MACINTOSH C CARBON: A Hobbyist's Guide To Programming the Macintosh in C
Version 1.0
© 2001 K. J. Bricknell

CHAPTER 11

QUICKDRAW PRELIMINARIES

QuickDraw and Imaging

QuickDraw is a collection of system software routines that your application uses to perform imaging operations, that is, the construction and display of graphical information for display on output devices such as screens and printers.

This chapter serves as a prelude to Chapter 12, and introduces certain matters which need to be discussed before the matter of actually drawing with QuickDraw is addressed. These matters include the history of QuickDraw, RGB colours, colour and the video device, the graphics port, translation of RGB values, and graphics devices.

RGB Colours and Pixels

In QuickDraw, colours are specified as RGB colours using an RGBColor structure:

     struct RGBColor
     {
       unsigned short red;    // Magnitude of red component.
       unsigned short green;  // Magnitude of green component.
       unsigned short blue;   // Magnitude of blue component.
     };
     typedef struct RGBColor RGBColor;

Note that an RGB colour is defined by three components (red, green and blue). When the red, green and blue fields of the RGBColor structure are assigned the maximum possible value (0xFFFF), the resulting colour is white. When these fields are assigned the minimum value (0x0000), the resulting colour is black.

A pixel (picture element) is the smallest dot that QuickDraw can draw. Each colour pixel represents up to 48 bits in memory.

Colour and the Video Device

QuickDraw supports a variety of screens of differing sizes and colour capabilities, and is thus device-independent. Accordingly, you do not have to concern yourself with the capabilities of individual screens. For example, when your application uses an RGBColor structure to specify a colour by its red, green and blue components, with each component defined in a 16-bit integer, QuickDraw compares the resulting 48-bit value with the colours actually available on a video device (such as a plug-in video card or a built-in video interface) at execution time and then chooses the closest match. What the user finally sees depends on the characteristics of the actual video device and screen.

The video device that controls a screen may have either:

• Indexed colours, which support pixels of 1-bit, 2-bit, 4-bit, or 8-bit pixel depths. The indexed colour system was introduced with the Macintosh II, that is, at a time when memory was scarce and moving megabyte images around was quite impractical.

  Pixel depth means the number of bits assigned to each pixel, and thus determines the maximum number of colours that can be displayed at the one time. A 4-bit pixel depth, for example, means that an individual pixel can be displayed in any one of 16 separate colours. An 8-bit pixel depth means that an individual pixel can be displayed in any one of 256 separate colours.

• Direct colours, which support pixels of 16-bit and 32-bit depths. Most video devices in the current day are direct colour devices. (However, as will be seen, there are circumstances in which a direct colour device will act like an indexed colour device.)

QuickDraw automatically determines which method is used by the video device and matches your requested 48-bit colour with the closest available colour.

Indexed Colour Devices

Video devices using indexed colours support a maximum of 256 colours at any one time, that is, with indexed colour, the maximum value of a pixel is limited to a single byte, with each pixel's byte specifying one of 256 different values.

Video devices implementing indexed colour contain a data structure called a colour lookup table (CLUT), which contains entries for all possible colour values. Most indexed video devices use a variable CLUT, which allows your application to load the CLUT with different sets of colours depending on the image being displayed.

When your application uses a 48-bit RGBColor structure to specify a colour, the Color Manager compares the CLUT entries on the video device with the specified RGBColor colour, determines which colour in the CLUT is closest, and passes QuickDraw the index to this colour. This is the colour that QuickDraw draws with. Fig 1 illustrates this process.

Direct Colour Devices

Video devices which implement direct colour eliminate the competition for limited colour lookup table spaces and remove the need for colour table matching. By using direct colour, video devices can support thousands or millions of colours.

When you specify a colour using a 48-bit RGBColor structure on a direct colour system, QuickDraw truncates the least significant bits of its red, green and blue components to either 16 bits (five bits each for red, green and blue, with one bit unused) or 32 bits (eight bits for red, green and blue, with eight bits unused). (See Translation of RGB Colours to Pixel Values, below.) Using 16 bits, direct video devices can display 32,768 different colours. Using 32 bits, the device can display 16,777,215 different colours

Fig 2 illustrates the direct colour system.

Direct colour not only removes much of the complexity of the CLUT mechanism for video device developers, but also allows the display of thousands or millions of colours simultaneously, resulting in near-photographic resolution.

