Develop Reference

How to add Caret to a Form control?

On the goal to learn how to create C# Form components. I decided to create a label which the text can be selected with caret showing the current selection position. Using the code below i successfully added the text with custom color and font. But the caret is not showing. I used CreateCaret and ShowCaret of user32 to create and display the caret.
class MyCustomLabel : Control
{
string[] lines;
public MyCustomLabel ()
{
lines = new string[] {
"public class MyApp {",
" System.Console.WriteLine(\"Hello,World\");",
"}"};
CreateCaret(Handle, IntPtr.Zero, 10, Height);
ShowCaret(Handle);
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
StringFormat fmt = StringFormat.GenericTypographic;
fmt.FormatFlags |= StringFormatFlags.MeasureTrailingSpaces;
for (int i = 0; i < lines.Length; ++i)
e.Graphics.DrawString(lines[i], Font, new SolidBrush(this.ForeColor),
0, Font.Height * i, StringFormat.GenericTypographic);
}
[DllImport("user32")]
private extern static bool ShowCaret(IntPtr hwnd);
[DllImport("user32")]
private extern static int CreateCaret(IntPtr hwnd, IntPtr hBitmap, int width, int height);
}
At first place i want to have the Caret displayed and it will be appreciate if there is an example with selection.

DwmGetWindowAttribute returns 0 with PInvoke

I'm trying to do screen captures by capturing a specific window and in order to accurately figure out the size of the window to capture I want to use DwmGetWindowAttribute(). When I call this function with PInvoke on Windows 10 the Rect structure is always empty even though the result value is 0 (success). The Window handle passed in is valid as well because there is fallback code that calls GetWindowRect() which works (albeit with border problems).
I'm a bit at a loss. I used this same code a while back (perhaps on Windows 8.1?) and the same code seemed to be working but now no matter what I do the call to the function always returns an empty structure.
Here's the relevant code.
Definitions:
[DllImport("dwmapi.dll")]
static extern int DwmGetWindowAttribute(IntPtr hwnd, int dwAttribute, out Rect pvAttribute, int cbAttribute);
[Flags]
public enum DwmWindowAttribute : uint
{
DWMWA_NCRENDERING_ENABLED = 1,
DWMWA_NCRENDERING_POLICY,
DWMWA_TRANSITIONS_FORCEDISABLED,
DWMWA_ALLOW_NCPAINT,
DWMWA_CAPTION_BUTTON_BOUNDS,
DWMWA_NONCLIENT_RTL_LAYOUT,
DWMWA_FORCE_ICONIC_REPRESENTATION,
DWMWA_FLIP3D_POLICY,
DWMWA_EXTENDED_FRAME_BOUNDS,
DWMWA_HAS_ICONIC_BITMAP,
DWMWA_DISALLOW_PEEK,
DWMWA_EXCLUDED_FROM_PEEK,
DWMWA_CLOAK,
DWMWA_CLOAKED,
DWMWA_FREEZE_REPRESENTATION,
DWMWA_LAST
}
[Serializable, StructLayout(LayoutKind.Sequential)]
public struct Rect
{
public int Left;
public int Top;
public int Right;
public int Bottom;
public Rectangle ToRectangle()
{
return Rectangle.FromLTRB(Left, Top, Right, Bottom);
}
}
Code to do the capture:
public static Rectangle GetWindowRectangle(IntPtr handle)
{
Rectangle rected = Rectangle.Empty;
Rect rect = new Rect();
if (Environment.OSVersion.Version.Major < 6)
{
GetWindowRect(handle, out rect);
rected = rect.ToRectangle();
}
else
{
int size = Marshal.SizeOf(typeof(Rect));
int res = DwmGetWindowAttribute(handle, (int)DwmWindowAttribute.DWMWA_EXTENDED_FRAME_BOUNDS, out rect, size);
Debug.WriteLine(res.ToString("x") + " " + size + " " + handle + " " + (int) DwmWindowAttribute.DWMWA_EXTENDED_FRAME_BOUNDS);
// allow returning of desktop and aero windows
if (rected.Width == 0)
{
GetWindowRect(handle, out rect);
rected = rect.ToRectangle();
Debug.WriteLine("Using GetWindowRect");
}
}
Debug.WriteLine(rected.ToString());
return rected;
}
It feels like something simple is missing here. Any ideas?

