Develop Reference

C# windows form circular button smoothing by anti-aliasing

I'm New in c sharp, i'm trying to make a circular button. the code below is making a ellipse for me but it is not looking smooth, also it is having partially hidden lines at right and bottom as shown in image
class ButtonEllipse: Button
{
protected override void OnPaint(PaintEventArgs e)
{
GraphicsPath graphics = new GraphicsPath();
Rectangle myEllipse = new Rectangle(0, 0, this.ClientSize.Width,this.ClientSize.Height);
graphics.AddEllipse(myEllipse);
Pen myPen = new Pen(Color.Black, 2);
this.Region = new System.Drawing.Region(graphics);
base.OnPaint(e);
}
}
can you please guide me how to get a exact and smooth circular button.

Try setting graphics.SmoothingMode = SmoothingMode.AntiAlias; Read more about antialiazing.
You should perhaps also paint the button graphics directly rather than using the Region. See DrawEllipse and FillEllipse.

Children inherit parents appearance

I have created a simple custom panel using ContainerControl as my base. I've added custom properties to create borders and gradient backgrounds. If I override OnPaint and OnPaintBackground all child controls of the parent inherit the gradient and border styles. As a work around I have used the parents BackgroundImage property which works fine but has a few random quirks. There has to be a better way of approaching this issue but I have found no solution. Are there any Window API functions via Interop or other C# methods to fix this? If so please provide an example.
EDIT! Here is the style being copied (ugly example but makes the point):
EDIT 2! Here is a simple hard-coded ContainerControl without all the properties, designer attributes, etc.
public class Container : ContainerControl
{
protected override void OnPaintBackground( PaintEventArgs e )
{
using ( var brush = new LinearGradientBrush( e.ClipRectangle, Color.Red, Color.Blue, LinearGradientMode.Vertical ) )
{
e.Graphics.FillRectangle( brush, e.ClipRectangle );
}
}
}

If a Label control is created with its BackColor property set to Color.Transparent, it will end up calling its parent's OnPaintBackground() implementation.
If you modify Jon's example like this:
var label = new Label {
Text = "Label",
Location = new Point(20, 50),
BackColor = Color.Transparent
};
Then you will reproduce the issue.
There is an easy workaround, however. The problem comes from the way you're creating the linear gradient brush. Since you're passing e.ClipRectangle to its constructor, the shape of the gradient will vary depending on the control being rendered (container or label). On the other hand, if you pass the ClientRectangle of the container, then the gradient will always have the same shape and the result should be what you're looking for:
protected override void OnPaintBackground(PaintEventArgs e)
{
using (var brush = new LinearGradientBrush(ClientRectangle,
Color.Red, Color.Blue, LinearGradientMode.Vertical)) {
e.Graphics.FillRectangle(brush, e.ClipRectangle);
}
}
The result is:

Initialize the properties on control create/load
Then "INVALIDATE" the control to force a redraw of the control

I can't reproduce this simply on my Windows 7 machine - which suggests it may be one of the properties you've set in the designer. Short but complete program:
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
public class GradientContainer : ContainerControl
{
protected override void OnPaintBackground(PaintEventArgs e)
{
using (var brush = new LinearGradientBrush(e.ClipRectangle,
Color.Red, Color.Blue, LinearGradientMode.Vertical))
{
e.Graphics.FillRectangle(brush, e.ClipRectangle);
}
}
}
class Test
{
static void Main()
{
var label = new Label {
Text = "Label",
Location = new Point(20, 50)
};
var container = new GradientContainer {
Size = new Size(200, 200),
Location = new Point(0, 0),
Controls = { label }
};
Form form = new Form {
Controls = { container },
Size = new Size(300, 300)
};
Application.Run(form);
}
}
And the result:

Highlight the Rectangular Area while Dragging it

I am creating a image viewer sort of application. I am on Windows and using .Net
In my app, I am trying to highlight a Particular area while dragging.
I have created a Rectangle.
Rectangle areaRect = new Rectangle(100,100, 300, 300);
Point ptOld = new Point(0, 0);
Pen rectPen = new Pen(Brushes.White, 3);
protected override void OnPaint(PaintEventArgs e)
{
Graphics dcPaint = e.Graphics;
dcPaint.DrawRectangle(rectPen, areaRect);
}
Now I am dragging this rectangular area along with my mouse movements.
protected override void OnMouseMove(MouseEventArgs e)
{
Point ptNew = new Point(e.X, e.Y);
int dx = ptNew.X - ptOld.X;
int dy = ptNew.Y - ptOld.Y;
areaRect.Offset(dx, dy);
MoveRect(ptNew);
ptOld = ptNew;
}
Here I am trying to move this rect along with my mouse
void MoveRect(Point point)
{
Graphics grfxClient = CreateGraphics();
Rectangle tempRectangle = new Rectangle(areaRect.Left, areaRect.Top, areaRect.Width, areaRect.Height);
grfxClient.DrawRectangle(rectPen, tempRectangle);
this.Invalidate();
grfxClient.Dispose();
}
My Code till this point is working fine.
Now I would like to darken the INVERSE drag Area (The area which is outside the drag region), I mean the area which is within this Rectangle should gets highlighted while dragging.
Any idea how to proceed.
Thanks.
-Pankaj

