Chapter 2: Drawing on the Screen - Programming Microsoft Windows Ce Net 3Rd [Electronic resources] نسخه متنی

Chapter 2: Drawing on the Screen

Overview

Chapter 1, the example program HelloCE had one task: to display a line of text on the screen. Displaying that line took only one call to DrawText, with Windows CE taking care of such details as the font and its color, the positioning of the line of text inside the window, and so forth. Given the power of a graphical user interface (GUI), however, an application can do much more than simply print a line of text on the screen. It can craft the look of the display down to the most minute of details.

Over the life of the Microsoft Windows operating system, the number of functions available for crafting these displays has expanded dramatically. With each successive version of Windows, functions have been added that extend the tools available to the programmer. As functions were added, the old ones remained so that even if a function had been superseded by a new function, old programs would continue to run on the newer versions of Windows. The approach in which function after function is piled on while the old functions are retained for backward compatibility was discontinued with the initial version of Windows CE. Because of the requirement to produce a smaller version of Windows, the CE team took a hard look at the Win32 API and replicated only the functions absolutely required by applications written for the Windows CE target market.

One of the areas of the Win32 API hardest hit by this reduction was graphical functions. It's not that you now lack the functions to do the job—it's just that the high degree of redundancy in the Win32 API led to some major pruning of the graphical functions. An added challenge for the programmer is that different Windows CE platforms have subtly different sets of supported APIs. One of the ways in which Windows CE graphics support differs from that of its desktop cousins is that Windows CE doesn't support the different Part I of this book, reviews the drawing features supported by Windows CE. One of the most important facts to remember is that while Windows CE doesn't support the full Win32 graphics API, its rapid evolution has resulted in it supporting some of the newest functions in Win32—some so new that you might not be familiar with them. This chapter shows you the functions you can use and how to work around the areas where certain functions aren't supported under Windows CE.