ch04.htm

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</DL>



<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> It's fastest to place all components of a particular type on your
	form at one time using this technique. Components can always be rearranged and resized
	at a later time. 
<HR>


</BLOCKQUOTE>


<DL>
	<DT></DT>
</DL>



<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> When placing multiple copies of a particular component, it's easy
	to forget to click the arrow button when you're done. If you accidentally place more
	components than you intend, you can simply delete any extras. 
<HR>


</BLOCKQUOTE>

<H3></H3>
<H3><A NAME="Heading8"></A>Placing and Centering a Component on the Form</H3>
<P>Delphi provides a shortcut method of placing a component on a form. Simply double-click
the component's button in the Component palette and the component will be placed
on the form. The component will be centered on the form both horizontally and vertically.
Components placed with this method can be moved to another location on the form just
like components placed in the usual method.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> Each time you double-click a button on the Component palette, a component
	will be placed on the center of the form in the component's default size. If you
	repeatedly double-click the component button, multiple copies of the component will
	be placed on the form. Each component will be placed in the center of the form and
	will be stacked on top of the previous one. It will appear as if you have a single
	component, so you might not realize that you have several components occupying the
	same space. If you accidentally place multiple components, just click the extra components
	and delete them from the form. 
<HR>


</BLOCKQUOTE>

<P>
<H3><A NAME="Heading9"></A>The Component Palette Context Menu</H3>
<P>When you place the mouse cursor over the Component palette and right-click, you
will see a menu specific to the Component palette (see Figure 4.5).</P>
<P><A HREF="javascript:popUp('28670405.gif')"><B>FIGURE 4.5.</B></A><B> </B><I>The
Component palette context menu.</I></P>
<P>The Show Hints item toggles the tooltips on and off for the component buttons.
Unless you really dislike tooltips, this should be left on. The Hide item on the
context menu hides the Component palette. In order to show the Component palette
again, you have to choose Component Palette from the toolbar context menu.</P>
<P>The Help item on the context menu brings up Delphi help with the Component Palette
page displayed. The Properties item brings up the Palette page of the Environment
Options dialog box, where you can customize the Component palette. Here you can add
and remove pages of the Component palette. You can also add, remove, or rearrange
the order of components on the individual pages. I'll discuss this in more detail
on Day 11, &quot;Delphi Tools and Options,&quot; when you learn about setting the
environment options.</P>
<P>
<H3><A NAME="Heading10"></A>Navigating the Component Palette</H3>
<P>When the Component palette is sized small enough so that it cannot display all
its tabs, you will see scroll buttons in the upper-right corner of the Component
palette. Click these scroll buttons to display tabs not currently in view. Likewise,
if a particular page of the Component palette contains more buttons than will fit
the width of the display window, scroll buttons will be enabled to allow you to scroll
through the available buttons. Figure 4.6 shows the Component palette with both types
of scroll buttons enabled.</P>
<P><A HREF="javascript:popUp('tyd0406.gif')"><B>FIGURE 4.6.</B></A><B> </B><I>The
Component palette scroll buttons.</I></P>
<P>The Component palette is not terribly complicated, but a basic understanding of
its use is vital for programming with Delphi. Now that you've finished with this
quick overview of the Delphi main window, you can return to the main topic again.</P>
<P>
<H2><A NAME="Heading11"></A>A Multiple-Form Application</H2>
<P>To illustrate how Delphi uses units, you can create an application with multiple
forms. You'll create a simple application that displays a second form when you click
a button:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Create a new project by choosing File | New Application from the main
	menu.
	<P>
	<DT></DT>
	<DD><B>2. </B>Change the Name property to MainForm and the Caption property to Multiple
	Forms Test Program.
	<P>
	<DD><B>3. </B>Save the project. Save the unit as Main and the project as Multiple.
	<DT></DT>
	<DD><B>4. </B>Now place a button on the form. Make the button's Name property ShowForm2
	and the Caption property Show Form 2.
	<P>
	<DT></DT>
	<DD><B>5. </B>Choose File | New Form from the main menu (or click the New Form button
	on the toolbar) to create a new form. At this point, the new form has a name of Form1
	and is placed exactly over the main form. You want the new form to be smaller than
	the main form and more or less centered on the main form.
	<P>
	<DT></DT>
	<DD><B>6. </B>Size and position the new form so that it is about 50 percent of the
	size of the main form and centered on the main form. Use the title bar to move the
	new form. Size the form by dragging the lower-right corner.
	<P>
	<DT></DT>
	<DD><B>7. </B>Change the new form's Name property to SecondForm and the form's Caption
	property to A Second Form.
	<P>
	<DT></DT>
	<DD><B>8. </B>Choose File | Save from the main menu (or click the Save File button
	on the toolbar) and save the new form with the name Second.
	<P>
	<DT></DT>
	<DD><B>9. </B>Choose a Label component and drop it on the new form. Change the label's
	Caption property to This is the second form. Change the label's size and color as
	desired. Center the label on the form. Your form should now look roughly similar
	to the one shown in Figure 4.7.
	<P>
</DL>

<P><A HREF="javascript:popUp('28670407.gif')"><B>FIGURE 4.7.</B></A><B> </B><I>The
form up to this point.</I></P>

