X Version 11 (Release 5)

XtAllocateGC(Xt)

XtAllocateGC -- obtain shareable GC with modifiable fields

Syntax

GC XtAllocateGC(object, depth, value_mask, values, dynamic_mask, unused_mask)
      Widget object;
      Cardinal depth;
      XtGCMask value_mask;
      XGCValues *values;
      XtGCMask dynamic_mask;
      XtGCMask unused_mask;

Arguments

depth: Specifies the depth for which the returned GC is valid, or 0.
dynamic_mask: Specifies fields of the GC that may be modified by the caller.
object: Specifies an object, giving the screen for which the returned GC is valid. Must be of class Object or any subclass thereof.
unused_mask: Specifies fields of the GC that will not be used by the caller.
values: Specifies the values for the initialized fields.
value_mask: Specifies fields of the GC that are initialized from values.

Description

The Intrinsics provide a mechanism whereby cooperating objects can share a graphics context (GC), thereby reducing both the number of GCs created and the total number of server calls in any given application. The mechanism is a simple caching scheme and allows for clients to declare both modifiable and nonmodifiable fields of the shared GCs.

The XtAllocateGC function returns a shareable GC that may be modified by the client. The object field of the specified widget or of the nearest widget ancestor of the specified object and the specified depth argument supply the root and drawable depths for which the GC is to be valid. If depth is zero the depth is taken from the depth field of the specified widget or of the nearest widget ancestor of the specified object.

The value_mask argument specifies fields of the GC that will be initialized with the respective member of the values structure. The dynamic_mask argument specifies fields that the caller intends to modify during program execution. The caller must insure that the corresponding GC field is set prior to each use of the GC. The unused_mask argument specifies fields of the GC that are of no interest to the caller. The caller may make no assumptions about the contents of any fields specified in unused_mask. The caller may assume that at all times all fields not specified in either dynamic_mask or unused_mask have their default value if not specified in value_mask or the value specified by values. If a field is specified in both value_mask and dynamic_mask, the effect is as if it were specified only in dynamic_mask and then immediately set to the value in values. If a field is set in unused_mask and also in either value_mask or dynamic_mask, the specification in unused_mask is ignored.

XtAllocateGC tries to minimize the number of unique GCs created by comparing the arguments with those of previous calls and returning an existing GC when there are no conflicts. XtAllocateGC may modify and return an existing GC if it was allocated with a nonzero unused_mask.

XtAllocateGC(Xt)

Syntax

Arguments

Description

See also