'Launch calculator' keyboard shortcut launches at least two instances of the calculator (and at most, *infinite* instances)

 * Cinnamon version: 4.2.4
 * Arch Linux
 * AMD Radeon RX 550 / Mesa 19.2.0
 * 64 bit

Issue

I have a standard microsoft wireless keyboard+mouse with a Calculator button. This button is configured in the Keyboard -> Shortcuts section of the system settings to launch the system's calculator (this is the default setting). I use the gnome-calculator.

When I press this button, it opens at least two instances of the calculator. If I press it for a little longer, it opens many instances. And if I keep it pressed, it'll open an awful lot of instances.

It always opens two instances of the calculator, no matter how quickly I press the button.

It also takes a noticeable amount of time (between 500ms and 1s) to launch the calculator instances. If I open the calculator via menu or quick launcher, it opens almost instantly, so this is an issue with the keyboard shortcut processing.

This behavior (multiple instances + delay) was definitely not present in older Cinnamon releases (I believe the 3.x series), so it is a regression.

Expected behaviour

When pressing the 'Calculator' keyboard button, only one instance of the calculator should be launched, no matter for how long the key is pressed.

Of course, if I press the button multiple times, I actually expect it to launch multiple instances of the calculator.

Start by reproducing the issue through Keyboard -> Shortcuts with the Calculator key, comparing a quick press with a held press. Trace the keyboard shortcut processing and verify that one press launches one calculator instance while repeated presses still launch separate instances.