1. A concise explanation of the problem you’re experiencing.
I provide the user the ability to draw an extent/rectangle for zooming to a specific area. The way they do this is by pressing the “Z” key and then left-clicking the mouse and dragging to draw the rectangle. In the latest Cesium (1.53) I have found that the ScreenSpaceEventType.LEFT_UP event does not fire when another key is being pressed. Its not until I let go of the “Z” key that the ScreenSpaceEventType.LEFT_UP event fires.
I downgraded my Cesium back to 1.48 which was the last version I had noticed this feature working properly. Sure enough in 1.48 the behavior is as expected. The user can press the “Z” button and left click to draw the rectangle and when they let up on the left mouse button still with “Z” suppressed the ScreenSpaceEventType.LEFT_UP event fires…
This seems like a bug to me. The ScreenSpaceEventType.LEFT_UP should fire regardless if another key is suppressed. Likewise for all mouse events.
4. The Cesium version you’re using, your operating system and browser.