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Notes on the model-view-control paradigm.
There is more in the old development wiki - not moved here yet though.
1) The Model: Buffer The Buffer is the in-memory representation of a LyX file format. The Buffer does not (should not) have any information on what part of it is represented on screen. There is one unique Buffer per opened LyX file. 2) The Controller: BufferView/Painter The BufferView is a tool used by the view that translates a part of the Buffer contents into drawing routines. The BufferView asks each inset of the Buffer to draw itself onto the screen using the Painter. There is only Buffer loaded per BufferView. While there is the possibility to switch Buffer inside the BufferView, the goal is to instantiate a new BufferView on each Buffer switch. The Painter is just a virtual interface to formalize each kind of drawing routines (text, line, rectangle, etc). The BufferView also contains a Cursor which may or may not be visible on screen. The cursor is really just a bookmark to remember where the next Buffer insertion/deletion is going to take place. 3) The View: WorkArea (and it's qt4 specialisation GuiWorkArea) This contains the real screen area where the drawing is done by the Painter. One WorkArea holds one unique BufferView. While it could be possible that multiple WorkArea share one BufferView, this is not possible right now. The WorkArea also provide a scrollbar which position is translated into scrolling command to the inner BufferView. The WorkArea use the BufferView to translate each keyboard or mouse events into terms that the Buffer can understand: - insert/delete char - select char - etc. 4) The Window: LyXView (and its qt4 specialisation GuiView) This is a full window containing a menubar, toolbars, a tabbar and a WorkArea. One LyXView could in theory contain multiple WorkArea (ex: with split window) but this number is limited to one only for now. In any case, there would be only one WorkArea that gets the focus at a time. Now, concerning the TabBar versus TabWidget issue. Right now, there is only one WorkArea and the TabBar just used to tell the BufferView inside the WorkArea to switch to this another Buffer. With a TabWidget, each Tab would own its own WorkArea. Clicking on a tab would switch a WorkArea instead of a Buffer.