ch12.htm

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shows the MemBmp program running.</P>
<P><A HREF="javascript:popUp('28671211.gif')"><B>FIGURE 12.11.</B></A><B> </B><I>The
MemBmp program running.</I></P>
<P>
<H4>LISTING 12.2. MemBmpU.pas.</H4>
<PRE>unit MemBmpU;
interface
</PRE>
<PRE></PRE>
<PRE>uses
  Windows, Messages, SysUtils, Classes, Graphics, 
  Controls, Forms, Dialogs, StdCtrls;
const
  DisplayText = `TurboPower Software Co.';
type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    { Private declarations } 
    Done : Boolean;
  public
    { Public declarations } 
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM} 
procedure TForm1.Button1Click(Sender: TObject);
var
  I : Integer;
begin
  Canvas.Font.Name := `Arial Bold';
  Canvas.Font.Size := 16;
  Canvas.Brush.Color := clSilver;
  Done := false;
  while not Done do begin
    for I := -Canvas.TextWidth(DisplayText) 
      to Pred(Width) do begin
      Sleep(1);
      Application.ProcessMessages;
      if Done then
        Break;
      Canvas.Font.Color := clGray;
      Canvas.Brush.Style := bsClear;
</PRE>
<PRE>      Canvas.TextOut(i + 2, 12, DisplayText);
</PRE>
<PRE>      Canvas.Font.Color := clBlack;
      Canvas.Brush.Style := bsClear;
      Canvas.TextOut(i, 10, DisplayText);
      Canvas.Font.Color := clSilver;
      Canvas.TextOut(i + 2, 12, DisplayText);
      Canvas.TextOut(i, 10, DisplayText);
    end;
  end;
end;
procedure TForm1.Button2Click(Sender: TObject);
var
  Bitmap : TBitmap;
  I : Integer;
begin
  Bitmap := TBitmap.Create;
  Bitmap.Width := Width;
  Bitmap.Height := 40;
  Bitmap.Canvas.Font.Name := `Arial Bold';
  Bitmap.Canvas.Font.Size := 16;
  Bitmap.Canvas.Brush.Color := clSilver;
  Bitmap.Canvas.FillRect(Rect(0, 0, Width, 40));
  Done := False;
  while not Done do begin
    for I := -Bitmap.Canvas.TextWidth(DisplayText) 
      to Pred(Width) do begin
      Application.ProcessMessages;
      if (Done) then
        Break;
      Sleep(1);
      Bitmap.Canvas.Font.Color := clGray;
      Bitmap.Canvas.Brush.Style := bsClear;
      Bitmap.Canvas.TextOut(2, 12, DisplayText);
      Bitmap.Canvas.Font.Color := clBlack;
      Bitmap.Canvas.Brush.Style := bsClear;
      Bitmap.Canvas.TextOut(0, 10, DisplayText);
      Canvas.Draw(I, 0, Bitmap);
    end;
  end;
  Bitmap.Free;
end;
procedure TForm1.Button3Click(Sender: TObject);
begin
  Done := True;
end;
end.
</PRE>
<P>The MemBmp program is included with the book's code, along with other example
programs (called BrushTst, Capture, Gradient, and Rotate) that illustrate the concepts
discussed today.</P>
<P>
<H2><A NAME="Heading12"></A>Multimedia Programming</H2>
<P><I>Multimedia programming</I> is a deceivingly innocent phrase. The reason for
this is that multimedia programming encompasses a wide range of possibilities. Multimedia
