1. Outline Event-driven programming paradigm Example: Event Handling
Class
Array/Collection
Graphics
Double Buffering

2. Event Handling Source Object Receiver Object H_Func(Event) { } Event
Registration/delegate

3. Source vs. Receiver
Source/Receiver
Receiver
Source
Source

4. Mouse Event Handling in C++/CLI
Event: MouseEventArgs
Mouse Event Handlers: Form1_MouseDown, Form1_MouseUp, Form1_MouseMove
Registration (delegate):
this->MouseDown += gcnew MouseEventHandler(…);
this->MouseUp += gcnew MouseEventHandler(…);
this->MouseMove += gcnew MouseEventHandler(…);

5. A look at Graphics using GDI+
GDI: Graphical Device Interface
Paint event is associated with all controls. Triggered when create, resize, restore, etc.
Graphics class
PaintEventHandler ()
Invalidate()
Manually trigger Paint event

6. Event-driven Programming
Programming paradigm
State representation
State presentation : Form1_Paint in C++/CLI
Event handling and state change
Request for presentation to reflect new state:Invalidate in C++/CLI
invalidates the entire client area of a window, which indicates that the area is out of date, and should be repainted. You would typically call this on a control that needs to be redrawn.

7. Double Buffering Flicking problem with single buffering
Front buffer for display
Back buffer for composition
Triple buffering

8. Single Buffering
Display
Frame Buffer
Composition

9. Double Buffering in Computer Graphics
Display
Front
Back
Composition
Swap Buffers
Display
Back
Front
Composition

10. Double Buffering in C++/CLI
Window
Image
Front
Back
Draw
Composition

11. Double Buffering in C++/CLI
Step 1: Create the back buffer and its graphics
Bitmap^ backBuffer = gcnew Bitmap(width, height);
Graphics^ gBackBuffer = Graphics::FromImage(backBuffer);
Step 2: Compose the scene in the back buffer
gBackBuffer->Clear(Color::White);
gBackBuffer->FillEllipse(…);
....
Step 3: copy the back buffer to the front
e->Graphics->DrawImageUnscaled(backBuffer, 0, 0);

12. An Example Event-driven programming paradigm Class Array/Clollection
Event Handling
Double Buffering