MATLAB: Mouse Motion and Object Handle

controlmouse motionobject

Hello,

Is there a way to get MATLAB to return an object handle for the GUI control the mouse is currently over?

I have tried using the 'WindowButtonMotionFcn' to monitor mouse movement, and have also tried setting the 'traverseFcn' field using 'iptSetPointerBehavior', but when the functions are called it appears that only the figure handle is available. For my current project, I need the handle to the 'axes' object the mouse is over, not the figure handle.

Thanks,

Mike

Best Answer

This is adapted from one of my GUI examples which tracks the location in axes data coordinates. I have altered it to simply display which axes the mouse is hovering over.

function [] = gui_which_axes()
% Display which axes the pointer is over....
S.fh = figure('units','pixels',...
              'position',[560 528 560 420],...
              'menubar','none',...
              'name','gui_which_axes',...
              'numbertitle','off',...
              'resize','off');
% Now make a simple plot.
x = 0:.1:2*pi;
S.ax(1) = subplot(2,2,1);
plot(x,sin(x))
S.ax(2) = subplot(2,2,2);
plot(x,cos(x))
S.ax(3) = subplot(2,2,3);
plot(x,tan(x))
S.ax(4) = subplot(2,2,4);
plot(x,x.^2)
set(S.ax,'unit','pix');
% Fill the structure with data.
S.AXP = get(S.ax,'pos');
S.tx(1) = uicontrol('style','tex',...
                    'unit','pix',...
                    'posit',[50 395 250 22],...
                    'backg',get(S.fh,'color'),...
                    'fontsize',12,'fontweight','bold',... 
                    'string','Current Pointer Axes:');
% This textbox will display the current position of the mouse.
S.tx(2) = uicontrol('style','tex',...
                    'unit','pix',...
                    'position',[310 395 120 25],...
                    'backg',get(S.fh,'color'),...
                    'fontsize',12,'fontweight','bold' );
set(S.fh,'windowbuttonmotionfcn',{@fh_wbmfcn,S}) % Set the motion detector.
function [] = fh_wbmfcn(varargin)
% WindowButtonMotionFcn for the figure.
S = varargin{3};  % Get the structure.
set(S.tx(2),'string','None')
F = get(S.fh,'currentpoint');  % The current point w.r.t the figure.
% Figure out of the current point is over the axes or not -> logicals.
for ii = 1:4
    tf1 = S.AXP{ii}(1) <= F(1) && F(1) <= S.AXP{ii}(1) + S.AXP{ii}(3);
    tf2 = S.AXP{ii}(2) <= F(2) && F(2) <= S.AXP{ii}(2) + S.AXP{ii}(4);
      if tf1 && tf2
          set(S.tx(2),'str',['Axes ' num2str(ii)])
          break
      end
  end

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Method 1.

One way of doing it, as explained in the documentation, is to create a uicontainer parent for the axes to enable correct legend/colorbar behavior.

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So simply change the axes creation line to the following:

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Method2.

While this should work perfectly fine for most cases, you may not like the slight (not easily noticeable) shifting of the axes position. I personally needed to come up with another solution for my own GUI due to my obsession on perfect positioning and alignment. This is not as neat as the above method, but does the job and no longer needs to deal with the positioning of a uicontainer object which can get tricky for some cases.

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In short, you can achieve this by replacing your axes creation lines of your code with the following lines:

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and add this callback function to the end of your code

function GUIAxesLegendFix(Handle,~,LegendLocation)
try Handle.Contents(2).Location = LegendLocation; catch, end
end

I just added try, catch to the callback to prevent giving any error during resizing in case you decide to add legend to the container later manually. I also attached an updated version of your sample code with method 2 solution. I suggest you to try the easier approach in the documentation and if you do not like the result, try the 2nd method.

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The first line draws the lines, while the 2nd line defined the ButtonDownFcn of the created line. This function is called, when the user clicks on the line. Then Matlab performs:

ax_bdfcn(ln, EventData, S)

Best Answer

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