Appendix A: System Routines — Graphing
601
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
gr_xres_pixel
Declaration:
USHORT
gr_xres_pixel
(USHORT
pixel
, BYTE
f
)
Category:
Graphing
Description:
Finds the first pixel column number greater than or equal to
pixel
that is a
multiple of the graph system variable xres. This is a valid point to be plotted
on a function graph which only computes values at xres multiples. If
f
is not
0,
gr_active->panshift
is added to
pixel
before determining the output
pixel column number. This is only necessary if panning may have occurred,
since the xres multiples in function graphing are relative to the original
viewing window, which may be different from the current viewing window.
For example, column 0 is always computed when a function graph is first
drawn, but after panning left or right, the current column 0 may not have a
computed point on it anymore depending on the xres value. So to find a
column on a valid multiple of xres after panning,
gr_active->panshift
must
be taken into account.
Inputs:
pixel
— Pixel column number. The leftmost column is column 0 in all
graph windows.
f
— If
f
is 0,
gr_active->panshift
is assumed to be 0 and nothing is
added to
pixel
before the computation occurs. If
f
is not 0,
gr_active->panshift
is added to
pixel
before computation.
Outputs:
The first pixel column number greater than or equal to
pixel
that is a
multiple of xres. This pixel is valid to be a computed point on a function
graph even if it is currently off-screen, as is the case when the rightmost
column in a function graph is not a multiple of xres and a point beyond the
graph must be computed in order to complete the graph to the edge of the
window.
Assumptions:
The current graph mode is function mode.
Side Effects:
None
Availability:
All versions of the TI-89 / TI-92 Plus.
TI
-
89 / TI
-
92 Plus
Differences:
None
See Also:
None
Example:
/* Find the first increment of xres >= rightmost column as last point to compute. */
lastpix = gr_xres_pixel(gr_active->xmaxpix, 0); /* last pt to cpt for func graph */
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