# Function Calls

The following Graphics folio calls control bitmaps, screens, and the display generator. They also write to bitmaps and frame buffers. See Graphics Folio Calls for complete descriptions of each call.

### Screen Calls

- `AddScreenGroup() Adds a screen group to the display.`
- `CreateScreenGroup()` Creates a screen group and all its screens, bitmaps, buffers, and VDLs.
- `DisplayScreen()` Displays the bitmap(s) of the specified screen (or screens).
- `RemoveScreenGroup()` Removes a screen group from the display.

### VDL Calls

- `SetVDL()` Sets a screen to display a specific VDL.
- `SubmitVDL()` Submits a VDL for approval by the 3DO system.
- `ModifyVDL()` Changes one or more attributes of a VDL.

### Screen Color Calls

- `MakeCLUTColorEntry()` Packs a color index and red, green, and blue values into a single word.
- `MakeCLUTBlueEntry()` Packs a color index and blue values into a single word.
- `MakeCLUTGreenEntry()` Packs a color index and green values into a single word.
- `MakeCLUTRedEntry()` Packs a color index and red values into a single word.
- `SetScreenColor()` Sets a color in the 3DO system's color palette.
- `SetScreenColors()` Sets a number of colors in the 3DO system's color palette.
- `ResetScreenColors()` Resets a screen's colors to a linear color palette.

### Drawing Calls

- `DrawTo()` Draws a line from the GrafCon's current position to a specified position.
- `FillRect()` Draws a filled rectangle.
- `GetPixelAddress()` Gets a pointer to the pixel at the specified GrafCon coordinates.
- `MakeRGB15()` Creates a 3DO RGB value out of separate red, green, and blue values.
- `MoveTo()` Moves the pen position of a GrafCon to a new location.
- `SetBGPen()` Sets the background pen of a GrafCon.
- `SetFGPen()` Sets the foreground pen of a GrafCon.
- `WritePixel()` Writes a pixel to a bitmap in a GrafCon's foreground color.

### Text Calls

- `DrawChar()` Draws a text character to a display window.
- `DrawText16()` Draws a text character to a display window.
- `GetCurrentFont()` Gets the pointer to the 3DO system's default font.
- `ResetCurrentFont()` Resets the 3DO system's default font.
- `SetCurrentFontCCB()` Sets the font.

### Clipping Calls

- `SetClipHeight()` Sets the clip height of a bitmap.
- `SetClipOrigin()` Sets the clip origin of a bitmap.
- `SetClipWidth()` Sets the clip width of a bitmap.

### Bitmap Copying Calls

- `CloneVRAMPages()` Copies one page of VRAM to a contiguous range of VRAM pages.
- `CopyVRAMPages()` Copies a contiguous number of VRAM pages to a VRAM destination.
- `MakeRGB15Pair()` Creates a double 3DO RGB value out of separate red, green, and blue values.
- `SetVRAMPages()` Sets contiguous pages of VRAM to a specified value.

### Display Timing Calls

- `WaitVBL() Waits the specified number of VBLs.`

### Interpolation Calls

- `DisableHAVG()` Disables horizontal averaging.
- `DisableVAVG()` Disables vertical averaging.
- `EnableHAVG()` Enables horizontal averaging.
- `EnableVAVG()` Enables vertical averaging.

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