Thinking and Coding: WPF + Windows7 Multi-touch(Part 1)

在Win32的程式中, 可以利用WndProc來接收WM_TOUCH / WM_GESTURE 訊息, 來得到觸控點和手勢的資訊(可參考這兩篇文章Get Touch Point , Windows 7 Gesture Sample), 可是在WPF中沒有WndProc函式可以呼叫, 因此, 下面的文章將介紹如何在WPF Window上使用Windows 7 Multi-Touch function.

在WPF Window使用Windows Touch SDK的步驟如下:

Step 1: 利用PInvoke的機制呼叫user32.dll中定義Touch / Gesture的資料型態, 結構和方法
此方法可參考這篇文章 : 如何在C#中使用Unmanaged dll

例如;我們要使用Winuser.h的 RegisterTouchWindow函式, 其轉換如下:

C

BOOL WINAPI RegisterTouchWindow(
__in  HWND hWnd,
__in  ULONG ulFlags
);

[Flags, Serializable]
public enum RegisterTouchFlags
{
TWF_NONE = 0x00000000,

TWF_FINETOUCH = 0x00000001
}
[DllImport("user32.dll", SetLastError = true)]
public static extern bool RegisterTouchWindow(IntPtr hwnd,
[MarshalAs(UnmanagedType.U4)] RegisterTouchFlags flags);

Step 2: 在WPF Window中利用HwndSource物件來取得的Windows訊息

由於WPF Window不能像Win32 Window, 可利用WndProc函式處理WM_TOUCH / WM_GESTURE訊息,但WPF Window可以用HwndSource來裝載最上層HWND的所有內容.

其方法如下;

(1) 利用 System.Windows.Interop.WindowInteropHelper類別來取得任何WPF Window的HWND

example:
using System.Windows.Interop;
IntPtr _hwnd = new WindowInteropHelper(this).Handle;

(2) 利用HWND取得相關的HwndSource物件(用HwndSource.FromHwnd)

example:
HwndSource src = HwndSource.FromHwnd(_hwnd);

(3) 利用HwndSource的AddHook方法, 即可攔截視窗訊息

example:

src.AddHook(WndProc);
private IntPtr WndProc( IntPtr hwnd,
int msg,
IntPtr wParam,
IntPtr lParam,
ref bool handled)
{
switch (msg)
{
case TouchMessage.WM_GESTURE:
OnGesture(lParam);
// 記得將handle設為true,告訴系統你已經處理該訊息
handled = true;
break;

default:
break;
}
return IntPtr.Zero;
}

看完上面的介紹, 我們就來寫一個 WPF + Win7 Gesture 的應用程式, 我們會在WPF Window上繪製一個rectangle, 並透過一些手勢操作來對此rectangle作放大,縮小,平移,旋轉和改變顏色(twp finger tap)

其步驟如下:

首先,我們會寫一個Win7TouchInterop.cs檔, 目的要將Winuser.h中的 touch和gesture資料作包裝
在WPF的程式碼中, 使用Win7TouchInterop的命名空間 using Win7TouchInterop;
利用HwndSource物件來取得的Windows訊息
處理手勢訊息

程式碼如下所示;

XAML檔 :

<Window x:Class="WPFGestureMessage.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Touch SDK+WPF" Height="600" Width="800">
<Grid>

<Grid.Resources>
<Storyboard x:Key="_twoFingerTap">
<ColorAnimation
Storyboard.TargetName="rect"
Storyboard.TargetProperty=
"(Rectangle.Fill).(SolidColorBrush.Color)"
From="SkyBlue"
To="YellowGreen"
Duration="00:00:00.5"
AutoReverse="true"
FillBehavior="HoldEnd" />
</Storyboard>
</Grid.Resources>

<Rectangle  x:Name="rect"
RadiusX="5"
RadiusY="5"
Width="300"
Height="200"
Stroke="DarkBlue"
StrokeThickness="5"
Fill="YellowGreen"
RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<TransformGroup>
<ScaleTransform
x:Name="_scaleTransform"
ScaleX="1"
ScaleY="1" />
<RotateTransform
x:Name="_rotateTransform"
Angle="0" />
<TranslateTransform
x:Name="_translateTransform"
X="0"
Y="0" />
</TransformGroup>
</Rectangle.RenderTransform>
</Rectangle>

