High CPU usage even when idle
On a linux laptop, with the appimage for musescore 4.0alpha2. My laptop is from 2019 and was high end laptop then (Dell XPS13).
I observe that MS4 uses a lot of CPU for scores with many instruments, even when idle, even with a new empty score.
To reproduce, I start MS4, select "New score", choose "symphonic orchestra". I wait about 10 seconds for Musescore to load all of its audio samples, minimize the window (to be sure it receives no mouse/keyboard event), and run "top" (for monitoring cpu usage). It tells me MS4 is using about 34% of my CPU, even though it does absolutely nothing.
If I do the same thing, but with a simple staff instead of a symphonic orchestra, Musescore's CPU usage is at about 8%, which is smaller but still big,
I expect a program such as Musescore to use CPU only when it receives some UI event, do some computation or perform some playback. When it is idle, it should use no CPU at all and should not drain one's battery: one should be able to have an unused opened musescore in some window without any bad consequence.
On a related note, I remark that when MS4 is running, the sound system on linux (pipewire for my distribution) uses 4 to 5 % of CPU instead of 0, even if no sound is being played. This tells me that MS4 is continuously sending some data to the sound server; in other words, MS4 is continuously playing some silence. For the same reason as above, I expect any program to send data to the sound server only when actually playing some sound. I am not sure whether this is an independent issue or is related to the previous issue.
As a comparison point, Musescore 3.6.2 on the same computer with an empty, freshly created, symphonic orchestral score uses about 4% CPU when idle. Still too big in my opinion, but much better than 34%. Pipewire (the sound server) uses hardly any CPU at all: MS3 is not sending a continuous stream of silence when not playing.