[Mac] "Refactor" DraggableButton into a mixin and impl.

chrome/browser/ui/cocoa/draggable_button.mm

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/draggable_button.h"
 
 #include "base/logging.h"
-#import "base/memory/scoped_nsobject.h"
-
-namespace {
-
-// Code taken from <http://codereview.chromium.org/180036/diff/3001/3004>.
-// TODO(viettrungluu): Do we want common, standard code for drag hysteresis?
-const CGFloat kWebDragStartHysteresisX = 5.0;
-const CGFloat kWebDragStartHysteresisY = 5.0;
-const CGFloat kDragExpirationTimeout = 0.45;
-
-}
 
 @implementation DraggableButton
 
-@synthesize draggable = draggable_;
-@synthesize actsOnMouseDown = actsOnMouseDown_;
-@synthesize durationMouseWasDown = durationMouseWasDown_;
-@synthesize actionHasFired = actionHasFired_;
-@synthesize whenMouseDown = whenMouseDown_;
-
-
 - (id)initWithFrame:(NSRect)frame {
   if ((self = [super initWithFrame:frame])) {
-    draggable_ = YES;
-    actsOnMouseDown_ = NO;
-    actionHasFired_ = NO;
+    draggableButtonImpl_.reset(
+        [[DraggableButtonImpl alloc] initWithButton:self]);
   }
   return self;
 }
 
 - (id)initWithCoder:(NSCoder*)coder {
   if ((self = [super initWithCoder:coder])) {
-    draggable_ = YES;
-    actsOnMouseDown_ = NO;
-    actionHasFired_ = NO;
+    draggableButtonImpl_.reset(
+        [[DraggableButtonImpl alloc] initWithButton:self]);
   }
   return self;
 }
 
-- (BOOL)deltaIndicatesDragStartWithXDelta:(float)xDelta
-                                   yDelta:(float)yDelta
-                              xHysteresis:(float)xHysteresis
-                              yHysteresis:(float)yHysteresis {
-  return (ABS(xDelta) >= xHysteresis) || (ABS(yDelta) >= yHysteresis);
-}
-
-- (BOOL)deltaIndicatesConclusionReachedWithXDelta:(float)xDelta
-                                           yDelta:(float)yDelta
-                                      xHysteresis:(float)xHysteresis
-                                      yHysteresis:(float)yHysteresis {
-  return (ABS(xDelta) >= xHysteresis) || (ABS(yDelta) >= yHysteresis);
-}
-
-
-// Determine whether a mouse down should turn into a drag; started as copy of
-// NSTableView code.
-- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
-                      withExpiration:(NSDate*)expiration
-                         xHysteresis:(float)xHysteresis
-                         yHysteresis:(float)yHysteresis {
-  if ([mouseDownEvent type] != NSLeftMouseDown) {
-    return NO;
-  }
-
-  NSEvent* nextEvent = nil;
-  NSEvent* firstEvent = nil;
-  NSEvent* dragEvent = nil;
-  NSEvent* mouseUp = nil;
-  BOOL dragIt = NO;
-
-  while ((nextEvent = [[self window]
-      nextEventMatchingMask:(NSLeftMouseUpMask | NSLeftMouseDraggedMask)
-                  untilDate:expiration
-                     inMode:NSEventTrackingRunLoopMode
-                    dequeue:YES]) != nil) {
-    if (firstEvent == nil) {
-      firstEvent = nextEvent;
-    }
-    if ([nextEvent type] == NSLeftMouseDragged) {
-      float deltax = [nextEvent locationInWindow].x -
-          [mouseDownEvent locationInWindow].x;
-      float deltay = [nextEvent locationInWindow].y -
-          [mouseDownEvent locationInWindow].y;
-      dragEvent = nextEvent;
-      if ([self deltaIndicatesConclusionReachedWithXDelta:deltax
-                                                   yDelta:deltay
-                                              xHysteresis:xHysteresis
-                                              yHysteresis:yHysteresis]) {
-        dragIt = [self deltaIndicatesDragStartWithXDelta:deltax
-                                                  yDelta:deltay
-                                             xHysteresis:xHysteresis
-                                             yHysteresis:yHysteresis];
-        break;
-      }
-    } else if ([nextEvent type] == NSLeftMouseUp) {
-      mouseUp = nextEvent;
-      break;
-    }
-  }
-
-  // Since we've been dequeuing the events (If we don't, we'll never see
-  // the mouse up...), we need to push some of the events back on.
-  // It makes sense to put the first and last drag events and the mouse
-  // up if there was one.
-  if (mouseUp != nil) {
-    [NSApp postEvent:mouseUp atStart:YES];
-  }
-  if (dragEvent != nil) {
-    [NSApp postEvent:dragEvent atStart:YES];
-  }
-  if (firstEvent != mouseUp && firstEvent != dragEvent) {
-    [NSApp postEvent:firstEvent atStart:YES];
-  }
-
-  return dragIt;
-}
-
-- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
-                      withExpiration:(NSDate*)expiration {
-  return [self dragShouldBeginFromMouseDown:mouseDownEvent
-                             withExpiration:expiration
-                                xHysteresis:kWebDragStartHysteresisX
-                                yHysteresis:kWebDragStartHysteresisY];
+- (DraggableButtonImpl*)draggableButton {
+  return draggableButtonImpl_.get();
 }
 
