pdf/fading_control.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "pdf/fading_control.h"
   6
   7 #include <math.h>
   8
   9 #include "base/logging.h"
  10 #include "pdf/draw_utils.h"
  11 #include "pdf/resource_consts.h"
  12
  13 namespace chrome_pdf {
  14
  15 FadingControl::FadingControl()
  16     : alpha_shift_(0), timer_id_(0) {
  17 }
  18
  19 FadingControl::~FadingControl() {
  20 }
  21
  22 void FadingControl::OnTimerFired(uint32 timer_id) {
  23   if (timer_id == timer_id_) {
  24     int32 new_alpha = transparency() + alpha_shift_;
  25     if (new_alpha <= kTransparentAlpha) {
  26       Show(false, true);
  27       OnFadeOutComplete();
  28       return;
  29     }
  30     if (new_alpha >= kOpaqueAlpha) {
  31       AdjustTransparency(kOpaqueAlpha, true);
  32       OnFadeInComplete();
  33       return;
  34     }
  35
  36     AdjustTransparency(static_cast<uint8>(new_alpha), true);
  37     timer_id_ = owner()->ScheduleTimer(id(), kFadingTimeoutMs);
  38   }
  39 }
  40
  41 // Fade In/Out control depending on visible flag over the time of time_ms.
  42 void FadingControl::Fade(bool show, uint32 time_ms) {
  43   DCHECK(time_ms != 0);
  44   // Check if we already in the same state.
  45   if (!visible() && !show)
  46     return;
  47   if (!visible() && show) {
  48     Show(show, false);
  49     AdjustTransparency(kTransparentAlpha, false);
  50     OnFadeOutComplete();
  51   }
  52   if (transparency() == kOpaqueAlpha && show) {
  53     OnFadeInComplete();
  54     return;
  55   }
  56
  57   int delta = show ? kOpaqueAlpha - transparency() : transparency();
  58   double shift =
  59       static_cast<double>(delta) * kFadingTimeoutMs / time_ms;
  60   if (shift > delta)
  61     alpha_shift_ = delta;
  62   else
  63     alpha_shift_ = static_cast<int>(ceil(shift));
  64
  65   if (alpha_shift_ == 0)
  66     alpha_shift_ = 1;
  67
  68   // If disabling, make alpha shift negative.
  69   if (!show)
  70     alpha_shift_ = -alpha_shift_;
  71
  72   timer_id_ = owner()->ScheduleTimer(id(), kFadingTimeoutMs);
  73 }
  74
  75 }  // namespace chrome_pdf