> The type of visual programming I'm thinking about here is a WYSIWYG drag and drop interface for building UIs.
The main challenge in this particular domain is describing what is supposed to happen to the layout when the size of the window changes, or if there are dependencies among visual elements (e.g. some element only appears when a check box is checked). When laying things out visually you can only ever design one particular instance of a layout. If all your elements are static, this works just fine. But if the layout is in any way dynamic (with window resizing being the most common case) you now have to either describe what you want to have happen when things change, or have the system guess. And there are a lot of options: scaling, cropping, letterboxing, overflowing, "smart" reflow... The possibilities are endless, so describing all of that complexity in general requires a full programming language. This is one the reasons that even CSS can be very frustrating, and people often resort to Javascript to get their UI to do the Right Thing.
Yes there are a lot of options but I don't think that it would be inconceivable to have such options split out as separate components.
I want an hide-overflow behavior to this component, then I just wrap it with a hide-overflow component. Doing that drag-and-drop should work. Then again you would need to design such components in a way that makes them intuitive to use, but that's always the case.
The main challenge in this particular domain is describing what is supposed to happen to the layout when the size of the window changes, or if there are dependencies among visual elements (e.g. some element only appears when a check box is checked). When laying things out visually you can only ever design one particular instance of a layout. If all your elements are static, this works just fine. But if the layout is in any way dynamic (with window resizing being the most common case) you now have to either describe what you want to have happen when things change, or have the system guess. And there are a lot of options: scaling, cropping, letterboxing, overflowing, "smart" reflow... The possibilities are endless, so describing all of that complexity in general requires a full programming language. This is one the reasons that even CSS can be very frustrating, and people often resort to Javascript to get their UI to do the Right Thing.