mac: Makeshift UI for scroll feedback.

chrome/browser/ui/cocoa/history_overlay_controller.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/history_overlay_controller.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+#include "base/logging.h"

[Mark Mentovai, 2011/08/16 01:01:20]

Used? Doesn’t look it.

[Nico, 2011/08/16 04:56:17]

Done.

+#include "base/memory/scoped_nsobject.h"
+#include "base/sys_string_conversions.h"

[Mark Mentovai, 2011/08/16 01:01:20]

Used? Doesn’t look it.

[Nico, 2011/08/16 04:56:17]

Done.

+
+// OverlayFrameView ////////////////////////////////////////////////////////////
+
+// The content view of the window that draws a custom frame.
+@interface OverlayFrameView : NSView {
+ @private
+  NSTextField* message_;  // Weak, owned by the view hierarchy.
+}
+- (void)setMessageText:(NSString*)text;
+@end
+
+// The content view of the window that draws a custom frame.
+@implementation OverlayFrameView
+
+- (id)initWithFrame:(NSRect)frameRect {

[Mark Mentovai, 2011/08/16 01:01:20]

I know where this code is ultimately ripped from:
chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm. Right down to the
comments and stuff. Do you want to refactor things to share the common code?

[Nico, 2011/08/16 04:56:17]

I'm hoping to get a bigger version of our back button picture from Cole, and
then I'll replace the text here with an NSImage thingie. So it might not be
worth to factor out right now.

+  if ((self = [super initWithFrame:frameRect])) {
+    scoped_nsobject<NSTextField> message(
+        // The frame will be fixed up when |-setMessageText:| is called.
+        [[NSTextField alloc] initWithFrame:NSMakeRect(0, 0, 0, 0)]);

[Mark Mentovai, 2011/08/16 01:01:20]

NSZeroRect?

[Nico, 2011/08/16 04:56:17]

Done.

+    message_ = message.get();
+    [message_ setEditable:NO];
+    [message_ setSelectable:NO];
+    [message_ setBezeled:NO];
+    [message_ setDrawsBackground:NO];
+    [message_ setFont:[NSFont boldSystemFontOfSize:72]];
+    [message_ setTextColor:[NSColor whiteColor]];
+    [self addSubview:message_];
+  }
+  return self;
+}
+
+- (void)drawRect:(NSRect)dirtyRect {
+  const CGFloat kCornerRadius = 5.0;
+  NSBezierPath* path = [NSBezierPath bezierPathWithRoundedRect:[self bounds]
+                                                       xRadius:kCornerRadius
+                                                       yRadius:kCornerRadius];
+
+  NSColor* fillColor = [NSColor colorWithCalibratedWhite:0.2 alpha:0.85];
+  [fillColor set];
+  [path fill];
+}
+
+- (void)setMessageText:(NSString*)text {
+  const CGFloat kHorizontalPadding = 30;  // In view coordinates.
+
+  // Style the string.
+  scoped_nsobject<NSMutableAttributedString> attrString(
+      [[NSMutableAttributedString alloc] initWithString:text]);
+  scoped_nsobject<NSShadow> textShadow([[NSShadow alloc] init]);
+  [textShadow.get() setShadowColor:[NSColor colorWithCalibratedWhite:0
+                                                               alpha:0.6]];
+  [textShadow.get() setShadowOffset:NSMakeSize(0, -1)];
+  [textShadow setShadowBlurRadius:1.0];
+  [attrString addAttribute:NSShadowAttributeName
+                     value:textShadow
+                     range:NSMakeRange(0, [text length])];
+  [message_ setAttributedStringValue:attrString];
+
+  // Fixup the frame of the string.

[Mark Mentovai, 2011/08/16 01:01:20]

“Fix up” as a verb is two words (although the problem is present in the file
that this borrows from.)

[Nico, 2011/08/16 04:56:17]

Done.

