Conditionally Required Graphics Driver Functions

Besides the functions that are always required, certain other functions may be required, depending on how a driver is implemented. The conditionally-required functions are listed in the following table. If the driver manages its own primary surface (using the EngCreateDeviceSurface function to get a handle to the surface), or its own offscreen bitmaps, the driver must also support several drawing functions. Drivers writing to standard format DIBs usually allow GDI to manage most or all of these operations. Displays that support settable palettes must also support the DrvSetPalette function.

It is more common for a printer driver than a display driver to define or draw fonts. A display driver is not required to handle fonts. If the hardware has a resident font, the driver must supply information to GDI about this font. This information includes font metrics, mappings from Unicode to individual glyph identities, individual glyph attributes, and kerning tables.

Entry Point	When Required	Description
DrvCopyBits	Device-managed surfaces	Translates between device-managed raster surfaces and GDI standard-format bitmaps.
DrvDescribePixelFormat	Displays that support windows with different pixel formats on a single surface	Describes a PDEV's pixel format.
DrvGetTrueTypeFile	TrueType font drivers	Gives GDI access to a memory-mapped TrueType font file.
DrvLoadFontFile	Font drivers	Specifies file to use for font realizations.
DrvQueryFont	Printer drivers	Retrieves a GDI structure for a given font.
DrvQueryFontCaps	Font drivers	Asks driver for font driver capabilities.
DrvQueryFontData	Printer drivers	Retrieves information about a realized font.
DrvQueryFontFile	Font drivers	Asks driver for font file information.
DrvQueryFontTree	Printer drivers	Queries a tree structure defining one of three types of font mapping.
DrvQueryTrueTypeOutline	TrueType font drivers	Returns TrueType glyph handles to GDI.
DrvQueryTrueTypeTable	TrueType font drivers	Gives GDI access to TrueType font files.
DrvResetPDEV	Devices that allow mode changes in documents	Transfers driver state from old PDEV to new PDEV.
DrvSetPalette	Displays that support settable palettes	Realizes the palette for a specified device.
DrvSetPixelFormat	Displays that support windows with different pixel formats on a single surface	Sets a window's pixel format.
DrvStrokePath	Device-managed surfaces	Renders a path on the display.
DrvSwapBuffers	Drivers that support a pixel format with double buffering	Displays contents of a surface's hidden buffer.
DrvTextOut	Device-managed surfaces or drivers that define fonts	Renders a set of character images (glyphs) at specified positions.
DrvUnloadFontFile	Font drivers	Informs driver that a font file is not needed.