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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Qt Toolkit - The Qt/Embedded-specific classes</title><style type="text/css"><!--
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<h1 align=center> The Qt/Embedded-specific classes</h1><br clear="all">
<p>
Qt/Embedded classes fall into two classes - the majority are used by
every Qt/Embedded program, some are used only by the Qt/Embedded server.
The Qt/Embedded server program can be a client as well, as in the case of a
single-process installation. All Qt/Embedded specific source files live
in src/kernel and are suffixed _qws. -> indicates inheritance.
<p>
Client classes:
<p>
QFontManager
There is one of these per application. At application startup time
it reads the font definition file from $QTDIR/etc/fonts/fontdir
(or /usr/local/etc/qt-embedded/fonts/fontdir if QTDIR is undefined). It keeps
track of all font information and holds a cache of rendered fonts.
It also creates the font factories - QFontManager::QFontManager is the place
to add constructors for new factories. It provides a high-level interface
to requesting a particular font and calls QFontFactories to load fonts
from disk on demand. Note that this only applies to BDF and Truetype fonts;
Qt/Embedded's optimised .qpf font file format bypasses the QFontManager
mechanism altogether.
<p>
QDiskFont
This contains information about a single on-disk font file (e.g.
/usr/local/etc/qt-embedded/times.ttf, would be an example). It holds the file
path, information about whether the font is scalable, its weight, size and
Qt/Embedded name and so on. This information is used so that QFontManager
can find the closest match disk font (it uses a scoring mechanism
weighted towards matching names, then whether the font's italic, then
weight)
<p>
QRenderedFont
There is one and only one QRenderedFont for every unique font currently
loaded by the system (that is, each unique combination of name,
size, weight, italic or not, anti-aliased or not)
QRenderedFonts are reference counted; once noone is using the QRenderedFont
it is deleted along with its cache of glyph bitmaps. The QDiskFont
it was loaded from remains opened by its QFontFactory however.
<p>
QFontFactory (and descendants QFontFactoryBDF,QFontFactoryTtf)
These provide support for particular font formats, for instance the
scalable Truetype and Type1 formats (both supported in QFontFactoryTtf,
which uses Freetype 2) and the bitmap BDF format used by X.
It's called to open an on-disk font; once a font is opened it remains
opened, for quickness in creating new font instances from the disk font.
It can also create a QRenderedFont and convert from unicode values
to an index into the font file - glyphs are stored in the order and indexes
they are defined in the font rather than in unicode order for compactness.
<p>
QGlyph
This describes a particular image of a character from a QRenderedFont -
for example, the letter 'A' at 10 points in Times New Roman, bold italic,
anti-aliased. It contains pointers to a QGlyphMetrics structure with
information about the character and to the raw data for the glyph -
this is either a 1-bit mask or an 8-bit alpha channel. Each QRenderedFont
creates these on demand and caches them once created (note that this is
not currently implemented for Truetype fonts)
<p>
QMemoryManagerPixmap/QMemoryManager
This handles requests for space for pixmaps and also keeps track of
QPF format fonts (these are small 'state dumps' of QRenderedFonts,
typically 2-20k in size; they can be mmap'd direct from disk in order
to save memory usage). If a QPF font is found which matches a font request
no new QRenderedFont need be created for it. It's possible to strip out
all QFontFactory support and simply use QPFs if your font needs are modest
(for instance, if you only require a few fixed point sizes). Note that
no best-match loading is performed with QPFs, as opposed to those
loaded via QFontManager, so if you don't have the correct QPF for a point
size text in that size will simply not be displayed.
<p>
QScreen -> QLinuxFbScreen -> accelerated screens, QTransformedScreen
-> QVfbScreen
<p>
These encapsulate the framebuffer Qt/Embedded is drawing to, provide
support for mapping of coordinates for rotating framebuffers, allow
manipulation of the colour palette and provide access to offscreen
graphics memory for devices with separate framebuffer memories.
