macOS Handling Magnification Events

[Blakeasd]

Hello,
I need some help getting pinch to zoom working. In my application I handle zooming in/out differently than you regularly would in a WebView I am using Google Maps so I need to use JavaScript in order to zoom in/out.
To zoom in I use this:

id map = [aMapView windowScriptObject];
    NSString *jsCmd = @"map.zoomIn();";
    [map evaluateWebScript:jsCmd];

To zoom out I use this

id map = [aMapView windowScriptObject];
    NSString *jsCmd = @"map.zoomOut();";
    [map evaluateWebScript:jsCmd];

How can I get Pinch to Zoom working with something like this. I already read the Cocoa Event-Handling Guide for Handling Trackpad Events, but I couldn't figure out how to implement pinch to zoom when you use to different methods for zooming in and zooming out.
Thanks

 

[kainjow]

You could try subclassing WebView and overriding magnifyWithEvent:

 

[Blakeasd]

I did use already tried that, but I wasn't sure how to use the event it passes in when you pinch to zoom.

 

[kainjow]

Take a look at NSEvent's magnification method.

 

[Blakeasd]

After reading the magnify method you suggested I tried this but it didn't work:

-(void)magnifyWithEvent:(NSEvent *)event{

    CGFloat magnifiedChangeValue = [event magnification];
    
    if (magnifiedChangeValue <0) {
        id map = [aMapView windowScriptObject];
        NSString *jsCmd = @"map.zoomOut();";
        [map evaluateWebScript:jsCmd];

    } else {
        id map = [aMapView windowScriptObject];
        NSString *jsCmd = @"map.zoomIn();";
        [map evaluateWebScript:jsCmd];
    }
    
}

I didn't get any errors, but the map didn't zoom in or out.

 

[GorillaPaws]

If you put an NSLog statement in each branch of your (magnifiedChangeValue < 0) conditional, are they firing?

Can you make a test app and manually trigger the JavaScript commands by wiring it up to a simple button to see if you can get the map to change?

 

[Blakeasd]

@GorillaPaws
If I use buttons to zoom in and out with that code it works. I added an NSLog to each of the if blocks and they didn't run, so the problem is handling the event. Any Ideas about why it isn't working?

 

[Blakeasd]

My code is randomly working now..(sort of). I ran my project again and now it is running the NSLogs, but my map doesn't zoom in. I know that code works because it works with a button. Why doesn't the map zoom in/out?

 

[kainjow]

Why doesn't the map zoom in/out?

Debug your code:

1. Is magnifyWithEvent: getting called every time?
2. What are the values of your variables (magnifiedChangeValue, map)?
3. What is the result of calling evaluateWebScript: ?

If the above debugging techniques all work out as expected, you may need to do some debugging within JavaScript.


BTW, even though I don't think it matters here, you can simplify your code (untested):

- (void)magnifyWithEvent:(NSEvent *)event {
    CGFloat magnifiedChangeValue = [event magnification];
    if (magnifiedChangeValue < 0) {
        [self stringByEvaluatingJavaScriptFromString:@"map.zoomOut();"];
    } else {
        [self stringByEvaluatingJavaScriptFromString:@"map.zoomIn();"];
    }
}

 

[Blakeasd]

I think my problem is this line

CGFloat magnifiedChangeValue = [event magnification];

When I print this out in an NSLog when I pinch to zoom I get this when I zoom out I get this value: 2.12273e-314
When I zoom in I get this value
2.12434e-314

I'm using this code to print out the values:

 NSLog([NSString stringWithFormat:@"%g"],magnifiedChangeValue);

 

[jiminaus]

I'm using this code to print out the values:

 NSLog([NSString stringWithFormat:@"%g"],magnifiedChangeValue);

The square bracket is in the wrong place in your code.

NSLog([NSString stringWithFormat:@"%g", magnifiedChangeValue[COLOR=RED]][/COLOR]);

But the first parameter to NSLog is a format, so it can be simplified to:

NSLog(@"%g", magnifiedChangeValue);

 

[Blakeasd]

@kainjow Oddly, when I used your simplified code it worked, Thanks!
Why didn't my code work?