typically includes wave audio, MIDI audio, AVI video clips, and animation. I don't
want to confuse multimedia programming with game programming.</P>
<PRE></PRE>
<P>Game programming certainly involves multimedia, but it is much more involved than
adding sound or video to an application. I'm going to lightly cover multimedia in
this section and show you what you can do given the tools that Delphi provides right
out of the box. I'm not going to talk about graphics or multimedia APIs such as OpenGL
or Direct Draw. For more information on graphics programming using those libraries,
get a good book that specializes in graphics programming. <I>Delphi 4 Unleashed</I>
(ISBN: 0-672-312-859) would be a good choice.</P>
<P>
<H3><A NAME="Heading13"></A>Wave Audio with the Windows API</H3>
<P>Normally I wouldn't talk a lot about Windows API functions because most of the
time VCL offers you a better way of performing a task than does the API. In the case
of playing a wave file, however, there is nothing more simple than the Win32 API
PlaySound function. Playing a wave file by using this function is very easy. The
first thing you need to do is add MmSystem to your unit's uses list. Then call PlaySound
with the proper parameters:</P>
<P>
<PRE>PlaySound(`test.wav', 0, SND_FILENAME);
</PRE>
<P>That's pretty simple, isn't it? As you can see, the first parameter to PlaySound
is used to specify a sound file to play. The last parameter is used to specify flags
that determine how the sound should be played. When playing a wave audio file on
disk, you specify SND_FILENAME as the last parameter (you can specify other flags
as well, but I'll get to that in just a bit).</P>
<P>The PlaySound function can also play system sounds as well as files on disk. To
play a system sound, specify the sound alias in the first parameter passed to PlaySound,
and SND_ALIAS in the flags parameter--for example,</P>
<P>
<PRE>PlaySound(`SystemAsterisk', 0, SND_ALIAS);
</PRE>
<P>This code plays the system sound associated with the Asterisk event (assuming
one has been set up on your system). To see a list of system sound events, look at
the Sound applet in the Control Panel. To determine the sound alias for the event,
you can look in the Windows Registration Database (the Registry). The aliases are
listed under the HKEY_CURRENT_USER key.</P>
<P>If the requested sound cannot be found, Windows will play the default sound (the
<I>ding</I> if you have the default sound scheme). You can prevent Windows from playing
the default sound by specifying the SND_NODEFAULT flag. For example, if you want
to play a system sound but don't want the default sound to play if the system sound
cannot be found, you could use this code:</P>
<P>
<PRE>PlaySound(`MailBeep', 0, SND_ALIAS or SND_NODEFAULT);
</PRE>
<PRE>Notice that the SND_ALIAS and SND_NODEFAULT flags are or'd together.
</PRE>


