Instead of giving me the tools to make a modal pop-up, but then leaving me to match that modal pop-up to the stylistic conventions of each OS GUI, why can't a UI framework give me a "YesNoModalPopup" that looks and acts however a "YesNoModalPopup" is supposed to act on the respective OS—even going so far as to actually be a modal sheet or a command-line prompt instead?
This, I think, is one of the bigger but oft-unstated reasons that people actually prefer to target the web rather than targeting native. Javascript's window.alert() is a function with a semantic behaviour-contract; it will alert the user. It doesn't specify how it'll alert the user, that's up to the browser to define. (And, therefore, up to the user to pick the browser whose definition they enjoy.)
Perhaps what I'm really craving, here, is a XAML-like or XUL-like constraint-based declarative view format, which has a very high-level and abstract set of controls available to be specified. Then, different GUIs could have renderer-clients for this system, that rendered those controls in all sorts of different ways. Maybe you could even mix-and-match your favourite concrete controls, like with browser extensions.
I want to agree with the spirit of what you're saying, but given the potential complexity and uniqueness of a GUI, I think it's an extremely hard problem in practice, if not impossible. You're asking for a toolkit that is both generic enough to provide the common functionality you're describing, yet also comprehensive and flexible enough to cope with the diverse needs of different applications and the diverse conventions and capabilities of different platforms.
How hard can it be to build a toolkit that supports a textbox on Mac OS X, Windows, and Linux? For a moment I thought you proposed a solution a thread up:
> have it translate into the correct API calls on each platform under the hood.
What if instead of writing controls for applications, the applications had low level access to create controls on their own?
Individual controls aren't the problem. Unique controls and idioms that cover multiple controls are.
For example settings dialogs on Mac are usually not modal and usually apply immediately. Meanwhile Windows dialogs are usually modal and transactional, with Cancel button to roll back and Apply to commit without closing.
Full fidelity inevitability ends up bifurcating the codebase or compromising the nativeness of the UI.
Simple things like button, text box, drop down, check box, radio button that have been in use for 30 years or more are just fine. But look at the list view in Windows; that has grown dozens of options to support Explorer, the file system browser. The deeper you go, the less you can keep common.
I see that the deeper you go, the less you can keep common. I learned a lot from your answers.
I didn't understand why the nativeness of the UI must bifurcate (fork) the codebase. In your example, can't non-modal on Mac vs modal on Windows be a config value in the cross-platform UI?
I also didn't get an answer to one of my questions. Why can't applications have low level access to create controls on their own?
> why can't a UI framework give me a "YesNoModalPopup" that looks and acts however a "YesNoModalPopup" is supposed to act on the respective OS
As a simple counter-example, macOS rarely uses Yes/No/OK/Cancel buttons. Instead, dialog buttons have meaningful names based on the task at hand, e.g. "Overwrite File" and "Keep Old File".
That's exactly what I meant, though. "YesNoModalPopup" is the name of a semantic behavioural contract, not a concrete implementation class whose name describes what you'll see. In instantiating a YesNoModalPopup, there would be required fields for button labels—even though those field-values will only be used on OSX.
With an abstract+declarative toolkit, you would still have to do just as much customization toward your use-case as you would if you were writing one view class for each GUI. You just get to skip the marginal cost of everything that's not that customization. You can have a single code path to create, and show, and receive input from, the instance of the pop-up abstraction.
This, I think, is one of the bigger but oft-unstated reasons that people actually prefer to target the web rather than targeting native. Javascript's window.alert() is a function with a semantic behaviour-contract; it will alert the user. It doesn't specify how it'll alert the user, that's up to the browser to define. (And, therefore, up to the user to pick the browser whose definition they enjoy.)
Perhaps what I'm really craving, here, is a XAML-like or XUL-like constraint-based declarative view format, which has a very high-level and abstract set of controls available to be specified. Then, different GUIs could have renderer-clients for this system, that rendered those controls in all sorts of different ways. Maybe you could even mix-and-match your favourite concrete controls, like with browser extensions.