Manual Pages for UNIX Darwin command on man Tk

Manual Pages for UNIX Darwin command on man Tk_CreateImageType

TkCreateImageType(3) Tk Library Procedures TkCreateImageType(3)

NAME

TkCreateImageType, TkGetImageMasterData, TkInitImageArgs - define

new kind of image

SYNOPSIS

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TTkkCCrreeaatteeIImmaaggeeTTyyppee(typePtr) ClientData | TTkkGGeettIImmaaggeeMMaasstteerrDDaattaa(interp, name, typePtrPtr) | TTkkIInniittIImmaaggeeAArrggss(interp, argc, argvPtr) | AARRGGUUMMEENNTTSS |

TkImageType *type- |

Ptr (in) | | Structure that defines the new | type of image. Must be static: | a pointer to this structure is | retained by the image code. | TclInterp *interp (in) || Interpreter in which image was | created. | CONST | char *name (in) | | Name of existing image. |

TkImageType **typeP- |

trPtr (out) | | Points to word in which to store | a pointer to type information | for the given image, if it | exists. | int argc (in) || Number of arguments | char ***argvPtr (in/out) || Pointer to argument list

DESCRIPTION

TTkkCCrreeaatteeIImmaaggeeTTyyppee is invoked to define a new kind of image. An image type corresponds to a particular value of the type argument for the iimmaaggee ccrreeaattee command. There may exist any number of different image

types, and new types may be defined dynamically by calling TTkkCCrreeaatteeIImm-

aaggeeTTyyppee. For example, there might be one type for 2-color bitmaps,

another for multi-color images, another for dithered images, another

for video, and so on. The code that implements a new image type is called an image manager. It consists of a collection of procedures plus three different kinds of data structures. The first data structure is a TkImageType structure,

which contains the name of the image type and pointers to five proce-

dures provided by the image manager to deal with images of this type: typedef struct TkImageType { char *name; TkImageCreateProc *createProc; TkImageGetProc *getProc; TkImageDisplayProc *displayProc; TkImageFreeProc *freeProc; TkImageDeleteProc *deleteProc; } TkImageType; The fields of this structure will be described in later subsections of this entry. The second major data structure manipulated by an image manager is

called an image master; it contains overall information about a par-

ticular image, such as the values of the configuration options speci-

fied in an iimmaaggee ccrreeaattee command. There will usually be one of these structures for each invocation of the iimmaaggee ccrreeaattee command. The third data structure related to images is an image instance. There will usually be one of these structures for each usage of an image in a

particular widget. It is possible for a single image to appear simul-

taneously in multiple widgets, or even multiple times in the same wid-

get. Furthermore, different instances may be on different screens or displays. The image instance data structure describes things that may vary from instance to instance, such as colors and graphics contexts

for redisplay. There is usually one instance structure for each -iimmaaggee

option specified for a widget or canvas item. The following subsections describe the fields of a TkImageType in more detail.

NAME

typePtr->name provides a name for the image type. Once TTkkCCrreeaatteeIImm-

aaggeeTTyyppee returns, this name may be used in iimmaaggee ccrreeaattee commands to cre-

ate images of the new type. If there already existed an image type by this name then the new image type replaces the old one. PPOORRTTAABBIILLIITTYY In Tk 8.2 and earlier, the createProc below had a different signature. If you want to compile an image type using the old interface which should still run on all Tcl/Tk versions, compile it with the flag

-DUSEOLDIMAGE. Further on, if you are using Stubs, you need to call

the function TkInitImageArgs(interp, argc, &argv) first in your cre-

ateProc. See below for a description of this function. CCRREEAATTEEPPRROOCC

typePtr->createProc provides the address of a procedure for Tk to call

whenever iimmaaggee ccrreeaattee is invoked to create an image of the new type.

typePtr->createProc must match the following prototype:

typedef int TkImageCreateProc( TclInterp *interp, char *name, int objc, TclObj *CONST objv[], TkImageType *typePtr, TkImageMaster master, ClientData *masterDataPtr); The interp argument is the interpreter in which the iimmaaggee command was

invoked, and name is the name for the new image, which was either spec-

ified explicitly in the iimmaaggee command or generated automatically by the

iimmaaggee command. The objc and objv arguments describe all the configura-

tion options for the new image (everything after the name argument to iimmaaggee). The master argument is a token that refers to Tk's information about this image; the image manager must return this token to Tk when invoking the TTkkIImmaaggeeCChhaannggeedd procedure. Typically createProc will parse objc and objv and create an image master data structure for the

