Texas Instruments TI89 Developer Guide - Page 630
CkValidDelta, CptDeltay, GR_WIN_VARS
UPC - 033317198566
View all Texas Instruments TI89 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 630 highlights
588 Appendix A: System Routines - Graphing CptDeltax Declaration: BYTE CptDeltax (GR_WIN_VARS * ptr) Category(ies): Graphing Description: Computes Window variable ∆x using the viewing window values and window width in the GR_WIN_VARS struct pointed to by ptr and sets the GR_DIRTY flag (ptr ->gr_win_flags & GR_DIRTY) if the newly computed ∆x is not equal to the old ∆x. CptDeltax verifies that there will be a unique x coordinate for each pixel column. Inputs: ptr - Pointer to the GR_WIN_VARS struct to use for viewing window values and window width (gr_active for the active graph window, gr_other for the second graph in two graph mode). Outputs: Returns 0 if ∆x could not be computed due to invalid viewing window values or if the new ∆x is so small that it will not insure unique values for each pixel column, otherwise returns 1. If valid, the new ∆x is stored in (ptr ->rngp)[GR_DELTAX]. Assumptions: Assumes the window width in ptr ->xmaxpix is correct. If the window size has been changed since the graph was last displayed, ptr ->xmaxpix will not have been updated, so the new ∆x will not be correct. In this case, ∆x will automatically be recomputed the next time the graph is displayed, using the correct window width. Side Effects: If the GR_DIRTY flag is set, the graph will be redrawn next time it is displayed. Availability: All versions of the TI-89 / TI-92 Plus. TI-89 / TI-92 Plus Differences: None See Also: CkValidDelta, CptDeltay Example: /* make sure deltax and deltay are correct */ if(gr_active->gr_win_flags & GR_DIRTY) /* viewing window values may have changed, recompute deltax and deltay */ if ( ! ( CptDeltax(gr_active) && CptDeltay(gr_active) ) ) ER_throw( ER_RANGE ); /* cannot compute valid deltax and deltay */ TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001