MATLAB: Can we list all possible values for a property of a MATLAB object without going via help/doc

language fundamentals

To be clear, I will be specific, but the question is for the general case (the more general, the better)

Consider that you have a graphics object, say axes with handle axH. You wish to set the 'NextPlot' property of that object to something else than the default value, but you cannot recall the possible notation to do so… Hence, you must open the documentation to find the acceptable values. In a perfect MATLAB world, it would be better to be able to do something similar to 'get', for example:

>> axH = axes();
>> getPossibleValues(axH.NextPlot)
ans = 
      'replace'
      'add'
      'replaceall'
      'replacechildren'

Best Answer

Not in any simple form, no. For graphics objects and for a number of other different kinds of objects, there is a method:

axH = axes();
set(axH,'NextPlot')
4×1 cell array
  'add'
  'replace'
  'replacechildren'
  'replaceall'

and when you do not know the property name:

set(axH)
                       ALim: {}
                   ALimMode: {'auto'  'manual'}
     ActivePositionProperty: {'position'  'outerposition'}
          AmbientLightColor: {1×0 cell}
                        Box: {'on'  'off'}
                   BoxStyle: {'full'  'back'}
                   [...]

This only displays non-hidden properties, and only works for objects that use the get/set interface. It does not, for example, work for Java objects.

Related Solutions

MATLAB: How to trigger ButtonDownFcn callback for an object with visible off in MATLAB R2014b

Starting in MATLAB R2014b, graphics objects have a new PickableParts property that controls if the object can capture mouse clicks. By default, the PickableParts property is set to 'visible' so the object can capture mouse clicks when the Visible property is set to 'on'. If you want an invisible object to capture mouse clicks, then set the PickableParts property to 'all'.

For example, create a marker and set the ButtonDownFcn callback so that clicking the marker displays 'hit' at the command line.

m = line(5,5,'Marker','o','MarkerSize',20,'ButtonDownFcn','disp hit');

Set the Visible property of the marker to 'off' to make it invisible.

m.Visible = 'off';
axis([4 6 4 6])

Clicking over the position of the invisible marker does not trigger the ButtonDownFcn callback because invisible objects do not capture clicks by default. Enable the invisible marker to capture clicks by setting the PickableParts property to 'all'.

m.PickableParts = 'all';

Note: When an object captures a mouse click, the HitTest property controls if the object responds to the click or if it passes the click to an ancestor. By default, the object responds. Set the HitTest to 'off' if you want an ancestor to respond, such as the parent axes.

MATLAB: Mouse click on Axes Problem

It is prone to bugs to rely on the current axes object by cla and gca. You have the handle of the axes available, so use it. Replace:

axes(handles.axes1); cla reset
hold on
ax = gca;

ax = handles.axes1;
cla(handles.axes1, 'reset')
ax.NextPlot = 'add';   % EDITED, was 'on'

The format bank influences all following output to the command window. It is not useful here.

Replace

startingRows = linspace(1, 8, 8);
startingRows = int32(startingRows(1:end))

by the much simpler:

startingRows = 1:8;

(1:end) can be omitted at all, because it wastes time only.

I assume, the only problem with your code is, that the text objects shadow the axes, such that a click on them does not trigger the ButtonDownFcn of the axes in the background. You can let the text objects pass through the event by setting their 'HitTest' to 'off':

text(xr, yr, sprintf('%d,%d', i, j), 'FontSize', 8, 'Color', [1 0 1], ...
     'HitTest', 'off');

Summary:

% ** UNTESTED CODE - WRITTEN IN THE FORUMS INTERFACE ONLY **
ax = handles.axes1;
cla(ax, 'reset')
ax.NextPlot = 'on';   % Equivalent to: hold on
ax.XGrid    = 'on';
ax.YGrid    = 'on';
ax.XTick = 1:13;
ax.YTick = 1:9;
ax.XLim  = [1 13];
ax.YLim  = [1 9];
ax.GridColor     = [0 .5 .5];
ax.GridLineStyle = '--';
ax.GridAlpha     = 0.5;
ax.Layer         = 'top';
for i = 1:8
   for j = 1:12
      text(j + 0.3, i + 0.5, sprintf('%d,%d', i, j), ...
           'FontSize', 8, 'Color', [1 0 1], ...
           'HitTest', 'off');
   end
end
ax.Visible = 'on';
ax.ButtonDownFcn = @ImageClickCallback;

And the callback:

function ImageClickCallback(AxesH, EventData)
cpt = get(AxesH, 'CurrentPoint');
pt  = cpt(1, 1:2);
x   = round(pt(1));
y   = round(pt(2));
... what to do with x and y?
end

Using the dot notation "ax.Property = ..." only looks nicer, but is is no error to mix it with "set(ax, 'Property', ...)" and the more abstract functions like xticks and hold on.

Best Answer

Related Solutions

MATLAB: How to trigger ButtonDownFcn callback for an object with visible off in MATLAB R2014b

MATLAB: Mouse click on Axes Problem

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