I suppose you can do it by creating a Region object that covers the outside of the rectangle and fill it with a semi-transparent SolidBrush to make it look darkened.
You also don't have to create a graphics and draw in OnMouseMove event, but just shift the rectangle and invalidate the surface of the control you are drawing on.
The code I used looks more or less like this:
Rectangle areaRect = new Rectangle(100,100, 300, 300);
Point ptOld = new Point(0, 0);
Pen rectPen = new Pen(Brushes.White, 3);
//A new field with a semi-transparent brush to paint the outside of the rectangle
Brush dimmingBrush = new SolidBrush(Color.FromArgb(128, 0, 0, 0));
protected override void OnPaint(PaintEventArgs e)
{
Region outsideRegion = new System.Drawing.Region(e.ClipRectangle);
outsideRegion.Exclude(areaRect);
Graphics dcPaint = e.Graphics;
dcPaint.FillRegion(dimmingBrush, outsideRegion);
dcPaint.DrawRectangle(rectPen, areaRect);
}
protected override void OnMouseMove(MouseEventArgs e)
{
Point ptNew = new Point(e.X, e.Y);
int dx = ptNew.X - ptOld.X;
int dy = ptNew.Y - ptOld.Y;
areaRect.Offset(dx, dy);
ptOld = ptNew;
this.Invalidate();
}
The method named MoveRect is not needed.
It now seems to work as you wanted it to.
Suggestions
I also have some suggestions. You don't have to use them, maybe they will be helpful for you.
You haven't written what kind of control you are using to draw on (or overriding Form methods and painting directly on it), but I suggest you to use a PictureBox control, create a custom control derived from it and override its events. This should make the painting process smooth and prevent flickering. To do it this way:
Create a new user control by selecting Add and User Control... and name a new control i.e. MyPictureBox
change the parent class of the control, so it should now contain the line:
public partial class MyPictureBox : PictureBox
open file MyPictureBox.Designer.cs and comment out these lines:
//this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
//this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
copy the code I posted in this answer and add line base.OnPaint(e); and the beginning of OnPaint method
compile the project
now you should be able to open designer of your main form, drag MyPictureBox control from the toolbox and use it without additional code needed
You also might consider changing the behaviour of the highlighted area, so mouse cursor was in the center of it. I suppose it would be more intuitive to the user.
If you have any issues with the code, just write it in the comments and I'll try to help :).

WinForms system-renderer Toolstrip item hover effect on button controls

If you take a look at the attached image, is there a way to get the drawing logic for this hover effect from the system renderer of the standard WinForms toolstrip ?
http://imageshack.us/photo/my-images/10/toolstriphovereffect.jpg/
EDIT: Anyway, I've manually implemented this with images, but if anyone comes here with a solution, please post.

Maybe this code helps. It draws red circle with black border around toolstripbutton when mouse is over it.
Set your toolstrip properties:
//Set render mode to professional
myToolStrip.RenderMode = ToolStripRenderMode.Professional;
//Assign new instance of your custom renderer
myToolStrip.Renderer = new MyCustomRenderer();
Custom renderer class:
public class MyCustomRenderer : ToolStripProfessionalRenderer
{
protected override void OnRenderButtonBackground(ToolStripItemRenderEventArgs e)
{
if (!e.Item.Selected)
base.OnRenderButtonBackground(e);
else
{
Rectangle rectangle = new Rectangle(0, 0, e.Item.Size.Width - 1, e.Item.Size.Height - 1);
//Draw red circle
e.Graphics.FillEllipse(Brushes.Red, rectangle);
//Draw black border
e.Graphics.DrawEllipse(Pens.Black, rectangle);
}
}
}

C# form drawing question

What is the easiest way to make a transparent overlay over the elements in my form?
I wish to make a simple black (with opacity = 0.5) overlay for my form and activate it if my application is doing something (like a fadescreen).
Thank you.

You can create a transparent control by inherit a control you want use
a Tranparent Panel example :
class TransparentPanel : Panel
{
protected override CreateParams CreateParams
{
get
{
CreateParams createParams = base.CreateParams;
createParams.ExStyle |= 0x00000020; // WS_EX_TRANSPARENT
return createParams;
}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
SolidBrush brush = new SolidBrush(Color.FromArgb(100, 0, 0, 0));
e.Graphics.FillRectangle(brush,0,0,this.Width,this.Height);
}
}
And Use this after form laded.s:
void Form1_Load(object sender, EventArgs e)
{
TransparentPanel overlay = new TransparentPanel();
overlay.BackColor = Color.FromArgb(50, Color.Black);
overlay.Width = this.Width;
overlay.Height = this.Height;
this.Controls.Add(overlay);
overlay.BringToFront();
}

The easiest is to override the application OnPaint method, and inside it add the following lines:
if( doingSomething )
{
using( SolidBrush brush = new SolidBrush( Color.FromArgb(128, 0, 0, 0)))
{
e.Graphics.FillRectangle( brush, 0, 0, width, height );
}
}
Then, at the place in code when your doing something, set doingSomething to true, and call Invalidate. When the work is complete, set doingSomething to false, and call Invalidate again.

Have you tried adding a semi-transparent control to your form that covers the entire form area? Have the control dock to the entire form, so that it resizes with the form. Make sure it is topmost in the Z-order, so that all the other controls are rendered below it.