ILI943x and GFXfont usage

[probso]

Please can you provide some simple documentation on the expected/normal parameters of these functions:
void drawChar(uint16_t x, uint16_t y, char c, uint16_t colour, GFXfont *font);
void charBounds(char c, int16_t *x, int16_t *y, int16_t *minx, int16_t *miny, int16_t *maxx, int16_t *maxy, GFXfont *font);
void textBounds(const char *str, int16_t x, int16_t y, int16_t *x1, int16_t *y1, uint16_t *w, uint16_t *h, GFXfont *font);

Specifically,

• what is passed for the GFXfont variable to access the font library?
• how are charBounds and textBounds used?
• Is it possible to pass a string to textBounds rather than single charecters?

Many thanks