Interactive rectangle on UIAxes for user to choose a region

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I have a dataset with scattered points that I plot on a UIAxes. The idea is to let the user draw a rectangle over the UI Axes only ( not the whole figure) and select a region so that it can be processed further.
plot(app.UIAxes,app.data(1,:),app.data(2,:),'k*');
disableDefaultInteractivity(app.UIAxes);
f = app.UIFigure;
f.Units = 'normalized';
waitforbuttonpress
pos = rbbox;
annotation('rectangle',pos,'Color','r');
The code above is what I tried. The first problem that i see is that waitforbuttonpress opens a new figure and does not operate on the app figure or the axes. What should be the way to get this working?

Accepted Answer

Walter Roberson
Walter Roberson on 27 May 2022
Edited: Walter Roberson on 30 May 2022
  6 Comments
Walter Roberson
Walter Roberson on 10 Jun 2022
The code you are replacing has
waitforbuttonpress
pos = rbbox;
rbbox() does not offer any way to move the initial coordinates of the box: it always uses the Current Point as the starting point. The waitforbuttonpress is there to give the user an opportunity to move the cursor to where they want to start the box, and then click, after which rbbox can then work.
When using App Designer, waitforbuttonpress() is not recommended. Instead, you would set the WindowButtonDownFcn callback for the uifigure that contains the area you want to draw into. The uiresume() callback you have should be fine.
However... rbbox and other similar calls outside of Image Processing Toolbox only work on traditional figures, and all of the recommendations that I can find for how to proceed lead back to drawrectangle() .
In order to proceed without the toolbox, you will need to program your own box dragging function. You might find it useful to look at https://www.mathworks.com/matlabcentral/answers/458264-using-windowbuttondownfcn-in-app-designer#comment_2132605
Walter Roberson
Walter Roberson on 10 Jun 2022
I just successfully tested this code:
fig.WindowButtonDownFcn = @(src,event)uiresume(src);
uiwait(fig);
out = uirbbox(fig);
disp(out)
Where uirbbox is a modified version of Mathwork's rrbox that expects a uifigure as the first parameter.
function finalRect = uirbbox(f, initialRectangle, anchorPoint, step)
and
arguments
f (1, 1) matlab.ui.Figure
and
for the chain of if nargin == add 1 to each of the counts, so like
if nargin == 1
initRect = [];
fixedPoint = [];
stepSize = [];
Then comment out
f = gcf;
With f now being a parameter that is a uifigure, and with the gcf commented out, and with the argument count incremented by 1 as appropriate... then it works.
... It does, however, take remarkably long to activate.

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