</Grid>
</Window>

C#檔 :

using System;
using System.Windows;

using Win7TouchInterop;
using System.Windows.Interop;
using System.Runtime.InteropServices;
using System.Windows.Media.Animation;

namespace WPFGestureMessage
{
/// 
/// Interaction logic for Window1.xaml
/// 
public partial class Window1 : Window
{
private IntPtr _hwnd;
const double scaleSensitivityMagicFactor = 200.0;
const double rotateSensitivityMagicFactor = 25.0;

private long _beginScale;

private bool captureAngle;
private double _beginAngle;

private Point firstPoint;

Storyboard _twoFingerTap;

public Window1()
{
InitializeComponent();
Loaded += new RoutedEventHandler(Window1_Loaded);
_twoFingerTap = rect.FindResource("_twoFingerTap") as Storyboard;

}

void Window1_Loaded(object sender, RoutedEventArgs e)
{
_hwnd = new WindowInteropHelper(this).Handle;
HwndSource src = HwndSource.FromHwnd(_hwnd);
if (src != null)
src.AddHook(WndProc);

// Setup the gestures
var gConfig = new[]
{
new GESTURECONFIG
{
dwID = GestureID.GID_ALL,

dwWant = WantGestures.GC_ANY
}   
};

Win7TouchMethod.SetGestureConfig(_hwnd,
0,
gConfig.Length,
gConfig,
Marshal.SizeOf(gConfig[0]));
}


private Point ConvertPoint(POINTS pts)
{
var pt = new POINT { X = pts.X, Y = pts.Y };
Win7TouchMethod.ScreenToClient(_hwnd, ref pt);
return new Point(pt.X, pt.Y);
}


private IntPtr WndProc(IntPtr hwnd,
int msg,
IntPtr wParam,
IntPtr lParam,
ref bool handled)
{

switch (msg)
{
case Win7TouchMessages.WM_GESTURE:
OnGesture(lParam);
handled = true;
break;
default:
break;
}


return IntPtr.Zero;
}

private void OnGesture(IntPtr gestureMsg)
{
GESTUREINFO gesture = new GESTUREINFO();
gesture.cbSize = Marshal.SizeOf(gesture);
if (Win7TouchMethod.GetGestureInfo(gestureMsg, out gesture))
{
switch (gesture.dwID)
{
case GestureID.GID_PAN:
OnPan(gesture.dwInstanceID,
ConvertPoint(gesture.ptsLocation),
gesture.dwFlags);
break;
case GestureID.GID_ROTATE:
OnRotate(gesture.ullArguments,
gesture.dwFlags);
break;
case GestureID.GID_TWOFINGERTAP:
_twoFingerTap.Stop();
_twoFingerTap.Begin();
break;
case GestureID.GID_ZOOM:
OnZoom(ConvertPoint(gesture.ptsLocation),
gesture.ullArguments,
gesture.dwFlags);
break;
default:
break;
}
}
Win7TouchMethod.CloseGestureInfoHandle(gestureMsg);
}



private void OnZoom(Point ptCenter,
long scale,
GestureFlags gestureFlags)
{

if ((gestureFlags & GestureFlags.GF_BEGIN) > 0)
{
_beginScale = scale;
}
else
{
double delta = scale - _beginScale;
_beginScale = scale;

double scaleX = (delta / scaleSensitivityMagicFactor);
double scaleY = (delta / scaleSensitivityMagicFactor);

_scaleTransform.ScaleX += scaleX;
_scaleTransform.ScaleY += scaleY;

}
}


private void OnPan(uint id,
Point point,
GestureFlags gestureFlags)
{

if ((gestureFlags & GestureFlags.GF_BEGIN) > 0)
{
firstPoint = point;
}
else
{
Point curPoint = point;
double xDelta = curPoint.X - firstPoint.X;
double yDelta = curPoint.Y - firstPoint.Y;

_translateTransform.X += xDelta;
_translateTransform.Y += yDelta;

firstPoint = curPoint;
}
}

private void OnRotate(double radians,
GestureFlags gestureFlags)
{

double angle = Win7TouchMethod.ROTATE_ANGLE_FROM_ARGUMENT(radians) * (180.0 / Math.PI);
if ((gestureFlags & GestureFlags.GF_BEGIN) > 0)
{
captureAngle = true;
}
else
{
if (captureAngle)
{
_beginAngle = angle;
captureAngle = false;
}
else
{
double delta = angle - _beginAngle;

_rotateTransform.Angle += 0 - (delta / rotateSensitivityMagicFactor);

if ((gestureFlags & GestureFlags.GF_END) > 0)
{
captureAngle = true;
_beginAngle = 0;
}
}
}//end else
}//end
}
}

成果如下圖所示: