DC functions, canvas methods

The Windows Way of performing graphics operations is to provide every sort of function you can imagine for every operation, no matter how obscure. The Basic Way is to provide the most important graphics operations through a few methods loaded with optional arguments. The Line method, for example, wraps up the functionality of several API functions. Table 7-3 compares device context functions in Windows with canvas methods in Visual Basic.

Operation	Windows Way	Basic Way
Point drawing	SetPixel	PSet
Point reading	GetPixel	Point
Line drawing	LineTo and MoveToEx	Line method or Line control
Circle, pie, and arc drawing	Ellipse, Chord, Arc, and Pie	Circle method or Shape control
Polygon drawing	Polygon, PolyPolygon, and SetPolyFillMode	Draw it line by line
Blitting	BitBlt, StretchBlt, PatBlt, and StretchDIBits	PaintPicture method, Image control with Stretch property
Filling shapes	FloodFill and other Fill functions	Visual Basic can create filled shapes but has no way of filling shapes later
Icon painting	LoadIcon, CreateIcon, Destroy-Icon, and DrawIcon	Picture object
Bitmap painting	Various Bitmap functions and SelectObject	Picture object
Metafile recording	CreateMetaFile and CloseMetaFile	No way
Metafile playing	CopyMetaFile, GetMetafile, and DeleteMetaFile functions	Picture object
Scrolling	ScrollDC	No way
Managing regions	Various Rgn and Path functions	No way
Printing	Escape and Doc functions	Methods on Print object
Text output	Many functions including Text-Out, ExtTextOut, and GrayString	Print
Text sizing	GetTextExtent	TextWidth and TextHeight
Text alignment	SetTextAlign, SetTextJustification, and SetTextCharacterExtra functions	No way

Table 7-3. Graphics methods in Windows and in Visual Basic.

To the hardcore programmer, what Visual Basic doesn’t do is more telling than what it does. Some points of interest:

Visual Basic doesn’t provide any way to fill a shape. QuickBasic had the Paint statement, but it didn’t survive the transition to Visual Basic. Usually, you don’t need to fill shapes as a separate step because you can specify filling when you draw the shape. Nevertheless, “The Windows Way of Drawing,” page 377, provides a function for those rare occasions when you need to fill after the fact.
Visual Basic doesn’t draw polygons. You can use the Line method to draw polygons one side at a time, but you might find the Windows
Way more convenient.
Regions are a somewhat obscure part of Windows that you might oc-
casionally need. Visual Basic doesn’t do them, and this book doesn’t either. But you should be able to apply the general principles described in this chapter to the problem.
You can draw irregular curves with Bezier curves as described on
page 382.
You can use paths (as described on page 385) to create irregularly shaped regions.