1. GUI Programming
Alex Feldmeier

2. Concepts Create GUI from scratch OpenGL has no built in GUI
Developers create new GUI for every game

3. What you have Mouse location Mouse button up/down Keyboard key events
Ability to draw images

4. Layout Managers Scalable to more complex projects
Resizable to resolutions and aspect ratios
Standardized format (XML)
Drag and drop controls

5. XML
Standardized format
Easier to edit
Easier to read
Less code

6. Component Overlap Which draws on top Which handles events
Should you clip

7. Clipping Used for windows Need to clip both image and boundaries
Can be hard clipping rotated component (Unity)

8. Types Retained mode Immediate mode Contains GUI state
Rendered when needed

9. Retained mode (pros) Industry standard for years More object oriented
Central control
Good for looping back
Ex: dragging
Only renders when updating

10. Retained mode (cons) Lots of callbacks Harder for changing components
Uses separate place for 2D and 3D

11. Immediate mode (pros) All GUI code in 1 place
Build into pre-existing rendering code
Easier to add widget to screen
Redraws whole screen every time (can be con)
Good for games
If component not needed, don’t draw it

12. Immediate mode (cons) Hard for program to traverse GUI 1 frame of lag
GUI doesn’t control everything
1 frame of lag
Needs watchers at end of renderer to check what happened
Ex: dragging
Code is decentralized

13. Event Handling (Retained Mode)
Event class
Component activated
EventListener interface
handleEvent(Event e);
User-side function to perform event (ex: button click)

14. Component States (Immediate Mode)
Active
Mouse click
Hot
Mouse hover
Focus
Used for keyboard input

15. Active Mouse click Ex: button pressed
Maintains state until mouse release
Only hot item can be active

16. Hot Mouse hover Ex: button highlights Loses state when mouse exits
Only obtainable if (one of the following)
It is active
Nothing else is active

17. Focus
Takes keyboard input
Acts like active but does not lock hot

18. References
Adams, Ernest, and Andrew Rollings. Fundamentals of Game Design. Berkeley, CA: New Riders, Print.
Astle, Dave, and Kevin Hawkins. Beginning OpenGL Game Programming. Boston, MA: Thomson/Course Technology, Print.
Eckstein, Robert, Marc Loy, and Dave Wood. Java Swing. Sebastopol, CA: O'Reilly, Print.
Harrington, Jan L. Object-oriented C Data Structures for Real Programmers. San Diego: Morgan Kaufmann, Print.
Thorn, Alan. "Game Engine Design and Implementation." Game Engine Design and Implementation. Jones & Bartlett Learning, n.d. Web. 13 Oct
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