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Lesson 13 Graphics, Help, and Deployment

• Microsoft Visual Basic .NET, Introduction to
  Programming

2
Objectives

• Use ToolTips to provide immediate Help to the
  user.
• Implement Graphics methods and scaling techniques
  to draw graphs.
• Provide Help to a user through a pop-up Help
  button on the form.
• Use the HelpProvider control to attach Help
  topics within a Help file to specific controls.
• Write HTML code for Web pages that serve online
  Help for an application.
• Deploy a simple application to another machine
  that hosts the .NET framework.

3
Vocabulary

• Deployment
• HelpProvider control
• High-level programming language
• Modal dialog box
• Source code

4
ToolTips

• ToolTips appear in the familiar yellow box that
  pops open when you hover the mouse pointer over a
  control, text box, or form. You affix ToolTips to
  controls and forms by adding a ToolTip control to
  an application and using its SetToolTip method to
  associate a particular control with a string that
  then becomes the controls ToolTip.

5
Adding a ToolTip

• There are two ways to add a ToolTip control to a
  project. In the forms Designer, you can add a
  ToolTip control to the forms component tray by
  dragging the control from the Toolbox to the form
  or by double-clicking the control in the Toolbox.
  
• You can also create a ToolTip control using the
  statement
• Dim ToolTip1 As New ToolTip()

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ToolTip

• The following statement associates the ToolTip,
  Enter a value for a with a button, Button1.
• ToolTip1.SetToolTip(Button1, "Enter a value for
  a")
• Typically, you would add a statement for each
  control to document its use.

7
Pens and Colors

• All the graphing methods work with a pen or
  brush. The pen component determines the color and
  thickness of lines and shapes drawn by the
  Graphics methods. A typical declaration for a pen
  appears below
• Dim myPenDraw As New System.Drawing.Pen(myColor,
  3)

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Colors

• The declaration of the myColor variable appears
  below
• Dim myColor As Color Color.DarkCyan
• A line to change myColor to Red appears below
• myColor Color.Red

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The Paint Event

• The Paint method of the picture box (or form) is
  used to invoke the Graphics methods that are used
  to draw shapes and text. The Paint method has a
  special parameter (e of type PaintEventArgs)
  through which the Graphics methods are called and
  executed.

10
ReDraw

• To force a picture box to redraw itself, the
  picture boxs Refresh method is called. This
  allows lines of code in a button to change the
  value for the coefficients of the equation and
  then call on the picture box to redraw itself and
  display the new graph.

11
Note

• All the Graphics methods use pixels to locate
  the points, lines, and shapes drawn on a form or
  picture box. Pixel is short for picture element.
  It is the smallest screen element that can
  represent a colored dot. In past versions of
  Visual Basic, properties of forms and picture
  boxes could impose a custom coordinate system
  that was, in turn, translated into pixel
  coordinates. Those properties are not included in
  Visual Basic .NET.

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DrawLine Method

• You use the DrawLine method to draw a single
  line from one point to another. There are several
  versions of the method which differ only in the
  number and data types of parameters sent to the
  method. The version used in the Graphing project,
  in addition to the pen parameter, requires four
  integer data type parameters. The first two
  represent the x and y coordinates of the first
  endpoint of the line. The third and fourth
  parameters represent the coordinates of the
  line's second endpoint. Another version accepts
  the pen parameter and four numeric parameters of
  the Single data type that represent the
  coordinates of the endpoints. Another accepts two
  parameters (beside the pen parameter) of the
  Point type.

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The Point Type

• The Point type is part of the System.Drawing
  library. Each point has an x and a y component
  specifying the x and y coordinates of a point.

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The DrawLines Method

• The DrawLines method draws lines from point to
  point. The parameter sent to the method (in
  addition to the pen parameter) is an array of the
  Point data type.
• When the x and y coordinates of the graph are
  generated, they are translated into pixel
  coordinates and stored in the Points array .

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Scaling the x and y Values

• The pixel coordinates of the points that make up
  the area of a picture box are very unlike the
  coordinates used in math classes to graph points
  and lines. In a picture box, the upper left
  corner is the origin of the coordinate system.
  The first value of the pixel coordinate
  represents the column number and the second
  number represents the row number. The column
  coordinates get larger from left to right, just
  as the x coordinate of a graph in math class. But
  the row pixel coordinates in a picture box gets
  larger going from top to bottom, not from bottom
  to top as in a math graph.

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Scaling

• A second consideration in converting from x, y
  coordinates to pixel coordinates is the number of
  pixels compared to the number of units
  represented in the graph. A typical math graph
  may span from 10 to 10 in both the x and y
  directions. The number of pixels in a medium to
  small picture box numbers in the hundreds and, of
  course, all the pixel coordinate values are
  positive.

