Implementing shift-drag for DragZoom

[Peter Brodersen]

Hi,

I'm tinkering a bit with DragZoom library. I would like to create a
setup where a user can just shift-drag to zoom in or out as many. I
have troble with the control zoom state though.

My current code: http://map.ter.dk/shiftdragzoom.html


It's easy to create a general DOM handler for checking if shift is
pressed (as Pamela mentioned in an old post) using document.onkeydown
and document.onkeyup. I can also create a global variable and store
the control here:

var dzc;

function load() {
  if (GBrowserIsCompatible()) {
    ...
    dzc = new DragZoomControl();
    map.addControl(dzc);
  }
}


And further on fire the zoom control using dzc.initiateZoom();

However it seems like as initiateZoom() just toggles the state and I
can't see any way to explicit set or check the current state (if the
control is selected/active) I run into problems when the zoom has been
executed (and initiateZoom() seem to be called when the zoom is
performed.


My key handler:

document.onkeydown = keyDownHandler;
document.onkeyup = keyUpHandler;

function keyDownHandler(e){
        if (!e) var e = window.event;
        if ( (e.shiftKey) && !shiftOn){
                dzc.initiateZoom();
                shiftOn = true;
        }
}

function keyUpHandler(e){
        if (!e) var e = window.event;
        if (shiftOn) {
                dzc.initiateZoom();
                shiftOn = false;
        }
}


My problems are:

1. When the zoom has been performed I'm in a reverse state. I might be
able to have a switch variable for this but it just seems like I'm
overcomplicating the feature. Furthermore I guess there are several
edge cases where an event is not registered. Other programs or windows
taking focus and so on.

2. I wouldn't like the control to be visible. I could just remove its
visibility using CSS. However I keep thinking I should just use some
methods in a more direct fashion instead of requiring a GControl at
first.

Is my current method just bad usage of a control where I would just
need some events instead or am I getting close to a pretty solution?


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