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

chrome/browser/ui/cocoa/draggable_button_mixin.mm

Index: chrome/browser/ui/cocoa/draggable_button_mixin.mm
diff --git a/chrome/browser/ui/cocoa/draggable_button.mm b/chrome/browser/ui/cocoa/draggable_button_mixin.mm
similarity index 50%
copy from chrome/browser/ui/cocoa/draggable_button.mm
copy to chrome/browser/ui/cocoa/draggable_button_mixin.mm
index 4d03b2790ec78127546126e082bdf5dd4854b47c..a704498046064e48cb597e8f90ef40d896f2acc9 100644
--- a/chrome/browser/ui/cocoa/draggable_button.mm
+++ b/chrome/browser/ui/cocoa/draggable_button_mixin.mm
@@ -4,6 +4,8 @@
 
 #import "chrome/browser/ui/cocoa/draggable_button.h"
 
+#include <cmath>
+
 #include "base/logging.h"
 #import "base/memory/scoped_nsobject.h"
 
@@ -17,7 +19,32 @@ const CGFloat kDragExpirationTimeout = 0.45;
 
 }
 
-@implementation DraggableButton
+// Private /////////////////////////////////////////////////////////////////////
+
+@interface DraggableButtonImpl (Private)
+
+- (BOOL)deltaIndicatesDragStartWithXDelta:(float)xDelta
+                                   yDelta:(float)yDelta
+                              xHysteresis:(float)xHysteresis
+                              yHysteresis:(float)yHysteresis;
+- (BOOL)deltaIndicatesConclusionReachedWithXDelta:(float)xDelta
+                                           yDelta:(float)yDelta
+                                      xHysteresis:(float)xHysteresis
+                                      yHysteresis:(float)yHysteresis;
+- (void)performMouseDownAction:(NSEvent*)theEvent;
+- (void)endDrag;
+- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
+                      withExpiration:(NSDate*)expiration;
+- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
+                      withExpiration:(NSDate*)expiration
+                         xHysteresis:(float)xHysteresis
+                         yHysteresis:(float)yHysteresis;
+
+@end
+
+// Implementation //////////////////////////////////////////////////////////////
+
+@implementation DraggableButtonImpl
 
 @synthesize draggable = draggable_;
 @synthesize actsOnMouseDown = actsOnMouseDown_;
@@ -25,9 +52,9 @@ const CGFloat kDragExpirationTimeout = 0.45;
 @synthesize actionHasFired = actionHasFired_;
 @synthesize whenMouseDown = whenMouseDown_;
 
-
-- (id)initWithFrame:(NSRect)frame {
-  if ((self = [super initWithFrame:frame])) {
+- (id)initWithButton:(NSButton<DraggableButtonMixin>*)button {
+  if ((self = [super init])) {
+    button_ = button;
     draggable_ = YES;
     actsOnMouseDown_ = NO;
     actionHasFired_ = NO;
@@ -35,29 +62,117 @@ const CGFloat kDragExpirationTimeout = 0.45;
   return self;
 }
 