This is used for cacheing pixmaps and allowing accelerated pixmap->screen
blt's. QLinuxFbScreen and the accelerated screens use the Linux /dev/fb
interface to get access to graphics memory and information about the
characteristics of the device. The framebuffer device to open is specified
by QWS_DISPLAY. Only QTransformedScreen implements the support for rotated
framebuffers. QVfbScreen provides an X window containing an emulated
framebuffer (a chunk of shared memory is set aside as the 'framebuffer'
and blt'd into the X window) - this is intended as a debugging device
allowing users to debug their applications under Qt/Embedded without leaving
X. The accelerated screen drivers check to see if they can drive the
device specified by QWS_CARD_SLOT (which defaults to the usual position
of an AGP slot if not specified) and mmap its on-chip registers from
/dev/mem. They may also do chip-specific setup (initialising registers to
known values and so on). Finally, QScreen's are used to create new
QScreenCursors and QGfxes.
<p>
QScreenCursor -> accelerated cursor
-> QVfbCursor
This handles drawing the on-screen mouse cursor, saving and restoring
the screen under it for the non-accelerated cursor types.
<p>
QGfx -> RasterBase -> Raster -> accelerated driver
-> QGfxVfb
-> QGfxTransformedRaster
This class encapsulates drawing operations, a little like a low-level
QPainter. QGfxRaster and its descendants are specifically intended
for drawing into a raw framebuffer. They can take an offset for drawing
operations and a clipping region in order to support drawing into windows.
<p>
QLock, QLockHolder
This encapsulates a System V semaphore, used for synchronising access
to memory shared between Qt/Embedded clients. QLockHolder is a utility class
to make managing and destroying QLocks easier.
<p>
QDirectPainter
This is a QPainter which also gives you a pointer to the framebuffer
of the window it's pointing to, the window's clip region and so on.
It's intended to easily allow you to do your own pixel-level manipulation
of window contents
<p>
QWSSoundServer,Client
The Qt/Embedded server contains a simple sound player and mixer. Clients
can request the server play sounds specified as files.
<p>
QWSWindow
This contains the server's notion of an individual top level window -
the region of the framebuffer it's allocated, the client that created it
and so forth
<p>
QWSKeyboardHandler->subtypes
This handles keyboard/button input. QWSKeyboardHandler is subclassed
to provide for reading /dev/tty, an arbitrary low-level USB event device
(for USB keyboards) and some PDA button devices.
<p>
QWSMouseHandler->QCalibratedMouseHandler->mouse types
->mouse types
This handles mouse/touchpanel input. Descendants of QCalibratedMouseHandler
make use of filtering code which pretends 'jittering' of the pointer on
touchscreens; some embedded devices do this filtering in the kernel in
which case the driver doesn't need to inherit from QCalibratedMouseHandler.
<p>
QWSDisplay
This class exists only in the Qt/Embedded server and keeps track of
all the top-level windows in the system, as well as the keyboard and mouse.
<p>
QWSServer
This manages the Qt/Embedded server's Unix-domain socket connections to
clients. It sends and receives QWS protocol events and calls QWSDisplay
in order to do such things as change the allocation region of windows.
<p>
QWSClient
This encapsulates the client side of a Qt/Embedded connection and can
marshal and demarshal events.
<p>
QWSDisplayData
This manages a client's QWSClient, reading and interpreting events
from the QWS server. It connects to the QWS server on application startup,
getting information about the framebuffer and creating the memory manager.
Other information about the framebuffer comes directly from /dev/fb
in QLinuxFbScreen.
<p>
QWSCommands
These encapsulate the data sent to and from the QWS server
<p>
QCopChannel
QCop is a simple IPC mechanism for communication between Qt/Embedded
applications. String messages with optional binary data can be sent
to different channels.
<p>
QWSManager
This provides Qt/Embedded window management, drawing a title bar
and handling user requests to move, resize the window and so on.
<p>
QWSDecoration
Descendants of this class are different styles for the Qt/Embedded
window manager, for instance QWSWindowsDecoration draws Qt/Embedded
window frames in the style of Windows CE.
<p>
QWSPropertyManager
This provides the QWS client's interface to the QWS property system
(a simpler version of the X property system, it allows you to attach
arbitrary data to top-level windows, keyed by an integer)
<p>
QWSRegionManager
Used by both client and server to help manage top-level window regions
<p>
QWSSocket, QWSServerSocket
Provide Unix-domain sockets
<p><address><hr><div align="center">
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<td>Copyright 2000 Trolltech<td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
<td align="right"><div align="right">Qt version 2.3.1</div>
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