Читать «Применение Windows API» онлайн - страница 51

 _timer.Set(50);

}

void Controller::Paint() {

 PaintCanvas canvas(_hwnd);

 _view.Paint(canvas);

}

The Update method of View is the workhorse of our program. It creates the image in the buffer. We then call InvalidateRectangle to force the repaint of our window (the last parameter, FALSE, tells Windows not to clear the previous image — we don't want it to flash white before every frame).

Here's the class View, with the three bitmaps.

class View {

public:

 View(HINSTANCE hInst);

 void SetSize(int cxNew, int cyNew) {

  _cx = cxNew;

  _cy = cyNew;

 }

 void Step() { ++_tick; }

 void Update(Canvas& canvas);

 void Paint(Canvas& canvas);

private:

 int _cx, _cy;

 int _tick;

 Bitmap _bitmapBuf; // for double buffering

 Bitmap _background;

 int _widthBkg, _heightBkg;

 Bitmap _sprite;

 Bitmap _mask;

 int _widthSprite, _heightSprite;

};

View::View(HINSTANCE hInst) : _tick (0) {

 // Load bitmap from file

 _background.Load("picture.bmp");

 // Load bitmap from resource

 _background.GetSize(_widthBkg, _heightBkg);

 // Load bitmaps from resources

 _sprite.Load(hInst, IDB_FANNY);

 _mask.Load(hInst, IDB_MASK);

 _sprite.GetSize(_widthSprite, _heightSprite);

 DesktopCanvas canvas;

 _bitmapBuf.CreateCompatible(canvas, 1, 1);

 _cx = 1;

 _cy = 1;

}

And here's the implementation of Update. We create a bitmap canvas in memory, making it compatible with the current display canvas. We blit the background image into it, then blit the mask and the sprite (notice the change of position for each frame). Finally, we transfer the complete bitmap into our buffer (overloaded assignment operator at work!).

void View::Update(Canvas& canvas) {

 const double speed = 0.01;

 Bitmap bmp(canvas, _cx, _cy);

 BitmapCanvas bmpCanvas(canvas, bmp);

 RECT rect = { 0, 0, _cx, _cy };

 bmpCanvas.WhiteWash(rect);

 // Do the off-line drawing

 Blitter bltBkg(_background);

 bltBkg.BlitTo(bmpCanvas);

 int xRange = (_widthBkg - _widthSprite) / 2;

 int yRange = (_heightBkg - _heightSprite) / 2;

 int x = xRange + static_cast<int>(xRange * sin(speed * _tick));

 int y = yRange + static_cast<int>(yRange * cos(4 * speed * _tick));

 Blitter bltMask(_mask);

 bltMask.SetMode(SRCPAINT);

 bltMask.SetDest(x, y);

 bltMask.BlitTo(bmpCanvas);

 Blitter bltSprite(_sprite);

 bltSprite.SetMode(SRCAND);

 bltSprite.SetDest(x, y);

 bltSprite.BlitTo(bmpCanvas);

 // update the buffer

 _bitmapBuf = bmp;

}

For completeness, here's the definition of bitmap canvas. You draw directly on this canvas using standard canvas methods, like Line, Text, SetPixel, etc... Here we only blit bitmaps into it.

class BitmapCanvas: public MemCanvas {

public:

 BitmapCanvas(HDC hdc, HBITMAP hBitmap) : MemCanvas(hdc) {

  // convert bitmap to format compatible with canvas

  _hOldBitmap = reinterpret_cast(::SelectObject(_hdc, hBitmap));

 }

 ~BitmapCanvas() {

  ::SelectObject(_hdc, _hOldBitmap);

 }

private:

 HBITMAP _hOldBitmap;

};

class MemCanvas: public Canvas {

public:

 MemCanvas(HDC hdc) : Canvas(::CreateCompatibleDC(hdc)) {}

 ~MemCanvas() {

  ::DeleteDC(_hdc);

 }

};

Now, if you want more speed, read about DirectDraw.