<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> The Win32 API MessageBeep function can also be used to play system
	sounds by their index number. See MessageBeep in the Win32 online help for more information.
	
<HR>


</BLOCKQUOTE>

<P>There are two other flags that are important when dealing with the PlaySound function:</P>

<UL>
	<LI>The SND_ASYNC flag stipulates that the sound should be played asynchronously.
	When this flag is used, the sound starts playing and immediately returns control
	to the calling application. This means that the sound can play while your application
	goes on its way.
	<P>
	<LI>The SND_SYNC flag stipulates that control should not return to the calling application
	until after the sound is finished playing. SND_SYNC is the default for PlaySound,
	so you shouldn't have to specifically set this flag.
</UL>

<P>There are many other flags that can be used to control how sounds are played with
PlaySound. For complete information, see the PlaySound topic in the Win32 online
help.</P>
<P>
<H3><A NAME="Heading14"></A>The TMediaPlayer Component</H3>
<P>VCL provides the MediaPlayer component for simple multimedia operations. This
component, located on the System tab of the Component palette, can play wave files,
MIDI files, AVI videos, and more. TMediaPlayer is easy to use, too. For just playing
wave files I usually use the PlaySound function as described in the previous section.
For anything more complex, though, you can use the MediaPlayer component.</P>
<P>The most obvious way of using TMediaPlayer is to simply drop one on a form. When
you do, the media player controller is displayed. This controller has buttons for
play, pause, stop, next, previous, step, back, record, and eject. Figure 12.12 shows
a form with a MediaPlayer.</P>
<P><A HREF="javascript:popUp('28671212.gif')"><B>FIGURE 12.12.</B></A><B> </B><I>A
form with a </I>MediaPlayer<I> component.</I></P>
<P><BR>
Using the media player in its most basic form is extremely simple. All you have to
do is set the FileName property to the name of a valid multimedia file and click
the Play button on the MediaPlayer. You can select any .WAV, .MID, or .AVI file.
The MediaPlayer knows what to do with the file automatically and no additional intervention
is required. Most of the time, you want to do something a little more interesting
with the MediaPlayer, and for those times you'll have to dig a little deeper.</P>
<P>Although the visual control bar of the MediaPlayer is nice in some situations,
you will probably use the MediaPlayer without the control bar at times. You can manipulate
the MediaPlayer through code to play, start, stop, or rewind the media. If you don't
want to see the MediaPlayer control bar at runtime, you'll have to set the Visible
property to False.</P>
<P>
<H3><A NAME="Heading15"></A>MediaPlayer Properties, Methods, and Events</H3>
<P>TMediaPlayer has a lot of properties. Most of them are pretty easy to understand,
but some are a bit more complicated. Table 12.5 lists the primary properties of TMediaPlayer.</P>
<P>
<H4>TABLE 12.5. PRIMARY TMediaPlayer PROPERTIES.</H4>
<P>
<TABLE BORDER="1">
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT"><I>Property</I></TD>
		<TD ALIGN="LEFT"><I>Description</I></TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">AutoOpen</TD>
		<TD ALIGN="LEFT">Specifies whether the device should be opened as soon as the media player is created.
			Default: False</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">AutoRewind</TD>
		<TD ALIGN="LEFT">When True, the media position pointer will be reset to the beginning of the media
			after the media has played. Default: True</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">DeviceType</TD>
		<TD ALIGN="LEFT">The type of the multimedia device. Set to dtAutoSelect to have the device type automatically
			selected based on the filename extension. Default: dtAutoSelect</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Display</TD>
		<TD ALIGN="LEFT">Used to set the display window to a specific component (for video devices).</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">DisplayRect</TD>
		<TD ALIGN="LEFT">Used to set the size and position of the playback window for video devices. The video
			is resized to fit this rectangle.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">EnabledButtons</TD>
		<TD ALIGN="LEFT">The buttons on the MediaPlayer that should be enabled. Default: All Buttons</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">EndPos</TD>
		<TD ALIGN="LEFT">The media ending position. The media is played from StartPos to EndPos. If EndPos
			is not specified, the media plays to the end. The value you assign to EndPos depends
			on the type of media being played.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Error</TD>
		<TD ALIGN="LEFT">The error code of the last operation.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">ErrorMessage</TD>
		<TD ALIGN="LEFT">A textual description of the last error.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Frames</TD>
		<TD ALIGN="LEFT">The number of frames to move when the Back or Next methods are called, or when the
			Back or Next buttons on the MediaPlayer control bar are clicked.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Length</TD>
		<TD ALIGN="LEFT">The length of the media. The value of Length depends on the type of media being played
			and the current value of TimeFormat.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Mode</TD>
		<TD ALIGN="LEFT">The state of the device. Can be mpNotReady, mpStopped, mpPlaying, mpRecording, mpSeeking,
			mpPaused, or mpOpen.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Notify</TD>
		<TD ALIGN="LEFT">When True, the OnNotify event is generated when the MediaPlayer finishes an operation.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">NotifyValue</TD>
		<TD ALIGN="LEFT">The results of the last notification operation. Can be nvSuccessful, nvSuperseded,
			nvAborted, or nvFailure.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Position</TD>
		<TD ALIGN="LEFT">The current position in the media.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">StartPos</TD>
		<TD ALIGN="LEFT">The media starting position. The media is played from StartPos to EndPos. If StartPos
			is not specified, the media is played from the beginning. The value you assign to
			StartPos depends on the type of media being played.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">TimeFormat</TD>
		<TD ALIGN="LEFT">The time format to use for this device. The time format can be specified in milliseconds,
			frames, bytes, samples, tracks/minutes/seconds, hours/minutes/seconds, and more.</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">Tracks</TD>
		<TD ALIGN="LEFT">The number of tracks the media contains (for CD audio devices).</TD>
	</TR>
	<TR ALIGN="LEFT" VALIGN="TOP">
		<TD ALIGN="LEFT">VisibleButtons</TD>
		<TD ALIGN="LEFT">Specifies the buttons that should be displayed on the Medi