Develop Reference

Drag Over PictureBox over other PictureBox with transparency

I would like to design a chess board and drag over pieces (shown in pictureBox Controls) all child of the main board (pictureBox1).
Problem I encounter is the transparency is only set to the Parent pictureBox1.
Which shows this effect: The square is showing.
private void CommonPiece_Mouse_Move(object sender, MouseEventArgs e)
{
if (Piece_Selected)
{
int MousePositionX = pictureBox1.PointToClient(Cursor.Position).X;
int MousePositionY = pictureBox1.PointToClient(Cursor.Position).Y;
(sender as PictureBox).Left = MousePositionX - 35;
(sender as PictureBox).Top = MousePositionY - 25;
}
}
What would be a good way to go about it?

There are several solutions for this problem. The one in the following screen recording, is based on drawing png images as movable shapes; it uses the idea that I've explained in How to drag and move shapes in C#. Basically there's only one control -the drawing surface, and all the other stuff are movable drawings.
You can use any image for the pieces by passing an Image to the ImageShape
You can modify the size of the Pieces by setting Height of the shape
It supports snapping to the grid
You can customize the texture, easily by setting the BackgroundImage of the drawing surface
You can change the grid size, by setting GridSize property of the drawing surface
You can change the Color of White and Grid grids, by assigning the color to WhiteColor and BlackColor
It's of course a quick example showing how to draw movable objects, including png images keeping their transparency. You know how to improve it :)
Drawing and moving shapes - Chess pieces
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Text;
using System.Linq;
using System.Windows.Forms;
public interface IShape
{
bool HitTest(Point p);
void Draw(Graphics g);
void Move(int dx, int dy);
Point Location { get; set; }
}
public class ImageShape : IShape
{
public int Height { get; set; } = 100;
public Point Location { get; set; }
private Image _image;
public ImageShape(Image image)
{
_image = image;
}
public void Draw(Graphics g)
{
var r = new Rectangle(Location, new Size(Height, Height));
r.Inflate(-5, -5);
g.DrawImage(_image, r);
}
public bool HitTest(Point p)
{
return new Rectangle(Location, new Size(Height, Height)).Contains(p);
}
public void Move(int dx, int dy)
{
Location = new Point(Location.X + dx, Location.Y + dy);
}
}
public class DrawingSurface : Control
{
public List<IShape> Shapes { get; private set; }
public int GridSize { get; set; } = 100;
public Color WhiteColor = Color.FromArgb(200, Color.White);
public Color BlackColor = Color.FromArgb(120, Color.Black);
IShape selectedShape;
bool moving;
Point previousPoint = Point.Empty;
public DrawingSurface()
{
DoubleBuffered = true;
ResizeRedraw = true;
Shapes = new List<IShape>();
}
protected override void OnMouseDown(MouseEventArgs e)
{
for (var i = Shapes.Count - 1; i >= 0; i--)
if (Shapes[i].HitTest(e.Location))
{
selectedShape = Shapes[i];
break;
}
if (selectedShape != null)
{
moving = true;
previousPoint = e.Location;
Invalidate();
}
base.OnMouseDown(e);
}
protected override void OnMouseMove(MouseEventArgs e)
{
if (moving)
{
var dx = e.X - previousPoint.X;
var dy = e.Y - previousPoint.Y;
selectedShape.Move(dx, dy);
previousPoint = e.Location;
this.Invalidate();
}
base.OnMouseMove(e);
}
protected override void OnMouseUp(MouseEventArgs e)
{
if (moving)
{
int i = (e.X / GridSize) * GridSize;
int j = (e.Y / GridSize) * GridSize;
selectedShape.Location = new Point(i, j);
selectedShape = null;
moving = false;
this.Invalidate();
}
base.OnMouseUp(e);
}
protected override void OnPaint(PaintEventArgs e)
{
var g = e.Graphics;
g.InterpolationMode = InterpolationMode.High;
g.SmoothingMode = SmoothingMode.HighQuality;
g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
g.CompositingQuality = CompositingQuality.HighQuality;
foreach (var shape in Shapes.Except(new[] { selectedShape }))
shape.Draw(g);
if (selectedShape != null)
selectedShape.Draw(g);
}
protected override void OnPaintBackground(PaintEventArgs e)
{
base.OnPaintBackground(e);
var g = e.Graphics;
using (var w = new SolidBrush(WhiteColor))
using (var b = new SolidBrush(BlackColor))
for (int i = 0; i < 8; i++)
for (int j = 0; j < 8; j++)
g.FillRectangle((i + j) % 2 == 0 ? b : w,
i * GridSize, j * GridSize, GridSize, GridSize);
}
}
To add pieces:
private void Form1_Load(object sender, EventArgs e)
{
this.drawingSurface1.Shapes.Add(new ImageShape(
Properties.Resources.KingWhite) { Location = new Point(0, 0) });
this.drawingSurface1.Shapes.Add(
new ImageShape(Properties.Resources.kingBlack) { Location = new Point(0, 100) });
}

