XtGetGC()XtGetGC()NameXtGetGC - obtain a read-only, sharable GC.
Synopsis
GC XtGetGC(object, value_mask, values)
Widget object;
XtGCMask value_mask;
XGCValues *values;
Inputs
object Specifies the object with which the GC is to be associated;
may be of class Object or any subclass thereof.
value_mask
Specifies which fields of the GC are to be filled in with
widget data.
values Specifies the actual values for this GC.
Returns
A read-only GC with fields as specified in value_mask and values.
DescriptionXtGetGC() returns a sharable, read-only GC with values as specified in
values for each bit set in value_mask. The GC is valid for the screen
and depth of object, or the nearest widget ancestor if object is not a
subclass of Core.
XtGetGC() shares only GCs in which all values in the GC are the same.
In particular, it does not use the value_mask provided to determine
which fields of the GC a widget considers relevant. value_mask is used
only to tell the server which fields should be filled in with widget
data and which it should fill in with default values.
Usage
The Intrinsics provide a mechanism whereby widgets can share a graphics
context (GC), reducing the number of GCs created and thereby improving
server performance. The mechanism is a simple caching scheme, and all
GCs obtained by means of this mechanism must be treated as read-only.
If a GC with modifiable fields is needed, in Release 4 or previous
releases the Xlib XCreateGC() function must be used. In Release 5,
XtAllocateGC() allows a widget to allocate a shared GC with modifiable
fields.
Generally only widgets will need to allocate GCs, though some applica‐
tions may also want to do so. When done with a shared GC, free it with
XtReleaseGC().
Structures
The XtGCMask type is defined as follows:
typedef unsigned long XtGCMask; /* Mask of values that are used by widget*/
Each of the symbols in the table below sets a single bit in an XtGC‐
Mask. The value_mask, argument is formed by combining these symbols
with the bitwise OR operator ( ):
GCArcMode GCFillRule GCLineWidth
GCBackground GCFillStyle GCPlaneMask
GCCapStyle GCFont GCStipple
GCClipMask GCForeground GCSubwindowMode
GCClipXOrigin GCFunction GCTile
GCClipYOrigin GCGraphicsExposures GCTileStipXOrigin
GCDashList GCJoinStyle GCTileStipYOrigin
GCDashOffset GCLineStyle
The XGCValues structure contains the GC fields:typedef struct {
int function; /* logical operation */
unsigned long plane_mask;/* plane mask */
unsigned long foreground;/* foreground pixel */
unsigned long background;/* background pixel */
int line_width; /* line width */
int line_style; /* LineSolid, LineOnOffDash,
LineDoubleDash */
int cap_style; /* CapNotLast, CapButt,
CapRound, CapProjecting */
int join_style; /* JoinMiter, JoinRound, JoinBevel */
int fill_style; /* FillSolid, FillTiled,
FillStippled, FillOpaqueStippled */
int fill_rule; /* EvenOddRule, WindingRule */
int arc_mode; /* ArcChord, ArcPieSlice */
Pixmap tile; /* tile pixmap for tiling operations */
Pixmap stipple; /* stipple 1 plane pixmap for stippling */
int ts_x_origin; /* offset for tile or
int ts_y_origin; * stipple operations */
Font font; /* default text font for text operations */
int subwindow_mode; /* ClipByChildren, IncludeInferiors */
Bool graphics_exposures;/* should exposures be generated? */
int clip_x_origin; /* origin for clipping */
int clip_y_origin;
Pixmap clip_mask; /* bitmap clipping; other calls for rects */
int dash_offset; /* patterned/dashed line information */
char dashes;
} XGCValues;
See AlsoXtAllocateGC(1), XtReleaseGC(1).
Xt - Graphics Context XtGetGC()