Direct Devices Operating Like Indexed Devices

Note that, when a user sets a direct colour device to use 256 colours (or less) as either a grayscale or colour device, the direct device creates a CLUT and operates like an indexed device.

Graphics Port

A graphics port defines a complete drawing environment. Amongst other things, a graphics port:

The term "graphics port" originally pertained to the one-bit graphics port used by the early black-and-white Macintoshes. The colour graphics port was introduced when colour came to the Macintosh with the Macintosh II. In the Carbon era, the black-and-white graphics port is irrelevant. Accordingly, where the term "graphics port" is used in this book, a colour graphics port should be assumed unless otherwise stated.

• Contains a handle to a pixel map which, in turn, contains a pointer to the area of memory in which your drawing operations take place.

• Contains a metaphorical graphics pen with which to perform drawing operations. (You can set this pen to different sizes, patterns and colours.)

• Holds information about text, which is styled and sized according to information in the graphics port.

The information in a graphics port is maintained by QuickDraw.

The graphics port is an opaque data structure. The data types CGrafPtr and GrafPtr are defined as pointers to such objects:

     typedef struct OpaqueGrafPtr* GrafPtr;
     typedef GrafPtr CGrafPtr;

Accessor Functions

Accessor functions are provided to access the information in colour graphic port objects. The main accessor functions are as follows:

Accessor Function	Description
GetPortPixMap	Get a handle to the graphics port's pixel map.
GetPortBounds SetPortBounds	Get and set the graphics port rectangle. Your application's drawing operations take place inside the port rectangle (which, for a window's graphics port is also called the content region.) The port rectangle uses the local coordinate system defined by the boundary rectangle in the portPixMap field of the PixMap structure (see below). The upper-left corner of the port rectangle has a vertical coordinate of 0 and a horizontal coordinate of 0.
GetPortVisRegion SetPortVisRegion	Get and set the visible region. The visible region (which, by default, is equivalent to the port rectangle) is the region of the graphics port that is actually visible on screen (see Fig 3).
GetPortClipRegion SetPortClipRegion SetClip	Get and set the clipping region. The clipping region is an arbitrary region used to limit drawing to any region within the port rectangle. The default clipping region is set arbitrarily large; however, your application can change this. At Fig 3, for example, SetPortClipRegion (or ClipRect) has been used to change Window B's clipping region so as to prevent the scroll bar areas being over-drawn.
GetPortForeColor RGBForeColor	Get and set the foreground colour. These functions get and set an RGBColor structure that contains the requested foreground colour. By default, the foreground colour is black.
GetPortBackColor RGBBackColor	Get and set the background colour. These functions get and set an RGBColor structure that contains the requested background colour. By default, the backgroundground colour is white.
GetPortBackPixPat SetPortBackPixPat BackPixPat BackPat	Get and set the background pixel pattern. These functions get and set a handle to a PixPat structure (see below) that describes the background pixel pattern. Various QuickDraw functions use this pattern for filling scrolled or erased areas.
GetPortPenPixPat SetPortPenPixPat PenPixPat PenPat	Get and set the pen pixel pattern. These functions get and set a handle to a PixPat structure (see below) that describes the pixel pattern used by the graphics pen for drawing lines and framed shapes, and for painting shapes.
GetPortFillPixPat	Get the fill pixel pattern. This function gets a handle to a PixPat structure (see below) that describes the pixel pattern used when you call QuickDraw shape filling functions.
GetPortPenLocation MoveTo	Get and set the pen location. The pen location is the point where QuickDraw will begin drawing the next line, shape, or character. It can be anywhere on the coordinate plane.
GetPortPenSize SetPortPenSize PenSize	Get and set the pen size. Pen size is the vertical height and horizontal width of the graphics pen. The default size is a 1-by-1 pixel square. If either the pen width or height is 0, the pen does not draw.
GetPortPenMode SetPortPenMode PenMode	Gets and sets the pen transfer mode. The pen transfer mode is a Boolean or arithmetic operation that determines how QuickDraw transfers the pen pattern to the pixel map during drawing operations. (See Chapter 12.)
HidePen ShowPen GetPortPenVisibility	Gets and sets pen visibility. The pen's visibility means whether it draws on the screen.
GetPortTextFont TextFont	Get and set the font number for text. These functions get and set a font family ID, that is, anumber that identifies the font to be used in the graphics port.
GetPortTextSize TextSize	Get and set the text size. The text size is expressed in pixels, and is used by the Font Manager to provide the bitmaps for text drawing.
GetPortTextFace TextFace	Get and set the text style. The style of the text means, for example, bold, italic, and/or underlined.
GetPortTextMode TextMode	Get and set the text mode. The text mode is the transfer mode for text drawing, which functions much like the transfer mode specified in the pnMode field (see above).
HiliteColor	Get the highlight colour. (The highlight colour is copied to the graphics port from the low memory global HiliteRGB.)

