How to set shortcuts for zoom tool in my own GUI?

I wrote a GUI in which the zoom tool was frequently used, so I wanted to give it a shortcut. I wrote the figure's KeyPressFcn as follows, but it didn't work.

Q1. The "Ctrl+0" means zoom out, and it worked just fine. But "Ctrl+E" to zoom on just didn't work. How should I wrote the function `zoomKeys`?

Q2. I wanted to use "ctrl+=", but it was used by the editor to zip the codes. Can I still somehow use "Ctrl+="?

function myfunc1(fig)
fig.KeyPressFcn = @zoomKeys;
hAxes = axes(fig);
% some codes
plot(1:10);

    function zoomKeys(~, event)
        if strcmp(event.Modifier, 'control')
            switch event.Key
                case 'E' %'='
                    zoom;
%                     zoom(gcf, 'on');
                case '0'
                    zoom out;
            end
        end
    end
end

[Mohammad Sami]

Using just zoom, will only toggle the mouse zoom on and off.

Pass a value to specifiy how much to zoom in.

zoomfactor = 2;

zoom(zoomfactor);

[Albert Bing]

Well, the question is the shortcut "ctrl+E" just doesn't work, no matter "zoom" or "zoom(2)".

Answer 1

[Mohammad Sami]

Just tested your code. turns out event key is in lower case. Just to safe (in case of capslock), lets convert the value to upper case before comparison.

function zoomKeys(~, event)
    if strcmp(event.Modifier, 'control')
        k = upper(event.Key);
        % disp(k); % for debugging
        switch k
            case 'E' %'='
                zoom;
%                     zoom(gcf, 'on');
            case '0'
                zoom out;
        end
    end
end

[Albert Bing]

Thanks! The previous code was wrong. And your answer just solved my 1st question.

I wanted to used "ctrl+=" which was more common in lots of softwares. Is that possible?

Q3. when the cursor is in zoom mode, is it possible to use shortcut to exit the zoom mode? So that I can use other shortcuts I defined.

[Mohammad Sami]

You can uncomment the disp(k). If it is working for "=" you will see it in the console.

For your Q3, you will need to remember if the zoom was enabled before and turn it off. Something like this might work

function zoomKeys(~, event)
    if strcmp(event.Modifier, 'control')
        persistent zoomenabled;
        if isempty(zoomenabled)
            zoomenabled = false;
        end
        k = upper(event.Key);
        % disp(k); % for debugging
        if k ~= 'E'
            zoom off;
            zoomenabled = false;
        end
        switch k
            case 'E' %'='
                zoom;
                zoomenabled = true;
%                     zoom(gcf, 'on');
            case '0'
                zoom out;
        end
    end
end

[Albert Bing]

This zoomenabled seems useless. I changed the function to use it. But still, no key can exit the zoom mode.

function zoomKeys(~, event)
persistent zoomenabled;
if strcmp(event.Modifier, 'control')
    if isempty(zoomenabled)
        zoomenabled = false;
    elseif zoomenabled
        zoom off;
    end
    if ~strcmpi(event.Key, 'e')
        zoom off;
        zoomenabled = false;
    end
    switch event.Key
        case 'e' %'='
            zoom;
            zoomenabled = true;
        case '0'
            zoom out;
    end
end
end

[Albert Bing]

By the way, I just found that the shortcut "ctrl+=" was actually "ctrl" + "equal".

[Albert Bing]

I just opened another question.

https://ww2.mathworks.cn/matlabcentral/answers/502085-how-to-exit-zoom-mode-by-shortcut-in-my-own-gui

[Mohammad Sami]

It seems as soon as zoom is enabled, the keypress function is replaced

% before

f.KeyPressFcn

ans =

function_handle with value:

@myfunc1/zoomKeys

% after

f.KeyPressFcn

ans =

3×1 cell array

{ @localModeKeyPressFcn}

{1×1 matlab.uitools.internal.uimode }

{@(obj,evd)localKeyPressFcn(obj,evd,hMode)}

On further testing it seems, it works if you just zoom in by a fixed factor.

that is replace zoom with zoom(2) or some other factor.

[Albert Bing]

Thanks! zoom(2) did work.

Just not perfect. zoom(2) would zoom the center of the axes without the cursor being in the zoom mode, so you can't zoom any area.

I guess the zoom mode can't be exit by shortcut in user defined functions.

[Mohammad Sami]

See if Yair Altman's solution works for you. It is quite an old post, so I don't know if it works for the current version.

http://undocumentedmatlab.com/articles/enabling-user-callbacks-during-zoom-pan

[Albert Bing]

Thanks!