Inside Macintosh: QuickDraw GX Objects /

Chapter 7 - View-Related Objects / View-Related Objects Reference

View Port Functions / Manipulating View Port Object Properties

GXGetViewPortTags

You can use the GXGetViewPortTags function to examine one or more of the tag objects associated with a view port object.

long GXGetViewPortTags(gxViewPort source, long tagType, 
                        long index, long count, gxTag items[]);

source

A reference to the view port whose tag list you want to examine.

tagType

The type of tag object to search for. A value of 0 indicates that you want to look for all tag types.

index

The (1-based) index of the first such tag reference to return.

count

The number of tag references to return.

items

An array to hold the returned tag references.

function result

The number of tag references found that fit the criteria.

DESCRIPTION

The GXGetViewPortTags function searches the tag list of the source view port object for references to tag objects with the tag type specified by the tagType parameter. If you specify 0 for the tagType parameter, the GXGetViewPortTags function searches all tag types.

You can use the index and the count parameters to specify which tag references of the appropriate type the GXGetViewPortTags function should return. The index parameter indicates the first tag reference to return and the count parameter indicates how many tag references to return. The index parameter must be greater than 0. The count parameter must be greater than 0 or equal to the gxSelectToEnd constant (-1), which indicates that all tag references (starting with the tag reference indicated by the index parameter) should be returned.

The function result is the number of tag references found that fit the criteria. If you pass a value other than nil for the items parameter, the GXGetViewPortTags function returns in it the tag references that were found.

Typically, you call this function once with a nil value for the items parameter to determine the number of matching tag references. Then you allocate an appropriately sized array and call the function a second time to obtain the references themselves.

ERRORS, WARNINGS, AND NOTICES

Errors
out_of_memory
invalid_viewPort_reference
index_is_less_than_one	(debugging version)
count_is_less_than_one	(debugging version)
Warnings
index_out_of_range
count_out_of_range

SEE ALSO

Tag objects are discussed in the chapter "Tag Objects" in this book.

To change the set of tag references associated with a view port, use the GXSetViewPortTags function, described next.