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| author | nyamatongwe <devnull@localhost> | 2000-03-08 01:36:00 +0000 |
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| committer | nyamatongwe <devnull@localhost> | 2000-03-08 01:36:00 +0000 |
| commit | bf3d80d54d696ad123f9415dda1c6fe62c7a20cc (patch) | |
| tree | 12898a1d1b9db690270b093a0182239d3aa85de6 /doc/Design.html | |
| download | scintilla-mirror-bf3d80d54d696ad123f9415dda1c6fe62c7a20cc.tar.gz | |
Initial revision
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diff --git a/doc/Design.html b/doc/Design.html new file mode 100644 index 000000000..d6fd6ee06 --- /dev/null +++ b/doc/Design.html @@ -0,0 +1,247 @@ +<?xml version="1.0"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta name="generator" content="HTML Tidy, see www.w3.org" /> + <meta name="generator" content="SciTE" /> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> + <title> + Scintilla and SciTE + </title> + </head> + <body bgcolor="#FFFFFF" text="#000000"> + <table bgcolor="#000000" width="100%" cellspacing="0" cellpadding="0" border="0"> + <tr> + <td> + <img src="SciTEIco.png" border="3" height="64" width="64" alt="Scintilla icon" /> + </td> + <td> + <a href="index.html" style="color:white;text-decoration:none"><font size="5">Scintilla + Component Design</font></a> + </td> + </tr> + </table> + <h2> + Top level structure + </h2> + <p> + Scintilla consists of three major layers of C++ code + </p> + <ul> + <li> + Portability Library + </li> + <li> + Core Code + </li> + <li> + Platform Events and API + </li> + </ul> + <p> + The primary purpose of this structure is to separate the platform dependent code from the + platform independent core code. This makes it easier to port Scintilla to a new platform and + ensures that most readers of the code do not have to deal with platform details. To minimise + portability problems and avoid code bloat, a conservative subset of C++ is used in Scintilla + with no exception handling, templates, run time type information or use of the standard C++ + library. + </p> + <p> + The currently supported platforms, Windows and GTK+/Linux are fairly similar in many ways. + Each has windows, menus and bitmaps. These features generally work in similar ways so each + has a way to move a window or draw a red line. Sometimes one platform requires a sequence of + calls rather than a single call. At other times, the differences are more profound. Reading + the Windows clipboard occurs synchronously but reading the GTK+ clipboard requires a request + call that will be asynchronously answered with a message containing the clipboard data. + </p> + <br /> + <h3> + Portability Library + </h3> + <p> + This is a fairly small and thin layer over the platform's native capabilities. + </p> + <p> + The portability library is defined in Platform.h and is implemented once for each platform. + PlatWin.cxx defines the Windows variants of the methods and PlatGTK.cxx the GTK+ variants. + </p> + <p> + Several of the classes here hold platform specific object identifiers and act as proxies to + these platform objects. Most client code can thus manipulate the platform objects without + caring which is the current platform. Sometimes client code needs access to the underlying + object identifiers and this is provided by the GetID method. The underlying types of the + platform specific identifiers are typedefed to common names to allow them to be transferred + around in client code where needed. + </p> + <h4> + Point, PRectangle + </h4> + <p> + These are simple classes provided to hold the commonly used geometric primitives. A + PRectangle follows the Mac / Windows convention of not including its bottom and right sides + instead of including all its sides as is normal in GTK+. It is not called Rectangle as this may be + the name of a macro on Windows. + </p> + <h4> + Colour, ColourPair, Palette + </h4> + <p> + Colour holds a platform specific colour identifier - COLORREF for Windows and GdkColor for + GTK+. The red, green and blue components that make up the colour are limited to the 8 bits of + precision available on Windows. ColourPairs are used because not all possible colours are + always available. Using an 8 bit colour mode, which is a common setting for both Windows and + GTK+, only 256 colours are possible on the display. Thus when an application asks for a dull + red, say #400000, it may only be allocated an already available colour such as #800000 or + #330000. With 16 or 2 colour modes even less choice is available and the application will + have to use the limited set of already available colours. + </p> + A Palette object holds a set of colour pairs and can make the appropriate calls to ask to + allocate these colours and to see what the platform has decided will be allowed. + <h4> + Font + </h4> + <p> + Font holds a platform specific font identifier - HFONT for Windows, GdkFont* for GTK+. It + does not own the identifier and so will not delete the platform font object in its + destructor. Client code should call Destroy at appropriate times. + </p> + <h4> + Surface + </h4> + <p> + Surface is an abstraction over each platform's concept of somewhere that graphical drawing + operations can be done. It may wrap an already created drawing place such as a window or be + used to create a bitmap that can be drawn into and later copied onto another surface. On + Windows it wraps a HDC and possibly a HBITMAP. On GTK+ it wraps a GdkDrawable* and possibly a + GdkPixmap*. Other platform specific objects are created (and correctly destroyed) whenever + required to perform drawing actions. + </p> + <p> + Drawing operations provided include drawing filled and unfilled polygons, lines, rectangles, + ellipses and text. The height and width of text as well as other details can be measured. + Operations can be clipped to a rectangle. Most of the calls are stateless with all parameters + being passed at each call. The exception to this is line drawing which is performed by + calling MoveTo and then LineTo. + </p> + <h4> + Window + </h4> + <p> + Window acts as a proxy to a platform window allowing operations such as showing, moving, + redrawing, and destroying to be performed. It contains a platform specific window identifier + - HWND for Windows, GtkWidget* for GTK+. + </p> + <h4> + ListBox + </h4> + <p> + ListBox is a subclass of Window and acts as a proxy to a platform listbox adding methods for + operations such as adding, retrieving, and selecting items. + </p> + <h4> + Menu + </h4> + <p> + Menu is a small helper class for constructing popup menus. It contains the platform specific + menu identifier - HMENU for Windows, GtkItemFactory* for GTK+. Most of the work in + constructing menus requires access to platform events and so is done in the Platform Events + and API layer. + </p> + <h4> + Platform + </h4> + <p> + The Platform class is used to access the facilities of the platform. System wide parameters + such as double click speed and chrome colour are available from Platform. Utility functions + such as DebugPrintf are also available from Platform. + </p> + <h3> + Core Code + </h3> + <p> + The bulk of Scintilla's code is platform independent. This is made up of the CellBuffer, + ContractionState, Document, Editor, Indicator, LineMarker, Style, ViewStyle, KeyMap, + ScintillaBase, CallTip, + and AutoComplete primary classes. + </p> + <h4> + CellBuffer + </h4> + <p> + A CellBuffer holds text and styling information, the undo stack, the assignment of line + markers to lines, and the fold structure. + </p> + <p> + A cell contains a character byte and its associated style byte. The current state of the + cell buffer is the sequence of cells that make up the text and a sequence of line information + containing the starting position of each line and any markers assigned to each line. + </p> + <p> + The undo stack holds a sequence of actions on the cell buffer. Each action is one of a text + insertion, a text deletion or an undo start action. The start actions are used to group + sequences of text insertions and deletions together so they can be undone together. To + perform an undo operation, each insertion or deletion is undone in reverse sequence. + Similarly, redo reapplies each action to the buffer in sequence. Whenever a character is + inserted in the buffer either directly through a call such as InsertString or through undo or + redo, its styling byte is initially set to zero. Client code is responsible for styling each + character whenever convenient. Styling information is not stored in undo actions. + </p> + <h4> + Document + </h4> + <p> + A document contains a CellBuffer and deals with some higher level abstractions such as + words, DBCS character sequences and line end character sequences. It is responsible for + managing the styling process and for notifying other objects when changes occur to the + document. + </p> + <h4> + Editor + </h4> + <p> + The Editor object is central to Scintilla. It is responsible for displaying a document and + responding to user actions and requests from the container. It uses ContractionState, Indicator, + LineMarker, Style, and ViewStyle objects to display the document and a KeyMap class to + map key presses to functions. + The visibility of each line is kept in the ContractionState which is also responsible for mapping + from display lines to documents lines and vice versa. + </p> + <p> + There may be multiple Editor objects attached to one Document object. Changes to a + document are broadcast to the editors through the DocWatcher mechanism. + </p> + <h4> + ScintillaBase + </h4> + <p> + ScintillaBase is a subclass of Editor and adds extra windowing features including display of + calltips, autocompletion lists and context menus. These features use CallTip and AutoComplete + objects. This class is optional so a lightweight implementation of Scintilla may bypass it if + the added functionality is not required. + </p> + <h3> + Platform Events and API + </h3> + <p> + Each platform uses different mechanisms for receiving events. On Windows, events are + received through messages and COM. On GTK+, callback functions are used. + </p> + <p> + For each platform, a class is derived from ScintillaBase (and thus from Editor). This is + ScintillaWin on Windows and ScintillaGTK on GTK+. These classes are responsible for + connecting to the platforms event mechanism and also to implement some virtual methods in + Editor and ScintillaBase which are different on the platforms. For example, this layer has to + support this difference between the synchronous Windows clipboard and the asynchronous GTK+ + clipboard. + </p> + <p> + The external API is defined in this layer as each platform has different preferred styles of + API - messages on Windows and function calls on GTK+. This also allows multiple APIs to be + defined on a platform. The currently available API on GTK+ is similar to the Windows API and + does not follow platform conventions well. A second API could be implemented here that did + follow platform conventions. + </p> + </body> +</html> + |