Why does Chrome raise a mousemove on mousedown?

google-chrome, javascript

Solution

strange issue indeed, however with a little flag this can be circumvented: http://jsfiddle.net/3a28p7ek/

the change is pretty straight forward, setting `ignoreNextMove` to `true` on each mouse down and canceling the move handler if this flag is set, after resetting the flag so that regular move events get handled properly:

ignoreNextMove = false;

$( "#txt" ).mousedown(function() {
    ignoreNextMove = true;
    document.getElementById("activity").innerHTML +="D";    
    update(false,true);
});
$( "#txt" ).mousemove(function() {
        if(ignoreNextMove)
    {
        ignoreNextMove = false;
        return;
    }
    document.getElementById("activity").innerHTML +="M";
    update(true,false);
});

Problem

I have noticed that in Chrome (I'm using Chrome 35.0.1916.114 [UPDATE: also occurs in "35.0.1916.153 m"], Windows 7 64-bit) when I click the left button not only is a mouseDown event raised (as I expect) but also a mouseMove. In this fiddle if you click in the input element you will see a 'D' for each mouseDown event raised and an 'M' for each mouseMove. HTML: ``` <input id="txt" type="text"/> <p>Moves</p><p id="moves">0</p> <p>Downs</p><p id="downs">0</p> <p id="activity">Activity</p> ``` JS: ``` $( "#txt" ).mousedown(function() { document.getElementById("activity").innerHTML +="D"; update(false,true); }); $( "#txt" ).mousemove(function() { document.getElementById("activity").innerHTML +="M"; update(true,false); }); function update(move, down) { var moves=document.getElementById("moves").innerHTML; if (move) { moves ++; document.getElementById("moves").innerHTML=moves; } var downs=document.getElementById("downs").innerHTML; if (down) { downs ++; document.getElementById("downs").innerHTML=downs; } var d=parseInt(downs); var m=parseInt(moves); if ((d+m)%25==0) { document.getElementById("activity").innerHTML +="<br>"; } } ``` In FF and IE11 once the cursor is in the input element then you will be able to get consecutive 'D's (ie, a click raises a single mouseDown event). In Chrome each mouse click raises a mouseDown and two mouseMove events. This is not due to any slight wobbling of the mouse as I use a trackball so the cursor is absolutely stationary. Is anyone aware of a workaround for this? Thanks Dave

Original source