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//
// PointerEventTrapView.cs
//
// Author:
// Vsevolod Kukol <sevoku@microsoft.com>
//
// Copyright (c) 2019
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#if MAC
using System;
using AppKit;
namespace MonoDevelop.Components.Mac
{
/// <summary>
/// DragEventTrapView base class to disable GDK events while an NSView is being dragged
/// </summary>
/// <remarks>
/// This NSView tracks pointer events and disables GDK events during a dragging operation.
/// This allows the cursor to shortly leave the view bounds and prevents losing of events
/// if the pointer enters a different view or Gtk widget shortly.
///
/// The main purpose is to support native views inside splitters without losing splitter
/// drag support. See <see cref="Docking.MacSplitterWidget"/> and <see cref="HPanedThin"/> for examples.
///
/// However DragEventTrapView does not handle the actual drag operation, so it could
/// be used for other use cases, where GDK events or other NSViews might interfere and
/// steal pointer events.
///
/// NOTE: this view should be added with NSWindowOrderingMode.Above to its superview, to
/// make sure the it's the first widget to receive pointer events.
/// </remarks>
abstract class DragEventTrapView : NSView
{
NSCursor currentCursor;
bool hover, dragging;
double lastEventTimestamp = Foundation.NSProcessInfo.ProcessInfo.SystemUptime;
bool enableGdkEventFiler;
bool gdkEventFilterInserted;
bool isDisposed;
protected DragEventTrapView ()
{
const NSTrackingAreaOptions options = NSTrackingAreaOptions.ActiveInKeyWindow |
NSTrackingAreaOptions.InVisibleRect |
NSTrackingAreaOptions.MouseEnteredAndExited;
var trackingArea = new NSTrackingArea (default, options, this, null);
AddTrackingArea (trackingArea);
}
/// <summary>
/// Override to supply a custom NSCursor during a drag operation
/// </summary>
/// <returns>NSCursor to be shown while dragging, or null to disable cursor changes</returns>
protected virtual NSCursor GetDragCursor ()
{
return null;
}
void SetDefaultCursor ()
{
if (currentCursor != null) {
currentCursor.Pop ();
currentCursor = null;
}
}
void SetDragCursor ()
{
var cursor = GetDragCursor ();
if (currentCursor != null) {
if (currentCursor == cursor)
return;
currentCursor.Pop ();
}
currentCursor = cursor;
currentCursor.Push ();
}
public override void MouseEntered (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
if (!dragging) {
SetDragCursor ();
}
hover = true;
base.MouseEntered (theEvent);
}
public override void MouseExited (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
if (!dragging) {
SetDefaultCursor ();
}
hover = false;
base.MouseExited (theEvent);
}
public override void MouseMoved (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
if (!dragging) {
SetDragCursor ();
}
base.MouseMoved (theEvent);
}
public override void MouseDown (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
dragging = true;
AddGdkEventFilter ();
}
public override void MouseUp (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
if (hover) {
SetDragCursor ();
} else {
SetDefaultCursor ();
}
RaiseEndDrag ();
base.MouseUp (theEvent);
}
public override void MouseDragged (NSEvent theEvent)
{
lastEventTimestamp = theEvent.Timestamp;
SetDragCursor ();
}
void RaiseEndDrag ()
{
if (dragging) {
dragging = false;
RemoveGdkEventFilter ();
}
}
public override void RemoveFromSuperview ()
{
RemoveGdkEventFilter ();
base.RemoveFromSuperview ();
}
protected override void Dispose (bool disposing)
{
isDisposed = true;
if (disposing)
RemoveGdkEventFilter ();
base.Dispose (disposing);
}
void AddGdkEventFilter ()
{
enableGdkEventFiler = true;
if (!gdkEventFilterInserted) {
Gdk.Window.AddFilterForAll (Filter);
gdkEventFilterInserted = true;
}
}
void RemoveGdkEventFilter ()
{
enableGdkEventFiler = false;
if (gdkEventFilterInserted) {
Gdk.Window.RemoveFilterForAll (Filter);
gdkEventFilterInserted = false;
}
}
Gdk.FilterReturn Filter (IntPtr xevent, Gdk.Event evnt)
{
if (enableGdkEventFiler && !isDisposed && Window != null) {
// always recover GDK events after 2 seconds of inactivity, this makes sure
// that we don't lose GDK events forever if some other native view steals events
// which are required for the drag exit condition.
if (Foundation.NSProcessInfo.ProcessInfo.SystemUptime - lastEventTimestamp < 2.0)
return Gdk.FilterReturn.Remove;
}
RemoveGdkEventFilter ();
return Gdk.FilterReturn.Continue;
}
}
}
#endif
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