Based on the Rick Strahl original code as well as Hans Passant correction I created a more compact version of GetWindowsRectangle. I tested it on Windows 10, here's the code in case it helps someone in the future:
public static Rectangle GetWindowRectangle(IntPtr handle)
{
Rect rect = new Rect();
if (Environment.OSVersion.Version.Major >= 6)
{
int size = Marshal.SizeOf(typeof(Rect));
DwmGetWindowAttribute(handle, (int)DwmWindowAttribute.DWMWA_EXTENDED_FRAME_BOUNDS, out rect, size);
}
else if (Environment.OSVersion.Version.Major < 6 || rect.ToRectangle().Width == 0)
{
GetWindowRect(handle, out rect);
}
return rect.ToRectangle();
}

Use GetWindowRect instead of DwmGetWindowAttribute to receive RECT of the window.
[DllImport("user32.dll", SetLastError = true)]
public static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect);

SendInput not working perfectly on extended screen

Mouse stimulation using SendInput works perfectly on MainDisplay. However when I use SendInput for extended screen (e.g. Second screen placed to the left of the main display in my case. Issues is replicable irrespective of the extended display any place around main display but with different resolution then main display):
If I use SendInput on extended screen, the mouse position has offset in both X and Y position, ever so slightly ranging from 40 to 80 points in x and 10 to 20 points in Y based on if X (width) and Y(height) of extended screen is different to main display width/height)
Thanks in advance for any support as to why difference on extended screen
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GetCursorPos(ref Win32Point pt);
[DllImport("user32.dll")]
internal static extern bool SetCursorPos(int X, int Y);
[StructLayout(LayoutKind.Sequential)]
internal struct Win32Point
{
public Int32 X;
public Int32 Y;
};
internal enum SendInputEventType : int
{
InputMouse,
InputKeyboard
}
[DllImport("user32.dll", SetLastError = true)]
private static extern uint SendInput(uint nInputs, ref Input pInputs, int cbSize);
public struct Input
{
public uint InputType;
public MouseInput MI;
}
public struct MouseInput
{
public int Dx;
public int Dy;
public uint MouseData;
public uint DwFlags;
public uint Time;
public IntPtr DwExtraInfo;
}
public enum MouseEventInfo
{
mouseEventfMove = 0x0001,
mouseEventfLeftdown = 0x0002,
mouseEventfLeftup = 0x0004,
mouseEventfRightdown = 0x0008,
mouseEventfRightup = 0x0010,
mouseEventfWheel = 0x0800,
mouseEventfAbsolute = 0x8000,
wheelDelta = 0x0078
}
static int CalculateAbsoluteCoordinateX(int x, System.Drawing.Rectangle currentBounds)
{
return ((currentBounds.X + x) * 65536) / (currentBounds.Width);
}
static int CalculateAbsoluteCoordinateY(int y, System.Drawing.Rectangle currentBounds)
{
return (((currentBounds.Y + y) * 65536) / currentBounds.Height);
}
// for me screen at index 0 (screen no 1) is main display. Screen id 2
//placed to the left of the main display as per resolution screen i.e.at
//index 1 (Screen.AllScreens[1]) is extended display and Bound.X is a -ve value
public static int ScreenId = 2;
public static System.Drawing.Rectangle CurrentBounds
{
get
{
return SysForms.Screen.AllScreens[ScreenId - 1].Bounds;
}
}
public static void ClickLeftMouseButton(int x, int y)
{
Input mouseInput = new Input();
mouseInput.InputType = SendInputEventType.InputMouse;
mouseInput.MI.Dx = CalculateAbsoluteCoordinateX(x, CurrentBounds);
mouseInput.MI.Dy = CalculateAbsoluteCoordinateY(y, CurrentBounds);
mouseInput.MI.MouseData = 0;
mouseInput.MI.DwFlags = MouseEventInfo.mouseEventfMove | MouseEventInfo.mouseEventfAbsolute;
SendInput(1, ref mouseInput, Marshal.SizeOf(new INPUT()));
mouseInput.MI.DwFlags = MouseEventInfo.mouseEventfLeftdown;
SendInput(1, ref mouseInput, Marshal.SizeOf(new INPUT()));
mouseInput.MI.DwFlags = MouseEventFlags.mouseEventfLeftup;
SendInput(1, ref mouseInput, Marshal.SizeOf(new INPUT()));
}
//Below is code of the WPF MainWindow for testing. Two buttons with click event.
// For main display with screenid as 1 both setcursor position and sendinput
//work perfectly, as I get the MousePosition, but when I apply this to
//extended screen (currently with two screen, main display is screen 1 in my
//case and screen 2 is extended screen, they put the mouse at two different positions.
//I have my doubts the way I am using the extended screen Bounds.X, but
//haven't will able to fix the issue
int x = 600;
int y = 300;
private void btnSend_Click(object sender, RoutedEventArgs e)
{
SetCursorPos(SysForms.Screen.AllScreens[ScreenId - 1].Bounds.X + x, SysForms.Screen.AllScreens[screenId - 1].Bounds.Y + y);
}
private void btnSend1_Click(object sender, RoutedEventArgs e)
{
ClickLeftMouseButton(x, y);
}

