On Draw

The OnDraw() function within the CWizCEView class is the document/view architecture's equivalent of the standard Windows OnPaint() call. It is here that we use the standard GDI calls to blit the background bitmap to the screen:

CDC memDC;
memDC.CreateCompatibleDC(pDC);

//Select Bitmap into Memory DC
memDC.SelectObject(&Background);

pDC->
BitBlt(CViewOffsetX,CViewOffsetY,
CViewWidth,ViewHeight,&memDC,0,0,
SRCCOPY);

The background is a lot easier to blit than the sprites will be. Windows CE supports a subset of the ROP calls that Windows 9x and Windows NT support. pDC represents the PaintDC pointer that is passed to OnDraw. The memDC allows us to prepare the Background bitmap before blitting it to the screen. SRCCOPY does a straight copy, overwriting everything underneath. Later, when we piece together the foreground and background imagery from separate bitmaps, we'll use other ROPcodes to create a stencil.

With the variables we've set up, we can use a bitmap of whatever size we choose, and automatically adjust display for PalmPCs, H/PCs, and even the newer Pro machines with the higher resolution display. If more display types become available, it might be preferable to change the if/else statements into a switch/case procedure.

What you should see in your desktop emulation if everything went right is shown in Figure 7. I have my emulation environment set to dimensions of 480x240, a remnant of another project.

Figure 7 [zoom]

Conclusion of Episode I

In this half of the tutorial, we examined the development environment, learned a couple of differences between Windows CE and Windows 9x, judged the pros and cons of MFC for use in Windows CE game development, and set up the basics for the display functions of a Windows CE game. In the second half, we'll really get busy. I'll go into the animation requirements for sprite images (including the required bitmasks,) discuss the unique control system involved in a pen-based interface, examine the "object store", and suggest a technique for storing image data in a reusable, extensible form.

Jim has been involved in developing software since 1980, and has developed a taste for operating systems as esoteric as AmigaDOS and PalmOS. He's currently working on an RPG engine for Windows CE. His only advice for someone trying to program Windows is, "Punching the monitor hurts you more than Microsoft". He can be reached as amok@ionet.net.