Returns the current graphics mode. The result value is one of the following:
| HaruPage::GMODE_PAGE_DESCRIPTION |
| HaruPage::GMODE_TEXT_OBJECT |
| HaruPage::GMODE_PATH_OBJECT |
| HaruPage::GMODE_CLIPPING_PATH |
| HaruPage::GMODE_SHADING |
| HaruPage::GMODE_INLINE_IMAGE |
| HaruPage::GMODE_EXTERNAL_OBJECT |