Found the issue. While using SendInput, the conversion of x,y in absolute value must be done in relation to Main/Primary screen.
Thus the changes:
static int CalculateAbsoluteCoordinateX(int x, System.Drawing.Rectangle currentBounds)
{
return ((currentBounds.X + x) * 65536) / (SystemParameters.PrimaryScreenWidth);
}
static int CalculateAbsoluteCoordinateY(int y, System.Drawing.Rectangle currentBounds)
{
return (((currentBounds.Y + y) * 65536) / SystemParameters.PrimaryScreenHeight);
}

Simulate Windows Dragging Effect in a Winform FlowLayoutPanel

I'm currently simulating the windows multiple selection rectangle when the user is dragging the mouse. To synchronize our understanding, this picture shows the effect I want to simulate:
Now I want to simulate this effect on a FlowLayoutPanel with some controls inside.
So far I am managed to get the effect almost done:
What I did here was putting a unfocused border-less semi-transparent (half the opacity) form on top the main form. To get the border simulated, I handled SizeChanged and Paint to draw the border.
However, this solution sometimes flickers, as in the owner border couldn't get cleared on-time:
I have tried using double buffering on the cover form by setting DoubleBuffer to true, and override CreateParam to set WM_EX_COMPOSITED, but neither works.
My question is: How to reduce this artifact?
Thanks a lot!
My code:
For the cover form:
public partial class CoverForm : Form
{
public CoverForm()
{
InitializeComponent();
BackColor = Color.CadetBlue;
FormBorderStyle = FormBorderStyle.None;
SizeChanged += (s, e) => Invalidate();
Paint += (s, e) =>
{
e.Graphics.Clear(BackColor);
using (var pen = new Pen(Color.DodgerBlue))
{
e.Graphics.DrawRectangle(pen, 1, 1, Size.Width - 2, Size.Height - 2);
}
};
}
protected override bool ShowWithoutActivation
{
get { return true; }
}
}
For the main form:
public Form1()
{
InitializeComponent();
// mainPanel is the panel that simulates the dragging effect
mainPanel.MouseDown += (s, e) =>
{
_isMouseDown = true;
_startPosition = e.Location;
coverForm.Location = mainPanel.PointToScreen(e.Location);
coverForm.Show();
};
mainPanel.MouseUp += (s, e) =>
{
_isMouseDown = false;
coverForm.Hide();
};
mainPanel.MouseMove += CoverPanelMouseMoveHandler;
DoubleBuffered = true;
}
~Form1()
{
if (coverForm != null && !coverForm.IsDisposed)
{
coverForm.Dispose();
}
}
# region Dragging Effect
private void CoverPanelMouseMoveHandler(object sender, MouseEventArgs e)
{
if (_isMouseDown)
{
_curPosition = e.Location;
// find the dragging rectangle
var rect = CreateRect(_curPosition, _startPosition);
coverForm.Size = rect.Size;
coverForm.Location = mainPanel.PointToScreen(rect.Location);
foreach (Control control in mainPanel.Controls)
{
// logic to get button backcolor changed
}
mainPanel.Invalidate(true);
}
}
Update
I have tried to override OnPaint and put my drawing there, but it gave even worse result: the old paints wouldn't get erased:
Code I modified for cover form:
public partial class CoverForm : Form
{
public CoverForm()
{
InitializeComponent();
BackColor = Color.CadetBlue;
FormBorderStyle = FormBorderStyle.None;
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.Clear(BackColor);
using (var pen = new Pen(Color.FromArgb(255, 0, 0, 255)))
{
e.Graphics.DrawRectangle(pen, 0, 0, Size.Width - 1, Size.Height - 1);
}
}
protected override bool ShowWithoutActivation
{
get { return true; }
}
}
Update 2
Actually the problem I am facing is about drawing above a FlowLayoutPanel, not a normal Panel. The reason I put Panel before was I was seeking answer for my flickering 2-layers design. But since someone approach the problem by adding control to the panel to get it drawn above all controls, I would like to point this out: adding control to a panel would be trivial, but FlowLayoutPanel will auto-align the newly added control to the next available position, which may screw up the expected effect.

