Mac canvas mouse x/y inaccurate to cursor?

BlitzMax Forums/BlitzMax Programming/Mac canvas mouse x/y inaccurate to cursor?

skn3	(Posted 2010) [#1]

I have found a bug in mac canvas. It seems the mouse x/y do not fall directly under the tip of the mouse cursor.

I am using the latest snow leopard with maxgui 1.38.

In the code below, try and draw a rect starting at the very top-left of the black area. It looks like the coordinates are offset x:+1 y:+2 from where the cursor actually lies...

Import maxgui.drivers

Local window:TGadget = CreateWindow("test me ",300,60,400,400)
Local panel:TGadget = CreatePanel(50,50,ClientWidth(window)-50,ClientHeight(window)-50,window)
Global canvas1:TGadget = CreateCanvas(0,0,ClientWidth(panel),ClientHeight(panel),panel)

Global rectx:Int,recty:Int,rectwidth:Int,rectheight:Int,rect:Int = False

SetGraphicsDriver GLMax2DDriver()

AddHook(EmitEventHook,hook,Null)

Repeat
	WaitEvent()
Forever

Function hook:Object(id:Int,data:Object,context:Object)
	Local event:TEvent = TEvent(data)
	
	' + make sure there is event data +
	If event
		Local gadget:TGadget = TGadget(Event.source)

		Select event.id
			Case EVENT_GADGETPAINT
				SetGraphics gadget.CanvasGraphics()
				Cls
				SetColor(255,0,0)
				DrawRect(rectx,recty,rectwidth,rectheight)
				Flip
			Case EVENT_MOUSEMOVE
				If rect
					rectwidth = event.x-rectx
					rectheight = event.y-recty
					RedrawGadget(canvas1)
				End If
			Case EVENT_MOUSEUP
				rect = False
				rectx = event.x
				recty = event.y
				RedrawGadget(canvas1)
			Case EVENT_MOUSEDOWN
				rect = True
				rectx = event.x
				recty = event.y
				RedrawGadget(canvas1)
			Case EVENT_WINDOWCLOSE
				End
		End Select
	End If
End Function

skn3	(Posted 2010) [#2]

It seems the offset for the click is based on the black inner part of the pointer instead of the white border part...

Beaker

(Posted 2010) [#3]

http://blitzmax.com/Community/posts.php?topic=88728
Related?

skn3	(Posted 2010) [#4]

Possibly, will have a look when get on my mac tomorrow. I temporarily got round the prolem by just offsetting all mouse positions by x and y offset constants.

SebHoll

(Posted 2010) [#5]

Hi skn3[ac],

I've had a quick look into this for you and this appears to be the correct behaviour. All mouse cursor images have a hotspot associated with them (the x,y coordinate within the icon that defined which pixel this multi-pixel cursor is pointing to).

For the Mac OS X arrow, Apple seems to have decided that this is the top right black part of the arrow. And this is how other Mac apps, such as Digital Color Meter work when dealing with precise pixel selection. In other words, Mac users may expect this behaviour to be consistent for their platform, so subtracting your offset might annoy some hardcore Mac users. :-) I guess it's a matter of taste.

Of course, different cursors have different hotspots, and if you are looking for a cursor to use for pixel precision, try calling SetPointer( POINTER_CROSS ) - the hotspot for this cursor appears to be dead-on in the middle of the cross-hairs.

Hope this clears things up. :-)