+  [message_ sizeToFit];
+  NSRect messageFrame = [message_ frame];
+  NSRect frameInViewSpace =
+      [message_ convertRect:[[self window] frame] fromView:nil];
+
+  if (NSWidth(messageFrame) > NSWidth(frameInViewSpace))
+    frameInViewSpace.size.width = NSWidth(messageFrame) + kHorizontalPadding;
+
+  messageFrame.origin.x =
+      (NSWidth(frameInViewSpace) - NSWidth(messageFrame)) / 2;
+  messageFrame.origin.y =
+      (NSHeight(frameInViewSpace) - NSHeight(messageFrame)) / 2;
+
+  [[self window] setFrame:[message_ convertRect:frameInViewSpace toView:nil]
+                  display:YES];
+  [message_ setFrame:messageFrame];
+}
+
+@end
+
+// HistoryOverlayController ////////////////////////////////////////////////////
+
+@implementation HistoryOverlayController
+
+- (id)initForMode:(HistoryOverlayMode)mode {
+  const NSRect kWindowFrame = NSMakeRect(0, 0, 120, 70);
+  scoped_nsobject<NSWindow> window(
+      [[NSWindow alloc] initWithContentRect:kWindowFrame
+                                  styleMask:NSBorderlessWindowMask
+                                    backing:NSBackingStoreBuffered
+                                      defer:NO]);
+  if ((self = [super initWithWindow:window])) {
+    mode_ = mode;
+
+    [window setDelegate:self];
+    [window setBackgroundColor:[NSColor clearColor]];
+    [window setOpaque:NO];
+    [window setHasShadow:NO];
+
+    // Create the content view. Take the frame from the existing content view.
+    NSRect frame = [[window contentView] frame];
+    scoped_nsobject<OverlayFrameView> frameView(
+        [[OverlayFrameView alloc] initWithFrame:frame]);
+    contentView_ = frameView.get();
+    [window setContentView:contentView_];
+
+    const unichar kBackArrowCharacter = 0x2190;
+    const unichar kForwardArrowCharacter = 0x2192;
+
+    unichar commandChar = mode_ == kHistoryOverlayModeForward ?
+        kForwardArrowCharacter : kBackArrowCharacter;
+    NSString* text =
+        [NSString stringWithCharacters:&commandChar length:1];
+    [contentView_ setMessageText:text];
+  }
+  return self;
+}
+
+- (void)setProgress:(CGFloat)gestureAmount {
+  CGFloat alpha = 0;
+  CGFloat x = 0;
+
+  NSRect windowFrame = [parent_ frame];
+  CGFloat minX = NSMinX(windowFrame);
+  CGFloat maxX = NSMaxX(windowFrame) - NSWidth([[self window] frame]);
+
+  if (mode_ == kHistoryOverlayModeForward) {
+    alpha = -(gestureAmount + 1) * (gestureAmount + 1) + 1;

[Mark Mentovai, 2011/08/16 01:01:20]

Can you pull the alpha computation out of the conditional by using std::abs? I
think that would be -(std::abs(gestureAmount) - 1) * (std::abs(gestureAmount) -
1) + 1.

I think squaring it as you’ve done is a good idea, but should the alpha be
scaled such that instead of being in the range of 0 to 1, it starts somewhere
higher than 0?

[Nico, 2011/08/16 04:56:17]

It feels good starting at 0 I think. Did the rest.

+    x = maxX + gestureAmount * (maxX - minX);
+  } else if (mode_ == kHistoryOverlayModeBack) {
+    alpha = -(gestureAmount - 1) * (gestureAmount - 1) + 1;
+    x = minX + gestureAmount * (maxX - minX);
+  }
+  [[self window] setAlphaValue:alpha];
+
+  NSPoint p = [parent_ frame].origin;
+  p.x = x;

[Mark Mentovai, 2011/08/16 01:01:20]

I wonder if we need a “target” for the arrow to hit to make it obvious that the
navigation happens when the things touch.

It might be obvious enough with the arrow inside the overlay now. I haven’t
actually looked at this implementation yet.

[Nico, 2011/08/16 04:56:17]

Yes, this will need tweaking.

+  p.y += (NSHeight(windowFrame) - NSHeight([[self window] frame])) * 0.65;
+  [[self window] setFrameOrigin:p];
+}
+
+- (void)dismiss {
+  const CGFloat kFadeOutDuration = 0.2;  // In seconds.

[Mark Mentovai, 2011/08/16 01:01:20]

Instead of the comment, name the variable kFadeOutDurationSeconds.

[Nico, 2011/08/16 04:56:17]

Done.

+
+  NSWindow* overlayWindow = [self window];
+
+  scoped_nsobject<CAAnimation> animation(
+      [[overlayWindow animationForKey:@"alphaValue"] copy]);
+  [animation setDelegate:self];
+  [animation setDuration:kFadeOutDuration];
+  NSMutableDictionary* dictionary =
+      [NSMutableDictionary dictionaryWithCapacity:1];
+  [dictionary setObject:animation forKey:@"alphaValue"];
+  [overlayWindow setAnimations:dictionary];
+  [[overlayWindow animator] setAlphaValue:0.0];
+}
+
+- (void)windowWillClose:(NSNotification*)notif {

[Mark Mentovai, 2011/08/16 01:01:20]

Don’t name variables notif, even if they’re unused, and even if the file you
took this from did it.

[Nico, 2011/08/16 04:56:17]

Done.

+  // Release all animations because CAAnimation retains its delegate (self),
+  // which will cause a retain cycle. Break it!
+  [[self window] setAnimations:[NSDictionary dictionary]];
+}
+
+- (void)showPanelForWindow:(NSWindow*)window {
+  parent_ = window;

[Mark Mentovai, 2011/08/16 01:01:20]

Is it possible for parent_ to go away while this object hangs on to a reference
to it? It seems like I can press command-W while my fingers are on the touchpad
in the middle of a rubber band, for example.

[Nico, 2011/08/16 04:56:17]

Great catch, done. I made it a scoped_nsobject (hitting cmd-w during a swipe
still hides the window immediately, but the track animation continues until
completion, and nothing crashes.)

+  [self setProgress:0];  // Set initial window position.
+  [self showWindow:self];
+}
+
+- (void)animationDidStop:(CAAnimation*)theAnimation finished:(BOOL)finished {
+  [self close];
+}
+
+@end