1Tk_CreateImageType(3) Tk Library Procedures Tk_CreateImageType(3)
2______________________________________________________________________________
6
8 Tk_CreateImageType, Tk_GetImageMasterData, Tk_InitImageArgs - define
9 new kind of image
10
12 #include <tk.h>
13 Tk_CreateImageType(typePtr)
15 ClientData │
17 Tk_GetImageMasterData(interp, name, typePtrPtr) │
18 Tk_InitImageArgs(interp, argc, argvPtr) │
20
22 Tk_ImageType *typePtr (in) │
23 Structure that defines the new │
24 type of image. Must be static: │
25 a pointer to this structure is │
26 retained by the image code. │
27 Tcl_Interp *interp (in) │
29 Interpreter in which image was │
30 created. │
31 CONST char *name (in) │
33 Name of existing image. │
34 Tk_ImageType **typePtrPtr (out) │
36 Points to word in which to store │
37 a pointer to type information │
38 for the given image, if it │
39 exists. │
40 int argc (in) │
42 Number of arguments │
43 char ***argvPtr (in/out) │
45 Pointer to argument list
46_________________________________________________________________
47
50 Tk_CreateImageType is invoked to define a new kind of image. An image
51 type corresponds to a particular value of the type argument for the
52 image create command. There may exist any number of different image
53 types, and new types may be defined dynamically by calling Tk_CreateIm‐
54 ageType. For example, there might be one type for 2-color bitmaps,
55 another for multi-color images, another for dithered images, another
56 for video, and so on.
57 The code that implements a new image type is called an image manager.
59 It consists of a collection of procedures plus three different kinds of
60 data structures. The first data structure is a Tk_ImageType structure,
61 which contains the name of the image type and pointers to five proce‐
62 dures provided by the image manager to deal with images of this type:
63 typedef struct Tk_ImageType {
64 char *name;
65 Tk_ImageCreateProc *createProc;
66 Tk_ImageGetProc *getProc;
67 Tk_ImageDisplayProc *displayProc;
68 Tk_ImageFreeProc *freeProc;
69 Tk_ImageDeleteProc *deleteProc;
70 } Tk_ImageType;
71 The fields of this structure will be described in later subsections of
72 this entry.
73 The second major data structure manipulated by an image manager is
75 called an image master; it contains overall information about a par‐
76 ticular image, such as the values of the configuration options speci‐
77 fied in an image create command. There will usually be one of these
78 structures for each invocation of the image create command.
79 The third data structure related to images is an image instance. There
81 will usually be one of these structures for each usage of an image in a
82 particular widget. It is possible for a single image to appear simul‐
83 taneously in multiple widgets, or even multiple times in the same wid‐
84 get. Furthermore, different instances may be on different screens or
85 displays. The image instance data structure describes things that may
86 vary from instance to instance, such as colors and graphics contexts
87 for redisplay. There is usually one instance structure for each -image
88 option specified for a widget or canvas item.
89 The following subsections describe the fields of a Tk_ImageType in more
91 detail.
92
95 typePtr->name provides a name for the image type. Once Tk_CreateIm‐
96 ageType returns, this name may be used in image create commands to cre‐
97 ate images of the new type. If there already existed an image type by
98 this name then the new image type replaces the old one.
99
102 In Tk 8.2 and earlier, the createProc below had a different signature.
103 If you want to compile an image type using the old interface which
104 should still run on all Tcl/Tk versions, compile it with the flag
105 -DUSE_OLD_IMAGE. Further on, if you are using Stubs, you need to call
106 the function Tk_InitImageArgs(interp, argc, &argv) first in your cre‐
107 ateProc. See below for a description of this function.
108
111 typePtr->createProc provides the address of a procedure for Tk to call
112 whenever image create is invoked to create an image of the new type.
113 typePtr->createProc must match the following prototype:
114 typedef int Tk_ImageCreateProc(
115 Tcl_Interp *interp,
116 char *name,
117 int objc,
118 Tcl_Obj *CONST objv[],
119 Tk_ImageType *typePtr,
120 Tk_ImageMaster master,
121 ClientData *masterDataPtr);
122 The interp argument is the interpreter in which the image command was
123 invoked, and name is the name for the new image, which was either spec‐
124 ified explicitly in the image command or generated automatically by the
125 image command. The objc and objv arguments describe all the configura‐
126 tion options for the new image (everything after the name argument to
127 image). The master argument is a token that refers to Tk's information
128 about this image; the image manager must return this token to Tk when
129 invoking the Tk_ImageChanged procedure. Typically createProc will
130 parse objc and objv and create an image master data structure for the
131 new image. createProc may store an arbitrary one-word value at *mas‐
132 terDataPtr, which will be passed back to the image manager when other
133 callbacks are invoked. Typically the value is a pointer to the master
134 data structure for the image.
