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1.1 root 1: .TH MOVETO 3L "630 MTG"
2: .SH NAME
3: moveto, sPtCurrent \- change and return the value current screen point
4: .SH SYNOPSIS
5: .ft B
6: #include <dmd.h>
7: .sp
8: void moveto (p)
9: .br
10: Point p;
11: .sp
12: \f3Point sPtCurrent ( )\f1
13: .sp
14: \f3extern int didmoveto;\f1
15: .ft R
16: .SH DESCRIPTION
17: These functions can be used to change or return the value
18: of the current screen point. The current screen point is simply a place holder
19: that applications can use to manage current screen position.
20: For example, the \fIlputchar\fR function uses
21: .I sPtCurrent
22: to find the point at which to print the next character and uses
23: .I moveto
24: to update the current screen point after it prints the character.
25:
26: The current screen point is similar to but distinct
27: from \fIPtCurrent\fR (see \fIglobals\fR(3R)). The primary difference is that
28: the current screen point is stored in screen coordinates, and
29: the
30: \fIPtCurrent\fR is stored in window coordinates (see \fItransform\fR(3R)).
31: This makes the
32: current screen point easier to deal with for applications that want to
33: work completely in screen coordinates.
34:
35: The \fImoveto\fR function will move the current screen
36: point to the point \fIp\fR. The \fIsPtCurrent\fR
37: function returns the value of the current screen point.
38:
39: The current screen point is actually stored in the variable
40: P->scurpt. It is stored as an offset from Drect.origin
41: (i.e., sub[p, Drect.origin]). Note that this refers only to internal
42: representation. The functions \fImoveto\fR and \fIsPtCurrent\fR work in actual
43: screen coordinates and translate the offset on each call.
44:
45: Storing the current screen point as
46: an offset from Drect.origin has the advantage that successive calls to
47: \fIsPtCurrent\fR will return the proper position within a window even if the
48: window was moved between calls.
49:
50: .bp
51: Reshapes of a window between successive calls to \fIsPtCurrent\fR are handled
52: as follows. If the offset of the current screen point from Drect.origin is
53: still within the window
54: after the reshape, \fIsPtCurrent\fR will
55: return the current screen point within the new window at the same offset from
56: Drect.origin that existed in the old window. If the offset from Drect.origin
57: is no longer within the window (i.e., the window was reshaped smaller),
58: \fIsPtCurrent\fR will return Drect.origin as the current screen point.
59: If an application wants to handle reshape more
60: elegantly, it can use the following code fragment after each call to the
61: \fIwait\fR function. This
62: code fragment will cause the current screen point to move to the upper
63: left-hand corner of the window after a reshape.
64: .PP
65: .RS 3
66: .ft CM
67: .nf
68: if(P->state&RESHAPED) {
69: if(!(P->state&MOVED))
70: moveto(Drect.origin);
71: P->state &= ~(MOVED|RESHAPED);
72: }
73: .fi
74: .ft R
75: .RE
76: .PP
77: The current screen point must be initialized with the
78: \fImoveto\fR function before \fIsPtCurrent\fR is called the first time.
79: Library routines which use this facility can check if initialization is
80: necessary by looking at the global variable \fIdidmoveto\fR each time they
81: are called. This variable will be set to 0 if \fImoveto\fR has not
82: been called. An example below shows how the \fIdidmoveto\fR
83: variable is used to determine if initialization is necessary within a
84: simple putchar function.
85: .SH EXAMPLES
86: There are two types of users of the current screen point. The first
87: type of user is calling existent library routines such as \fIlprintf\fR
88: and \fIlputchar\fR, and is only interested in using the
89: \fImoveto\fR function to control the library routines.
90: The following code fragment illustrates how \fImoveto\fR can be used
91: with \fIlprintf\fR to display a prompt at the bottom of the window.
92: .PP
93: .RS 3
94: .ft CM
95: .nf
96: .S -2
97: #include <dmd.h>
98: #include <font.h>
99:
100: extern Point fPt();
101: Point p;
102:
103: p = fPt( Drect.origin.x,
104: Drect.corner.y - FONTHEIGHT(largefont) );
105: moveto(p);
106: lprintf("Choose an Option> ");
107: .fi
108: .ft R
109: .S +2
110: .RE
111: .bp
112: .PP
113: The second type of user of the current screen point is writing
114: new library routines which use this facility. The following example
115: shows how to accomplish this by implementing a simple putchar routine.
116: In the example below, didmoveto is checked first
117: to see if initialization of the current point is required. Then the code
118: obtains
119: the value of the current screen point, prints a character, and updates
120: the current screen point for the next call to myputchar.
121: .PP
122: .RS 3
123: .ft CM
124: .nf
125: myputchar(c)
126: char c;
127: {
128: extern int didmoveto;
129: extern Point sPtCurrent();
130: extern Point string();
131: char s[2];
132: Point curpos;
133:
134: s[0] = c;
135: s[1] = '\e0';
136:
137: if(!didmoveto)
138: moveto(Drect.origin);
139:
140: curpos = sPtCurrent();
141: curpos = string(&largefont, s, &display,
142: curpos, F_STORE);
143: moveto(curpos);
144:
145: }
146: .fi
147: .ft R
148: .RE
149: .SH SEE ALSO
150: globals(3R), jmove(3R), lprintf(3L), lputchar(3L),
151: resources(3R), structures(3R), transform(3R/3L).
152: .SH BUGS
153: The \fBdidmoveto\fR initialization scheme will not work with
154: shared text applications because \fIdidmoveto\fR is a global variable shared
155: by all invocations of a shared text application. Shared text applications
156: must explicitly initialize the current screen point by calling
157: \fImoveto\fR.
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