Develop Reference

How can I find the x and y scale components for pinch and stretch gestures?

I am using pinch/stretch to resize objects. I was surprised to find that ManipulationDeltaRoutedEventArgs has a single Scale property. I would like to allow pinching/stretching to increase/decrease the width and height in the same proportion as the stretch's increase in x and y finger positions. In other words, if the stretch is vertical, I would like to make my object taller, but not wider.
If that's not supported, is it possible to determine the starting and ending finger positions of the pinch/stretch gesture?

You can not get the scaleX and scaleY directly for setting the corresponding Scale value in x and y. But you can get the starting and ending finger positions from the PointerEntered and PointerExited event. You can get the point in these event handler,
private void MyImage_PointerExited(object sender, PointerRoutedEventArgs e)
{
var point= e.GetCurrentPoint(sender as Image).Position;
}
private void MyImage_PointerEntered(object sender, PointerRoutedEventArgs e)
{
var point = e.GetCurrentPoint(sender as Image).Position;
}
But the position value is base on your UIElement left top corner(0,0). So you should set a fixed coordinate. You can try to use the PointerEntered and PointerExited event of the Root panel which includes your resized objects to get the positions of the pinch/stretch gesture.
//MyGrid is the root panel and includes the Image which would be resized.
private void MyGrid_PointerEntered(object sender, PointerRoutedEventArgs e)
{
Debug.WriteLine("EN>>>"+e.GetCurrentPoint(MyGrid).Position);
}
private void MyGrid_PointerExited(object sender, PointerRoutedEventArgs e)
{
Debug.WriteLine("ET>>>"+e.GetCurrentPoint(MyGrid).Position);
}

Visual Studio C# how to move a button's X position by mouse without flicker

So I'm trying to make a slider. I'm using my cursor to move a button's x position.
I have 3 functions, the mouseDown, mouseUp and the mouseMove function. In the mouseUp and mouseDown functions I set a variable to true and false to tell the program that the mouse is clicked or not. In the mouseMove function I tell the program to set the button's x position to the x position of the mouse when the mouse is clicked. This works but has 2 problems.
The first problem is that when I press the button and move it, the button moves along with the mouse's x but it has a space between the mouse and the button. It looks a bit like this:
CURSOR.......BUTTON
The space between the cursor and button change when I change the resolution of the form.
The second problem is that when I move the button it flickers a bit. It only does this at higher speeds but it is a problem in my case.
My code looks like this:
bool mouseDown = false;
private void volumeGrabBT_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
mouseDown = true;
}
}
private void volumeGrabBT_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
mouseDown = false;
}
}
private void volumeGrabBT_MouseMove(object sender, MouseEventArgs e)
{
if (mouseDown == true)
{
Point volumeBTPoint = new Point();
volumeBTPoint.X = Cursor.Position.X;
volumeBTPoint.Y = volumeGrabBT.Location.Y;
volumeGrabBT.Location = volumeBTPoint;
}
}
The volumeGrabBT is the button I'm trying to move along with the mouse.
The volumeBTPoint is the point of the button I'm trying to set the button's position to.
I hope someone can help me fix these problems. Thanks in advance!

I believe that flickering can be fixed by setting some additional form styles: SetStyle(ControlStyles.AllPaintingInWmPaint |ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);
in form's constructor. It will use double buffering and generally just draws faster.
For the Cursor class, it's relative to the screen, not your form. You can use this.PointToClient() function to get client's space position of cursor, like this:
Point clientCursor = this.PointToClient(Cursor.Position);
and then use clientCursor to get exact X in your client space.

You have to translate screen coordinates to client coordinates.
Point volumeBTPoint = new Point();
Point point = this.PointToClient(Cursor.Position);
volumeBTPoint.X = point.X;
volumeBTPoint.Y = volumeGrabBT.Location.Y;
volumeGrabBT.Location = volumeBTPoint;
Instead of this you should use button's parent control (Panel, GroupBox, etc).

How to get toolTip on CursorPosition not on MousePosition?

im working on code-editor (windows forms application) and I just want to ask how to get tooltip position instead of mouseposition will make it on cursor something like this 1:
Get current cursor lower left position so that tooltip could be displayed properly
specifically this code:
private void panel1_MouseClick(object sender, MouseEventArgs e) {
int x = e.X;
int y = e.Y + Cursor.Current.Size.Height - Cursor.Current.HotSpot.Y;
toolTip1.Show("test", panel1, x, y);
}
but i dont have panel i only got richtextbox[rtb](serve as code editor) and a labelbox[lb](serve as contexthint) .
anyone pls? really in need thanks!