You can open many graphics ports at the same time. Each has its own local coordinate system, drawing pattern, background pattern, pen size and location, foreground colour, background colour, pixel map, etc. You can instantly switch from one graphics port to another using the functions SetPort, SetPortDialogPort, and SetPortWindowPort.

When you use Window Manager and Dialog Manager functions to create windows, dialogs, and alerts, those managers automatically create graphics ports for you

Pixel Maps

QuickDraw draws in a pixel map. The graphics port object contains a handle to a pixel map, which is a data structure of type PixMap. A PixMap structure contains a pointer to a pixel image, as well as information on the image's storage format, depth, resolution, and colour usage. The PixMap structure is as follows:

struct PixMap
{
  Ptr         baseAddr;    // Pointer to image data.
  short       rowBytes;    // Flags, and bytes in a row.
  Rect        bounds;      // Boundary rectangle.
  short       pmVersion;   // Pixel Map version number.
  short       packType;    // Packing format.
  long        packSize;    // Size of data in packed state.
  Fixed       hRes;        // Horizontal resolution in dots per inch.
  Fixed       vRes;        // Vertical resolution in dots per inch.
  short       pixelType;   // Format of pixel image.
  short       pixelSize;   // Physical bits per pixel.
  short       cmpCount;    // Number of components in each pixel.
  short       cmpSize;     // Number of bits in each component.
  long        planeBytes;  // Offset to next plane.
  CTabHandle  pmTable;     // Handle to a colour table for this image.
  long        pmReserved;  // (Reserved.)
};
typedef struct PixMap PixMap,*PixMapPtr,**PixMapHandle;

Field Descriptions

baseAddr	In the case of an onscreen pixel image, a pointer to the first byte of the image. The pixel image that appears on the screen is normally stored on a graphics card rather than in main memory. Note that there can be several pixel maps pointing to the same pixel image, each imposing its own coordinate system on it. A pixel image is analogous to the bit image. A bit image is a collection of bits in memory that form a grid. Fig 4 illustrates a bit image, which can be visualised as a matrix of rows and columns of bits with each row containing the same number of bytes. Each bit corresponds to one screen pixel. If a bit's value is 0, its screen pixel is white; if the bit's value is 1, the screen pixel is black. A pixel image is essentially the same as a bit image, except that a number of bits, not just one bit, are assigned to each pixel. The number of bits per pixel in a pixel image is called the pixel depth.
rowBytes	The offset in bytes from one row of the image to the next.
bounds	Mac OS 8/9 On Mac OS 8/9,the boundary rectangle defines the area of the pixel image into which QuickDraw can draw and provides the link between the local coordinate system of a graphics port and QuickDraw's global coordinate system. All drawing in a graphics port occurs in the intersection of the boundary rectangle and the port rectangle (and, within that intersection, all drawing is cropped to the graphics port's visible region and its clipping region). As shown at Fig 5, on Mac OS 8/9, QuickDraw assigns the entire screen as the boundary rectangle. The boundary rectangle shares the same local coordinate system as the port rectangle of the window. You should not, incidentally, use the bounds field to determine the size of the screen; instead, use the gdRect field of the GDevice structure (see below). Mac OS X On Mac OS X, this field contains the bounds of the Core Graphics window that backs the Carbon window, and different mechanisms are employed to determine where the window's pixel map should be drawn.
pmVersion	The QuickDraw version number that created this PixMap structure.
packType	The packing algorithm used to compress image data.
packSize	The size of the packed image.
hRes	The horizontal resolution of the pixel image in pixels per inch, abbreviated as dpi (dots per inch). By default, the value here is 0x00480000 (for 72 dpi), but QuickDraw supports PixMap structures of other resolutions. For example, PixMap structures for scanners can have dpi resolutions of 150, 200, 300, or greater.
vRes	The vertical resolution. (See hRes).
pixelType	The storage format. 0 indicates indexed pixels. 16 (RGBDirect) indicates direct pixels.
pixelSize	The number of bits used to represent a pixel.
cmpCount	The number of components used to represent a colour for a pixel. For indexed pixels, this field contains 1. For direct pixels this field contains the value 3.
cmpSize	The size of each colour component. For indexed devices, this is the same value as that in the pixelSize field. For direct devices, each of the three colour components can be either 5 bits for a 16-bit pixel (one of these 16 bits is unused), or 8 bits for a 32 bit pixel (8 of these 32 bits are unused). (See Translation of RGB Colours to Pixel Values, below.)
planeBytes	QuickDraw does not support multiple-plane images, so the value of this field is always 0.
pmTable	A handle to the ColorTable structure. ColorTable structures define the colours available for pixel images on indexed devices. Pixel images on direct devices do not need a colour table because the colours are stored right in the pixel values. In the case of direct devices, pmTable points to a dummy colour table.

