chrome/browser/ui/cocoa/tabs/throbber_view.mm

// Copyright (c) 2009 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/tabs/throbber_view.h"

#include <set>

#include "base/logging.h"
#include "base/mac/scoped_nsobject.h"

static const float kAnimationIntervalSeconds = 0.03;  // 30ms, same as windows

@interface ThrobberView(PrivateMethods)
- (id)initWithFrame:(NSRect)frame delegate:(id<ThrobberDataDelegate>)delegate;
- (void)maintainTimer;
- (void)animate;
@end

@protocol ThrobberDataDelegate <NSObject>
// Is the current frame the last frame of the animation?
- (BOOL)animationIsComplete;

// Draw the current frame into the current graphics context.
- (void)drawFrameInRect:(NSRect)rect;

// Update the frame counter.
- (void)advanceFrame;
@end

@interface ThrobberFilmstripDelegate : NSObject
                                       <ThrobberDataDelegate> {
  base::scoped_nsobject<NSImage> image_;
  unsigned int numFrames_;  // Number of frames in this animation.
  unsigned int animationFrame_;  // Current frame of the animation,
                                 // [0..numFrames_)
}

- (id)initWithImage:(NSImage*)image;

@end

@implementation ThrobberFilmstripDelegate

- (id)initWithImage:(NSImage*)image {
  if ((self = [super init])) {
    // Reset the animation counter so there's no chance we are off the end.
    animationFrame_ = 0;

    // Ensure that the height divides evenly into the width. Cache the
    // number of frames in the animation for later.
    NSSize imageSize = [image size];
    DCHECK(imageSize.height && imageSize.width);
    if (!imageSize.height)
      return nil;
    DCHECK((int)imageSize.width % (int)imageSize.height == 0);
    numFrames_ = (int)imageSize.width / (int)imageSize.height;
    DCHECK(numFrames_);
    image_.reset([image retain]);
  }
  return self;
}

- (BOOL)animationIsComplete {
  return NO;
}

- (void)drawFrameInRect:(NSRect)rect {
  float imageDimension = [image_ size].height;
  float xOffset = animationFrame_ * imageDimension;
  NSRect sourceImageRect =
      NSMakeRect(xOffset, 0, imageDimension, imageDimension);
  [image_ drawInRect:rect
            fromRect:sourceImageRect
           operation:NSCompositeSourceOver
            fraction:1.0];
}

- (void)advanceFrame {
  animationFrame_ = ++animationFrame_ % numFrames_;
}

@end

@interface ThrobberToastDelegate : NSObject
                                   <ThrobberDataDelegate> {
  base::scoped_nsobject<NSImage> image1_;
  base::scoped_nsobject<NSImage> image2_;
  NSSize image1Size_;
  NSSize image2Size_;
  int animationFrame_;  // Current frame of the animation,
}

- (id)initWithImage1:(NSImage*)image1 image2:(NSImage*)image2;

@end

@implementation ThrobberToastDelegate

- (id)initWithImage1:(NSImage*)image1 image2:(NSImage*)image2 {
  if ((self = [super init])) {
    image1_.reset([image1 retain]);
    image2_.reset([image2 retain]);
    image1Size_ = [image1 size];
    image2Size_ = [image2 size];
    animationFrame_ = 0;
  }
  return self;
}

- (BOOL)animationIsComplete {
  if (animationFrame_ >= image1Size_.height + image2Size_.height)
    return YES;

  return NO;
}

// From [0..image1Height) we draw image1, at image1Height we draw nothing, and
// from [image1Height+1..image1Hight+image2Height] we draw the second image.
- (void)drawFrameInRect:(NSRect)rect {
  NSImage* image = nil;
  NSSize srcSize;
  NSRect destRect;

  if (animationFrame_ < image1Size_.height) {
    image = image1_.get();
    srcSize = image1Size_;
    destRect = NSMakeRect(0, -animationFrame_,
                          image1Size_.width, image1Size_.height);
  } else if (animationFrame_ == image1Size_.height) {
    // nothing; intermediate blank frame
  } else {
    image = image2_.get();
    srcSize = image2Size_;
    destRect = NSMakeRect(0, animationFrame_ -
                                 (image1Size_.height + image2Size_.height),
                          image2Size_.width, image2Size_.height);
  }

  if (image) {
    NSRect sourceImageRect =
        NSMakeRect(0, 0, srcSize.width, srcSize.height);
    [image drawInRect:destRect
             fromRect:sourceImageRect
            operation:NSCompositeSourceOver
             fraction:1.0];
  }
}

