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Brush callbacks: what am I missing?

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Hi, folks! So, the Tips for the brush command state (I've spliced the following up a little to focus on ActionPostCallback but still include all the pertinent available info): "You can program the following callbacks for brush mode operations. ActionPostCallback < function_handle > — Function to execute after brushing Use this callback to execute code when a brush operation ends. The function handle should reference a function with two implicit arguments: function myfunction(obj,event_obj) % obj handle to the figure that has been clicked % event_obj object containing struct of event data The event data struct has the following field: AxesThe handle of the axes that is being brushed"
OK, so I do the following:
>> f = @(x,y) disp([x y]);
>> f(1,2)
1 2
>> plot(1:10, 1:10)
>> bO = brush(1)
bO =
graphics.brush
>> set(bO, 'ActionPostCallback', f, 'enable', 'on')
>> get(bO)
ButtonDownFilter: @localButtonDownFilter
ActionPreCallback: []
ActionPostCallback: @(x,y)disp([x,y])
Enable: 'on'
FigureHandle: 1
Color: [1 0 0]
Then, when I brush the plot, the figure disappears and back in the command window I get:
"Warning: An error occurred during the mode callback.
> In uitools.uimode.fireActionPostCallback at 14
In datamanager.brushup at 114
In brush>@(es,ed)datamanager.brushup(es,ed)
In hgfeval at 63
In uitools.uimode.modeWindowButtonUpFcn at 46
In uitools.uimode.modeControl>localModeWindowButtonUpFcn at 155"
and no display of either the figure's handle nor the axis' handle.
What am I missing?
Thanks,
OlyDLG

Accepted Answer

per isakson
per isakson on 27 Mar 2013
Run this script and try the brush. | 1 2| will be displayed in the command window.
%%Script
plot( 1:10, 1:10 )
bO = brush( gcf );
x = 1;
y = 2;
set( bO, 'ActionPostCallback', @(ohf,s) BrushAction(ohf,s,x,y), 'enable', 'on' )
where
function BrushAction( varargin )
disp([ varargin{3:4} ])
end
I guess this does what you expected. It is much easier to debug ordinary functions.
  1 Comment
David Goldsmith
David Goldsmith on 27 Mar 2013
Thanks, Per, that showed me what I was missing: I thought that "The function handle should reference a function with two implicit arguments" meant that I didn't need to actually include those implicit arguments in the value of the 'ActionPostCallback' property (what I provided was a simplified example of what I'm really trying to do, which is make an object method the callback). Your example--with explicit inclusion of the implied arguments in the property value specification, along w/ the use of varargin in the callback definition--showed me, quite litterally, what I was missing. Thanks!!!

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