135 If createProc encounters an error, it should leave an error message in
137 interp->result and return TCL_ERROR; otherwise it should return
138 TCL_OK.
139 createProc should call Tk_ImageChanged in order to set the size of the
141 image and request an initial redisplay.
142
145 typePtr->getProc is invoked by Tk whenever a widget calls Tk_GetImage
146 to use a particular image. This procedure must match the following
147 prototype:
148 typedef ClientData Tk_ImageGetProc(
149 Tk_Window tkwin,
150 ClientData masterData);
151 The tkwin argument identifies the window in which the image will be
152 used and masterData is the value returned by createProc when the image
153 master was created. getProc will usually create a data structure for
154 the new instance, including such things as the resources needed to dis‐
155 play the image in the given window. getProc returns a one-word token
156 for the instance, which is typically the address of the instance data
157 structure. Tk will pass this value back to the image manager when
158 invoking its displayProc and freeProc procedures.
159
162 typePtr->displayProc is invoked by Tk whenever an image needs to be
163 displayed (i.e., whenever a widget calls Tk_RedrawImage). displayProc
164 must match the following prototype:
165 typedef void Tk_ImageDisplayProc(
166 ClientData instanceData,
167 Display *display,
168 Drawable drawable,
169 int imageX,
170 int imageY,
171 int width,
172 int height,
173 int drawableX,
174 int drawableY);
175 The instanceData will be the same as the value returned by getProc when
176 the instance was created. display and drawable indicate where to dis‐
177 play the image; drawable may be a pixmap rather than the window speci‐
178 fied to getProc (this is usually the case, since most widgets double-
179 buffer their redisplay to get smoother visual effects). imageX,
180 imageY, width, and height identify the region of the image that must be
181 redisplayed. This region will always be within the size of the image
182 as specified in the most recent call to Tk_ImageChanged. drawableX and
183 drawableY indicate where in drawable the image should be displayed;
184 displayProc should display the given region of the image so that point
185 (imageX, imageY) in the image appears at (drawableX, drawableY) in
186 drawable.
187
190 typePtr->freeProc contains the address of a procedure that Tk will
191 invoke when an image instance is released (i.e., when Tk_FreeImage is
192 invoked). This can happen, for example, when a widget is deleted or a
193 image item in a canvas is deleted, or when the image displayed in a
194 widget or canvas item is changed. freeProc must match the following
195 prototype:
196 typedef void Tk_ImageFreeProc(
197 ClientData instanceData,
198 Display *display);
199 The instanceData will be the same as the value returned by getProc when
200 the instance was created, and display is the display containing the
201 window for the instance. freeProc should release any resources associ‐
202 ated with the image instance, since the instance will never be used
203 again.
204
207 typePtr->deleteProc is a procedure that Tk invokes when an image is
208 being deleted (i.e. when the image delete command is invoked). Before
209 invoking deleteProc Tk will invoke freeProc for each of the image's
210 instances. deleteProc must match the following prototype:
211 typedef void Tk_ImageDeleteProc(
212 ClientData masterData);
213 The masterData argument will be the same as the value stored in *mas‐
214 terDataPtr by createProc when the image was created. deleteProc should
215 release any resources associated with the image.
216
219 The procedure Tk_GetImageMasterData may be invoked to retrieve informa‐ │
220 tion about an image. For example, an image manager can use this proce‐ │
221 dure to locate its image master data for an image. If there exists an │
222 image named name in the interpreter given by interp, then *typePtrPtr │
223 is filled in with type information for the image (the typePtr value │
224 passed to Tk_CreateImageType when the image type was registered) and │
225 the return value is the ClientData value returned by the createProc │
226 when the image was created (this is typically a pointer to the image │
227 master data structure). If no such image exists then NULL is returned │
228 and NULL is stored at *typePtrPtr.
229
232 The function Tk_InitImageArgs converts the arguments of the createProc │
233 from objects to strings when necessary. When not using stubs, not using │
234 the old interface, or running under an older (pre-8.3) Tk version, this │
235 function has no effect. This function makes porting older image han‐ │
236 dlers to the new interface a lot easier: After running this function, │
237 the arguments are guaranteed to be in string format, no matter how Tk │
238 deliverd them. │
239
242 Tk_ImageChanged, Tk_GetImage, Tk_FreeImage, Tk_RedrawImage, Tk_Size‐ │
243 OfImage │
244
247 image manager, image type, instance, master │
248Tk 8.3 Tk_CreateImageType(3)