How do find the width of a Text Picture in gloss?

Question

In the Haskell Gloss library, one draws text with the Text constructor of the Picture type. But how, then does one find the width (and height) of such a picture?

Answer 1

Here's how text is rendered in Gloss:

        Text str
         -> do
                GL.blend        $= GL.Disabled
                GL.preservingMatrix $ GLUT.renderString GLUT.Roman str
                GL.blend        $= GL.Enabled

The important point here is that it calls renderString. Looking at the documentation for renderString, we immediately see two other useful functions: stringWidth and fontHeight. As such, you can get your width and height like this:

import Graphics.UI.GLUT.Fonts

do
    width <- stringWidth Roman str
    height <- fontHeight Roman