- (void)advanceFrame {
  ++animationFrame_;
}

@end

typedef std::set<ThrobberView*> ThrobberSet;

// ThrobberTimer manages the animation of a set of ThrobberViews.  It allows
// a single timer instance to be shared among as many ThrobberViews as needed.
@interface ThrobberTimer : NSObject {
 @private
  // A set of weak references to each ThrobberView that should be notified
  // whenever the timer fires.
  ThrobberSet throbbers_;

  // Weak reference to the timer that calls back to this object.  The timer
  // retains this object.
  NSTimer* timer_;

  // Whether the timer is actively running.  To avoid timer construction
  // and destruction overhead, the timer is not invalidated when it is not
  // needed, but its next-fire date is set to [NSDate distantFuture].
  // It is not possible to determine whether the timer has been suspended by
  // comparing its fireDate to [NSDate distantFuture], though, so a separate
  // variable is used to track this state.
  BOOL timerRunning_;

  // The thread that created this object.  Used to validate that ThrobberViews
  // are only added and removed on the same thread that the fire action will
  // be performed on.
  NSThread* validThread_;
}

// Returns a shared ThrobberTimer.  Everyone is expected to use the same
// instance.
+ (ThrobberTimer*)sharedThrobberTimer;

// Invalidates the timer, which will cause it to remove itself from the run
// loop.  This causes the timer to be released, and it should then release
// this object.
- (void)invalidate;

// Adds or removes ThrobberView objects from the throbbers_ set.
- (void)addThrobber:(ThrobberView*)throbber;
- (void)removeThrobber:(ThrobberView*)throbber;
@end

@interface ThrobberTimer(PrivateMethods)
// Starts or stops the timer as needed as ThrobberViews are added and removed
// from the throbbers_ set.
- (void)maintainTimer;

// Calls animate on each ThrobberView in the throbbers_ set.
- (void)fire:(NSTimer*)timer;
@end

@implementation ThrobberTimer
- (id)init {
  if ((self = [super init])) {
    // Start out with a timer that fires at the appropriate interval, but
    // prevent it from firing by setting its next-fire date to the distant
    // future.  Once a ThrobberView is added, the timer will be allowed to
    // start firing.
    timer_ = [NSTimer scheduledTimerWithTimeInterval:kAnimationIntervalSeconds
                                              target:self
                                            selector:@selector(fire:)
                                            userInfo:nil
                                             repeats:YES];
    [timer_ setFireDate:[NSDate distantFuture]];
    timerRunning_ = NO;

    validThread_ = [NSThread currentThread];
  }
  return self;
}

+ (ThrobberTimer*)sharedThrobberTimer {
  // Leaked.  That's OK, it's scoped to the lifetime of the application.
  static ThrobberTimer* sharedInstance = [[ThrobberTimer alloc] init];
  return sharedInstance;
}

- (void)invalidate {
  [timer_ invalidate];
}

- (void)addThrobber:(ThrobberView*)throbber {
  DCHECK([NSThread currentThread] == validThread_);
  throbbers_.insert(throbber);
  [self maintainTimer];
}

- (void)removeThrobber:(ThrobberView*)throbber {
  DCHECK([NSThread currentThread] == validThread_);
  throbbers_.erase(throbber);
  [self maintainTimer];
}

- (void)maintainTimer {
  BOOL oldRunning = timerRunning_;
  BOOL newRunning = throbbers_.empty() ? NO : YES;

  if (oldRunning == newRunning)
    return;

