1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
|
{
This file is part of the Free Pascal run time library.
Copyright (c) 2003 by the Free Pascal development team
Clipping support.
See the file COPYING.FPC, included in this distribution,
for details about the copyright.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
**********************************************************************}
{$mode objfpc}{$h+}
unit Clipping;
interface
uses classes;
procedure SortRect (var rect : TRect);
procedure SortRect (var left,top, right,bottom : integer);
function PointInside (const x,y:integer; bounds:TRect) : boolean;
procedure CheckRectClipping (ClipRect:TRect; var Rect:Trect);
procedure CheckRectClipping (ClipRect:TRect; var x1,y1, x2,y2 : integer);
procedure CheckLineClipping (ClipRect:TRect; var x1,y1, x2,y2 : integer);
implementation
procedure SortRect (var rect : TRect);
begin
with rect do
SortRect (left,top, right,bottom);
end;
procedure SortRect (var left,top, right,bottom : integer);
var r : integer;
begin
if left > right then
begin
r := left;
left := right;
right := r;
end;
if top > bottom then
begin
r := top;
top := bottom;
bottom := r;
end;
end;
function PointInside (const x,y:integer; bounds:TRect) : boolean;
begin
SortRect (bounds);
with Bounds do
result := (x >= left) and (x <= right) and
(y >= bottom) and (y <= top);
end;
procedure CheckRectClipping (ClipRect:TRect; var Rect:Trect);
begin
with ClipRect do
CheckRectClipping (ClipRect, left,top,right,bottom);
end;
procedure CheckRectClipping (ClipRect:TRect; var x1,y1, x2,y2 : integer);
procedure ClearRect;
begin
x1 := -1;
x2 := -1;
y1 := -1;
y2 := -1;
end;
begin
SortRect (ClipRect);
SortRect (x1,y1, x2,y2);
with ClipRect do
begin
if ( x1 < Left ) then // left side needs to be clipped
x1 := left;
if ( x2 > right ) then // right side needs to be clipped
x2 := right;
if ( y1 < top ) then // top side needs to be clipped
y1 := top;
if ( y2 > bottom ) then // bottom side needs to be clipped
y2 := bottom;
if (x1 > x2) or (y1 < y2) then
ClearRect;
end;
end;
procedure CheckLineClipping (ClipRect:TRect; var x1,y1, x2,y2 : integer);
var a,b : single;
Calculated : boolean;
xdiff,n : integer;
procedure CalcLine;
begin
if not Calculated then
begin
xdiff := (x1-x2);
a := (y1-y2) / xdiff;
b := (x1*y2 - x2*y1) / xdiff;
Calculated := true;
end;
end;
procedure ClearLine;
begin
x1 := -1;
y1 := -1;
x2 := -1;
y2 := -1;
end;
begin
Calculated := false;
SortRect (ClipRect);
xdiff := (x1-x2);
with ClipRect do
if xdiff = 0 then
begin // vertical line
if y1 > bottom then
y1 := bottom
else if y1 < top then
y1 := top;
if y2 > bottom then
y2 := bottom
else if y2 < top then
y2 := top;
end
else if (y1-y2) = 0 then
begin // horizontal line
if x1 < left then
x1 := left
else if x1 > right then
x1 := right;
if x2 < left then
x2 := left
else if x2 > right then
x2 := right;
end
else
if ( (y1 < top) and (y2 < top) ) or
( (y1 > bottom) and (y2 > bottom) ) or
( (x1 > right) and (x2 > right) ) or
( (x1 < left) and (x2 < left) ) then
ClearLine // completely outside ClipRect
else
begin
if (y1 < top) or (y2 < top) then
begin
CalcLine;
n := round ((top - b) / a);
if (n >= left) and (n <= right) then
if (y1 < top) then
begin
x1 := n;
y1 := top;
end
else
begin
x2 := n;
y2 := top;
end;
end;
if (y1 > bottom) or (y2 > bottom) then
begin
CalcLine;
n := round ((bottom - b) / a);
if (n >= left) and (n <= right) then
if (y1 > bottom) then
begin
x1 := n;
y1 := bottom;
end
else
begin
x2 := n;
y2 := bottom;
end;
end;
if (x1 < left) or (x2 < left) then
begin
CalcLine;
n := round ((left * a) + b);
if (n <= bottom) and (n >= top) then
if (x1 < left) then
begin
x1 := left;
y1 := n;
end
else
begin
x2 := left;
y2 := n;
end;
end;
if (x1 > right) or (x2 > right) then
begin
CalcLine;
n := round ((right * a) + b);
if (n <= bottom) and (n >= top) then
if (x1 > right) then
begin
x1 := right;
y1 := n;
end
else
begin
x2 := right;
y2 := n;
end;
end;
end;
end;
end.
|
