Thanks Alain,

Its not quite there but its close.
I've been getting my butt kicked trying to understand why scaling 
affects drawing the way it does.  I have to compensate for scaling.
Last week I had some elaborate method for doing what I did and just
as I thought it was going to work, poof.  It didn't work.

Thank you much for you effort.  I hope to get it to work soon.


W.


-----Original Message-----
From: Alain Pastor [mailto:apastor@...]
Sent: Tuesday, March 01, 2005 5:53 AM
To: futurebasic@...
Subject: Re: [FB] scaling, centering and rotating


Edwards, Waverly a écrit :
> I'm probably missing the obvious but I'm having a hard time centering
> a rect within a rect.  The coordinate system I'm using is the same as
> CG not QD where the Y axis is upside down.  When I scale the rect it
> becomes more and more off center.  I also planned on rotating the
> object from its center but I haven't gotten past getting the object 
> scaled and centered.
> 
> Any help would be much appreciated.
> 

Please, don't even try to ask me why, but your example *seems* to work 
doing the following (I don't think it is correct, though):


include "Tlbx CoreGraphics.incl"

local fn rotateOnCenter( ctx as CGContextRef , sRect as ^CGRect, dRect 
as ^CGRect, angle as single )
dim as single left,top,right,bottom
dim as CGPoint p

left   = sRect.origin.x
top    = sRect.origin.y
right  = left + sRect.size.width
bottom = top + sRect.size.height

// draw our RECT so that top of RECT is at the port origin. To do this
// we offset our rect so that the Y value is at (portHeight - 
drawRectHeight)
fn CGRectOffset(sRect, sRect, 0, (bottom - top) - sRect.size.height)

// in case we want to rotate about the center of the RECT
p.x = sRect.origin.x + sRect.size.width\2
p.y = sRect.origin.y + sRect.size.height\2
fn CGContextTranslateCTM(ctx, p.x, p.y)
fn CGContextRotateCTM(ctx, -angle)
fn CGContextTranslateCTM(ctx, -p.x, -p.y)

end fn

LOCAL
dim tmpR as CGRect
dim as single t,l,b,r
dim as single tt,ll,bb,rr
DIM as single cy,cx
LOCAL FN centerCGRect( ctx as CGContextRef, sRect as ^CGRect ,dRect as 
^CGRect, scale as single )

tmpR = sRect
l = sRect.origin.x
t = sRect.origin.y
r = l + sRect.size.width
b = t + sRect.size.height

ll = dRect.origin.x
tt = dRect.origin.y
rr = ll + dRect.size.width
bb = tt + dRect.size.height

FN CGContextSetRGBStrokeColor( ctx, 1, 0, 0, 1 )// show centered rect in red
fn CGRectOffset( sRect, sRect, -l, -t )// offset to zero
//cx = (rr + ll)\2// horz center
//cy = (bb + tt)\2// Vert center
//fn CGRectOffset( sRect, sRect, cx-r\2, cy-b\2 )//Center in Rect

cx = (dRect.origin.x + dRect.size.width\2)\scale - sRect.size.width + 
dRect.origin.x\scale
cy = (dRect.origin.y + dRect.size.height\2)\scale - sRect.size.height + 
dRect.origin.y\scale
fn CGRectOffset( sRect, sRect, cx, cy )//Center in Rect

FN CGContextTranslateCTM( ctx, sRect.origin.x  , sRect.origin.y  )
FN CGContextScaleCTM( ctx, scale, scale )// use natural coordinate 
system, not flipped as in QD
fn CGContextSetLineWidth(ctx, 1\scale)

//FN CGContextStrokeRect( ctx, tmpR )
FN CGContextStrokeRect( ctx, sRect )
END FN


local fn drawCenteredRectsBetter( ctx as CGContextRef , arbitrarySrc as 
long )
'~'1
dim as CGRect  cgR,cgRR
dim as single left,top,right,bottom
dim as single hh,wd,scale

fn CGContextSaveGState( ctx )

long if ( arbitrarySrc )
// arbitrary source in arbitrary destination
left   = -89.57098
top    =  36.49728
right  = -81.96504
bottom =  39.14807
fn CGRectMake( cgRR, 100, 100, 400 , 300 )
xelse
left   =  10
top    =  10
right  =  20
bottom =  20
fn CGRectMake( cgRR, 0, 0, 800 , 600 )
end if

wd     = right - left
hh     = bottom - top
scale  = 10// how much do we want to scale the object?

fn CGRectMake( cgR, left, top, wd , hh )

FN CGContextSetRGBStrokeColor( ctx, 0, 0, 1, 1 )
fn CGRectInset( cgRR, cgRR, 20, 20 )// shrink destination rect
FN CGContextStrokeRect( ctx, cgRR )// display destination rect

FN centerCGRect( ctx, cgR ,cgRR, scale )

fn CGContextRestoreGState( ctx )
fn CGContextFlush( ctx )


end fn



local fn createWindowAndContext( windNum as long, name as str255 )
'~'1
dim as CGContextRef @ ctx
dim as OSStatus       err
dim as CGRect         cgR

appearance window windNum, name , (0,0) - (800,600), 
_kDocumentWindowClass, 0
err = fn QDBeginCGContext( window( _wndPort ), @ctx )

fn CGRectMake( cgR, 0, 0, window( _width ), window( _height) )

// draw a light gray background
fn CGContextSetRGBFillColor( ctx, 0.85, 0.85, 0.85, 1.0 )
fn CGContextFillRect( ctx, cgR )

fn drawCenteredRectsBetter( ctx, _false )
//fn drawCenteredRectsBetter( ctx, _true )


fn CGContextFlush( ctx )
err = fn QDEndCGContext( window( _wndPort ), @ctx )

end fn


fn createWindowAndContext( 33 , "test" )

do
handleevents
until 0

--