17
TabPage Collection Editor Showing the Addition
of the First Tab Page
18
The Quadratic Tab Page Showing the Final
Placement of Controls
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Step-by-Step 13.1

• Dim myColor As Color Color.Red
• Dim xMax As Integer 10
• Dim yMax As Integer 10
• Dim a, b, c As Double
• Dim Points(100) As Point

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Step-by-Step 13.1

• Dim myPenDraw As New Pen(myColor, 3)
• Dim myPenAxis As New Pen(Color.Green, 2)
• Dim halfx As Integer picQuadratic.Size.Width /
  2
• Dim halfy As Integer picQuadratic.Size.Height /
  2
• e.Graphics.DrawLine(myPenAxis, 0, halfy, 2
  halfx, halfy)
• e.Graphics.DrawLine(myPenAxis, halfx, 0, halfx, 2
  halfy)

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Appearance of the Application after the First
Installment of Code in the Paint Method
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Step-by-Step 13.1

• Dim xWidth As Integer picQuadratic.Size.Width
• Dim yHeight As Integer picQuadratic.Size.Height
• Dim xMultiple As Double xWidth / (2 xMax)
• Dim yMultiple As Double -yHeight / (2 yMax)
• Dim xOffset As Integer xWidth \ 2
• Dim yOffset As Integer yHeight \ 2

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Step-by-Step 13.1

• a CDbl(txtA.Text)
• b CDbl(txtB.Text)
• c CDbl(txtC.Text)
• Dim x, y As Double
• Dim Increment As Integer xWidth / 100
• Dim Index As Integer 0

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Step-by-Step 13.1

• For x -xMax To xMax Step 2 xMax / 100
• y a x x b x c
• With Points(Index)
• .X CInt(x xMultiple) xOffset
• .Y CInt(y yMultiple) yOffset
• End With
• Index 1
• Next
• e.Graphics.DrawLines(myPenDraw, Points)

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Step-by-Step 13.1

• Dim Answer MessageBox.Show("Would you like to
  change the graphing window?", _
• "Graphing Window", MessageBoxButtons.YesNo,
  MessageBoxIcon.Question)
• If Answer MsgBoxResult.Yes Then
• xMax CInt(InputBox("Enter maximum value for
  x"))
• yMax CInt(InputBox("Enter maximum value for
  y"))
• End If

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Step-by-Step 13.1

• If TabControl1.SelectedTab Is tpQuadratic Then
• If txtA.Text "" Then
• MessageBox.Show("Enter values for a, b,
  and c.")
• Exit Sub
• End If
• picQuadratic.Refresh()
• End If

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Step-by-Step 13.1

• ToolTip1.SetToolTip(picQuadratic, "Max x "
  xMax vbCrLf "Max y " yMax)

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Note

• The constant vbCrLf is a shortcut for the
  carriage return and linefeed characters.
  Including this constant in the string shown by
  the ToolTip forces the second part of the string,
  "Max y ...", to appear on a second line.

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Pop-Up Help

• A Help button is another way to provide Help to
  the user. The Help button replaces a forms
  Minimize and Maximize buttons. The user clicks
  the Help button and then clicks on the control
  with which he or she wants Help. If provided,
  Help appears in the form of a pop-up window, not
  unlike a larger, shadowed version of a ToolTip.

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HelpProvider Control

• The HelpProvider control resides in the
  component tray and has no visible appearance in
  the application.
• After you add the HelpProvider control to a
  form, change the HelpButton property of the form
  from its default setting of False to True. The
  Help button cannot appear with a forms Minimize
  and Maximize buttons, so you need to turn them
  off by setting the MinimizeBox and MaximizeBox
  properties of the form to False.

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The Help Button
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HelpString Property

• To provide pop-up help for a particular control,
  you enter a help string into the controls
  HelpString property. The Help string can be
  hundreds of words long. It is a good idea to work
  on the text of the Help string in a text editor
  and then copy and paste it to the HelpString
  property of the control in the controls Property
  window.

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Note

• Once you have clicked the Help button, you
  activate pop-up Help for the tab page by clicking
  any of the controls on the page. Clicking the
  body of the page or the tab itself does not
  activate the Help window.

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Online Help

• Online Help lets you provide help in the format
  of Web pages, either resident in the application
  on a local machine or on the Internet.
• Once you link your application through the
  HelpProvider control introduced in the last
  section to a Web page on the Internet or an HTML
  page stored locally, the extent of the Help you
  can provide is almost unlimited. A Help page
  stored on the Internet means that, if necessary,
  the contents of the page can be changed to give
  the user the most up-to-date information about
  running an application. Hyperlinks on the Help
  page can send a user to other Web pages and even
  more information.

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Note

• Although it is customary to launch Help by
  pressing the F1 key when the control for which
  you want help has the focus, you can also launch
  help by clicking the Help button (if present) and
  clicking again on the control.

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Note

• Setting the HelpKeyword and HelpNavigator
  properties are necessary to activate online Help
  but, in this exercise, these properties are not
  used.

