Gradient overlay for constrained window

chrome/renderer/webview_animating_overlay.cc

+// Copyright (c) 2012 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.
+
+#include "chrome/renderer/webview_animating_overlay.h"
+
+#include "content/public/renderer/render_view.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkRect.h"
+#include "third_party/skia/include/effects/SkGradientShader.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
+#include "ui/gfx/size.h"
+#include "ui/gfx/skia_util.h"
+
+const int kAnimationDurationMiliseconds = 500;
+
+WebViewAnimatingOverlay::WebViewAnimatingOverlay(
+    content::RenderView* render_view)
+    : render_view_(render_view),
+      state_(HIDDEN) {
+}
+
+WebViewAnimatingOverlay::~WebViewAnimatingOverlay() {
+  if (render_view_->GetWebView())
+    render_view_->GetWebView()->removePageOverlay(this);
+}
+
+void WebViewAnimatingOverlay::Show() {
+  if (state_ == ANIMATING_IN || state_ == VISIBLE)
+    return;
+
+  if (state_ == ANIMATING_OUT) {
+    start_time_ = base::Time::Now() - GetAnimationTimeRemaining();
+  } else {

[Nico, 2012/08/14 21:14:12]

DCHECK(state_ == HIDDEN);

Alternatively, you could switch(state_), then the compiler makes sure you handle
all cases (assuming you don't add a default: branch)

[sail, 2012/08/15 05:26:20]

Done.

+    start_time_ = base::Time::Now();
+    if (render_view_->GetWebView())
+      render_view_->GetWebView()->addPageOverlay(this, 0);
+  }
+
+  state_ = ANIMATING_IN;
+  timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(16), this,

[Nico, 2012/08/14 21:14:12]

constant

[sail, 2012/08/15 05:26:20]

Done.

+               &WebViewAnimatingOverlay::OnTimer);
+}
+
+void WebViewAnimatingOverlay::Hide() {
+  if (state_ == ANIMATING_OUT || state_ == HIDDEN)
+    return;
+
+  if (state_ == ANIMATING_IN)
+    start_time_ = base::Time::Now() - GetAnimationTimeRemaining();
+  else
+    start_time_ = base::Time::Now();
+
+  state_ = ANIMATING_OUT;
+  timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(16), this,
+               &WebViewAnimatingOverlay::OnTimer);
+}
+
+void WebViewAnimatingOverlay::paintPageOverlay(WebKit::WebCanvas* canvas) {
+  SkRect rect = gfx::RectToSkRect(gfx::Rect(render_view_->GetSize()));
+
+  // The center of the radial gradient should be near the top middle.
+  SkPoint center_point;
+  center_point.iset(rect.width() * 0.5, rect.height() * 0.05);
+
+  // Animate in or out using the alpha.
+  int alpha = GetAnimationProgress() * 191;

[Nico, 2012/08/14 21:14:12]

This looks like a linear animation. Could ui/base/animation/linear_animation.h
make this class simpler?

[sail, 2012/08/15 05:26:20]

Done.

+  SkColor colors[] = {
+    SkColorSetARGB(alpha, 255, 255, 255),
+    SkColorSetARGB(alpha, 127, 127, 127)
+  };
+
+  SkShader* shader = SkGradientShader::CreateRadial(center_point,
+      SkIntToScalar(rect.width()), colors, NULL, arraysize(colors),
+      SkShader::kClamp_TileMode);
+  SkPaint paint;
+  paint.setShader(shader);
+  paint.setDither(true);
+  shader->unref();

[jamesr, 2012/08/14 19:08:24]

Could you use SkAutoTUnref<> here instead of manual derefing?

[sail, 2012/08/15 05:26:20]

Done.

+
+  canvas->drawRect(rect, paint);
+}
+
+void WebViewAnimatingOverlay::OnTimer() {
+  if (GetAnimationTimeRemaining() <= base::TimeDelta()) {
+    timer_.Stop();
+    if (state_ == ANIMATING_IN) {
+      state_ = VISIBLE;
+    } else {
+      DCHECK(state_ == ANIMATING_OUT);
+      state_ = HIDDEN;
+      if (render_view_->GetWebView())
+        render_view_->GetWebView()->removePageOverlay(this);
+    }
+  }
+  render_view_->Repaint(render_view_->GetSize());
+}
+
+base::TimeDelta WebViewAnimatingOverlay::GetAnimationTimeRemaining() const {
+  base::Time end_time = start_time_ +
+      base::TimeDelta::FromMilliseconds(kAnimationDurationMiliseconds);
+  return end_time - base::Time::Now();

[jamesr, 2012/08/14 19:08:24]

we drive most web-based animations of of base::TimeTicks for better
precision+accuracy (for instance, if the user adjusts the system clock).

[sail, 2012/08/15 05:26:20]

Done.
Switched to ui/base/animation which already uses base::TimeTicks.

+}
+
+float WebViewAnimatingOverlay::GetAnimationProgress() const {
+  if (state_ != ANIMATING_IN && state_ != ANIMATING_OUT)
+    return 1.0;
+
+  base::TimeDelta delta = base::Time::Now() - start_time_;
+  float progress = delta.InMillisecondsF() / kAnimationDurationMiliseconds;
+  if (state_ == ANIMATING_OUT)
+    progress = 1.0 - progress;
+  return std::max(std::min(progress, 1.0f), 0.0f);
+}