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Дата изменения: Unknown Дата индексирования: Sat Jan 17 05:27:08 2009 Кодировка: Поисковые слова: galaxy cluster |
The active elements in this program are
two text input fields, two analog valuators and a QUIT button.
The text fields and valuators produce the parameters A and B which are used in the evaluation of the expression A*sin(B*x). Every time a parameter is changed, the corresponding graph is drawn. (After any previous graph is erased.)
Drawing is done in so-called XOR-mode. This facilitates erasing previous graphs: the graph is erased by simply drawing it again.
As an exercise you might want to replace the function by an other one with more parameters. Or you can add a menu which enables the user to choose the graph's colour.
The next example shows how cursor interaction
can be added to the plot field.
/* example3.c -XT */ #define NPTS 100 #include "stddef.h" #include "math.h" #include "gipsyc.h" #include "cmain.h" #include "init.h" #include "finis.h" #include "userfio.h" #include "pgplot.h" #include "ggi.h" static float a=1.0, b=1.0; static float xmin=0.0, xmax=6.2831853; static float ymin=-1.1, ymax=1.1; /* * Plot initialization routine */ static void initplot(char *plotname) { fint zero=0, one=1, green=3; pgbeg_c(&zero, tofchar(plotname), &one, &one); /* open plot device */ pgenv_c(&xmin, &xmax, &ymin, &ymax, &zero, &zero); /* draw frame */ pgsci_c(&green); /* set colour index */ GgiPlotXor(TRUE); /* XOR plot mode */ } /* * Plot drawing routine */ static void drawplot(void) { static float xvals[NPTS], yvals[NPTS]; static bool present=FALSE; float incr=(xmax-xmin)/NPTS; int i; fint npts=NPTS; if (present) pgline_c(&npts, xvals, yvals); /* erase previous graph */ else present=TRUE; for (i=0; i<npts; i++) { float x=xmin+i*incr; xvals[i] = x; yvals[i] = a*sin(b*x); } /* calculate new graph */ pgline_c(&npts, xvals, yvals); /* draw new graph */ } /* * Keyword handler for QUIT= */ static void quit(ident id, char *key, int code, void *arg) { bool finished=toflog(FALSE); (void)userflog(&finished, 1, 2, key, " "); if (tobool(finished)) { cancel_c(tofchar(key)); finis_c(); } } /* * Keyword handler for both A= and B= */ static void number(ident id, char *key, int code, void *parameter) { (void)userfreal((float*)parameter, 1, 2, key, " "); drawplot(); } /* * Main program */ MAIN_PROGRAM_ENTRY { ident button, text1, text2, gauge1, gauge2, plot, label; init_c(); /* * Specify explicit layout and postponed realization. */ GgiAutoLayout(FALSE); /* layout done explicitly by program */ GgiPostponeRealize(TRUE); /* show after all elements have been positioned */ /* * Create elements. */ button = GgiButton("QUIT=", "Terminate program"); text1 = GgiTextField("A=", NULL, 10); text2 = GgiTextField("B=", NULL, 10); gauge1 = GgiGauge("A=", NULL, 200, -1.0, 1.0); gauge2 = GgiGauge("B=", NULL, 200, 0.5, 5.0); plot = GgiPlotField("MYPLOT", 400, 300); label = GgiLabel("y = A*sin(B*x)"); /* * Modify some elements' properties. */ (void)GgiSetLabel(gauge1, " ", 1); /* suppress gauge's keyword label */ (void)GgiSetLabel(gauge2, " ", 1); /* suppress gauge's keyword label */ /* * Position the elements. */ GgiSetPosition(button, 0, NULL, 0, NULL); /* top left */ GgiSetPosition(plot, 0, NULL, 30, button); /* right below button */ GgiSetPosition(label, -(GgiWidth(plot)+GgiWidth(label))/2, plot, -GgiHeight(plot)-GgiHeight(label)-5, plot); /* above plot */ GgiSetPosition(text1, 0, NULL, 10, plot); /* below plot */ GgiSetPosition(gauge1, 0, text1, 10, plot); /* right of text1 */ GgiSetPosition(text2, 0, NULL, 0, text1); /* below text1 */ GgiSetPosition(gauge2, 0, text2, 0, text1); /* right of text1 */ /* * Show what has been created until now. */ GgiRealize(); /* * Initialize plot field */ initplot("MYPLOT"); /* must be done after GgiRealize call */ /* * Register keyword callbacks. */ (void)ScheduleKeyevent(quit, "QUIT=", KEYCHANGE, NULL); (void)ScheduleKeyevent(number, "A=", KEYCHANGE, &a); (void)ScheduleKeyevent(number, "B=", KEYCHANGE, &b); /* * Initialize parameters causing first plot te be drawn */ if (!TriggerKey("A=")) wkeyf("A=0.7"); /* use "macro" values if present, */ if (!TriggerKey("B=")) wkeyf("B=1.0"); /* ... otherwise program defaults */ /* * Put things into action. */ MainLoop(); }
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