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Step-by-Step 13.3

• lthtmlgt
• ltheadgt
• lttitlegtGraphing Help Jump Pagelt/titlegt
• lt/headgt
• ltbodygt
• lth1gtGraphing Helplt/h1gt
• lthrgt
• lttablegt
• lttrgt
• lttdgt

• ltligtClick here for help with
• lta href "EnteringValues.htm"gtEntering
  Valueslt/agtlt/ligt
• ltligtClick here to read about
• lta href "Quadratic.htm"gtQuadratic
  Equationslt/agtlt/ligt
• lt/tdgt
• lt/trgt
• lt/tablegt
• lt/bodygt
• lt/htmlgt

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JumpPage.htm
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Step-by-Step 13.3

• lthtmlgt
• ltheadgt
• lttitlegtEntering Values Help Pagelt/titlegt
• lt/headgt
• ltbodygt
• lth1gtEntering Valueslt/h1gt
• lthrgt

• ltpgtEnter decimal or integer values for the
• coefficients of the equation.lt/pgt
• lt/bodygt
• lt/htmlgt

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The Entering Values Help Page
41
Deployment

• Deployment of an application means making your
  application available to others.

42
Languages

• Programs are written in source code. Source code
  is the program code written by the programmer to
  solve a problem. What the source code looks like
  depends on the programming language. Visual Basic
  .NET is a high-level programming language. This
  means that it is a language easily understood by
  a programmer, used to provide instructions to a
  computer about the input, processing, and display
  of data.
• To get from source code in Visual Basic to the
  language used by the processor to actually
  manipulate data and turn it into information
  requires several steps and the help of the
  operating system, a language compiler, and the
  common language run-time files.

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Languages

• The language compiler turns the source code into
  Microsoft intermediate language (MSIL) code. All
  the high-level languages in Visual Studio are
  converted to the same intermediate language. This
  is one of the reasons that applications can be
  built using several languages. The pieces, once
  compiled, are able to work together.
• Once the application is converted to MSIL code,
  it can run on any computer that supports the .NET
  framework. The .NET framework supplies the common
  language run-time file that executes the code and
  the .NET framework class library. The class
  library includes objects available to all the
  .NET programming languages, objects for file I/O,
  messaging, networking, and security.

44
Languages

• Moving a program from one computer to another is
  easy, as long as the target computer supports the
  .NET framework. Indeed, .NET is Microsofts
  vision for the future and all of its applications
  will one day be written in a .NET language.
  Remember, the future in the world of computers
  cannot be predicted for more than about five
  years.

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Deployment

• Deploy a simple .NET application by moving its
  .exe file to the new computer or by copying the
  file through a network, disk, or the Internet. If
  the new computer supports the .NET framework,
  thats all the program needs to run on the local
  machine. No entries are made in the local
  machine's registry.
• To remove the application from the target
  machine, merely erase its file from its folder.
  No other action needs to be taken there are no
  hidden DLL files lurking in folders taking up
  disk space.

46
Historically Speaking

• In the past, many computer languages have been
  translated from high-level source code to the
  code actually used by the processor by passing
  through more than one stage. In an early version
  of the C programming language, source code was
  first translated to Microsoft Assembly language.
  The Microsoft Assembler then translated the
  assembly language program into machine code
  executed by the machines processor. A language
  called Forth was compiled to a special language
  that was then executed by a program called the
  Forth Virtual Machine. This program turned an
  actual processor into a Forth processor created
  by the program.

47
Historically Speaking

• A similar system was used by an early version of
  the programming language Pascal. The high-level
  code was turned into P-code. The P-code was, in
  turn, executed by an interpreter, which turned
  each line of P-code into machine language and
  executed it on the local processor. Even Java
  passes through an intermediate step called
  Bytecode. A program that becomes part of the
  browser then executes the Bytecode.

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Summary

• All users expect extensive online Help to run an
  application.
• ToolTips are attached to controls by executing
  the SetToolTip method of the ToolTip control.
  When you hover the mouse pointer over a control
  with a ToolTip, Help text appears (for a limited
  time) in a yellow box at the site of the mouse
  pointer.
• Pen objects are required to draw figures on the
  screen.

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Summary

• The Paint method of the picture box (or form) is
  used to invoke the Graphics methods used to draw
  shapes and text. The Paint method has a special
  parameter (e of type PaintEventArgs) through
  which the Graphics methods are called and
  executed.
• Since the coordinate system of a picture box does
  not match the coordinate system used to graph
  mathematical equations, x and y values generated
  by mathematical equations have to be scaled and
  altered.
• The HelpProvider control is necessary to provide
  pop-up and online Help to an application.

50
Summary

• Pop-up help is activated when a controls
  HelpString property is set to a text message.
• Online help is activated when the HelpProviders
  HelpNamespace property is set to a Web page's URL
  or local path name and a controls HelpProvider
  and HelpNavigator properties are set.
• Although it is only as good as the effort that
  has gone into creating it, online Help has no
  limits. Its size depends on local disk space or
  space on the Internet server. If it is on the
  Internet, it can be updated to provide
  up-to-the-minute information about running an
  application.