Having trouble with clipping? If you''re having trouble because you are passing the blitter coordinates that are off the screen (example: (-5,-6) or (805,606) on an 800x600 screen), use code like the stuff below. I was doing this the hard way for a long time before I realized how easy it was:
if ( xTo < 0 )
{
rcFrom.left -= xTo;
xTo = 0;
}
if ( yTo < 0 )
{
rcFrom.top -= yTo;
yTo = 0;
}
if ( xTo + rcFrom.right - rcFrom.left >= SCREEN_W )
{
rcFrom.right -= xTo + rcFrom.right - rcFrom.left - SCREEN_W;
}
if ( yTo + rcFrom.bottom - rcFrom.top >= SCREEN_H )
{
rcFrom.bottom -= yTo + rcFrom.bottom - rcFrom.top - SCREEN_H;
}
if ( rcFrom.right - rcFrom.left <= 0 // rcFrom.bottom - rcFrom.top <= 0 )
return TRUE;
rcFrom is the source rectangle and xTo and yTo are the destination coordinates. This could, of course, be used for any rectangle; it doesn''t need to be the screen. Hope this helps someone...
- mallen22@concentric.net
- http://mxf_entertainment.tripod.com/
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INFO: Clipping Help
This is what I do when using the IDirectDrawSurface3->Blt() function, to fill out the Src RECT and Destination RECT structures:
ddctrl_Scr* is the height and width of the screen
x and y are the desired screen coordinates. Width and Height are the sprite''s (src surface''s) dimensions...
For some reason, specifying the real right and bottom coordinate for a 10x10 image (meaning bottom = 9 and right = 9) makes it become 9x9 on screen. So, I pass a 11x11 rectangle for a 10x10 surface, etc. ...
if ((y >= ddctrl_ScrHeight) // (x >= ddctrl_ScrWidth) // (y+height) < 0 // (x+width) < 0)
{
return FALSE;
}
if (y < 0)
{
SpriteRect.top = -y;
ScreenRect.top = 0;
}
else
{
SpriteRect.top = 0;
ScreenRect.top = y;
}
if (y+height > ddctrl_ScrHeight)
{
SpriteRect.bottom = ddctrl_ScrHeight - y;
ScreenRect.bottom = ddctrl_ScrHeight;
}
else
{
SpriteRect.bottom = height;
ScreenRect.bottom = y+height;
}
if (x < 0)
{
SpriteRect.left = -x;
ScreenRect.left = 0;
}
else
{
SpriteRect.left = 0;
ScreenRect.left = x;
}
if (x+width > ddctrl_ScrWidth)
{
SpriteRect.right = ddctrl_ScrWidth - x;
ScreenRect.right = ddctrl_ScrWidth;
}
else
{
SpriteRect.right = width;
ScreenRect.right = x+width;
}
Åke Wallebom
ddctrl_Scr* is the height and width of the screen
x and y are the desired screen coordinates. Width and Height are the sprite''s (src surface''s) dimensions...
For some reason, specifying the real right and bottom coordinate for a 10x10 image (meaning bottom = 9 and right = 9) makes it become 9x9 on screen. So, I pass a 11x11 rectangle for a 10x10 surface, etc. ...
if ((y >= ddctrl_ScrHeight) // (x >= ddctrl_ScrWidth) // (y+height) < 0 // (x+width) < 0)
{
return FALSE;
}
if (y < 0)
{
SpriteRect.top = -y;
ScreenRect.top = 0;
}
else
{
SpriteRect.top = 0;
ScreenRect.top = y;
}
if (y+height > ddctrl_ScrHeight)
{
SpriteRect.bottom = ddctrl_ScrHeight - y;
ScreenRect.bottom = ddctrl_ScrHeight;
}
else
{
SpriteRect.bottom = height;
ScreenRect.bottom = y+height;
}
if (x < 0)
{
SpriteRect.left = -x;
ScreenRect.left = 0;
}
else
{
SpriteRect.left = 0;
ScreenRect.left = x;
}
if (x+width > ddctrl_ScrWidth)
{
SpriteRect.right = ddctrl_ScrWidth - x;
ScreenRect.right = ddctrl_ScrWidth;
}
else
{
SpriteRect.right = width;
ScreenRect.right = x+width;
}
Åke Wallebom
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