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CGLIB - Constraint-based Graphics Library

CGLIB is a powerful constraint-based graphics library that enables developers to specify layouts and interactions within graphics applications. With implementations in B-Prolog, Java, and C, it supports a wide array of applications including drawing editors, interactive user interfaces, and games. Features include the ability to use constraints for positioning objects and defining action rules for events. The library simplifies the creation of complex graphic systems by managing object attributes and event handling through a robust constraint programming model.

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CGLIB - Constraint-based Graphics Library

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  1. CGLIB - Constraint-based Graphics Library • Features • Use constraints to specify the layouts of objects • Use action rules to specify interactions • Implementation • Implemented in B-Prolog, Java, and C • Applications • Drawing editors, interactive user interfaces, document authoring, animation, information visualization, intelligent agents, and games.

  2. An Illustrative Example go:- cgButton(B), (1) B^text #= “Hello World!”, (2) handleButtonClick(B), (3) cgShow(B). (4) handleButtonClick(B), (5) {actionPerformed(B)} (6) => (7) halt. (8)

  3. cgButton(X) Create a button X cgButton([X1,…,Xn]) Create a list of buttons Objects

  4. Base Derivative Attributes of Objects B is a button y B^window B^x B^y B^width B^height B^text B^color B^font B^rightX B^bottomY B^centerX B^centerY B^leftTopPoint B^leftBottomPoint B^rightTopPoint B^rightBottomPoint B^center x height width

  5. Constraints • Arithmetic constraints • O1^x +O1^width//2 #= O2^x • O1^centerX #= O2^x • Positioning constraints • cgLeft(O1,O2) • Same property constraints • cgSame([O1,O2],size) • cgSame([O1,O2],width,100)

  6. Constraints (Cont.) • Grid constraints cgGrid([[_, S1,_], [S2,S3,S4], [_,S5,_]]) cgGrid([[Bc,Bdiv,Bmul,Bsub], [B7,B8, B9, Badd], [B4,B5, B6, Badd], [B1,B2, B3, Beq], [B0,B0, Bdot,Beq]],1,1),

  7. Constraints (Cont.) • Table constraints cgTable([[Larc,Arc,Button,Lbutton], [Lcheckbox, Checkbox, Choice, Lchoice], [Lcircle,Circle,Image,Limage], [Llabel,Label,Line,Lline], [Llist,List,Oval,Loval], [Lrrectangle,Rrectangle,Rectangle,Lrectangle], [Lpolygon,Polygon,Square,Lsquare], [Lstar,Star,TextArea,Ltextarea], [Ltextfield,TextField,TextBox,Ltextbox], [Ltriangle,Triangle,_,_]],20,20),

  8. Constraints (Cont.) • Tree constraints T=node(C0,[node(C1,[node(C3,[] node(C4,[])]), node(C2,[node(C5,[]), node(C6,[])])]), cgTree(T,top_down,10,10,centered).

  9. Event Handling • Action rule • Examples Agent ConditionSeq {Event} => ActionSeq handleButtonClick(B),{actionPerformed(B)} => … handleMousePress(O),{mousePressed(O,E)} => E^x #= X, E^y #= Y, write(mouse_pressed_at(X,Y)),nl. handleKeyType(O),{keyTyped(O,E)} => E^char #= Char, write(Char).

  10. Other Primitives in CGLIB • Packing and showing objects • cgPack(O)& cgShow(O) • Altering and moving objects • O^attr #:= Value • cgScale(O,F)& cgResize(O,W,H) • cgMove(O,X,Y) • Animation • cgSleep(Time) • Generating Java applets • cgStartRecord(FileName) & cgStopRecord

  11. Demo of CGLIB

  12. Related Work • Postscript & Latex • Every detail must be specified • Java & Tcl/Tk • Layout managers are helpful for certain layouts • Functional programming • New data types and functions for events, time, and behaviors • Constraints & Constraint programming • Sketchpad, ThinkLab, Amulet, SubArctic

  13. Further Work • Extension of the set of base objects • Application-specific objects • 3D objects • Constructs for users to define their own objects • Non-linear and soft constraints • Improving the performance • Constraint solving • Graphics rendering

  14. Papers • N.F. Zhou: CGLIB - A Constraint-based Graphics Library, Software - Practice and Experience, Vol. 33, No.13, pp.1199-1216, 2003. • N.F. Zhou: Authoring Graphics-rich and Interactive Documents in CGLIB - A Constraint-based Graphics Library, Proceedings of the ACM Symposium on Document Engineering, pp.28-38, November, 2001.

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