Functions

Carbon introduced the following functions relating to pixel maps:

Pixel Patterns and Bit Patterns

Pixel Patterns

The graphics port object stores handles to pixel patterns, structures of type PixPat.

Pixel patterns, which define a repeating design, can use colours at any pixel depth, and can be of any width and height that is a power of 2. You can create your own pixel patterns in your program code, but it is usually more convenient to store them in resources of type 'ppat'. Fig 6 shows an 8-by-8 pixel 'ppat' resource being created using Resorcerer.

Bit Patterns

Bit patterns date from the era of the black-and-white Macintosh, but may be stored in a graphics port object. (PixPat structures can contain bit patterns as well as pixel patterns.) Bit patterns are defined in data structures of type Pattern, a 64-pixel image of a repeating design organised as an 8-by-8 pixel square.

Five bit patterns are pre-defined as QuickDraw global variables. The five pre-defined patterns are available not only through the QuickDraw globals but also as system resources. Fig 7 shows images drawn using some of the 38 available system-supplied bit patterns.

You can create your own bit patterns in your program code, but it is usually more convenient to store them in resources of type 'PAT ' or 'PAT#'. Fig 8 shows a 'PAT ' resource being created using Resorcerer, together with the contents of the pat field of the structure of type Pattern that is created when the resource is loaded.

Creating Graphics Ports

Your application creates a graphics port using either the GetNewCWindow, NewCWindow, or NewGWorld function. These functions automatically call CreatePort, which opens the port.

Translation of RGB Colours to Pixel Values

As previously stated, the graphics port object contains a pointer to the beginning of the onscreen pixel image. When your application specifies an RGB colour for a pixel in the pixel image, QuickDraw translates that colour into a value appropriate for display on the user's screen. QuickDraw stores this value in the pixel. The pixel value is a number used by system software and a graphics device to represent a colour. The translation from the colour you specify in an RGBColor structure to a pixel value is performed at the time you draw the colour. The process differs for direct and indexed devices as follows:

• When drawing on indexed devices, QuickDraw calls the Color Manager to supply the index to the colour that most closely matches the requested colour in the current device's CLUT. This index becomes the pixel value for that colour.

• When drawing on direct devices, QuickDraw truncates the least significant bits from the red, green and blue fields of the RGBColor structure. The result becomes the pixel value that QuickDraw sends to the graphics device.

Your application never needs to handle pixel values. However, to clarify the relationship between RGBColor structures and the pixels that are actually displayed, the following presents some examples of the derivation of pixel values from RGBColor structures.

Derivation of Pixel Values on Indexed Devices

Fig 9 shows the translation of an RGBColor structure to an 8-bit pixel value on an indexed device.

An application might call GetCPixel to determine the colour of a pixel set by the pixel value at Fig 9. As shown at Fig 10, the Color Manager uses the pixel value (an index number) to find the RGBColor structure stored in the CLUT for that pixel's colour. This is the colour returned by GetCPixel. As shown at Fig 10, this is not necessarily the exact colour first specified.

Derivation of Pixel Values on Direct Devices

Fig 11 shows how QuickDraw converts an RBGColor structure into a 16-bit pixel value on a direct device. The most significant 5 bits of each field of the RGBColor structure are stored in the lower 15 bits of the pixel value. The high bit is unused. Fig 11 also shows how QuickDraw expands a 16-bit pixel value to a 48-bit RGBColor structure. Each 5-bit component, and the most significant bit, are inserted into each 16-bit field of the RGBColor structure. Note the difference between the result and the original 48-bit value.

