Chapter 1

The clipping region defines the region to which you want your graphics to be clipped.
You can specify a simple rectangle or a region that may be arbitrarily complex. Use
SetClippingRect() to set a rectangular clipping region and CancelClippingRect()
to cancel it. By default, no clipping region (other than the device limits) applies.
Justification
Specialized justification settings for a variant of DrawText() can be set, although it's best
not to call these directly from your own code. Instead, use the FORM component in Symbian
OS to create text views for you.
Use Reset() to set all contexts to default values.
11.2.3 Drawing Functions
Once you’ve set up the GC to your liking, there are numerous ways to draw to the screen. All
GC functions are virtual so they can be implemented in derived classes. Furthermore, all GC
functions are designed to succeed and so don’t return anything (in C++ declarations, they
return void). This requirement is such that multiple GC commands can be batched into a
single message and sent to a server for execution – this would not be possible if any GC
command had a return value.
Note that line drawing (including arcs and the last line in a polyline) excludes the last point of
the line. As with the specification of TRect,this is a mixed blessing: sometimes it makes
things easier, sometimes harder. If the last pixel was plotted automatically, it would be
harder to unplot it in the cases in which this behavior was not desired. However, it's easy
enough to fix tricky cases by using Plot().
Check out the SDK for the interpretation of DrawArc() parameters. DrawPolyLine()
starts at the current cursor position set with MoveTo(), any XxxTo() or XxxBy() function,
or DrawPolyLine(). Effectively, DrawPolyLine() uses DrawLineTo() to draw to every
point specified.
Points and lines
You can plot a single point or draw an arc, a line, or a polyline. These functions all use the
current pen; here are their declarations in gdi.h:
virtual void MoveTo(const TPoint& aPoint) = 0;
virtual void MoveBy(const TPoint& aVector) = 0;
virtual void Plot(const TPoint& aPoint) = 0;
virtual void DrawArc(const TRect& aRect,
const TPoint& aStart,
const TPoint& aEnd) = 0;
virtual void DrawLine(const TPoint& aPoint1,
const TPoint& aPoint2) = 0;
virtual void DrawLineTo(const TPoint& aPoint) = 0;
virtual void DrawLineBy(const TPoint& aVector) = 0;
virtual void DrawPolyLine(const CArrayFix* aPointList) = 0;