Adding a Views scrollbar implementation.

views/controls/scrollbar/base_scroll_bar_thumb.cc

+// 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.
+
+#include "views/controls/scrollbar/base_scroll_bar_thumb.h"
+
+#include "views/controls/scrollbar/base_scroll_bar.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/rect.h"
+
+namespace {
+// The distance the mouse can be dragged outside the bounds of the thumb during
+// dragging before the scrollbar will snap back to its regular position.
+static const int kScrollThumbDragOutSnap = 100;
+}
+
+namespace views {
+
+BaseScrollBarThumb::BaseScrollBarThumb(BaseScrollBar* scroll_bar)
+    : scroll_bar_(scroll_bar),
+      drag_start_position_(-1),
+      mouse_offset_(-1),
+      state_(CustomButton::BS_NORMAL) {
+}
+
+BaseScrollBarThumb::~BaseScrollBarThumb() {
+}
+
+void BaseScrollBarThumb::SetSize(int size) {
+  // Make sure the thumb is never sized smaller than its minimum possible
+  // display size.
+  gfx::Size prefsize = GetPreferredSize();
+  size = std::max(size, scroll_bar_->IsHorizontal() ? prefsize.width() :
+                                                      prefsize.height());
+  gfx::Rect thumb_bounds = bounds();
+  if (scroll_bar_->IsHorizontal()) {
+    thumb_bounds.set_width(size);
+  } else {
+    thumb_bounds.set_height(size);
+  }
+  SetBoundsRect(thumb_bounds);
+}
+
+int BaseScrollBarThumb::GetSize() const {
+  if (scroll_bar_->IsHorizontal())
+    return width();
+  return height();
+}
+
+void BaseScrollBarThumb::SetPosition(int position) {
+  gfx::Rect thumb_bounds = bounds();
+  gfx::Rect track_bounds = scroll_bar_->GetTrackBounds();
+  if (scroll_bar_->IsHorizontal()) {
+    thumb_bounds.set_x(track_bounds.x() + position);
+  } else {
+    thumb_bounds.set_y(track_bounds.y() + position);
+  }
+  SetBoundsRect(thumb_bounds);
+}
+
+int BaseScrollBarThumb::GetPosition() const {
+  gfx::Rect track_bounds = scroll_bar_->GetTrackBounds();
+  if (scroll_bar_->IsHorizontal())
+    return x() - track_bounds.x();
+  return y() - track_bounds.y();
+}
+
+void BaseScrollBarThumb::OnMouseEntered(const MouseEvent& event) {
+  SetState(CustomButton::BS_HOT);
+}
+
+void BaseScrollBarThumb::OnMouseExited(const MouseEvent& event) {
+  SetState(CustomButton::BS_NORMAL);
+}
+
+bool BaseScrollBarThumb::OnMousePressed(const MouseEvent& event) {
+  mouse_offset_ = scroll_bar_->IsHorizontal() ? event.x() : event.y();
+  drag_start_position_ = GetPosition();
+  SetState(CustomButton::BS_PUSHED);
+  return true;
+}
+
+bool BaseScrollBarThumb::OnMouseDragged(const MouseEvent& event) {
+  // If the user moves the mouse more than |kScrollThumbDragOutSnap| outside
+  // the bounds of the thumb, the scrollbar will snap the scroll back to the
+  // point it was at before the drag began.
+  if (scroll_bar_->IsHorizontal()) {
+    if ((event.y() < y() - kScrollThumbDragOutSnap) ||
+        (event.y() > (y() + height() + kScrollThumbDragOutSnap))) {
+      scroll_bar_->ScrollToThumbPosition(drag_start_position_, false);
+      return true;
+    }
+  } else {
+    if ((event.x() < x() - kScrollThumbDragOutSnap) ||
+        (event.x() > (x() + width() + kScrollThumbDragOutSnap))) {
+      scroll_bar_->ScrollToThumbPosition(drag_start_position_, false);
+      return true;
+    }
+  }
+  if (scroll_bar_->IsHorizontal()) {
+    int thumb_x = event.x() - mouse_offset_;
+    scroll_bar_->ScrollToThumbPosition(GetPosition() + thumb_x, false);
+  } else {
+    int thumb_y = event.y() - mouse_offset_;
+    scroll_bar_->ScrollToThumbPosition(GetPosition() + thumb_y, false);
+  }
+  return true;
+}
+
+void BaseScrollBarThumb::OnMouseReleased(const MouseEvent& event) {
+  OnMouseCaptureLost();
+}
+
+void BaseScrollBarThumb::OnMouseCaptureLost() {
+  SetState(CustomButton::BS_HOT);
+}
+
+CustomButton::ButtonState BaseScrollBarThumb::GetState() const {
+  return state_;
+}
+
+void BaseScrollBarThumb::SetState(CustomButton::ButtonState state) {
+  state_ = state;
+  SchedulePaint();
+}
+
+}  // namespace views