ClickablePoint.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / UIAutomation / UIAutomationClient / MS / Internal / Automation / ClickablePoint.cs / 1305600 / ClickablePoint.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: Class to get a point that some can click on 
//
// History: 
//  06/03/2003 : preid Created
//
//---------------------------------------------------------------------------
 
using System.Windows.Automation;
using MS.Internal.Automation; 
using MS.Win32; 
using System;
 
namespace System.Windows.Automation
{
    static internal class ClickablePoint
    { 
        //-----------------------------------------------------
        // 
        //  Public Methods 
        //
        //----------------------------------------------------- 

        #region Public Methods

        // We will not always find the clickable point.   There are times when it would take so long 
        // to locate the point that it is just not worth it, so make a reason effort than quit.
        public static bool  HitTestForClickablePoint(AutomationElement el, out Point pt) 
        { 
            Rect rect = el.Current.BoundingRectangle;
 
            pt = new Point(0, 0);
            if (rect.Left >= rect.Right || rect.Top >= rect.Bottom)
                return false;
 
            // if this is not on any monitor than there is no point in going on.  If the element is
            // off the screen hit testing actually works and would end up returning a point offscreen. 
            NativeMethods.RECT winRect = new NativeMethods.RECT((int)rect.Left, (int)rect.Top, (int)rect.Height, (int)rect.Bottom); 
            if (SafeNativeMethods.MonitorFromRect( ref winRect, SafeNativeMethods.MONITOR_DEFAULTTONULL ) == IntPtr.Zero)
                return false; 


            // try the center point first
            pt = new Point((rect.Left + rect.Right) / 2, (rect.Top + rect.Bottom) / 2); 

            AutomationElement hitElement; 
            if ( TryPoint( ref pt, el, out hitElement ) ) 
                return true;
 
            if ( IsTopLevelWindowObscuring( el, rect, hitElement ) )
                return false;

            // before we start hit testing more there are some control types that we know where the 
            // clickable point is or we know does not have a clickable point so take care of those here.
            if ( el.Current.ControlType == ControlType.ScrollBar ) 
                return false; 

            // Try  the mid point of all four sides 
            pt = new Point(rect.Left + (rect.Width /2),  rect.Top + 1);
            if ( TryPoint( ref pt, el ) )
                return true;
 
            pt = new Point(rect.Left + (rect.Width /2),  rect.Bottom - 1);
            if ( TryPoint( ref pt, el ) ) 
                return true; 

            pt = new Point( rect.Left + 1, rect.Top + (rect.Height /2) ); 
            if ( TryPoint( ref pt, el) )
                return true;

            pt = new Point(  rect.Right - 1, rect.Top + (rect.Height /2) ); 
            if ( TryPoint( ref pt, el ) )
                return true; 
 

            if ( TrySparsePattern( out pt, ref rect, el ) ) 
                return true;

            if ( TryLinePattern( out pt, ref rect, el ) )
                return true; 

            return false; 
        } 

        #endregion Public Methods 

        //------------------------------------------------------
        //
        //  Private Methods 
        //
        //----------------------------------------------------- 
 
        #region Private Methods
 
        // Go from the top left on a diagonal the lower right but don't do more than 25 hits
        private static bool TryLinePattern( out Point pt, ref Rect rect,  AutomationElement el)
        {
            double x = rect.Left + 1; 
            double y = rect.Top + 1;
            int hits; 
 
            // Adjust the number of hits we do based on how big something is
            Double size = rect.Width * rect.Height; 
            if ( size < 2500 )
                hits = 10;
            else if ( size < 20000 )
                hits = 18; 
            else
                hits = 25; 
 
            double xIncr = rect.Width / hits;
            double yIncr = rect.Height / hits; 
            for ( int i = 0; i < hits; i++)
            {
                pt = new Point(x,  y);
                if ( TryPoint( ref pt, el ) ) 
                    return true;
 
                x += xIncr; 
                y += yIncr;
            } 

            pt = new Point(0,  0);
            return false;
        } 

        // Hit test in a fairly uniform pattern like a grid adjusting the spacing based on the 
        // size of element.  Don't more than about 25 hits. 
        private static bool TrySparsePattern( out Point pt, ref Rect rect,  AutomationElement el)
        { 
            int hits;

            // Adjust the number of hits we do based on how big somting is
            Double size = rect.Width * rect.Height; 
            if ( size < 2500 )
                hits = 3; 
            else if ( size < 20000 ) 
                hits = 4;
            else 
                hits = 5;

            // make the scatter pattern fit the proportions of the rect
            double xHits = hits * (rect.Width / rect.Height); 
            double yHits = hits * (rect.Height / rect.Width);
 
            double xMovePixels = rect.Width / xHits; 
            double yMovePixels = rect.Height / yHits;
 
            return TryPattern( xMovePixels, yMovePixels, out pt, ref rect, el );
        }

        // this goes across the rect in icrements of x pixels and the down y pixels and across again... 
        private static bool TryPattern(double x, double y, out Point pt, ref Rect rect, AutomationElement el )
        { 
            for ( double down = rect.Top + y; down < rect.Bottom; down += y  ) 
            {
                for ( double across = rect.Left + x; across < rect.Right; across += x ) 
                {
                    pt = new Point(across,  down);
                    if ( TryPoint(ref pt, el) )
                        return true; 
                }
            } 
 
            pt = new Point(0,  0);
            return false; 
        }

        private static bool TryPoint( ref Point pt, AutomationElement el )
        { 
            AutomationElement hitEl;
            return TryPoint( ref pt, el, out hitEl ); 
        } 

        private static bool TryPoint( ref Point pt, AutomationElement el, out AutomationElement hitEl ) 
        {
            // If the element is obscured by another window or hidden somehow when we try to hit test we don't get back
            //  the same element.  We want to make sure if someone clicks they click on what they expected to click on.
            hitEl = AutomationElement.FromPoint(pt); 

            return hitEl == el; 
        } 

        // figure out if there is a top level window totally obscuring the element.  If that is the case 
        // there is not point in going on.  This code assumes that toplevel windows are rects and that
        // everything in that rect covers up what is underneath.
        private static bool IsTopLevelWindowObscuring( AutomationElement target, Rect targetRect, AutomationElement hitTarget)
        { 
            // get the toplevel window for the element that we hit on our first try and the element the we are
            // trying to find a clickable point for.   If they are part of the same top level hwnd than there is 
            // no toplevel window obscuring this element. 
            // There is a rather strange case that can occur with apps like media player where the
            // hitTarget could be something underneth the element.  In this case zorder might be something to 
            // check but this is hwnd specific it may be better for the provider to provide a clickable point.
            AutomationElement hitTargetAncestor = GetTopLevelAncestor(hitTarget);
            if ( GetTopLevelAncestor(target) == hitTargetAncestor || hitTargetAncestor == null )
                return false; 

            // If this toplevel widow completely covers the element than we are obscured. 
            Rect hitTargetAncestorRect = hitTargetAncestor.Current.BoundingRectangle; 
            if (hitTargetAncestorRect.Contains( targetRect ) )
                return true; 

            return false;
        }
 
        private static AutomationElement GetTopLevelAncestor( AutomationElement target )
        { 
            AutomationElement root = AutomationElement.RootElement; 
            AutomationElement targetAncestor = null;
 
            while (target != root)
            {
                targetAncestor = target;
 
                target = TreeWalker.ControlViewWalker.GetParent( target );
            } 
 
            return targetAncestor;
        } 

    }
    #endregion Private Methods
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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ClickablePoint.cs source code in C# .NET

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