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
|
unit sdlticks;
{
$Id: sdlticks.pas,v 1.2 2006/11/08 08:22:48 savage Exp $
}
{******************************************************************************}
{ }
{ JEDI-SDL : Pascal units for SDL - Simple DirectMedia Layer }
{ SDL GetTicks Class Wrapper }
{ }
{ }
{ The initial developer of this Pascal code was : }
{ Dominique Louis <Dominique@SavageSoftware.com.au> }
{ }
{ Portions created by Dominique Louis are }
{ Copyright (C) 2004 - 2100 Dominique Louis. }
{ }
{ }
{ Contributor(s) }
{ -------------- }
{ Dominique Louis <Dominique@SavageSoftware.com.au> }
{ }
{ Obtained through: }
{ Joint Endeavour of Delphi Innovators ( Project JEDI ) }
{ }
{ You may retrieve the latest version of this file at the Project }
{ JEDI home page, located at http://delphi-jedi.org }
{ }
{ The contents of this file are used with permission, subject to }
{ the Mozilla Public License Version 1.1 (the "License"); you may }
{ not use this file except in compliance with the License. You may }
{ obtain a copy of the License at }
{ http://www.mozilla.org/MPL/MPL-1.1.html }
{ }
{ Software distributed under the License is distributed on an }
{ "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or }
{ implied. See the License for the specific language governing }
{ rights and limitations under the License. }
{ }
{ Description }
{ ----------- }
{ SDL Window Wrapper }
{ }
{ }
{ Requires }
{ -------- }
{ SDL.dll on Windows platforms }
{ libSDL-1.1.so.0 on Linux platform }
{ }
{ Programming Notes }
{ ----------------- }
{ }
{ }
{ }
{ }
{ Revision History }
{ ---------------- }
{ }
{ September 23 2004 - DL : Initial Creation }
{
$Log: sdlticks.pas,v $
Revision 1.2 2006/11/08 08:22:48 savage
updates tp sdlgameinterface and sdlticks functions.
Revision 1.1 2004/09/30 22:35:47 savage
Changes, enhancements and additions as required to get SoAoS working.
}
{******************************************************************************}
interface
uses
sdl;
type
TSDLTicks = class
private
FStartTime : UInt32;
FTicksPerSecond : UInt32;
FElapsedLastTime : UInt32;
FFPSLastTime : UInt32;
FLockFPSLastTime : UInt32;
public
constructor Create;
destructor Destroy; override; // destructor
{*****************************************************************************
Init
If the hi-res timer is present, the tick rate is stored and the function
returns true. Otherwise, the function returns false, and the timer should
not be used.
*****************************************************************************}
function Init : boolean;
{***************************************************************************
GetGetElapsedSeconds
Returns the Elapsed time, since the function was last called.
***************************************************************************}
function GetElapsedSeconds : Single;
{***************************************************************************
GetFPS
Returns the average frames per second.
If this is not called every frame, the client should track the number
of frames itself, and reset the value after this is called.
***************************************************************************}
function GetFPS : single;
{***************************************************************************
LockFPS
Used to lock the frame rate to a set amount. This will block until enough
time has passed to ensure that the fps won't go over the requested amount.
Note that this can only keep the fps from going above the specified level;
it can still drop below it. It is assumed that if used, this function will
be called every frame. The value returned is the instantaneous fps, which
will be less than or equal to the targetFPS.
***************************************************************************}
procedure LockFPS( targetFPS : Byte );
end;
implementation
{ TSDLTicks }
constructor TSDLTicks.Create;
begin
inherited;
FTicksPerSecond := 1000;
end;
destructor TSDLTicks.Destroy;
begin
inherited;
end;
function TSDLTicks.GetElapsedSeconds : Single;
var
currentTime : Cardinal;
begin
currentTime := SDL_GetTicks;
result := ( currentTime - FElapsedLastTime ) / FTicksPerSecond;
// reset the timer
FElapsedLastTime := currentTime;
end;
function TSDLTicks.GetFPS : Single;
var
currentTime, FrameTime : UInt32;
fps : single;
begin
currentTime := SDL_GetTicks;
FrameTime := ( currentTime - FFPSLastTime );
if FrameTime = 0 then
FrameTime := 1;
fps := FTicksPerSecond / FrameTime;
// reset the timer
FFPSLastTime := currentTime;
result := fps;
end;
function TSDLTicks.Init : boolean;
begin
FStartTime := SDL_GetTicks;
FElapsedLastTime := FStartTime;
FFPSLastTime := FStartTime;
FLockFPSLastTime := FStartTime;
result := true;
end;
procedure TSDLTicks.LockFPS( targetFPS : Byte );
var
currentTime : UInt32;
targetTime : single;
begin
if ( targetFPS = 0 ) then
targetFPS := 1;
targetTime := FTicksPerSecond / targetFPS;
// delay to maintain a constant frame rate
repeat
currentTime := SDL_GetTicks;
until ( ( currentTime - FLockFPSLastTime ) > targetTime );
// reset the timer
FLockFPSLastTime := currentTime;
end;
end.
|
