I don’t exactly understand argument about frame rates, I thought these GUIs ran at very high frame rates and 1 frame wouldn’t be perceptible by humans. Is there really a human perceptible significant latency with them?
There are a lot of hidden traps when rendering anything on modern operating systems that add small latencies and those small latencies add up quickly (it was much easier on old 8- and 16-bit computers).
For instance rendering something that "sticks" to the system mouse pointer and doesn't lag a few pixels behind when moving the mouse is surprisingly hard if you're rendering through a 3D API (compared to going through the native window system), at least if you also want to be energy efficient (e.g. not spam 1000 frames per second).
What strikes me as odd is describing the ImGui idea as an "ideology" when it's the most pragmatic way to describe user interfaces in a long time, for me that's the opposite of an ideology.
I think if it as Casey Muratori's "brain fart" that made sense in his context but that other developers have latched on to because of his influence in indie game circles.
I have massive respect for him, and followed everything he did back in the late '90s and early aughts, but he's quite opinionated and has some peculiar code aesthetics / trade-offs.
e.g. you basically tie the state to the... ahem.. source code line (you need really something unique). Obviously Dear ImGUI has better approaches there (use the widget's contents, like text/label contents, or add your own with ##).
Anectodal etc etc, but when I started using Dear ImGui a few years ago I had no idea about the origins of immediate mode UI, or what "immediate mode UI" even means, and neither had heard of Casey Muratori nor Omar Cornut.
All I saw was a very enjoyable way to create UIs, something I loathed before (like most other programmers I guess). So far I haven't come across another UI toolkit which is as enjoyable to use as Dear ImGui (and that includes a couple of other ImGui libraries), and that's the reason why I stick to it, not because of some sort of cult of personality ;)
Dragging around a pointer, or scrubbing a line will be noticeably laggy with > 0 frame delay. It leads to a sluggish feeling that may be okay in the web world, but is kind of against the whole aesthetic of performant native apps. What's strange to me is that Muratori is a huge stickler for performance, like Jon Blow. I can't imagine him being happy with any kind of lag.
Cursors are done with hardware cursor sprites on the video card and so run perfectly at the full frame rate of the monitor. In game cursors will be different.
Let's say you're dragging something at 3 cm/s. Rendered at 30 Hz, a one frame latency translates into 30/30 mm which is 1 mm. A 1mm gap between the cursor and the thing you're dragging is definitely perceptible, and this is for a relatively slow drag. It's at least enough to destroy the illusion that the thing is locked to your cursor.
