Seems to me that the tooltip text is created when it is initialized from the values the variables have -at that time-. If you want the tooltip to change as the variables change, you will have to re-format the text each time the variables change. Basically, your format statement creates a QString, and this QString is passed in as the tooltip text. The tooltip itself knows nothing about the variables used to create the string.
The behavior you are seeing seems pretty reasonable to me - what if you -didn't- want the tooltip to change with the variables? If it was automatically updated each time, there would be no way to prevent that.
In QMessageBox, I assume you are passing the text every time you post it (using one of the static methods - warning(), information() whatever). If you created a QMessageBox, set the text, and then just called show() and hide(), I'll bet you won't see updated text, just the text as it was when created.
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