Considering light on Vermeer’s paintings

After having watched the film The Girl with a Pear Earring I have noticed that many of Vermeer’s paintings are composed in a similar way, in the sense that they are set in a room with only one window that provides light to the place. Some examples are The Girl with a wine glass, A Maid Asleep, A Girl Reading a letter by an open window, Officer and Laughing Girl or The Milk Maid among others. All of them seem to be placed in the same room. They all have a window on the left of the picture, sometimes half-opened, other times closed. This window is the source of light for the picture. The light is strategically placed in the sense that it is directed to the main figures in the painting. Analysing the picture I have chosen, The Girl with a Wine Glass, the light draws parallel lines that start in the window and open up across the picture until the opposite side. The two diagonal lines of light enclose inside the two main figures, the girl holding the wine glass and the patron. The person by the window is regarded to a secondary position with nearly no light.