Here's an example that makes the PictureBox Non-Rectangular. The PB will literally not exist where the transparent areas were:
using System.Runtime.InteropServices;
namespace CS_Scratch_WindowsFormsApp2
{
public partial class Form1 : Form
{
public const int HT_CAPTION = 0x2;
public const int WM_NCLBUTTONDOWN = 0xA1;
[System.Runtime.InteropServices.DllImportAttribute("user32.dll")]
public static extern bool ReleaseCapture();
[System.Runtime.InteropServices.DllImportAttribute("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
public Form1()
{
InitializeComponent();
pbChessPiece.MouseMove += PbChessPiece_MouseMove;
}
private void PbChessPiece_MouseMove(object sender, MouseEventArgs e)
{
PictureBox pb = (PictureBox)sender;
if (!DesignMode && e.Button == MouseButtons.Left)
{
ReleaseCapture();
SendMessage(pb.Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
}
}
private void button1_Click(object sender, EventArgs e)
{
Bitmap bmp = (Bitmap)pbChessPiece.Image;
Region rgn = new Region();
rgn.Union(new Rectangle(0, 0, bmp.Width, bmp.Height));
for(int x=0; x<bmp.Width; x++)
{
for(int y=0; y<bmp.Height; y++)
{
if (bmp.GetPixel(x, y).A == 0)
{
rgn.Exclude(new Rectangle(x, y, 1, 1));
}
}
}
pbChessPiece.Region = rgn;
}
}
}
Example run:

I did something similar, but I did not use Drag & Drop events
On MouseDown I assumed a drag operation started, I've opened a translucent unfocused window on top of the drop area, and started drawing dragged image on that form. Since the form is translucent it can show images with transparency on top of everything. I did not use images, but instead draw rectangles where users could drop. If my memory serves me correct, MouseMove events are forwarded to the dragged component, the original chess piece in your case, or the opened but unfocused form, so I can easily track the location. On MouseUp event I wrapped everything.
Since you can draw the image on the new form you can tilt image chess piece image to the left or right for a nice touch.
I developed a very strict forms designer application using this technique.

You can use the panel instead of using the pictureBox and display the image in the background of the controls. Remember that your images must be "png" and the surrounding of the image must be completely transparent. Also, the background color of the controls of the panels Set by events so that it becomes transparent during drag and returns to the cell color after drag and drop.
Good luck.

ContainerControl Won't Draw Controls On Scroll Properly

I have a custom CheckListBox control that is supposed to function the same way as the CheckedListBox control but it is not. The problem is when I scroll down, the drawing gets all messed up. The container won't actually scroll down, it will just "jitter" the check boxes around, draw random lines, etc.
Update: I changed the code so the location of each CheckBox was set in the OnControlAdded method instead of the OnPaint method. It now scrolls fine, but the drawing is still messed up! The border is missing, the BackColor changes, the lines for the check boxes are not straight; just a whole mess of things. It works perfectly in the designer (the scrolling and drawing), but not when I run the program.
Here's the code for the control:
public class ChromeCheckListBox : ChromeContainerControl
{
[Description("Determines what corner(s) will be rounded.")]
public Utilities.RoundedRectangle.RectangleCorners Corners { get; set; }
private int cornerRadius;
[Description("Determines the radius of the the corners")]
public int CornerRadius
{
get { return cornerRadius; }
set
{
if (value < 1)
Utilities.ThrowError("The radius cannot be less than 1. If you want no radius, set Corners to None.");
else
cornerRadius = value;
}
}
[Description("Determines the list of ChromeRadioButton controls that are displayed.")]
private ChromeCheckBox[] items;
public ChromeCheckBox[] Items
{
get { return items; }
set
{
items = value;
Controls.Clear();
Controls.AddRange(items);
}
}
public ChromeCheckListBox()
{
this.AutoScroll = true;
this.Corners = Utilities.RoundedRectangle.RectangleCorners.All;
this.CornerRadius = 1;
this.Items = new ChromeCheckBox[0];
this.Size = new Size(100, 100);
}
protected override void OnControlAdded(ControlEventArgs e)
{
for (int i = 0; i < Items.Length; i++)
{
if (i == 0)
Items[i].Location = new Point(2 + Padding.Left, 2 + Padding.Top);
else
Items[i].Location = new Point(2 + Padding.Left, Items[i - 1].Location.Y + Size.Ceiling(this.CreateGraphics().MeasureString(Items[i - 1].Text, Items[i - 1].Font)).Height);
}
base.OnControlAdded(e);
}
protected override void OnPaint(PaintEventArgs e)
{
Graphics canvas = e.Graphics;
canvas.SmoothingMode = SmoothingMode.HighQuality;
Rectangle region = new Rectangle(0, 0, ClientRectangle.Width - 1, ClientRectangle.Height - 1);
GraphicsPath path = Utilities.RoundedRectangle.Create(region, CornerRadius, Corners);
canvas.FillPath(new LinearGradientBrush(region, fillColors[0], fillColors[1], 90), path);
canvas.DrawPath(new Pen(borderColor), path);
}
}