<DL>
	<DT><I></I></DT>
	<P>
	<DT><I></I></DT>
	<DD><B>10. </B>Click on the main form. The second form is covered by the main form.
	Double-click the Show Form 2 button. The Code Editor is displayed and the cursor
	is placed just where you need to begin typing code (double-clicking a button is a
	shortcut way of generating an OnClick event handler).
	<P>
	<DT></DT>
	<DD><B>11. </B>Type in code so that the function looks like this (you have to type
	only one line of code):
	<P>
</DL>



<BLOCKQUOTE>
	<PRE>procedure TMainForm.ShowFrom2Click(Sender: TObject);
begin
  SecondForm.ShowModal;
</PRE>
	<PRE>end;</PRE>

</BLOCKQUOTE>

<PRE></PRE>

<DL>
	<DT></DT>
	<DD><B>12. </B>Run the program.
	<P>
</DL>

<P>At this point you get a message box that says, Form `MainForm' references form
`SecondForm' declared in unit `second' which is not in your USES list. Do you wish
to add it? Click Yes and Delphi will add the unit Second to the uses list of the
unit Main. Click the Run button again and this time the application will run. When
you click the Show Form 2 button on the main form, the second form is displayed.
You can close the second form by clicking the system close box on the form's title
bar.</P>
<P>
<H3><A NAME="Heading12"></A>Adding Units</H3>
<P>Rather than having Delphi prompt you to add a unit to your uses list, you can
add units yourself. You can manually type the unit name in the uses list for the
form, or you can choose File | Use Unit from the main menu. When you choose the latter
method, the Use Unit dialog box is displayed, as shown in Figure 4.8. The Use Unit
dialog box shows a list of available units. Choose the unit you want to add and click
OK. Delphi will add the unit to the current form's uses list. Note that the Use Unit
dialog box will show only those units that exist in the project <I>and</I> have not
yet been included in this unit. Units that have already been included do not show
up in the list of available units.</P>
<P><A HREF="javascript:popUp('28670408.gif')"><B>FIGURE 4.8.</B></A><B> </B><I>The
Use Unit dialog box.</I></P>
<P>As you can see, Delphi does a good job of managing units for you. Later, when
your programming needs are more sophisticated, you'll have to do a little more source
file management, but at this stage of the game Delphi does most of the work for you.</P>
<P>Now let's take a moment to look at the different compiling options available to
you when writing programs in Delphi.</P>
<P>
<H3><A NAME="Heading13"></A>Compiling, Building, and Linking</H3>
<P>Each time you click the Run button, Delphi compiles and links your program. But
it doesn't necessarily compile every unit in the project. It only compiles any units
that have changed since the last compile. This feature saves you time because you
don't have to wait for the compiler to compile files that haven't changed. Delphi
keeps track of which files have changed and which haven't, so you don't need to do
anything special to use this feature--it's automatic.</P>
<P>Most of the time you want to see the results of any changes you have made in action.
In those cases, click the Run button and the program is compiled, linked, and executed.
Sometimes, however, you don't want to run the program. For example, you might just
want to compile the program to see whether there are any errors.</P>
<P>Delphi has three menu items in addition to Run that enable you to control the
compile/link process. If you choose the Project menu item on the main menu, you see
three menu items called Compile, Build, and Syntax Check. These menu items' text
changes to reflect the name of the active project. For example, when you first start
Delphi, these menu items will say Compile Project1, Build Project1, and Syntax Check
Project 1. (There are also menu items called Compile All Projects and Build All Projects,
but I'll save that discussion for Day 9 when I discuss project groups.) Let's take
these in order of simplest to most complex (from the compiler's perspective):</P>

<UL>
	<LI>The Syntax Check option is one I really like. This feature causes Delphi to compile
	the project and report any errors and warnings. This is the fastest way to check
	for errors in your code. Delphi only compiles the project--it does not perform a
	link. The purpose of the Syntax Check option is to check your code for syntax errors
	as quickly as possible. Because the link phase takes extra time, the Syntax Check
	option skips that step.
	<P>
	<LI>The Compile option compiles any units that have changed since the last compile
	just as Syntax Check does, but it also links the entire project. Naturally, this
	takes slightly longer than the Syntax Check option. Use the Compile option when you
	want to be sure the program will compile and link but you don't want to run the program.
</UL>



<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> The keyboard shortcut for the Compile option is Ctrl+F9. 
<HR>


</BLOCKQUOTE>


<UL>
	<LI>The Build option takes the longest to perform. This option compiles every unit
	in the project regardless of whether it has changed since the last build. After compiling
	all units, Delphi links the entire project.
</UL>

<P>So far, you have been letting Delphi add units to your projects. Further on down
the road you might have to do some hand-editing of your source files to add units
or compiler directives. You might even end up editing the project source. From time
to time things can get goofed up (hey, we all make mistakes). Performing a build
will bring everything up-to-date so that you can better sort out any problems you
might be running into. Sometimes a build resolves compiler and linker errors without
the need for you to do anything further.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> Any time you get unexpected (out of the ordinary) compiler or linker
	errors, first try a build. It could just be that something is out of sync, and a
	build might cure it. If performing a build doesn't fix the problem, you'll have to
	go to work figuring out where the problem lies. 
<HR>


</BLOCKQUOTE>

<P>Delphi gives you the option of displaying a compile status dialog box during compiles.
You can turn on this option through the Environment Options dialog box (Preferences
page). When this option is on, the compile status dialog box shows the filename of