OverlayView.m

/*
     File: OverlayView.m
 Abstract: The OverlayView class is a subclass of NSView which will be drawn on top of other views.
 
  Version: 1.2
 
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#import "OverlayView.h"
#import "DimensionLineDrawing.h"
 
#define HIGHLIGHT_THICKNESS 3.0
 
@implementation OverlayView
 
@synthesize overlaidView;
 
- (id)initWithFrame:(NSRect)frameRect {
    
    self = [super initWithFrame:frameRect];
    if (self) {
        // Create a tracking area that will give our view mouseMoved events.
        NSTrackingArea *trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
                                                                    options:NSTrackingMouseMoved | NSTrackingInVisibleRect | NSTrackingActiveInKeyWindow
                                                                      owner:self
                                                                   userInfo:nil];
        [self addTrackingArea:trackingArea];
        [trackingArea release];
    }
    return self;
}
 
- (BOOL)acceptsFirstResponder {
    
    return YES; // We want to be able to receive mouseMoved: events when we're the firstResponder view.
}
 
- (void)setSelectionHighlightNeedsDisplay {
    
    if (selectedView != nil) {
        NSView *superviewOfSelectedView = [selectedView superview];
        if (superviewOfSelectedView != nil) {
 
            // We could invalidate several rectangles that more tightly bound the area we
            // actually need to redraw, if that proved to yield a worthwhile performance benefit,
            // but since we're drawing dimension lines to all four edges of the selectedView's
            // superview, we'll just invalidate the superview's bounds for simplicity.
            //
            NSRect superviewRect = [self convertRect:[superviewOfSelectedView bounds] fromView:superviewOfSelectedView];    
            [self setNeedsDisplayInRect:superviewRect];
 
            // Make sure we'll also draw the entire box rectangle, in case half its stroke thickness exceeds the margin to the superview's bounds.
            NSRect boundingRect = NSInsetRect([self convertRect:[selectedView bounds] fromView:selectedView], -0.5 * HIGHLIGHT_THICKNESS, -0.5 * HIGHLIGHT_THICKNESS); // Outset by half of stroke width.
            [self setNeedsDisplayInRect:boundingRect];
        }
    }
}
 
- (NSView *)selectedView {
    
    return selectedView;
}
 
- (void)setSelectedView:(NSView *)newSelectedView {
    
    if (selectedView != newSelectedView) {
 
        // Schedule to erase highlight of previously selected view (if any).
        [self setSelectionHighlightNeedsDisplay];
 
        // Remember new selected view.
        [selectedView release];
        selectedView = [newSelectedView retain];
 
        // Schedule to draw highlight of newly selected view (if any).
        [self setSelectionHighlightNeedsDisplay];
    }
}
 
- (void)selectViewForEvent:(NSEvent *)theEvent {
    
    // Find out which view in the overlaid view this event would be associated with by using hitTest.
    // Be sure to convert the point into the correct coordinate space.
    //
    NSView *hitView = [overlaidView hitTest:[[overlaidView superview] convertPoint:[theEvent locationInWindow] fromView:nil]];
    if (hitView) {
        // Choose the immediately enclosing NSBox instead, if the hitView is the NSBox's contentView, or the immediately enclosing NSScrollView, if the hitView is its documentView.
        NSView *parent = [hitView superview];
        if (parent && [parent isKindOfClass:[NSBox class]] && hitView == [(NSBox *)parent contentView]) {
            hitView = parent;
        } else {
            NSScrollView *enclosingScrollView = [hitView enclosingScrollView];
            if (enclosingScrollView && hitView == [enclosingScrollView documentView]) {
                hitView = enclosingScrollView;
            }
        }
    }
    [self setSelectedView:hitView];
}
 
- (void)drawRect:(NSRect)rect {
    
    // Fill with a mostly transparent tint color to make the presence of the OverlayView
    // more obvious for demo purposes.  There's no other need to do this; you may draw
    // whatever you like in an overlay view.
    //
    [[NSColor colorWithCalibratedRed:0.0 green:1.0 blue:0.0 alpha:0.2] set];
    [NSBezierPath fillRect:rect];
 
    // Draw around/atop the selectedView to show the user that it's selected.
    if (selectedView != nil) {
 
        // Enforce cliping to the selectedView's superview's bounds.
        NSView *superviewOfSelectedView = [selectedView superview];
        NSRectClip([self convertRect:[superviewOfSelectedView bounds] fromView:superviewOfSelectedView]);
 
        NSRect selectionRect = [self convertRect:[selectedView bounds] fromView:selectedView];
        NSRect enclosingRect = [self convertRect:[superviewOfSelectedView bounds] fromView:superviewOfSelectedView];
 
        // Stroke a rect surrounding the view.
        [[NSColor redColor] set];
        NSBezierPath *path = [NSBezierPath bezierPathWithRect:selectionRect];
        [path setLineWidth:HIGHLIGHT_THICKNESS];
        [path stroke];
 
        // Draw dimension lines.
        DrawHorizontalDimensionLine(NSMinX(enclosingRect), NSMinX(selectionRect), NSMidY(selectionRect)); // -x line
        DrawHorizontalDimensionLine(NSMaxX(selectionRect), NSMaxX(enclosingRect), NSMidY(selectionRect)); // +x line
        DrawVerticalDimensionLine(NSMinY(enclosingRect), NSMinY(selectionRect), NSMidX(selectionRect)); // -y line
        DrawVerticalDimensionLine(NSMaxY(selectionRect), NSMaxY(enclosingRect), NSMidX(selectionRect)); // -y line
    }
}
 
- (void)mouseMoved:(NSEvent *)theEvent {
    
    // Figure out which view (if any) was clicked, and select it.
    [self selectViewForEvent:theEvent];
}
 
- (void)mouseDown:(NSEvent *)theEvent {
    
    // Figure out which view (if any) was clicked, and make sure it's selected.
    [self selectViewForEvent:theEvent];
 
    // Remember start point for drag.
    lastWindowPoint = [theEvent locationInWindow];
}
 
- (void)mouseDragged:(NSEvent *)theEvent {
    
    // Let the user drag the selected view, if any.
    if (selectedView != nil) {
 
        // Calculate (dx,dy) for this mouse move, in the selected view's superview's coordinate space.
        NSView *superview = [selectedView superview];
        NSPoint windowPoint = [theEvent locationInWindow];
        NSPoint lastSuperviewPoint = [superview convertPoint:lastWindowPoint fromView:nil];
        NSPoint superviewPoint = [superview convertPoint:windowPoint fromView:nil];
        CGFloat dx = superviewPoint.x - lastSuperviewPoint.x;
        CGFloat dy = superviewPoint.y - lastSuperviewPoint.y;
 
        // Move view's frameOrigin by (dx,dy).
        NSRect frame = [selectedView frame];
        frame.origin.x += dx;
        frame.origin.y += dy;
        [self setSelectionHighlightNeedsDisplay]; // Schedule erase of selection highlight for old position.
        [selectedView setFrameOrigin:frame.origin];
        [self setSelectionHighlightNeedsDisplay]; // Schedule erase of selection highlight for new position.
 
        // Save windowPoint as the lastWindowPoint for the next drag increment.
        lastWindowPoint = windowPoint;
    }
}
 
- (void)dealloc {
    
    [selectedView release];
    [super dealloc];
}
 
@end