  // To start the timer, set its next-fire date to an appropriate interval from
  // now.  To suspend the timer, set its next-fire date to a preposterous time
  // in the future.
  NSDate* fireDate;
  if (newRunning)
    fireDate = [NSDate dateWithTimeIntervalSinceNow:kAnimationIntervalSeconds];
  else
    fireDate = [NSDate distantFuture];

  [timer_ setFireDate:fireDate];
  timerRunning_ = newRunning;
}

- (void)fire:(NSTimer*)timer {
  // The call to [throbber animate] may result in the ThrobberView calling
  // removeThrobber: if it decides it's done animating.  That would invalidate
  // the iterator, making it impossible to correctly get to the next element
  // in the set.  To prevent that from happening, a second iterator is used
  // and incremented before calling [throbber animate].
  ThrobberSet::const_iterator current = throbbers_.begin();
  ThrobberSet::const_iterator next = current;
  while (current != throbbers_.end()) {
    ++next;
    ThrobberView* throbber = *current;
    [throbber animate];
    current = next;
  }
}
@end

@implementation ThrobberView

+ (id)filmstripThrobberViewWithFrame:(NSRect)frame
                               image:(NSImage*)image {
  ThrobberFilmstripDelegate* delegate =
      [[[ThrobberFilmstripDelegate alloc] initWithImage:image] autorelease];
  if (!delegate)
    return nil;

  return [[[ThrobberView alloc] initWithFrame:frame
                                     delegate:delegate] autorelease];
}

+ (id)toastThrobberViewWithFrame:(NSRect)frame
                     beforeImage:(NSImage*)beforeImage
                      afterImage:(NSImage*)afterImage {
  ThrobberToastDelegate* delegate =
      [[[ThrobberToastDelegate alloc] initWithImage1:beforeImage
                                              image2:afterImage] autorelease];
  if (!delegate)
    return nil;

  return [[[ThrobberView alloc] initWithFrame:frame
                                     delegate:delegate] autorelease];
}

- (id)initWithFrame:(NSRect)frame delegate:(id<ThrobberDataDelegate>)delegate {
  if ((self = [super initWithFrame:frame])) {
    dataDelegate_ = [delegate retain];
  }
  return self;
}

- (void)dealloc {
  [dataDelegate_ release];
  [[ThrobberTimer sharedThrobberTimer] removeThrobber:self];

  [super dealloc];
}

// Manages this ThrobberView's membership in the shared throbber timer set on
// the basis of its visibility and whether its animation needs to continue
// running.
- (void)maintainTimer {
  ThrobberTimer* throbberTimer = [ThrobberTimer sharedThrobberTimer];

  if ([self window] && ![self isHidden] && ![dataDelegate_ animationIsComplete])
    [throbberTimer addThrobber:self];
  else
    [throbberTimer removeThrobber:self];
}

// A ThrobberView added to a window may need to begin animating; a ThrobberView
// removed from a window should stop.
- (void)viewDidMoveToWindow {
  [self maintainTimer];
  [super viewDidMoveToWindow];
}

// A hidden ThrobberView should stop animating.
- (void)viewDidHide {
  [self maintainTimer];
  [super viewDidHide];
}

// A visible ThrobberView may need to start animating.
- (void)viewDidUnhide {
  [self maintainTimer];
  [super viewDidUnhide];
}

// Called when the timer fires. Advance the frame, dirty the display, and remove
// the throbber if it's no longer needed.
- (void)animate {
  [dataDelegate_ advanceFrame];
  [self setNeedsDisplay:YES];

  if ([dataDelegate_ animationIsComplete]) {
    [[ThrobberTimer sharedThrobberTimer] removeThrobber:self];
  }
}

// Overridden to draw the appropriate frame in the image strip.
- (void)drawRect:(NSRect)rect {
  [dataDelegate_ drawFrameInRect:[self bounds]];
}

@end