For my own amusement, when ever I get a new OS build on my machine, I'd open up a task manager and watch CPU load just by wiggling the mouse a lot or maybe simply pressing page up and down. I'm pretty sure it's always pretty easy to generate 25% CPU doing very little. Another thing would be just opening a local file from within a running application and wondering why multiple seconds and hence billions of CPU cycles seems to be consumed what one expects should be doing a fairly menial task. (I am pretty sure in DOS 3.3 with Norton Commander it was quicker )
I'm pretty sure it's always pretty easy to generate 25% CPU doing very little
not for me, just tried mouse wiggling, scrolling, page up/down in browsers/file managers on Windows 7, 10 and Ubuntu 16 and none of those have such behaviour. Likewise for opening a file dialog. And I didn't expect otherwise actually, what OS are you talking about?
That used to be true back when the CPU did all of the GUI rendering. But now most all of it is offloaded to the GPU. Any GPU that can render Quake 3 Arena at 120 FPS (and that's ALL of them even Intel IGPs) can wiggle a window around very easily.
Not sure about file opens. Simple applications like GVIM don't seem to have seconds of delay for me, but I know what you mean with things like spreadsheet or word processor files. I guess it is all of the unzipping and XML processing.
Basically, the GPU card vendors could hook any part of the win32 GDI pre windows vista, and they did. Post vista, only a tiny portion of the GDI is accelerated. In theory you can avoid this by writing your application using a more modern API, but the vast majority of native windows applications continue to basically be GDI based due to age, or various GUI toolkits still being GDI based. Worse there are a number of toolkits (or browsers) which implement their own drawing routines rather than calling the system supplied ones.
The final composited results with aero are of course accelerated, but that only really tends to add additional latency. Switching to one of the basic themes makes win7 noticeably more responsive, but also tends to tear a lot. I've got an incredibly high end desktop machine, carefully tweaked/optimized and I can frequently see it the ~1/10 of a second lags while windows update after being maximized/etc. Compared to the 10 year old pretty high end XP machine (with upgraded SSD/etc, and also carefully tuned) it doesn't seem to be faster on basic desktop type operations. Fire up a recent game, or doing builds its massively faster but running word/firefox/whatever the old machine "feels" faster.
(tuned, as in I have a dozen or so, tweaks I've been collecting/researching for the past decade+, on ways to make the machine feel more responsive, it all started with MenuShow delay in win95, and has grown from there and now includes all the usual stuff plus tweaking power profiles, and a bunch of less obvious "feel" things like high DPI mice with fast base speeds).
I wonder if this accurately captures the time spent on the task. I am surprised opening a file takes that long. I primarily live in a Linux environment, but I also run some Java code for R&D data collection on Windows also. It opens 10-20 files on startup which does not lead to a perceptible delay. I have not measured exact performance, but if opening (all 20) took more than half a second or so I would have surely noticed this.
macOS has always had really smooth window wiggling because each window is a separate layer rendered on the GPU. Windows has had problems in the past because wiggling windows causes repaints in the background ones, they had no such buffer, but Windows Aero uses a model a lot like the macOS one.