-- (id)initWithCoder:(NSCoder*)coder {
-  if ((self = [super initWithCoder:coder])) {
-    draggable_ = YES;
-    actsOnMouseDown_ = NO;
-    actionHasFired_ = NO;
+// NSButton/NSResponder Implementations ////////////////////////////////////////
+
+- (DraggableButtonResult)mouseUp:(NSEvent*)theEvent {
+  durationMouseWasDown_ = [theEvent timestamp] - whenMouseDown_;
+
+  if (actionHasFired_)
+    return kDraggableButtonImplDidWork;
+
+  if (!draggable_)
+    return kDraggableButtonMixinCallSuper;
+
+  // There are non-drag cases where a |-mouseUp:| may happen (e.g. mouse-down,
+  // cmd-tab to another application, move mouse, mouse-up), so check.
+  NSPoint viewLocal = [button_ convertPoint:[theEvent locationInWindow]
+                                   fromView:[[button_ window] contentView]];
+  if (NSPointInRect(viewLocal, [button_ bounds]))
+    [button_ performClick:self];
+
+  return kDraggableButtonImplDidWork;
+}
+
+// Mimic "begin a click" operation visually.  Do NOT follow through with normal
+// button event handling.
+- (DraggableButtonResult)mouseDown:(NSEvent*)theEvent {
+  [[NSCursor arrowCursor] set];
+
+  whenMouseDown_ = [theEvent timestamp];
+  actionHasFired_ = NO;
+
+  if (draggable_) {
+    NSDate* date = [NSDate dateWithTimeIntervalSinceNow:kDragExpirationTimeout];
+    if ([self dragShouldBeginFromMouseDown:theEvent
+                            withExpiration:date]) {
+      [button_ beginDrag:theEvent];
+      [self endDrag];
+    } else {
+      if (actsOnMouseDown_) {
+        [self performMouseDownAction:theEvent];
+        return kDraggableButtonImplDidWork;
+      } else {
+        return kDraggableButtonMixinCallSuper;
+      }
+    }
+  } else {
+    if (actsOnMouseDown_) {
+      [self performMouseDownAction:theEvent];
+      return kDraggableButtonImplDidWork;
+    } else {
+      return kDraggableButtonMixinCallSuper;
+    }
   }
-  return self;
+
+  return kDraggableButtonImplDidWork;
 }
 
+// Idempotent Helpers //////////////////////////////////////////////////////////
+
 - (BOOL)deltaIndicatesDragStartWithXDelta:(float)xDelta
                                    yDelta:(float)yDelta
                               xHysteresis:(float)xHysteresis
                               yHysteresis:(float)yHysteresis {
-  return (ABS(xDelta) >= xHysteresis) || (ABS(yDelta) >= yHysteresis);
+  if ([button_ respondsToSelector:@selector(deltaIndicatesDragStartWithXDelta:
+                                            yDelta:
+                                            xHysteresis:
+                                            yHysteresis:
+                                            indicates:)]) {
+    BOOL indicates = NO;
+    DraggableButtonResult result = [button_
+        deltaIndicatesDragStartWithXDelta:xDelta
+        yDelta:yDelta
+        xHysteresis:xHysteresis
+        yHysteresis:yHysteresis
+        indicates:&indicates];
+    if (result != kDraggableButtonImplUseBase)
+      return indicates;
+  }
+  return (std::abs(xDelta) >= xHysteresis) || (std::abs(yDelta) >= yHysteresis);
 }
 
 - (BOOL)deltaIndicatesConclusionReachedWithXDelta:(float)xDelta
                                            yDelta:(float)yDelta
                                       xHysteresis:(float)xHysteresis
                                       yHysteresis:(float)yHysteresis {
-  return (ABS(xDelta) >= xHysteresis) || (ABS(yDelta) >= yHysteresis);
+  if ([button_ respondsToSelector:
+          @selector(deltaIndicatesConclusionReachedWithXDelta:
+                    yDelta:
+                    xHysteresis:
+                    yHysteresis:
+                    indicates:)]) {
+    BOOL indicates = NO;
+    DraggableButtonResult result = [button_
+        deltaIndicatesConclusionReachedWithXDelta:xDelta
+        yDelta:yDelta
+        xHysteresis:xHysteresis
+        yHysteresis:yHysteresis
+        indicates:&indicates];
+    if (result != kDraggableButtonImplUseBase)
+      return indicates;
+  }
+  return (std::abs(xDelta) >= xHysteresis) || (std::abs(yDelta) >= yHysteresis);
+}
+
+- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
+                      withExpiration:(NSDate*)expiration {
+  return [self dragShouldBeginFromMouseDown:mouseDownEvent
+                             withExpiration:expiration
+                                xHysteresis:kWebDragStartHysteresisX
+                                yHysteresis:kWebDragStartHysteresisY];
 }
 