How to clear the fill of a rectangle in C#?

How can I clear the fill of a rectangle? I only want to keep the border.
g.FillRectangle(Brushes.Transparent, x, y, w, h);
Didn't work, neither did aRGB with alpha, I want to delete the fill so there's only the border left.

So what you want is
g.DrawRectangle(Pens.Black,x,y,w,h);
I think
EDIT: due to a change in the OP requirements this is not exactly the answer he wants, though it is not incorrect, therefore I choose to leave it here, for now.

you must set new clip for your graphics after set clip clear it, then restore clip to normal.
g.SetClip(new Rectangle(x,y,w,h), CombineMode.Replace);
g.Clear(Color.Transparent);

Ok so you are after a selection tool, you might have wanted to tell us that in the first place.
Create a new windows form application.
in the form events use mousedown, mouseup and mousemove
public Point MouseXY = new Point(0, 0);
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
MouseXY = e.Location;
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
int width = e.Location.X - MouseXY.X;
int height = e.Location.Y-MouseXY.Y;
this.Refresh();
CreateGraphics().DrawRectangle(Pens.Blue, new Rectangle(MouseXY, new Size(width,height)));
}
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
this.Refresh();
}
This code is not perfect and I don't pretend it is. What this will do is draw a blue rectangle that starts where you click and follows your mouse. It does not draw a negative rectangle, you would have to determine whether your mouse is currently to the left or up from your starting point then draw the rectangle accordingly, but I think you can figure that out on your own. as well the rectangle is not persistent, though I do not believe you would want it to be.

Move a PictureBox with mouse

I'm developing an app for windows mobile (Compact Framework 2.0). It has a WinForms with a PictureBox.
I want to move the image of the PictureBox but I don't know how to do it so I choose to move the hole PictureBox.
To do it I use this event:
private void imagenMapa_MouseMove(object sender, MouseEventArgs e)
{
imagenMapa.Left = e.X;
imagenMapa.Top = e.Y;
this.Refresh();
}
But when I move the PictureBox it blinks and moves every where.
What I'm doing wrong?

Actual Code (Requires .NET Framework 3.5 and beyond, not sure if this is available in the Compact Framework)...
// Global Variables
private int _xPos;
private int _yPos;
private bool _dragging;
// Register mouse events
pictureBox.MouseUp += (sender, args) =>
{
var c = sender as PictureBox;
if (null == c) return;
_dragging = false;
};
pictureBox.MouseDown += (sender, args) =>
{
if (args.Button != MouseButtons.Left) return;
_dragging = true;
_xPos = args.X;
_yPos = args.Y;
};
pictureBox.MouseMove += (sender, args) =>
{
var c = sender as PictureBox;
if (!_dragging || null == c) return;
c.Top = args.Y + c.Top - _yPos;
c.Left = args.X + c.Left - _xPos;
};

The e.X and e.Y are relative to the picture box (e.g. if the mouse is in the upper left of the picture box, that's 0,0) .
The values for imagenMapa.Left and imagenMapa.Top are relative to the form (or whatever control contains imagenMapa)
If you try to mix values from these two systems without conversion, you're going to get jumps (like you're seeing).
You're probably better off converting the mouse position to the same coordinate system used by the thing that contains the picture box.
You could use imagenMapa.PointToScreen to get the mouse coordinates in screen coordinates (or Cursor.Position to get the position directly), and yourForm.PointToClient to get them back in the form coordinates.
Note that depending on your needs, you could accomplish "moving an image within a control" by overriding/handling the Paint event of a control and drawing the image yourself. If you did this, you could keep everything in the picturebox coordinates, since those are likely what you would use when you called graphicsObject.DrawImage.

e.X & e.Y is in the coordinate space of the pictureBox, imagenMapa.Left & imagenMapa.Top is in the coordinate space of the Form. :-)

Also don't forget to set your form to double buffered, that might help with the flickering, but for the actual positioning of it, I like Daniel L's suggestion

Embrace math!
control.Left = control.Left - (_lastMousePos.X - currentMousePos.X);
control.Top = control.Top - (_lastMousePos.Y - currentMousePos.Y);
Quick explanation:
You get the difference from the mouse positions and apply it to the object you want to move.
Example:
If the old mouse X position is 382, and the new one is 385, then the difference is -3. If the controls current X position is 10 then 10 - (-3) = 13
Why:
It works for anything, and is much cheaper than constantly converting coordinates back and forth.

Actually what you have done is correct. But you gave the MouseMove property to the picturebox. You should give that property to the Form(background).
ex:
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
imagenMapa.Left = e.X;
imagenMapa.Top = e.Y;
}