Video Demo of the Solution: Remember to Switch to 1080p
Recorded in a VM on a crappy machine. So kinda slow.
You are getting those artifacts because you're doing a combination of 3 things all at once.
The two big ones are moving the form to another location and resizing the form. It also doesn't help if the form is semi transparent :) To get a better understanding of what I mean, just open VS2013 up and resize the window very quickly (at the top-left corner, and run in random directions really fast), you will see that around the edges it can't keep up. And yes, you will get different results when you're resizing from a different position around the window (just think about it for a minute and you will figure it out).
Aybe, provided a pretty clever solution but it doesn't allow you to see through it or see if any updates to the panel....since it basically just copies the last output to a bitmap and uses that as a back buffer (much like what you assume someone might do when doing the selection thing in a paint program).
If you really want to do it with an overlay form and keep it semi-transparent then you will need to eliminate those three things if you don't want artifacts.
The code requires quite a bit of WIN32 knowledge.... lucky for you Microsoft has already done the hard part. We are going to enable per pixel transparency in your cover frame by using the PerPixelAlphaForm by Microsoft (you can google it) I will paste the code here. It basically just creates a Window with a Style of WS_EX_LAYERED. Keeps a Backbuffer which is AlphaBlended with the screen (simple huh?).
/******************************** Module Header ********************************\
Module Name: PerPixelAlphaForm.cs
Project: CSWinFormLayeredWindow
Copyright (c) Microsoft Corporation.
This source is subject to the Microsoft Public License.
See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
All other rights reserved.
THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
\*******************************************************************************/
#region Using directives
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
#endregion
namespace CSWinFormLayeredWindow
{
public partial class PerPixelAlphaForm : Form
{
public PerPixelAlphaForm()
{
InitializeComponent();
}
protected override CreateParams CreateParams
{
get
{
// Add the layered extended style (WS_EX_LAYERED) to this window.
CreateParams createParams = base.CreateParams;
createParams.ExStyle |= WS_EX_LAYERED;
return createParams;
}
}
/// <summary>
/// Let Windows drag this window for us (thinks its hitting the title
/// bar of the window)
/// </summary>
/// <param name="message"></param>
protected override void WndProc(ref Message message)
{
if (message.Msg == WM_NCHITTEST)
{
// Tell Windows that the user is on the title bar (caption)
message.Result = (IntPtr)HTCAPTION;
}
else
{
base.WndProc(ref message);
}
}
/// <summary>
///
/// </summary>
/// <param name="bitmap"></param>
public void SelectBitmap(Bitmap bitmap)
{
SelectBitmap(bitmap, 255);
}
/// <summary>
///
/// </summary>
/// <param name="bitmap">
///
/// </param>
/// <param name="opacity">
/// Specifies an alpha transparency value to be used on the entire source
/// bitmap. The SourceConstantAlpha value is combined with any per-pixel
/// alpha values in the source bitmap. The value ranges from 0 to 255. If
/// you set SourceConstantAlpha to 0, it is assumed that your image is
/// transparent. When you only want to use per-pixel alpha values, set
/// the SourceConstantAlpha value to 255 (opaque).
/// </param>
public void SelectBitmap(Bitmap bitmap, int opacity)
{
// Does this bitmap contain an alpha channel?
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new ApplicationException("The bitmap must be 32bpp with alpha-channel.");
}
// Get device contexts
IntPtr screenDc = GetDC(IntPtr.Zero);
IntPtr memDc = CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr hOldBitmap = IntPtr.Zero;
try
{
// Get handle to the new bitmap and select it into the current
