Weird things happening with framerate

Hi friends,
while playing with of0.10 with Qt creator 4.6.1 and Ubuntu 18.04 I came across some weird behavior that I am not able to explain.

Starting from a new blank project the doe is like this:

//--------------------------------------------------------------
void ofApp::setup(){
    font.load("Helvetica", 16);

    ofSetFrameRate(60);
    ofSetVerticalSync(true);
}

//--------------------------------------------------------------
void ofApp::update(){

}

//--------------------------------------------------------------
void ofApp::draw(){
    static float currentX = 40;
    static float delta = 2;

    ofSetColor(ofColor::crimson);
    font.drawString("Frame rate test: " + ofToString(ofGetFrameRate(), 1), 20, 50);

    // ofLogNotice() << ofGetFrameRate();

    ofSetColor(ofColor::aliceBlue);
    ofDrawCircle(currentX, 150, 10);

    currentX += delta;

    if(currentX > 280 || currentX < 40)
    {
        delta = -delta;
    }
}

font is defined in ofApp.h as an instance of ofTrueTypeFont, nothing fancy.

What happens is that when I make the of windows quite small, at 320 x 200, the framerate drops randomly drops to 41 - 42 then slowly goes back to 60 and so on. It is not just a matter of measuring it since the small moving circle does noticeable jumps and slows down when fr is lower.

If I remove the // comment mark from the ofLogNotice() line then everything runs smooth @ 60 fps while inside Qt Creator, but not if the app is launched from the console.

Setting window size to something larger (640 x 200 is enough) also solves the problem.

Of course this is not an end-of-the-world tragedy, but I’d like to know what’s happening.

ciao
Davide

Edit: I forgot to mention that Ubuntu is running as a VM inside a OSX host. Memory and CPU usage is always very low even when framerate drops.

not sure what might be going on but don’t use ofSetFrameRate(60); in combination with ofSetVerticalSync(true); vsync already adjusts the framerate and using set framerate might make the app sleep some frames using the system timer which in a virtual machine can be quite unprecise

Also in general inside a vm you can’t expect things to run super smoothly

Yes it was there just for testing, adding or removing it did not change anything. May be as you say the problem is related to the VM… never mind, I was just curious about its randomness.