Fig 12 shows how QuickDraw converts an RBGColor structure into a 32-bit pixel value on a direct device. The most significant 8 bits of each 16-bit field of the RGBColor structure are stored in the lower 3 bytes of the pixel value. 8 bits in the high byte of the pixel value are unused. Fig 12 also shows how QuickDraw expands a 32-bit pixel value to an RBGColor structure. Each of the 8-bit components is doubled. Note the difference between the result and the original 48-bit value.

Colours on Grayscale Screens

When QuickDraw displays a colour on a grayscale screen, it computes the luminance, or intensity of light, of the desired colour and uses that value to determine the appropriate gray value to draw.

A grayscale device can be a colour graphics device that the user sets to grayscale. For such a graphics device, Colour QuickDraw places an evenly spaced set of grays in the graphics device's CLUT.

Graphics Devices and GDevice Structures

As previously stated, QuickDraw provides a device-independent interface. Your application can draw images in the graphics port for a window and QuickDraw automatically manages the path to the screen - even if the user is using multiple screens. QuickDraw communicates with a video device, such as a plug-in video card or a built-in video interface, by automatically creating and managing a structure of type GDevice.

Types of Graphics Device

A graphics device is anything QuickDraw can draw into. There are three types of graphics device:

• Video devices, such as video cards and built-in video interfaces, that control screens.

• Offscreen graphics worlds, which allow your application to build complex images offscreen before displaying them. (See Chapter 13.)

• Printing graphics ports. (See Chapter 15.)

In the case of a video device for an offscreen graphics world, QuickDraw automatically creates, and stores state information in, a GDevice structure.

GDevice Structure

QuickDraw creates and initialises a GDevice structure for each video device found during startup. QuickDraw also automatically creates a GDevice structure when you call NewGWorld to create an offscreen graphics world.

A list called a device list links together all existing GDevice structures. The current device, which is sometimes called the active device, is that device in the device list into which drawing is currently taking place.

Your application generally never needs to create GDevice structures; however, in may need to examine GDevice structures to determine the capabilities of the user's screens. The GDevice structure is as follows:

     struct GDevice
     {
       short         gdRefNum;     // Reference Number of Driver.
       short         gdID;         // Client ID for search procedures.
       short         gdType;       // Type of device (indexed or direct).
       ITabHandle    gdITable;     // Handle to inverse lookup table for Color Manager.
       short         gdResPref;    // Preferred resolution.
       SProcHndl     gdSearchProc; // Handle to list of search functions.
       CProcHndl     gdCompProc;   // Handle to list of complement functions.
       short         gdFlags;      // Graphics device flags.
       PixMapHandle  gdPMap;       // Handle to pixel map for displayed image.
       long          gdRefCon;     // Reference value.
       Handle        gdNextGD;     // Handle to next GDevice structure.
       Rect          gdRect;       // Device's global boundaries.
       long          gdMode;       // Device's current mode.
       short         gdCCBytes;    // Width of expanded cursor data.
       short         gdCCDepth;    // Depth of expanded cursor data.
       Handle        gdCCXData;    // Handle to cursor's expanded data.
       Handle        gdCCXMask;    // Handle to cursor's expanded mask.
       long          gdReserved;   // (Reserved.  Must be 0.)
     };
     typedef struct GDevice GDevice;
     typedef GDevice *GDPtr, **GDHandle;

Main Field Descriptions

Setting a Device's Pixel Depth

The gdPMap field of the GDevice structure contains a handle to a PixMap structure which, in turn, contains the PixelSize field to which is assigned the pixel depth of the device.

The user can change the pixel depth of video devices. Accordingly, although your application may have a preferred pixel depth, it should be flexible enough to accommodate other pixel depths.

Your application can change the pixel depth using SetDepth. However, before calling this function, you should call the HasDepth function to confirm that the hardware can support the desired pixel depth. Generally speaking, you should not change pixel depth without first seeking the consent of the user via an alert or dialog.

Other Graphics Managers

In addition to the QuickDraw functions, several other collections of system software functions are available to assist you in drawing images.

Palette Manager

Your application can use the Palette Manager to provide more sophisticated colour support on indexed graphics devices. The Palette Manager allows your application to specify sets of colours that it needs on a window-by-window basis.

