DragZoom: Respond to righ-click drag

[GoogleCodeExporter]

Enhancement request for DragZoom:

I would like to be able to activate DragZoom and select the region in one step 
by right clicking and 
dragging the mouse. This would eliminate the need to click a button to activate 
DragZoom before 
selecting the region and would be much more convenient. This can probably be 
done by hooking 
into the singlerightclick event somehow.

Original issue reported on code.google.com by garylitt...@gmail.com on 28 Jun 2008 at 9:19

[GoogleCodeExporter]

Hmm, interesting. We recently added the ability to turn on right-click to 
reverse
zoom. So this option and the right-click zoom out feature couldn't be enabled 
at the
same time. (Which might be OK).

If you end up implementing this yourself, feel free to attach a patch to the 
issue.

Original comment by pamela.fox on 1 Jul 2008 at 10:26

• Added labels: Class-MarkerManager, Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

This would probably also run into the Safari right-drag-problem: Issue 33.  A 
right-click to activate with a 
subsequent left drag to zoom would be easier and more cross-browser to 
implement, but probably less 
functional too.

Original comment by lem...@gmail.com on 3 Jul 2008 at 5:49

• Added labels: Class-DragZoomControl
• Removed labels: Class-MarkerManager

[GoogleCodeExporter]

OK, I've finally figured out how to get this to work. To avoid the right-click 
problem, I've instead figured out a 
way to begin a drag zoom operation when you hold down the Option key 
(Macintosh) or Alt key (PC). The 
tricky part is canceling the operation properly when the Option key is released 
-- that requires a knowledge 
of the DragZoom implementation details.

Here's what you need to do. 

1. Add onkeydown and onkeyup handlers to your document:

    document.onkeydown = keyDown;
    document.onkeyup = keyUp;

2. Here's what the handlers look like (gDragZoom is an instance of the control 
created with new 
DragZoomControl(...)):

function keyDown( e ) {

    if ( !e ) { e = window.event; }

    if ( e.altKey ) { gDragZoom.initiateZoom(); }
}

function keyUp( e ) {

    if ( !e ) { e = window.event; }

    if ( !e.altKey ) { gDragZoom.cancelZoom(); }

3. The cancelZoom() function is currently not part of DragZoom. The following 
code needs to be added to the 
library:

/**
 * Method called to cancel a dragZoom as if the user had clicked the dragZoom button
 * after the dragZoom operation has started.
 * (Works even if the drag is already in progress.)
 *
 * Added by Gary Little
 */
DragZoomControl.prototype.cancelZoom = function(){
  var G = this.globals; 
  if (G.mapCover.style.display == 'block') {  
    G.draggingOn = false; // ignore further mousemove events
    this.initiateZoom(); // cancels the zoom in progress
  }
};

4. If you turn dragzoom on and off with Option/Alt, you no longer need to 
clutter the screen with a button to 
begin and end the operation. To make sure it doesn't appear on the screen, set 
the display option of the 
buttonStartingStyle to none when you create the instance of the DragZoom 
control.

Now you can quickly perform a DragZoom simply by holding down Option/Alt and 
dragging the mouse. You 
can cancel the operation by releasing the Option/Alt key, even if you're in the 
middle of drag operation (that's 
something new you couldn't do before).

Original comment by garylitt...@gmail.com on 19 Dec 2008 at 5:29

[GoogleCodeExporter]

Oh, and by the way, you can now see the "Option DragZoom" technique in action 
on my real estate map at 
map.GaryLittle.ca

Original comment by garylitt...@gmail.com on 19 Dec 2008 at 5:41

[GoogleCodeExporter]

Hey Gary-

That works for me on my PC, but fails in Linux as it appears that alt in Linux 
serves 
to move the current application window. Do you know if there's an equivalent 
button 
to trigger this kind of thing in on Linux machines?

Original comment by pamela.fox on 28 Dec 2008 at 3:09

[GoogleCodeExporter]

Pamela -

It appears that both KDE and GNOME bind Alt + Left Button to the window move 
operation you mentioned. If 
the Google Maps application developer doesn't want to use a "hot" key other 
than Alt when using the 
technique I described above, a Linux user will have to deactivate the Alt + 
Left Button binding. See how to do 
this for KDE at 
http://www.infohit.net/blog/post/firefox-one-click-download-and-kde-4.html 
where there 
is also a discussion of another clash involving Alt clicks on Linux. I'm sure 
that GNOME has a similar utility for 
changing key bindings.