new image. createProc may store an arbitrary one-word value at *mas-

terDataPtr, which will be passed back to the image manager when other callbacks are invoked. Typically the value is a pointer to the master data structure for the image. If createProc encounters an error, it should leave an error message in

interp->result and return TTCCLLEERRRROORR; otherwise it should return

TTCCLLOOKK. createProc should call TTkkIImmaaggeeCChhaannggeedd in order to set the size of the image and request an initial redisplay. GGEETTPPRROOCC

typePtr->getProc is invoked by Tk whenever a widget calls TTkkGGeettIImmaaggee

to use a particular image. This procedure must match the following prototype: typedef ClientData TkImageGetProc( TkWindow tkwin, ClientData masterData); The tkwin argument identifies the window in which the image will be used and masterData is the value returned by createProc when the image master was created. getProc will usually create a data structure for

the new instance, including such things as the resources needed to dis-

play the image in the given window. getProc returns a one-word token

for the instance, which is typically the address of the instance data structure. Tk will pass this value back to the image manager when invoking its displayProc and freeProc procedures. DDIISSPPLLAAYYPPRROOCC

typePtr->displayProc is invoked by Tk whenever an image needs to be

displayed (i.e., whenever a widget calls TTkkRReeddrraawwIImmaaggee). displayProc must match the following prototype: typedef void TkImageDisplayProc( ClientData instanceData, Display *display, Drawable drawable, int imageX, int imageY, int width, int height, int drawableX, int drawableY); The instanceData will be the same as the value returned by getProc when

the instance was created. display and drawable indicate where to dis-

play the image; drawable may be a pixmap rather than the window speci-

fied to getProc (this is usually the case, since most widgets double-

buffer their redisplay to get smoother visual effects). imageX, imageY, width, and height identify the region of the image that must be redisplayed. This region will always be within the size of the image as specified in the most recent call to TTkkIImmaaggeeCChhaannggeedd. drawableX and drawableY indicate where in drawable the image should be displayed; displayProc should display the given region of the image so that point (imageX, imageY) in the image appears at (drawableX, drawableY) in drawable. FFRREEEEPPRROOCC

typePtr->freeProc contains the address of a procedure that Tk will

invoke when an image instance is released (i.e., when TTkkFFrreeeeIImmaaggee is invoked). This can happen, for example, when a widget is deleted or a image item in a canvas is deleted, or when the image displayed in a widget or canvas item is changed. freeProc must match the following prototype: typedef void TkImageFreeProc( ClientData instanceData, Display *display); The instanceData will be the same as the value returned by getProc when the instance was created, and display is the display containing the

window for the instance. freeProc should release any resources associ-

ated with the image instance, since the instance will never be used again. DDEELLEETTEEPPRROOCC

typePtr->deleteProc is a procedure that Tk invokes when an image is

being deleted (i.e. when the iimmaaggee ddeelleettee command is invoked). Before invoking deleteProc Tk will invoke freeProc for each of the image's instances. deleteProc must match the following prototype: typedef void TkImageDeleteProc( ClientData masterData);

The masterData argument will be the same as the value stored in *mas-

terDataPtr by createProc when the image was created. deleteProc should release any resources associated with the image. TTKKGGEETTIIMMAAGGEEMMAASSTTEERRDDAATTAA

The procedure TTkkGGeettIImmaaggeeMMaasstteerrDDaattaa may be invoked to retrieve informa- |

tion about an image. For example, an image manager can use this proce- |

dure to locate its image master data for an image. If there exists an | image named name in the interpreter given by interp, then *typePtrPtr | is filled in with type information for the image (the typePtr value | passed to TTkkCCrreeaatteeIImmaaggeeTTyyppee when the image type was registered) and | the return value is the ClientData value returned by the createProc | when the image was created (this is typically a pointer to the image | master data structure). If no such image exists then NULL is returned | and NULL is stored at *typePtrPtr. TTKKIINNIITTIIMMAAGGEEAARRGGSS The function TTkkIInniittIImmaaggeeAArrggss converts the arguments of the ccrreeaatteePPrroocc | from objects to strings when necessary. When not using stubs, not using |

the old interface, or running under an older (pre-8.3) Tk version, this |

function has no effect. This function makes porting older image han- |

dlers to the new interface a lot easier: After running this function, | the arguments are guaranteed to be in string format, no matter how Tk | deliverd them. |