I would like to use a white background on the OLED display for one of my projects.

I can fill the screen prior to writing any text on the display, and when I write text I can use one of the modes as per the flashing inverted text example.  However if you change the text that is displayed the screen will will see the earlier drawn text behind the new text.  In order to cleanly draw the new text you have to draw a box with the background color first prior to drawing the new text.

Since there are no functions for determine the pixel sizes of the font used you need to guess at the sizes

It would be very nice to have the ability to set a background color when you draw text.

 Just answered your question on another topic, you can try AND and XOR mode

 The font's width and height are difference even in same size of font's structure, such 'A' is wider than 'l'.