IUP Portable User Interface might be a bit more popular than Ultimate++. We know about 1 link to it since March 2021 and only 1 link to Ultimate++. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
I've recently mentioned Ultimate++, if you want something application-oriented, portable, and lightweight. And on Windows, it even comes with its own compiler so you can just unpack and run it. But if you happen to have closed-source binary libraries for a specific compiler (such as MSVC, as is common on Windows) than you need consume, the IDE included with Ultimate++ can work with your own compiler, too. Because... Source: about 2 years ago
As C libraries, I can recommend IUP. You can also choose immediate mode which has the same look on all platforms, there are some wrappers around imgui in Zig like zig-upaya. Source: almost 3 years ago
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