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_header(PushMatrix,push and pop the current matrix stack)
_names(PushMatrix)
_names(PopMatrix)
.SH DESCRIPTION
There is a stack of matrices for each of the matrix modes.
In _const(MODELVIEW) mode,
the stack depth is at least 32.
In the other modes,
_const(COLOR), const(PROJECTION), and _const(TEXTURE),
the depth is at least 2.
The current matrix in any mode is the matrix on the top of the stack
for that mode.
.P
_cmnd pushes the current matrix stack down by one,
duplicating the current matrix.
That is,
after a _cmnd call,
the matrix on top of the stack is identical to the one below it.
.P
_cmnd(PopMatrix) pops the current matrix stack,
replacing the current matrix with the one below it on the stack. 
.P
Initially, each of the stacks contains one matrix, an identity matrix.
.P
It is an error to push a full matrix stack,
or to pop a matrix stack that contains only a single matrix.
In either case, the error flag is set
and no other change is made to GL state.
.SH ERRORS
_const(STACK_OVERFLOW) is generated if _cmnd(PushMatrix) is called while
the current matrix stack is full.
.P
_const(STACK_UNDERFLOW) is generated if _cmnd(PopMatrix) is called while
the current matrix stack contains only a single matrix.
.P
_const(INVALID_OPERATION) is generated if _cmnd(PushMatrix) or _cmnd(PopMatrix)
is executed between the execution of _cmnd(Begin)
and the corresponding execution of _cmnd(End).
.SH ASSOCIATED GETS
_cmnd(Get) with argument _const(MATRIX_MODE)
.br
_cmnd(Get) with argument _const(COLOR_MATRIX)
.br
_cmnd(Get) with argument _const(MODELVIEW_MATRIX)
.br
_cmnd(Get) with argument _const(PROJECTION_MATRIX)
.br
_cmnd(Get) with argument _const(TEXTURE_MATRIX)
.br
_cmnd(Get) with argument _const(COLOR_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(MODELVIEW_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(PROJECTION_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(TEXTURE_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(MAX_MODELVIEW_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(MAX_PROJECTION_STACK_DEPTH)
.br
_cmnd(Get) with argument _const(MAX_TEXTURE_STACK_DEPTH)
.SH SEE ALSO
_cmnd(Frustum), 
_cmnd(LoadIdentity),
_cmnd(LoadMatrix),
_cmnd(MatrixMode),
_cmnd(MultMatrix),
_cmnd(Ortho),
_cmnd(Rotate),
_cmnd(Scale),
_cmnd(Translate),
_cmnd(Viewport)