Rubber banding in BlitzMax

BlitzMax Forums/BlitzMax Beginners Area/Rubber banding in BlitzMax

Oso	(Posted 2009) [#1]

How do you do clean, smooth rubber banding in BlitzMax (in a MaxGui window on a canvas that is) - perhaps something similar to what happens when you drag the mouse on the Mac desktop ? I wrote many things in BlitzPlus for years and have downloaded the trial version of BlitzMax because I now have a Mac. So far it seems excellent but this one thing I cannot yet get to work decently after a few days trying. What I want is something equivalent to the following in BlitzPlus, which works fine. I used arrays of pixels then to redraw areas of the canvas but I'm sure a very simple standard method of events and flips must exist in BlitzMax to achieve such a common effect.

Function zoomout()
.l4
	WaitEvent()
	If EventID()=$201 Then
		mx1=MouseX(workarea1)
		my1=MouseY(workarea1)
		Color 255,255,255
		For i=0 To 800
			pix(i)=ReadPixel(i,my1)
		Next
		For i=0 To 600
			piy(i)=ReadPixel(mx1,i)
		Next


		While MouseDown(1)
			mx2=MouseX(workarea1)
			my2=MouseY(workarea1)
			For i=0 To 800
				pixu(i)=ReadPixel(i,my2)
			Next
			For i=0 To 600
				piyu(i)=ReadPixel(mx2,i)
			Next
			Line mx1,my1,mx2,my1
			Line mx1,my1,mx1,my2
			Line mx1,my2,mx2,my2
			Line mx2,my1,mx2,my2
			FlipCanvas workarea1
			For i=0 To 800
				WritePixel i,my1,pix(i)
			Next
			For i=0 To 600
				WritePixel mx1,i,piy(i)
			Next
			For i=0 To 800
				WritePixel i,my2,pixu(i)
			Next
			For i=0 To 600
				WritePixel mx2,i,piyu(i)
			Next
		Wend
		Line mx1,my1,mx2,my1
		Line mx1,my1,mx1,my2
		Line mx1,my2,mx2,my2
		Line mx2,my1,mx2,my2
		If mx1=mx2 Or my1=my2 Then
			Return
		EndIf
		If mx1>mx2 Then
			mxswap=mx1
			mx1=mx2
			mx2=mxswap
		EndIf
		dxiu=mx2
		dxil=mx1
		If my1>my2 Then
			myswap=my1
			my1=my2
			my2=myswap
		EndIf
'Do some calculations with selected area.
		dyiu=my2
		dyil=my1
		dxiuf#=Float(dxiu)
		dxilf#=Float(dxil)
		dyilf#=Float(dyil)
		dyiuf#=Float(dyiu)
		newdxl#=dxl#-dxilf#*dxdiff#/800
		newdxu#=dxu#+dxdiff#-dxiuf#*dxdiff#/800
		newdyu#=dyu#+dyilf#*dydiff#/600
		newdyl#=dyl#-dydiff+dyiuf#*dydiff#/600
		dxl#=newdxl#
		dxu#=newdxu#
		dyl#=newdyl#
		dyu#=newdyu#
		dxdiff#=dxu#-dxl#
		dydiff#=dyu#-dyl#
		cx#=0.5*(dxl#+dxu#)
		cy#=0.5*(dyl#+dyu#)
		draw()
	Else
		Goto l4
	EndIf

End Function

jkrankie

(Posted 2009) [#2]

what's rubber banding?

Cheers
Charlie

Arabia

(Posted 2009) [#3]

I think he means like when you hold down the mouse on your desktop (windows) and drag a rectangle around icons.

I know how to do it, but not with MaxGui since I don't own it.

Midimaster

(Posted 2009) [#4]

do you want to grap only things on the canvas background picture , or do you plan also to send messages to the other gadgets to tell them that they are "grapped"

what is the target og the rubber band? what will you select?

Oso	(Posted 2009) [#5]

I do not need to grab anything, just select the four corner points for calculations. A picture is drawn on the canvas and the functions which use the rubber banding select new coordinates for redrawing the picture - zoom in, zoom out, move centre and so on. Of course the drawn canvas has to be preserved during the process, which should be smooth and clear. Once the mouse button is raised it does not matter whether or not the box or rectangle remains as it will be drawn over anyway.

I've tried many ways but there is something simple I haven't understood which works differently in BlitzMax from in BlitzPlus.

Midimaster

(Posted 2009) [#6]

why not simply draw the picture on the canvas and on it the rubber band every time the mouse has been moved?

sorry i have no maxgui here, so i wrote it in blitz3d, but the way sould be the same on a canvas

Graphics 800,600
SeedRnd MilliSecs()
Image=CreateImage(800,600)
For i=0 To 1000
	SetColor Rand(155),Rand(155),Rand(155)
	DrawRect Rand(0,800),Rand(0,600),Rand(0,60),Rand(0,60)
Next
GrabImage image,0,0
SetColor 255,255,255
Global RubberX%,RubberY%
RubberX=-1
Repeat
	Cls
	DrawImage image,0,0
	If MouseDown(1) Then
		If RubberX=-1 Then
			RubberX=MouseX()
			RubberY=MouseY()
		Else
			DrawNotFilledRect RubberX,RubberY,MouseX(),MouseY()
		EndIf
	Else
		RubberX=-1
	EndIf
	Flip 
Until KeyHit(Key_Escape)

Function DrawNotFilledRect(X1%, Y1%, X2%, Y2%)
	DrawLine x1,y1,x1,y2
	DrawLine x2,y1,x2,y2
	DrawLine x1,y1,x2,y1
	DrawLine x1,y2,x2,y2
End Function

Oso	(Posted 2009) [#7]

Thanks very much for that. My problem therefore lies, not in the method, but in lack of understanding about the exact timing and effect of the various Event commands involving the mouse in MaxGui. I'll spend a few hours writing little programs printing event data until I work out what they all do. Thanks again for your time.

Oso	(Posted 2009) [#8]

Okay, I've sorted it all out now. As well as failing to understand event checking I had not set the blend to solid. Owing to the nature of my background this was producing a mess of random lines. As is often the case, what we assume is one mistake is actually several.

Thanks to all who answered.