High Level Languages

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High Level Languages

• Delphi
• Lecture 6

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Last Lecture

• Last Lecture we covered the following
• Menus in Delphi
• The menu designer
• Creating menus by hand
• Example menu item code
• Databases
• Borland Database
• SQL in Delphi

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This Lecture

• In Todays Lecture we will cover
• Basic Graphics Components
• Device Contexts
• Graphics the Windows API way
• Graphics the Delphi way
  (Examples of Graphical Objects in Action)
• Bitmaps
• Multimedia Programming

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1. Delphi Graphics

• Graphics programming can seem intimidating but it
  need not be. In fact Delphi provides VCL
  components that can make it positively easy.
• Three simple examples are
• Shape Component
• Image Component
• PaintBox Component

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TShape Component
Simply Drag and Drop a Shape component onto your
Form.

• In Additional Tab of the Component Palette.
• Just drag, drop and alter the Brush, Pen and
  Shape properties as your heart desires.
• Produces circles, ellipses, squares, rectangles.
• Brush changes the Background Colour of the shape,
  Pen the shapes border colour and thickness.

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TImage Component

• Used to display a Bitmap (as a TPicture) on a
  form.
• Useful for all sorts of graphical operations,
  including a bitmap background for a form.
• You can select the bmp at Design time or Run
  Time
• Image1.Picture.Bitmap.LoadFromFile(BritneySpears.
  bmp)
• Useful properties are Stretch, Center and
  Autosize.

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PaintBox Component

• If you want drawing confined to a certain part of
  a form, the PaintBox component provides a canvas
  upon which you can draw.
• Anything that spills outside the PaintBox area is
  clipped.
• The only significant property of PaintBox is
  Canvas. This property is an instance of the
  TCanvas Class.

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2. Device Contexts

• Device Context is a Windows term, describing any
  digital canvas upon which you can draw.
• These surfaces can take many forms such as
• - To a client area in a form
• - To the whole window
• - To the whole desktop
• - To memory
• - To a printer

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3. Graphics the Windows way

• Procedure TForm1.RedCircleBlueOutline(Sender
  TObject)
• var DC HDC
• Brush, OldBrush HBrush
• Pen, OldPen HPen
• begin
• DC GetDC(Handle)
• Brush CreateSolidBrush(RGB(255, 0, 0))
• Pen CreatePen(PS_SOLID, 1,
  RGB(0,0,255))
• OldBrush SelectObject(DC, Brush)
• OldPen SelectObject(DC, Pen)
• Ellipse(DC, 20, 20, 120, 120)
• SelectObject(DC, OldBrush)
• SelectObject(DC, OldPen)
• ReleaseDC(Handle, DC)
• end

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4. Graphics the Delphi Way

• Canvas.Brush.Color ClRed
• Canvas.Pen.Color ClBlue
• Canvas.Ellipse(20, 20, 120, 120)

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Object Orientation Again!

• The above code used a TCanvas component from the
  VCL to simplify the graphical process.
• Not only is the code shorter and more readable it
  is more robust - The TCanvas class takes care of
  freeing resources as needed for you.
• Hence TCanvas is a simpler and more effective way
  of approaching graphics than using the API.

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TCanvas Properties

• Font
• Pen
• Brush
• Handle
• PenPos
• Pixels
• ClipRect

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Some TCanvas Methods

• Arc - Draws an arc on the canvas.
• Ellipse - Draws an ellipse on the canvas
• Polygon - Draws polygon from an array of
  points
• Pie - Places a pie shape on the canvas
• Rectangle - Draws a rectangle on the canvas
• RoundRect - Draws a filled rectangle with
  rounded corners
• Draw - Copies an image from memory to the canvas
• Floodfill - Fills an area of the canvas with the
  brush colour
• LineTo - Draws a line to the specified (x,y)
  position
• MoveTo - Sets the current drawing start position
• TextExtent, TextHeight, Textout, TextRect.