Color Picker Utilities

To solicit colour choices from users, your application can use the Color Picker Utilities. The Color Picker Utilities also provide functions that allow your application to convert between colours specified in RGBColor structures and colours specified for other colour models, such as the CMYK (cyan, magenta, yellow, black) model used for many colour printers. (See Chapter 25.)

Coping With Multiple Monitors

Image optimisation in a multiple monitors environment is addressed at Chapter 25.

Relevant QuickDraw Constants, Data Types, and Functions

Constants

Flag Bits of gdType Field of GDevice Structure

clutType    = 0
fixedType   = 1
directType  = 2

Flag Bits of gdFlags Field of GDevice Structure

gdDevType     = 0
burstDevice   = 7
ext32Device   = 8
ramInit       = 10
mainScreen    = 11
allInit       = 12
screenDevice  = 13
noDriver      = 14
screenActive  = 15

Pixel Type

RGBDirect  = 16  // 16 and 32 bits-per-pixel pixelType value.

Data Types

typedef struct OpaqueGrafPtr* GrafPtr;
typedef GrafPtr CGrafPtr;

Pixel Map

struct PixMap
{
  Ptr         baseAddr;    // Pointer to image data.
  short       rowBytes;    // Flags, and bytes in a row.
  Rect        bounds;      // Boundary rectangle.
  short       pmVersion;   // Pixel Map version number.
  short       packType;    // Packing format.
  long        packSize;    // Size of data in packed state.
  Fixed       hRes;        // Horizontal resolution in dots per inch.
  Fixed       vRes;        // Vertical resolution in dots per inch.
  short       pixelType;   // Format of pixel image.
  short       pixelSize;   // Physical bits per pixel.
  short       cmpCount;    // Number of components in each pixel.
  short       cmpSize;     // Number of bits in each component.
  long        planeBytes;  // Offset to next plane.
  CTabHandle  pmTable;     // Handle to a colour table for this image.
  long        pmReserved;  // (Reserved.)
};
typedef struct PixMap PixMap,*PixMapPtr,**PixMapHandle;

BitMap

struct BitMap
{
  Ptr    baseAddr;  // Pointer to bit image.
  short  rowBytes;  // Row width.
  Rect   bounds;    // Boundary rectangle.
};
typedef struct BitMap BitMap;
typedef BitMap *BitMapPtr, **BitMapHandle;

Pixel Pattern

struct PixPat 
{
  short         patType;    // Type of pattern.
  PixMapHandle  patMap;     // The pattern's pixel map.
  Handle        patData;    // Pixel map's data.
  Handle        patXData;   // Expanded Pattern data (internal use).
  short         patXValid;  // Flags whether expanded Pattern valid.
  Handle        patXMap;    // Handle to expanded Pattern data (reserved).
  Pattern       pat1Data;   // Bit map's data.
};
typedef struct PixPat PixPat;
typedef PixPat *PixPatPtr;
typedef PixPatPtr *PixPatHandle;

Pattern

struct Pattern
{
  UInt8  pat[8];
};
typedef struct Pattern Pattern;
typedef Pattern *PatPtr;
typedef PatPtr *PatHandle;

GDevice

struct GDevice
{
  short         gdRefNum;     // Reference Number of Driver.
  short         gdID;         // Client ID for search procedures.
  short         gdType;       // Type of device (indexed or direct).
  ITabHandle    gdITable;     // Handle to inverse lookup table for Color Manager.
  short         gdResPref;    // Preferred resolution.
  SProcHndl     gdSearchProc; // Handle to list of search functions.
  CProcHndl     gdCompProc;   // Handle to list of complement functions.
  short         gdFlags;      // Graphics device flags.
  PixMapHandle  gdPMap;       // Handle to pixel map for displayed image.
  long          gdRefCon;     // Reference value.
  Handle        gdNextGD;     // Handle to next GDevice structure.
  Rect          gdRect;       // Device's global boundaries.
  long          gdMode;       // Device's current mode.
  short         gdCCBytes;    // Width of expanded cursor data.
  short         gdCCDepth;    // Depth of expanded cursor data.
  Handle        gdCCXData;    // Handle to cursor's expanded data.
  Handle        gdCCXMask;    // Handle to cursor's expanded mask.
  long          gdReserved;   // (Reserved.  Must be 0.)
};
typedef struct GDevice GDevice;
typedef GDevice *GDPtr, **GDHandle;

