SplitButton style

[jbooth88]

Bug explanation

Some button properties in the new materialDesign:SplitButton control are unable to be changed without overriding the ButtonStyle.

For example, altering the font size affects the popup, but the left button (PART_LeftButton) is stuck at 14pt.
I don't know if this is a bug or by design.

Version

5.0

[nicolaihenriksen]

@jbooth88 seems like a bug to me. We should probably forward some additional common, non-inheritable, properties (like FontSize) down to the nested button here.

[Keboo]

So right now the ButtonStyle is what is used to configured the internal buttons. If we do template bindings (which I think might be the right answer), then anything with a template binding can't be set via that style.

I am thinking we might want to just obsolete that property and use template bindings for everything as that is a more common use case. Thoughts?

[nicolaihenriksen]

@Keboo So the SplitButton.ButtonStyle DP, in my mind, is an implementation detail. It is really only public to allow for consumers to copy-paste-modify the style and still have it compile. The same result could have been achieved without a DP, but simply a well-known resource key (this approach is used for the DatePicker; see here), or an attached property.

The DP serves a single purpose: Mapping an MDIX SplitButton style to the corresponding MDIX Button style. E.g.:
MaterialDesignFlatDarkSplitButton -> MaterialDesignFlatDarkButton,
MaterialDesignOutlinedLightSplitButton -> MaterialDesignOutlinedLightButton,
etc.

Thus the DP is used to make the SplitButton have a correct baseline-look, but should still allow for modifications via its properties as any other control. As such, I think it is fair to simply forward the "common properties" through via TemplateBindings just like it is already doing for a number of the properties. "Common properties" probably covers any property that is intended to have a visual (and/or possibly behavioral) effect that is relevant to the SplitButton.