Rendering a GUI can be done in real time on ancient CPUs. This has been true since the 1980s and continues to be true today. If your app has a performance issue then you should consider cutting down on the animations/special effects/abstractions.
That depends on the style of GUI. As soon as you introduce any amount of animation (even something as trivial as drag-and-drop, never mind touch-swipe or touch-zoom gestures), hardware acceleration can be quite useful.
Didn’t Windows XP (and prior) not render the window as it was dragged, but just a dashed box? And when you release the window, it’d be redrawn in the new spot.
In Windows 98, it's under the Control Panel → Display → Effects → Show window contents while dragging
https://copy.sh/v86/?profile=windows98
(The VM here is slower than a machine of the era.)
(I also want to say Transport Tycoon Deluxe's windows were draggable without needing a frame / in real time, and that was in DOS?)
Mind you, I can do real-time 1080p mp4 video scrubbing on haiku running on a thin client so...
CPUs are more than capable of rendering graphics needed for gestures like you mentioned.
This has been my experience too with an old GMA GPU, I have to keep disabling hardware acceleration in everything I try to run (browsers, electron apps if possible, desktop environments). The UI runs order of magnitude faster on the CPU than on the GPU through OpenGL.
Immediate mode GUI creation. Very straightforward and just requires an OpenGL context (which can be software of course, so all CPU based if you want). A lot of games use it because it can be easily added as an additional layer to your final image (and is represented as just an image).
You should look at GTK+, motif, or TCL/Tk. They're very straightforward and don't turn people's devices into hand warmers.
Motif, along with X11 is just completely obsolete platform. (btw, this is what UHH thinks about it: "What Motif does is make Unix slow. Real slow.")
There's some weird GPU hate in this thread that I don't quite understand. Try to render dragging content of 1080p window at 60fps on cheap mobile ARM core, and you will likely blow your whole time budget just on filling the window with solid color...
I'm not a mobile developer so this is all new to me. Thanks for the info.