Functions

Opening and Closing Graphics Ports

CGrafPtr  CreateNewPort(void);
Void      DisposePort(CGrafPtr port);

Saving and Restoring Graphics Ports

void  GetPort(GrafPtr *port);
void  SetPort(GrafPtr port);
void  SetPortDialogPort(DialogPtr dialog);
void  SetPortWindowPort(WindowRef window);

Getting a Pointer to the Owning Window

WindowRef  GetWindowFromPort(CGrafPtr port);

Graphics Port Accessors

PixMapHandle  GetPortPixMap(CGrafPtr port);
Rect          GetPortBounds(CGrafPtr port,Rect *rect);
void          SetPortBounds(CGrafPtr port,const Rect *rect);
RgnHandle     GetPortVisibleRegion(CGrafPtr port,RgnHandle visRgn);
void          SetPortVisibleRegion(CGrafPtr port,RgnHandle visRgn);
RgnHandle     GetPortClipRegion(CGrafPtr port,RgnHandle clipRgn);
void          SetPortClipRegion(CGrafPtr port,RgnHandle clipRgn);
void          SetClip(RgnHandle rgn);
RGBColor      GetPortForeColor(CGrafPtr port,RGBColor *foreColor);
void          RGBForeColor(const RGBColor *color);
RGBColor      GetPortBackColor(CGrafPtr port,RGBColor *backColor);
void          RGBBackColor(const RGBColor *color);
PixPatHandle  GetPortBackPixPat(CGrafPtr port,PixPatHandle backPattern);
void          SetPortBackPixPat(CGrafPtr port,PixPatHandle backPattern);
void          BackPat(const Pattern *pat);
PixPatHandle  GetPortPenPixPat(CGrafPtr port,PixPatHandle penPattern);
void          SetPortPenPixPat(CGrafPtr port,PixPatHandle penPattern);
void          PenPat(const Pattern *pat);
PixPatHandle  GetPortFillPixPat(CGrafPtr port,PixPatHandle fillPattern);
Point         GetPortPenLocation(CGrafPtr port,Point *penLocation);
void          MoveTo(short h,short v);
Point         GetPortPenSize(CGrafPtr port,Point *penSize);
void          SetPortPenSize(CGrafPtr port,Point penSize);
void          PenSize(short width,short height);
SInt32        GetPortPenMode(CGrafPtr port);
void          SetPortPenMode(CGrafPtr port,SInt32 penMode);
void          PenMode(short mode);
short         GetPortTextFont(CGrafPtr port);
void          TextFont(short font);
void          HidePen(void);
void          ShowPen(void);
short         GetPortPenVisibility(CGrafPtr port);
short         GetPortTextSize(CGrafPtr port);
void          TextSize(short size);
Style         GetPortTextFace(CGrafPtr port);
void          TextFace(StyleParameter face);
short         GetPortTextMode(CGrafPtr port);
void          TextMode(short mode)
RGBColor      GetPortHiliteColor(CGrafPtr port,RGBColor *hiliteColor);

Creating, Setting, Disposing of, and Accessing Pixel Maps

PixMapHandle  NewPixMap(void);
void          CopyPixMap(PixMapHandle srcPM,PixMapHandle dstPM);
void          SetPortPix(PixMapHandle pm);
void          DisposePixMap(PixMapHandle pm);
Rect          GetPixBounds(PixMapHandle pixMap,Rect *bounds);
short         GetPixDepth(PixMapHandle pixMap);

Creating, Setting and Disposing of Graphics Device Structures

GDHandle  NewGDevice(short refNum,long mode);
void      InitGDevice(short qdRefNum,long mode,GDHandle gdh);
void      SetDeviceAttribute(GDHandle gdh,short attribute,Boolean value);
void      SetGDevice(GDHandle gd);
void      DisposeGDevice(GDHandle gdh);

Getting the Available Graphics Devices

GDHandle  GetGDevice(void);
GDHandle  GetMainDevice(void);
GDHandle  GetNextDevice(GDHandle curDevice);
GDHandle  GetDeviceList(void);

Determining the Characteristics of a Video Device

Boolean  TestDeviceAttribute(GDHandle gdh,short attribute);
void     ScreenRes(short *scrnHRes,short *scrnVRes);

Changing the Pixel Depth of a Video Device

OSErr  SetDepth(GDHandle gd,short depth,short whichFlags,short flags);
short  HasDepth(GDHandle gd,short depth,short whichFlags,short flags);