Jürg,
While it is true that the Text_Image function has to create and process a new list of vectors every time, the purpose of this exercise is not the application "Test Test". The Test Test is just a test function to debug the Text_Image function which is intended to stand alone and be used in any application to write text to any image tile in any dialog box.
To make the performance change you are talking about would require the main application to store the list of vectors along with all of the parameters to determine what changed and then process the same list of vectors. This would only increase the speed of subsequent changes to the same vector list. While this is applicable to my test function, in normal application one would typically not write text to a image and than change just the rotation of the same text unless they were trying to create some kind of animated effect. Normally, the Text_Image function would be called to write a string to an image and then called again to write another string to the same or another image.
One performance increase that I could do is not calculate the rotation if it is set to 0, which will be most cases.
Thank you for your input, Jürg.