Python for Bioinformatics: Mouse entering View

Tuesday, August 5, 2008

Mouse entering View

On p. 274, Hillegass has an aside about how to pick up the event when a mouse enters and exits a view, e.g. to highlight the view, as we'll do here. Not the most exciting screenshot in the world, I know. I tried to get the mouse, but couldn't figure it out. The mouse tracking code is set up in "viewDidMoveToWindow," which I gather is called when that happens during launch. If we do that then we get events sent as calls to "mouseEntered_" and "mouseExited_." The highlighting part is handled in "drawRect_", with an important clean-up method below that. The other thing in this code is a demo of how to get additional colors besides the standard Apple ones, from the color list called "Crayons." Here is the code:

class MyView(NSView):
    def initWithFrame_(self, frame):
        self = super(MyView, self).initWithFrame_(frame)
        if self:
            return self
        
    def awakeFromNib(self):
        self.colorL = NSColorList.colorListNamed_('Crayons')
        self.isHighlighted = False
        
    def acceptsFirstResponder(self):    return True
        
    def viewDidMoveToWindow(self):
        print 'viewDidMoveToWindow'
        print self.window().description()
        
        opts = NSTrackingMouseEnteredAndExited |\
               NSTrackingActiveAlways |\
               NSTrackingInVisibleRect
               
        ta = NSTrackingArea.alloc()
        ta.initWithRect_options_owner_userInfo_(
                self.bounds(), opts, self, None)
        self.addTrackingArea_(ta)
        
    def mouseEntered_(self, event):
        print 'mouseEntered_'
        self.isHighlighted = True
        self.setNeedsDisplay_(True)
        
    def mouseExited_(self, event):
        print 'mouseExited_'
        self.isHighlighted = False
        self.setNeedsDisplay_(True)

    def drawRect_(self, rect):
        salmon = self.colorL.colorWithKey_('Salmon')
        salmon.set()
        R = self.bounds()
        p = NSBezierPath.bezierPathWithRect_(R)
        p.fill()

        if self.window().firstResponder() == self:
            if NSGraphicsContext.currentContextDrawingToScreen():
                if self.isHighlighted:
                    NSGraphicsContext.saveGraphicsState()
                    NSSetFocusRingStyle(NSFocusRingOnly)
                    NSBezierPath.fillRect_(R)
                    NSGraphicsContext.restoreGraphicsState()
                
    def resignFromFirstResponder_(self,sender):
        self.setKeyboardFocusRingNeedsDisplayInRect_(R)
        return YES