I was considering using the Meta key (i.e., the Apple command key), but I 
believe this key on a PC (the 
"Windows" key) pops up the Startup menu (Windows) or Launch menu (Linux). I'll 
report back once I've had a 
chance to investigate this further.

Original comment by garylitt...@gmail.com on 28 Dec 2008 at 8:11

[GoogleCodeExporter]

I always thought the drag icon is not necessary. Hold a extra key while 
dragging is
the most efficient way to zoom in a point of interest. I do not own a mac, but 
in a
GIS environment, hold shift key is common. See this example:
http://resources.esri.com/help/9.3/arcgisserver/apis/javascript/arcgis/demos/map
/map_add.html

I think a new drag zoom util can be implemented with this behavior with a lot 
less code.

Original comment by nian...@gmail.com on 29 Dec 2008 at 11:57

[GoogleCodeExporter]

It's up to the application developer which key to use to trigger the start of a 
drag zoom -- I wouldn't like to see 
it hard-coded into the dragzoom.js code. The Shift key could certainly be used 
(perhaps avoiding the Linux 
issue noted above). On my map, however, I use a Shift-click to select a marker 
as a favorite.

I picked the Alt (Option) key as the modifier key because I've seen it used for 
a drag zoom on several other real 
estate maps I've seen which are based on (ugh) Visual Earth.

Original comment by garylitt...@gmail.com on 29 Dec 2008 at 5:58

[GoogleCodeExporter]

Pamela -

Regarding possible use of the Meta (Windows) key instead of Alt to trigger the 
start of a drag zoom: this isn't a 
good choice because if you press it and immediately release it (to cancel the 
drag zoom), the Startup menu will 
pop up on Windows.

Using the Shift key might be the best choice in order to avoid clashing with 
Linux (GNOME/KDE) bindings.

Original comment by garylitt...@gmail.com on 29 Dec 2008 at 6:07

[GoogleCodeExporter]

See this example:

http://gmaps-utility-gis.googlecode.com/svn/trunk/dragboxzoom/examples/dragzoom.
html

It is a much smaller implementation (actual code ~100 lines). It also allows you
customize the style and which key you want to use. 

Original comment by nian...@gmail.com on 29 Dec 2008 at 8:52

[GoogleCodeExporter]

Nianwei -

Very nice implementation, I like it. You might as well add support for all the 
modifier keys, including Caps 
Lock and Meta.

I don't think the code works if the user begins the drag over a marker or a map 
control (such as the zoom 
slider) -- would be nice if it did otherwise users will be confused as to why 
it doesn't work in certain 
situations. The current dragzoom uses a large rectangle to cover the entire map 
to make this happen (this 
allows it to capture the mouseclick before anything else).

Gary

Original comment by garylitt...@gmail.com on 29 Dec 2008 at 10:15

[GoogleCodeExporter]

Nianwei and I have teamed up to create a very nice "interfaceless" utility 
library for zooming to a rectangle which 
is drawn while holding down a "hot" key (Shift, Alt, or Control). It's called 
KeyDragZoom and you can investigate 
it here: 
http://code.google.com/p/gmaps-utility-gis/source/browse/#svn/trunk/keydragzoom

Original comment by garylitt...@gmail.com on 3 Mar 2009 at 10:57

[GoogleCodeExporter]

That's quite nice. Let's add it -- nothing wrong with giving developers a 
variety of 
options. The bigger issue is that there's no standard UI for drag-to-zoom or 
hot key, 
since Google Maps doesn't have those features. But for now developers can 
indicate on 
their maps what the technique for drag zooming is.

Original comment by pamela.fox on 4 Mar 2009 at 5:44

[GoogleCodeExporter]

The  standard for GIS applications seems to be to hold down the Shift key while 
dragging the rectangle -- so 
that's what I'm now using in my application. This also avoids the problems with 
Alt/Option and Meta noted 
earlier.

Microsoft's VE uses the Alt/Option key.

By the way, I strongly believe this feature should be built into the Google API 
-- every map should have the 
benefit of Shift-drag zoom by default.... Of course, I'm biased.

Original comment by garylitt...@gmail.com on 4 Mar 2009 at 6:16

[GoogleCodeExporter]

OK. I added the lib in r952.

Original comment by nian...@gmail.com on 5 Mar 2009 at 3:34

[GoogleCodeExporter]

Awesome, just one issue: http://code.google.com/p/gmaps-utility-library-
dev/issues/detail?id=93

Original comment by pamela.fox on 8 Mar 2009 at 8:28