The initial problem solved by this commit is that it was possible to get
into a situation where a mounting/rendering was started, then the component was
updated, but then another mounting operation begins, and it tries to
reuse the previous rendering operation, which is no longer uptodate.
The underlying issue is that Owl did not track properly the various
internal state change of a component. These issue should be solved by
the introduction of the status enum, which currently tracks 6 possible
states:
- CREATED
- WILLSTARTED
- RENDERED
- MOUNTED
- UNMOUNTED
- DESTROYED
This status number replaces the isMounted and isDestroyed boolean flags.
It has the advantage of making sure that the component is in a
consistent state (it is no longer possible to be destroyed and mounted,
for example)
Another advantage is that it gives us an easy way to track the fact that
a component has been rendered, but is not in the DOM. This is a subtle
situation where some various events can happen, and we need to be able
to react to that case.
Note that there is a change of behaviour: if a component is mounted in a
specific target, then before the mounting is complete, the component is
mounted in another target, we no longer reject the first mounting
operation.
This commit tries to improve the interactions involving unmounted
components, or components mounted in an htmelement which is detached
from the main DOM, and rendering actions.
The main example is mounting a component in detached div, to prepare all
children. If we just mount the component, it will work as expected: the
full component tree is rendered in memory, and ready to be really
mounted at the desired target.
However, if before doing that, we update the component and call render
on it (for example, with a change in an observed state), then this
rendering will be ignored, and therefore, the full subcomponent tree is
not uptodate.
This commit will also solve another issue in the compatibility layer in
odoo: in the form renderer, we mount components with the adapter in a
div, which is not yet attached to the DOM. We then manually call the
mounted hook when on_attach_callback is called. This means that before
this commit, any change to the components between the initial rendering
and the call to mounted will be ignored.
As a bonus, this commit has the effect of bringing closer the semantics
of render and mount operations, which is certainly good.
closes#823
Géry Debongnie