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IRIX Base Documentation 1998 November
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IRIX 6.5.2 Base Documentation November 1998.img
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catman
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g_man
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cat3
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underlay.z
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underlay
Wrap
Text File
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1998-10-20
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6KB
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133 lines
uuuunnnnddddeeeerrrrllllaaaayyyy((((3333GGGG)))) uuuunnnnddddeeeerrrrllllaaaayyyy((((3333GGGG))))
NNNNAAAAMMMMEEEE
uuuunnnnddddeeeerrrrllllaaaayyyy - allocates bitplanes for display of underlay colors
CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
vvvvooooiiiidddd uuuunnnnddddeeeerrrrllllaaaayyyy((((ppppllllaaaannnneeeessss))))
lllloooonnnngggg ppppllllaaaannnneeeessss;;;;
PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
_p_l_a_n_e_s expects the number of bitplanes to be allocated for underlay
colors. Valid values are 0 (the default), 2, 4, and 8.
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
The IRIS physical framebuffer is divided into four separate GL
framebuffers: normal, popup, overlay, underlay. Because a single
physical framebuffer is used to implement the four GL framebuffers,
bitplanes must be allocated among the GL framebuffers. uuuunnnnddddeeeerrrrllllaaaayyyy
specifies the number of bitplanes to be allocated to the underlay
framebuffer. uuuunnnnddddeeeerrrrllllaaaayyyy does not take effect immediately. Rather, it is
considered only when ggggccccoooonnnnffffiiiigggg is called, at which time all requests for
bitplane resources are resolved.
While only one of the four GL framebuffers can be drawn to at a time (see
ddddrrrraaaawwwwmmmmooooddddeeee), all four are displayed simultaneously. The decision of which
to display at each pixel is made based on the contents of the four
framebuffers at that pixel location, using the following hierarchical
rule:
_i_f the popup pixel contents are non-zero
_t_h_e_n display the popup bitplanes
_e_l_s_e _i_f overlay bitplanes are allocated AND
the overlay pixel contents are non-zero
_t_h_e_n display the overlay bitplanes
_e_l_s_e _i_f the normal pixel contents are non-zero OR
no underlay bitplanes are allocated
_t_h_e_n display the normal bitplanes
_e_l_s_e display the underlay bitplanes
Thus images drawn into the overlay framebuffer appear over images in the
normal framebuffer, and images drawn into the underlay framebuffer appear
under images in the normal framebuffer. Popup images appear over
everything else.
The default configuration of the underlay framebuffer is 0 bitplanes. To
make a change to this configuration other than to change the bitplane
size, the drawing mode must be UUUUNNNNDDDDEEEERRRRDDDDRRRRAAAAWWWW. For example, the underlay
framebuffer can be configured to be double buffered by calling
PPPPaaaaggggeeee 1111
uuuunnnnddddeeeerrrrllllaaaayyyy((((3333GGGG)))) uuuunnnnddddeeeerrrrllllaaaayyyy((((3333GGGG))))
ddddoooouuuubbbblllleeeebbbbuuuuffffffffeeeerrrr while draw mode is UUUUNNNNDDDDEEEERRRRDDDDRRRRAAAAWWWW.
On models that cannot support overlay and underlay bitplanes
simultaneously, calling uuuunnnnddddeeeerrrrllllaaaayyyy with a non-zero argument forces oooovvvveeeerrrrllllaaaayyyy
to zero. When simultaneous overlay and underlay operation is supported,
calling uuuunnnnddddeeeerrrrllllaaaayyyy may have no effect on the number of overlay bitplanes.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
doublebuffer, drawmode, gconfig, getgdesc, singlebuffer, underlay
NNNNOOOOTTTTEEEESSSS
This routine is available only in immediate mode.
IRIS-4D G, GT, and GTX models, and the Personal Iris, support only single
buffered, color map mode underlay bitplanes.
The Iris Indy supports 8 underlay single buffered bitplanes, if
configured with 24 bit normal color planes.
The Personal Iris supports 0 or 2 underlay bitplanes. There are no
overlay or underlay bitplanes in the minimum configuration of the
Personal Iris.
IRIS-4D GT and GTX models support 0, 2, or 4 underlay bitplanes. Because
4-bitplane allocation reduces the popup framebuffer to zero bitplanes,
however, its use is strongly discouraged. The window manager cannot
operate properly when no popup bitplanes are available.
IRIS-4D VGX models support 0, 2, 4, or 8 underlay bitplanes, either
single or double buffered, in color map mode only. The 4 and 8 bitplane
allocations utilize the alpha bitplanes, which must be present, and which
therefore are unavailable in draw mode NNNNOOOORRRRMMMMAAAALLLLDDDDRRRRAAAAWWWW.
Use ggggeeeettttggggddddeeeesssscccc to determine the maximum number of bitplanes supported for
the underlay framebuffer.
Iris Indigo does not support uuuunnnnddddeeeerrrrllllaaaayyyy so ggggeeeettttggggddddeeeesssscccc returns zero for the
number of underlay bitplanes on Iris Indigo.
BBBBUUUUGGGGSSSS
The Personal Iris does not support shade model GGGGOOOOUUUURRRRAAAAUUUUDDDD in the underlay
framebuffer.
PPPPaaaaggggeeee 2222