currIndex == 0)
>> return;
>> listEditor.getList().move(currIndex, currIndex - 1);
>>
>> I works, but I can't shake off the feeling that I'm over-engineering it
>> and that there is a better (simpler) way for doing this. After all, Lists
>> are ordered collections and editing that order should not be this
>> complicated.
>>
>> Any advice?
>>
>
> I dug into one of our apps and something I've seen is that we did the same
> kind of things except "around" ListEditor rather than duplicating it:
> The widget is a ValueAwareEditor<List<T>>, has a child @Path("")
> ListEditor<T, E> and has *two* fields of type List<T>: the actual value
> being edited (called 'value'), and a copy of it to track changes (called
> 'list').
> Our flush() and setValue() from ValueAwareEditor are:
> @Override
> public void flush() {
> this.value.clear();
> this.value.addAll(this.list);
> }
>
> @Override
> public void setValue(List<P> value) {
> this.value = value;
> this.list.clear();
> this.list.addAll(value);
> }
>
> The other methods are no-ops.
> And our moveUp/moveDown manipulate the widgets/editors themselves (I note
> that the widgets aren't IsEditor<T>, but directly Editor<T>, if that makes
> a difference) and the 'list' (but not 'value').
> In other words, we only manipulate 'value' on setValue/flush, which I
> believe is to not break the editor contract.
>
> I can't tell if this was over-engineered as well or not, or hackish
> (probably a bit), as that code is nearly 6 years old already.
>
> (btw, instead of "workingCopy.add(toIndex, workingCopy.remove(fromIndex))"
> we use "Collections.swap(this.list, index, newIndex)"; probably does the
> same but is more readable; and we limit ourselves to a delta of -1/1)
>
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