// device context.
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
hOldBitmap = SelectObject(memDc, hBitmap);
// Set parameters for layered window update.
Size newSize = new Size(bitmap.Width, bitmap.Height);
Point sourceLocation = new Point(0, 0);
Point newLocation = new Point(this.Left, this.Top);
BLENDFUNCTION blend = new BLENDFUNCTION();
blend.BlendOp = AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = (byte)opacity;
blend.AlphaFormat = AC_SRC_ALPHA;
// Update the window.
UpdateLayeredWindow(
this.Handle, // Handle to the layered window
screenDc, // Handle to the screen DC
ref newLocation, // New screen position of the layered window
ref newSize, // New size of the layered window
memDc, // Handle to the layered window surface DC
ref sourceLocation, // Location of the layer in the DC
0, // Color key of the layered window
ref blend, // Transparency of the layered window
ULW_ALPHA // Use blend as the blend function
);
}
finally
{
// Release device context.
ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
SelectObject(memDc, hOldBitmap);
DeleteObject(hBitmap);
}
DeleteDC(memDc);
}
}
#region Native Methods and Structures
const Int32 WS_EX_LAYERED = 0x80000;
const Int32 HTCAPTION = 0x02;
const Int32 WM_NCHITTEST = 0x84;
const Int32 ULW_ALPHA = 0x02;
const byte AC_SRC_OVER = 0x00;
const byte AC_SRC_ALPHA = 0x01;
[StructLayout(LayoutKind.Sequential)]
struct Point
{
public Int32 x;
public Int32 y;
public Point(Int32 x, Int32 y)
{ this.x = x; this.y = y; }
}
[StructLayout(LayoutKind.Sequential)]
struct Size
{
public Int32 cx;
public Int32 cy;
public Size(Int32 cx, Int32 cy)
{ this.cx = cx; this.cy = cy; }
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
struct ARGB
{
public byte Blue;
public byte Green;
public byte Red;
public byte Alpha;
}
[StructLayout(LayoutKind.Sequential, Pack = 1)]
struct BLENDFUNCTION
{
public byte BlendOp;
public byte BlendFlags;
public byte SourceConstantAlpha;
public byte AlphaFormat;
}
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst,
ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pprSrc,
Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern IntPtr CreateCompatibleDC(IntPtr hDC);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern IntPtr GetDC(IntPtr hWnd);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool DeleteDC(IntPtr hdc);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool DeleteObject(IntPtr hObject);
#endregion
}
}
OK, that should eliminate your semi-transparent problem. Remember to get rid of the override of the WndProc (you won't need it). Set Double-Buffer to false and TopMost to true.
Now to eliminate the other two problems. I hope you thought of a way of doing it....but I will give you my solution. Always keep the PerPixelAlphaForm the size of your MainForm. Same location, Same SIZE. :) And resize the PerPixelAlphaForm's backbuffer bitmap to the same size as well. When you do it this way, all you have to do is redraw the Selection Rectangle. Why? because it overlays the entire MainForm perfectly.
So basically
`OnMouseDown` = Save initial point of mouse, show the Cover layer
`OnMouseMove` = clear the PerPixelAlphaForm bitmap, draw your rectangle
call SelectBitmap again update the form
`OnMouseUp` = hide the Cover layer (or whatever you want to do)
I personally have all this hook up to the Control-Key
To clear the PerPixelAlphaForm we need to do in a certain way. Give all values an Alpha of 0.
public void ClearBackbuffer()
{
Graphics g = Graphics.FromImage(_reference_to_your_backbuffer_);
g.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
SolidBrush sb = new SolidBrush(Color.FromArgb(0x00, 0x00, 0x00, 0x00));
g.FillRectangle(sb, this.ClientRectangle);
sb.Dispose();
g.Dispose();
}
Video Demo of the Solution: Remember to Switch to 1080p
If you need more help, let me know I can find some time to rip the code out of the larger program. But it seems to me you're the kind of person that likes tinkering with stuff :D

