HippoCanvas
HippoCanvas is a generic user interface element that can draw Cairo graphics, respond to key and mouse events, and lay out other widgets. It is currently used to implement a number of Sugar's custom widgets (toolbars, rounded buttons, etc.) and to lay out the screen.
On the OLPC, HippoCanvas is a GTK widget and it can contain other GTK widgets, so the programmer can freely combine HippoCanvas and other widgets. While Sugar does not require that activities be written using HippoCanvas, those that do can look more visually consistent with other activities.
Contents
- 1 Rationale
- 2 Classes and Interfaces
- 3 Enumerations
- 3.1 PackFlags enumeration
- 3.2 CascadeMode enumeration
- 3.3 StockColor enumeration
- 3.4 CanvasPointer enumeration
- 3.5 ItemAlignment enumeration
- 3.6 CanvasSizeMode enumeration
- 3.7 ScrollbarPolicy enumeration
- 3.8 EventType enumeration
- 3.9 MotionDetail enumeration
- 3.10 Key enumeration
- 3.11 Orientation enumeration
- 3.12 Side enumeration
- 3.13 Gravity enumeration
- 4 Internal objects
- 5 Links
Rationale
HippoCanvas was originally designed to be a cross-platform UI layer built on top of other windowing systems. It is used in Sugar to work around deficiencies GTK's layout system. [1] HippoCanvas also makes it easier to prototype custom widgets, and its Python interface can be somewhat simpler than native GTK widgets.
Classes and Interfaces
Canvas object
Derives from GtkContainer. This is a GTK widget that hosts a root CanvasItem.
CanvasItem interface
CanvasContext interface
CanvasBox object
Derives from GObject, implements CanvasItem, CanvasContext.
CanvasWidget object
Derives from CanvasBox.
CanvasImage object
Derives from CanvasBox.
CanvasText object
Derives from CanvasBox.
CanvasLink object
Derives from CanvasText.
Enumerations
PackFlags enumeration
CascadeMode enumeration
StockColor enumeration
CanvasPointer enumeration
ItemAlignment enumeration
CanvasSizeMode enumeration
ScrollbarPolicy enumeration
EventType enumeration
MotionDetail enumeration
Key enumeration
Orientation enumeration
Side enumeration
Gravity enumeration
Internal objects
Event object
Encapsulates information about a mouse action or keypress. It is currently only used internally.
Rectangle object
Describes a rectangle on the screen in integer coordinates. It is currently only used internally.
Fields:
- x
- y
- width
- height
Methods:
- rectangle.intersect(rect2, dest)
- rectangle.equals(rect2) => boolean
Links
- A blog entry on the rationale for HippoCanvas.
- A mailing list post about HippoCanvas.
- HippoCanvas source v. 0.2.6