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5. The TBitmap Object

• It is easy to put a Bitmap onto a canvas without
  using the TImage component.
• The TBitmap class encapsulates a bitmap object in
  Delphi - simply load a bitmap from file into a
  TBitmap instance, and use the draw method to
  place it on the canvas
• var Bitmap TBitmap
• begin
• Bitmap TBitmap.create
• Bitmap.LoadFromFile(HearSay.bmp)
• Canvas.Draw(0, 0, Bitmap)
• Bitmap.free
• end

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Memory

• Memory, its properties and organization is a very
  simple idea to comprehend.
• One should keep in mind the simple idea that a
  computer is little more than a over-grown
  calculator with better I/O
• Memory is nothing more than a linear set of
  bytes.  The computer needs a method to access all
  the memory on the system and it does this through
  addressing giving each byte in memory an
  identity. 

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Segments

• Memory within a computer typically is made of
  segments - These segments are simply regions of
  memory with a starting and ending address,
  assigned attributes. 
• A program cannot write to a segment that does
  not have the write permission attribute assigned
  to it. 
• To do with common problems like General
  Protection Faults, Unrecoverable Application
  Errors, and such like

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Segments

• When a program runs in memory, it has the
  following memory organization
•      

EVERYTHING ELSE!
Where the statements themselves are stored
This is where the programs global variables are.
The home of all the local variables
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Bits you need to know about

• Stack
• Heap
• Create()
• Free()
• We can create any type of object in runtime.
• Memory Leaks

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6. Memory Bitmaps

• Offscreen Bitmaps are commonly used in windows
  programming.
• They enable you to build up an image in memory
  before you draw it onscreen.
• Why?
• To avoid flicker
• Good for complex drawing programs
• Animation
• Most Popular use is in the Microsoft DirectX SDK

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Creating a memory Bitmap

• This is a 3 step process
• - Create an Offscreen bitmap in memory
• - Draw upon this memory bitmap
• - Copy the memory bitmap to screen
• This is exactly what we did in the last example,
  except we didnt draw on the memory bitmap but
  rather loaded a picture onto it from file.
• However we could just as easily drawn on it
  before we put it on screen

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Example

• Bitmap TBitmap.create
• Bitmap.LoadFromFile(HearSay.bmp)
• Bitmap.Canvas.Brush.Color ClRed
• Bitmap.Canvas.LineTo(100,100)
• Bitmap.Canvas.MoveTo(0,100)
• Bitmap.Canvas.LineTo(100,0)
• Bitmap.Canvas.MoveTo(50,50)
• Bitmap.Canvas.TextOut(STOP! Please)
• Canvas.Draw(0, 0, Bitmap)
• Bitmap.free

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7. Multimedia Programming

• Wave Playback is one of the simplest functions
  that the Windows API has. As such a Delphi VCL
  component isnt necessary.
• Just add uses MMSystem to the start of your
  program and use the PlaySound Function
• Playsound(test.wav, 0, SND_FILENAME)

SND Flag
API Command
File Path
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Wave Playback

• The SND Flag controls how PlaySound acts. Other
  options are
• SND_ALIAS
• tells the program to play a system sound. EG
• SND_SYNC
• control is only returned to the program after the
  wave has finished playing
• SND_ASYNC
• The wave is played while your program goes about
  the rest of its business

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TMediaPlayer Component

• This is the component that the Delphi VCL
  provides to perform multimedia operations.
• It can play wave sounds, avi movies and even
  control the cd player.
• Like all other components from the VCL it can be
  dragged and dropped onto the form, and then
  referred to in your code by its name.
• Has too many features to go through now - refer
  to the online tutorials or Delphi help to get the
  most out of it.

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Avi Example

• Simply create a TMediaPlayer component on your
  form an use code such as
• Player.wait True
• Player.FileName Film.avi
• Player.Open
• Player.Play
• If you use the default settings this will play
  the video in a seprate pop up window. However if
  you set up a panel on your form called AVIPanel
  the following code would make the video appear in
  that panel.

MediaPlayer.Display AVIPanel
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Final Words

• Multimedia can make your programs entertaining
  but do not go overboard!
• The coursework Deadline is March 21st 5pm. Make
  sure that you submit the coursework in the
  required way.
• Do not leave the coursework to the last minute.
  Start now. The coursework is not easy, but should
  be rewarding.
• Thats it! Its all over! Good luck with perl,
  Thank You and Goodnight.