Adapt to user zooming into axis

Share icon

I have a graph with some data, attached to it a free axis and an axis hook function. The axis hook function should run some code whenever a user zooms in or out of an trace/image.

Fuction Setup()
    Make/O data = p
    Make/O largedata = p + 100
End

Function AxisHook(s)
	STRUCT WMAxisHookStruct &s
	
	print "called with", s
End

Window Graph0() : Graph
	PauseUpdate; Silent 1		// building window...
	Display /W=(95.25,263,612,634.25) data
	NewFreeAxis/O/L test
	ModifyFreeAxis/Z test,master= bottom,hook= AxisHook
	ModifyGraph nticks(test)=0
	ModifyGraph axThick(test)=0
	ModifyGraph lblPos(left)=47
	ModifyGraph freePos(test)=-50
	SetAxis left -7.63192488262911,144.768075117371
EndMacro

Now this works for my use case.

But when I add more data to it via

AppendToGraph largeData

my hook function get's also called. But I would like to distinguish the case of users zooming into the axis and code changing the axis limits. Or to rephrase I actually want to run the code *only* when the user zooms in/out interactively and not when doing it programmatically.

Is that possible? Am I doing it right?

Hmm, that is surprisingly difficult. There seems to be no way to tell from the axis hook what event called the hook function. I came up with a somewhat kludgy workaround which saves the latest axis scaling in the graph's user data and only calls code if the axis range has changed (which happens when zooming):

Function AxisHook(s)
	STRUCT WMAxisHookStruct &s
	
	String putRange, lastZoom = GetUserData(s.win,"","axisRange")
	sprintf putRange, "%f;%f;", s.min, s.max
	SetWindow $(s.win), userdata(axisRange)=putRange
	
	Variable zoomCall = 0
	if (strlen(lastZoom) > 0)
		Variable left = str2num(StringFromList(0,lastZoom))
		Variable right = str2num(StringFromList(1,lastZoom))
		if ( ((left - s.min) > 1e-6) || ((right - s.max) > 1e-6))
			zoomCall = 1	
		endif
	endif
	
	if (zoomCall)
		print "called with", s
	endif
End

 

November 5, 2020 at 04:51 pm - Permalink

Unfortunately, the axis range changes when you add a trace with different range, and also when the user changes the axis range.

November 5, 2020 at 04:56 pm - Permalink

Oh, that's right! So my example was not very useful. That's really an uphill battle, but one could use the same method to store a list of displayed traces on the graph and compare if something has changed between calls. I don't see how one can distinguish user's zooming in from any other event which changes the axis range.

November 5, 2020 at 05:03 pm - Permalink

You may need to have a button to turn the zoom feature (your hook function) on/off.

You may need to lock out any ability to manually add data to the graph and instead force the user to run a function instead (e.g. myappendtograph).

Doesn't Igor give an option to know what the last issued command was? Can that be tested in the hook function to distinguish a command-line input appendtograph and thereby ignore break from the hook?

Of these three, I might find the first the easiest to do even as it adds the overhead for the UI on the user.

November 5, 2020 at 05:15 pm - Permalink

Thanks all for your input. I've now found a solution. I've ditched the axis hook approach and went with a normal window hook. The code is basically


Function PA_TraceWindowHook(s)
	STRUCT WMWinHookStruct &s

	string traceGraph

	switch(s.eventcode)
		case 22: // mouse wheel
		case 6: // resize
			traceGraph = s.winName
			Execute/P/Q "PA_UpdateScaleBars(\"" + traceGraph + "\", 0)"
			break
		case 10: // menu
			if(!cmpstr(s.menuName, "Graph") && !cmpstr(s.menuItem, "Autoscale Axes"))
				traceGraph = s.winName
				Execute/P/Q "PA_UpdateScaleBars(\"" + traceGraph + "\", 1)"
			endif
			break
	endswitch

	return 0
End

where PA_UpdateScaleBars reacts to the user zooming into an axis via the mouse wheel, and the menu reset the scale bars on Ctrl+a. I had to use the operation queue here so that it is executed after the axis has been rescaled by IP.

November 15, 2020 at 07:43 am - Permalink