EDIT : using an additional PictureBox and Bitmap makes the whole thing working
The following Panel draws a rectangle without flickering:
internal sealed class MyPanel : Panel
{
private readonly PictureBox _pictureBox;
private Bitmap _bitmapContent;
private Bitmap _bitmapForeground;
private Point? _point1;
private Point? _point2;
public MyPanel()
{
DoubleBuffered = true;
_pictureBox = new PictureBox();
}
protected override void OnSizeChanged(EventArgs e)
{
if (_bitmapForeground != null) _bitmapForeground.Dispose();
_bitmapForeground = new Bitmap(Size.Width, Size.Height);
if (_bitmapContent != null) _bitmapContent.Dispose();
_bitmapContent = new Bitmap(Size.Width, Size.Height);
_pictureBox.Size = Size;
_pictureBox.Image = _bitmapForeground;
base.OnSizeChanged(e);
}
protected override void OnMouseDown(MouseEventArgs e)
{
_point1 = e.Location;
DrawToBitmap(_bitmapContent, new Rectangle(0, 0, Size.Width, Size.Height));
SetControlsVisibility(false);
Controls.Add(_pictureBox);
base.OnMouseDown(e);
}
private void SetControlsVisibility(bool visible)
{
IEnumerable<Control> ofType = Controls.OfType<Control>();
foreach (Control control in ofType)
{
control.Visible = visible;
}
}
protected override void OnMouseUp(MouseEventArgs e)
{
Controls.Remove(_pictureBox);
SetControlsVisibility(true);
_point1 = null;
_point2 = null;
Refresh();
base.OnMouseUp(e);
}
protected override void OnMouseMove(MouseEventArgs e)
{
if (_point1 != null)
{
_point2 = e.Location;
if (_point1 != null && _point2 != null)
{
Point p1 = _point1.Value;
Point p2 = _point2.Value;
int x1 = p1.X;
int y1 = p1.Y;
int x2 = p2.X;
int y2 = p2.Y;
int xmin = Math.Min(x1, x2);
int ymin = Math.Min(y1, y2);
int xmax = Math.Max(x1, x2);
int ymax = Math.Max(y1, y2);
using (Graphics graphics = Graphics.FromImage(_bitmapForeground))
{
graphics.DrawImageUnscaled(_bitmapContent, 0, 0, _bitmapContent.Width, _bitmapContent.Height);
graphics.DrawRectangle(Pens.Red, new Rectangle(xmin, ymin, xmax - xmin, ymax - ymin));
}
_pictureBox.Refresh();
}
}
base.OnMouseMove(e);
}
}
However, the rectangle will be below the controls, not sure why ...