 - (void)mouseUp:(NSEvent*)theEvent {
-  durationMouseWasDown_ = [theEvent timestamp] - whenMouseDown_;
+  if ([draggableButtonImpl_ mouseUp:theEvent] == kDraggableButtonMixinCallSuper)
+    [super mouseUp:theEvent];
+}
 
-  if (actionHasFired_)
-    return;
-
-  if (!draggable_) {
-    [super mouseUp:theEvent];
-    return;
-  }
-
-  // There are non-drag cases where a mouseUp: may happen
-  // (e.g. mouse-down, cmd-tab to another application, move mouse,
-  // mouse-up).  So we check.
-  NSPoint viewLocal = [self convertPoint:[theEvent locationInWindow]
-                                fromView:[[self window] contentView]];
-  if (NSPointInRect(viewLocal, [self bounds])) {
-    [self performClick:self];
+- (void)mouseDown:(NSEvent*)theEvent {
+  if ([draggableButtonImpl_ mouseDown:theEvent] ==
+          kDraggableButtonMixinCallSuper) {
+    [super mouseDown:theEvent];
   }
 }
 
-- (void)secondaryMouseUpAction:(BOOL)wasInside {
-  // Override if you want to do any extra work on mouseUp, after a mouseDown
-  // action has already fired.
-}
-
-- (void)performMouseDownAction:(NSEvent*)theEvent {
-  int eventMask = NSLeftMouseUpMask;
-
-  [[self target] performSelector:[self action] withObject:self];
-  actionHasFired_ = YES;
-
-  while (1) {
-    theEvent = [[self window] nextEventMatchingMask:eventMask];
-    if (!theEvent)
-      continue;
-    NSPoint mouseLoc = [self convertPoint:[theEvent locationInWindow]
-                                 fromView:nil];
-    BOOL isInside = [self mouse:mouseLoc inRect:[self bounds]];
-    [self highlight:isInside];
-
-    switch ([theEvent type]) {
-      case NSLeftMouseUp:
-        durationMouseWasDown_ = [theEvent timestamp] - whenMouseDown_;
-        [self secondaryMouseUpAction:isInside];
-        break;
-      default:
-        /* Ignore any other kind of event. */
-        break;
-    }
-  }
-
-  [self highlight:NO];
-}
-
-// Mimic "begin a click" operation visually.  Do NOT follow through
-// with normal button event handling.
-- (void)mouseDown:(NSEvent*)theEvent {
-  [[NSCursor arrowCursor] set];
-
-  whenMouseDown_ = [theEvent timestamp];
-  actionHasFired_ = NO;
-
-  if (draggable_) {
-    NSDate* date = [NSDate dateWithTimeIntervalSinceNow:kDragExpirationTimeout];
-    if ([self dragShouldBeginFromMouseDown:theEvent
-                            withExpiration:date]) {
-      [self beginDrag:theEvent];
-      [self endDrag];
-    } else {
-      if (actsOnMouseDown_) {
-        [self performMouseDownAction:theEvent];
-      } else {
-        [super mouseDown:theEvent];
-      }
-
-    }
-  } else {
-    if (actsOnMouseDown_) {
-      [self performMouseDownAction:theEvent];
-    } else {
-      [super mouseDown:theEvent];
-    }
-  }
-}
-
 - (void)beginDrag:(NSEvent*)dragEvent {
   // Must be overridden by subclasses.
   NOTREACHED();
 }
 
-- (void)endDrag {
-  [self highlight:NO];
-}
-
 @end  // @interface DraggableButton