+// Implementation Details //////////////////////////////////////////////////////
 
 // Determine whether a mouse down should turn into a drag; started as copy of
 // NSTableView code.
@@ -75,8 +190,8 @@ const CGFloat kDragExpirationTimeout = 0.45;
   NSEvent* mouseUp = nil;
   BOOL dragIt = NO;
 
-  while ((nextEvent = [[self window]
-      nextEventMatchingMask:(NSLeftMouseUpMask | NSLeftMouseDraggedMask)
+  while ((nextEvent = [[button_ window]
+      nextEventMatchingMask:NSLeftMouseUpMask | NSLeftMouseDraggedMask
                   untilDate:expiration
                      inMode:NSEventTrackingRunLoopMode
                     dequeue:YES]) != nil) {
@@ -122,107 +237,53 @@ const CGFloat kDragExpirationTimeout = 0.45;
   return dragIt;
 }
 
-- (BOOL)dragShouldBeginFromMouseDown:(NSEvent*)mouseDownEvent
-                      withExpiration:(NSDate*)expiration {
-  return [self dragShouldBeginFromMouseDown:mouseDownEvent
-                             withExpiration:expiration
-                                xHysteresis:kWebDragStartHysteresisX
-                                yHysteresis:kWebDragStartHysteresisY];
-}
-
-- (void)mouseUp:(NSEvent*)theEvent {
-  durationMouseWasDown_ = [theEvent timestamp] - whenMouseDown_;
-
-  if (actionHasFired_)
-    return;
-
-  if (!draggable_) {
-    [super mouseUp:theEvent];
-    return;
-  }
+- (void)secondaryMouseUpAction:(BOOL)wasInside {
+  if ([button_ respondsToSelector:_cmd])
+    [button_ secondaryMouseUpAction:wasInside];
 
-  // 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];
-  }
+  // No actual implementation yet.
 }
 
-- (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*)event {
+  if ([button_ respondsToSelector:_cmd] &&
+      [button_ performMouseDownAction:event] != kDraggableButtonImplUseBase) {
+      return;
+  }
 
-- (void)performMouseDownAction:(NSEvent*)theEvent {
   int eventMask = NSLeftMouseUpMask;
 
-  [[self target] performSelector:[self action] withObject:self];
+  [[button_ target] performSelector:[button_ action] withObject:self];
   actionHasFired_ = YES;
 
   while (1) {
-    theEvent = [[self window] nextEventMatchingMask:eventMask];
-    if (!theEvent)
+    event = [[button_ window] nextEventMatchingMask:eventMask];
+    if (!event)
       continue;
-    NSPoint mouseLoc = [self convertPoint:[theEvent locationInWindow]
-                                 fromView:nil];
-    BOOL isInside = [self mouse:mouseLoc inRect:[self bounds]];
-    [self highlight:isInside];
+    NSPoint mouseLoc = [button_ convertPoint:[event locationInWindow]
+                                    fromView:nil];
+    BOOL isInside = [button_ mouse:mouseLoc inRect:[button_ bounds]];
+    [button_ highlight:isInside];
 
-    switch ([theEvent type]) {
+    switch ([event type]) {
       case NSLeftMouseUp:
-        durationMouseWasDown_ = [theEvent timestamp] - whenMouseDown_;
+        durationMouseWasDown_ = [event timestamp] - whenMouseDown_;
         [self secondaryMouseUpAction:isInside];
         break;
       default:
-        /* Ignore any other kind of event. */
+        // 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();
+  [button_ highlight:NO];
 }
 
 - (void)endDrag {
-  [self highlight:NO];
+  if ([button_ respondsToSelector:_cmd] &&
+      [button_ endDrag] != kDraggableButtonImplUseBase) {
+    return;
+  }
+  [button_ highlight:NO];
 }
 
-@end  // @interface DraggableButton
+@end