C# - Form user button click, get next window clicked by user

This shouldnt be a difficult question, but it is difficult to google the question and get the idea across.
The problem is simple: I have a windows form where the user presses a button, then, it will wait on the user to click another window. It stores that selected window information for manipulation later (specifically the dimensions).
How can I get the active window of the next user click after a button is pressed?
Thanks

You need to get the foreground window.
[DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();
[DllImport("user32.dll", SetLastError = true)]
static extern bool GetWindowRect(IntPtr hWnd, out Rectangle lpRect);
Rect rect = new Rect ();
GetWindowRect(GetForegroundWindow(), out rect);
//calculate width and height from rect
using (Bitmap bitmap = new Bitmap(width, height))
{
using (Graphics g = Graphics.FromImage(bitmap))
{
Size size = new System.Drawing.Size(width, height);
g.CopyFromScreen(new Point(rect.Left, rect.Top), Point.Empty, size);
}
bitmap.Save("C://test.jpg", ImageFormat.Jpeg);
}
[StructLayout(LayoutKind.Sequential)]
public struct Rect {
public int Left;
public int Top;
public int Right;
public int Bottom;
}
I found most of the code in these two answers on SO. Modifed it to suit your question
Capture window
Find window width and height

Interested by your question i have created this small screen capture app.
It has strange workarounds:
Timer used to capture mouse position outside winform is strange but was easier to implement than using Global System Hooks . You might try to use lib from link or implement it by yourself. You wouldn't need than to use Timer and what is more important you could drop this constant reactivation of form.
I have found somewhere in SE info about overriding CreateParams but i can't find link to it anymore it allows you to click trough form (i think that not all of added params are neccessery but as i said i lost link :) ).
Only visible part of window is captured + all windows overlapping it (probably sinc u got a windowHandle to it u might try to show/activate it somehow).
For some windows it gets controls inside window.
Provided app is probably very unprofessional and unsafe and might blow up your computer so beware ;P
Used form is borderless with opacity set to 80%.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace WindowInfo
{
public partial class CurrentWindow : Form
{
Rectangle GDIrect = new Rectangle(0, 0, 100, 100);
[DllImport("user32.dll")]
public static extern IntPtr WindowFromPoint(Point lpPoint);
[DllImport("user32.dll")]
public static extern bool GetCursorPos(out Point lpPoint);
[DllImport("user32.dll")]
private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rect rect);
[DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();
[StructLayout(LayoutKind.Sequential)]
public struct Rect
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}
public CurrentWindow()
{
InitializeComponent();
}
protected override CreateParams CreateParams
{
get
{
CreateParams baseParams = base.CreateParams;
baseParams.ExStyle |= (int)(
0x00080000 |
0x08000000 |
0x00000080 |
0x00000020
);
return baseParams;
}
}
public static IntPtr GetWindowUnderCursor()
{
Point ptCursor = new Point();
GetCursorPos(out ptCursor);
return WindowFromPoint(ptCursor);
}
public Bitmap CaptureScreen()
{
var result = new Bitmap(this.DisplayRectangle.Width, this.DisplayRectangle.Height);
using (var g = Graphics.FromImage(result))
{
g.CopyFromScreen(this.Location.X, this.Location.Y, 0, 0, this.DisplayRectangle.Size);
}
return result;
}
private void timer1_Tick(object sender, EventArgs e)
{
IntPtr windowHandle = GetWindowUnderCursor();
Rect rect = new Rect();
GetWindowRect(windowHandle, ref rect);
GDIrect = new Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top);
this.Location = new Point(GDIrect.Left, GDIrect.Top);
this.Size = GDIrect.Size;
this.Activate();
}
private void CurrentWindow_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == 'c')
{
this.Visible = false;
Bitmap bmp = CaptureScreen();
bmp.Save(Application.StartupPath + "\\example.png");
this.Visible = true;
}
else if (e.KeyChar == 'x')
{
this.Close();
}
}
}
}
U might add it to your app and run after button click, it should work but i have tested it only separately. Good luck :).