Drawing Text

The very important topic of displaying text is left until this late in the chapter because drawing text to the screen is (in general) more complex than drawing simple graphics. Although displaying a line or two of text when you're not that bothered about the appearance is extremely easy — it takes one single call to the Graphics.DrawString() method; if you are trying to display a document that has a fair amount of text in it, you rapidly find that things become a lot more complex. This is for two reasons:

• If you're concerned about getting the appearance just right, you must understand fonts. Whereas shape drawing requires brushes and pens as helper objects, the process of drawing text requires fonts as helper objects. And understanding fonts is not a trivial task.

• Text needs to be very carefully laid out in the window. Users generally expect words to follow naturally from one word to another and to be lined up with clear spaces in between. Doing that is harder than you might think. For starters, you don't usually know in advance how much space on the screen a word is going to take up. That has to be calculated (using the Graphics.MeasureString() method). Also, the space a word occupies on the screen affects where in the document every subsequent word is placed. If your application does any line wrapping, it'll need to assess word sizes carefully before deciding where to place the line break. The next time you run Microsoft Word, look carefully at the way Word is continually repositioning text as you do your work: there's a lot of complex processing going on there. Chances are that any GDI+ application you work on won't be nearly as complex as Word. However, if you need to display any text, many of the same considerations apply.

In short, high-quality text processing is tricky to get right. However, putting a line of text on the screen, assuming you know the font and where you want it to go, is actually very simple. Therefore, the next section presents a quick example that shows how to display some text, followed by a short review of the principles of fonts and font families and a more realistic (and involved) text-processing example, CapsEditor.