estanglerbm opened a new pull request #1027:
URL: https://github.com/apache/royale-asjs/pull/1027
Remove @royaleignorecoercion from several UIComponent methods (which
affected "return" statements), because they allowed non-IUIComponent objects to
be returned (in JS) when the method declaration promised an IUIComponent
object. Also add code to easily detect non-IUIComponent child objects during
get measuredWidth() / measuredHeight() in JS.
(I was originally going to submit with a temporary workaround by doing a
typeof(child.getExplicitOrMeasuredHeight) != "function" in measuredHeight(),
for example, to detect non-IUIComponent objects. But PR #1026 was merged, so I
changed this to the real fixes.)
Several UIComponent methods, like getChildAt(), would return non-null values
that did not actually implement IUIComponent, even though the return value for
the methods promised that. There are multiple ways to handle that, but at the
end of the day, it's really really bad for a typed language to allow this
(without a really good reason). The only reason was performance, but that
should be much better now.
Several people have reported (and several maintainers have correctly
diagnosed) an error similar to the following:
```
Uncaught TypeError: child.getExplicitOrMeasuredHeight is not a function
get__measuredHeight .../mx/core/UIComponent.js:3091
getExplicitOrMeasuredHeight .../mx/core/UIComponent.js:1432
getPreferredUBoundsHeight .../mx/core/LayoutElementUIComponentUtils.js:72
getPreferredBoundsHeight .../mx/core/LayoutElementUIComponentUtils.js:166
getPreferredBoundsHeight .../mx/core/UIComponent.js:1950
spark_layouts_VerticalLayout_getElementHeight
.../spark/layouts/VerticalLayout.js:556
```
The error is caused by UIComponent.getChildAt() returning an object that
does not actually implement IUIComponent. This typically happens because an
emulation class derived from a non-MX / non-Spark class doesn't implement
IUIComponent.
Essentially the same issue was reported in #789 and #983.
With the changes in this PR, the following are some of the
classes--identified by the new trace() code--that don't implement IUIComponent:
```
Child class not IUIComponent:
mx.controls.advancedDataGridClasses.AdvancedDataGridButtonBar
Child class not IUIComponent:
mx.controls.advancedDataGridClasses.AdvancedDataGridListArea
```
And sure enough, they are thin wrappers on non-MX classes, with no
implementation of IUIComponent.
[Aside: I don't know the best way to implement getExplicitOrMeasuredWidth()
/ getExplicitOrMeasuredHeight() for these classes, off-hand. (Explicit
width/height is there, but don't know the measured values.) I don't know how
much work is needed for the other IUIComponent pieces.]
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