I got it! Instead of setting the location of the check boxes in the OnPaint method, I should set them in the OnControlAdded method. Also, on the OnScroll method, I need to Invalidate the control causing it to redraw.
So, it should (well maybe not should, but could) look like this:
public class ChromeCheckListBox : ChromeContainerControl
{
[Description("Determines what corner(s) will be rounded.")]
public Utilities.RoundedRectangle.RectangleCorners Corners { get; set; }
private int cornerRadius;
[Description("Determines the radius of the the corners")]
public int CornerRadius
{
get { return cornerRadius; }
set
{
if (value < 1)
Utilities.ThrowError("The radius cannot be less than 1. If you want no radius, set Corners to None.");
else
cornerRadius = value;
}
}
[Description("Determines the list of ChromeRadioButton controls that are displayed.")]
private ChromeCheckBox[] items;
public ChromeCheckBox[] Items
{
get { return items; }
set
{
items = value;
Controls.Clear();
Controls.AddRange(items);
}
}
public ChromeCheckListBox()
{
this.AutoScroll = true;
this.Corners = Utilities.RoundedRectangle.RectangleCorners.All;
this.CornerRadius = 1;
this.Items = new ChromeCheckBox[0];
this.Size = new Size(100, 100);
}
protected override void OnControlAdded(ControlEventArgs e)
{
for (int i = 0; i < Items.Length; i++)
{
if (i == 0)
Items[i].Location = new Point(2 + Padding.Left, 2 + Padding.Top);
else
Items[i].Location = new Point(2 + Padding.Left, Items[i - 1].Location.Y + Size.Ceiling(this.CreateGraphics().MeasureString(Items[i - 1].Text, Items[i - 1].Font)).Height);
}
base.OnControlAdded(e);
}
protected override void OnScroll(ScrollEventArgs se)
{
base.OnScroll(se);
base.Invalidate();
}
protected override void OnPaint(PaintEventArgs e)
{
Graphics canvas = e.Graphics;
canvas.SmoothingMode = SmoothingMode.AntiAlias;
Rectangle region = new Rectangle(0, 0, ClientRectangle.Width - 1, ClientRectangle.Height - 1);
GraphicsPath path = Utilities.RoundedRectangle.Create(region, CornerRadius, Corners);
canvas.FillPath(new LinearGradientBrush(region, fillColors[0], fillColors[1], 90), path);
canvas.DrawPath(new Pen(borderColor), path);
}

Problems with custom canvas

I tried to write my own custom Canvas and wanted to draw a little labyrinth which consist of little rectangles. My Problem is, that I just get 4 little points on my screen and not 4 Rectangles (when trying it with a 2 X 2 field).
Here is some Code:
public class LabyrinthCanvas : System.Windows.Controls.Canvas
{
public static readonly int RectRadius = 60;
public ObservableCollection<ObservableCollection<Rect>> Rectangles;
public LabyrinthCanvas()
{
Rectangles = new ObservableCollection<ObservableCollection<Rect>>();
}
public void AddRectangles(int Height, int Width)
{
for (int iHeight = 0; iHeight < Height; iHeight++)
{
ObservableCollection<Rect> newRects = new ObservableCollection<Rect>();
newRects.CollectionChanged += RectanglesChanged;
Rectangles.Add(newRects);
for (int iWidth = 0; iWidth < Width; iWidth++)
{
Rect rect = new Rect(iHeight * RectRadius, iWidth * RectRadius);
Rectangles[iHeight].Add(rect);
}
}
}
public void RectanglesChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
{
foreach (object rect in e.NewItems)
{
if (rect is Rect)
{
this.Children.Add(((Rect)rect).innerRectangle);
System.Windows.Controls.Canvas.SetTop(((Rect)rect).innerRectangle, ((Rect)rect).YPos);
System.Windows.Controls.Canvas.SetLeft(((Rect)rect).innerRectangle, ((Rect)rect).XPos);
}
}
}
else if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
{
foreach (Rect rect in e.OldItems)
{
this.Children.Remove(rect.innerRectangle);
}
}
}
}
public class Rect : INotifyPropertyChanged
{
public Rect(int YPos, int XPos)
{
innerRectangle.Stroke = System.Windows.Media.Brushes.Black;
innerRectangle.Fill = System.Windows.Media.Brushes.Blue;
this.YPos = YPos;
this.XPos = XPos;
}
public System.Windows.Shapes.Rectangle innerRectangle = new System.Windows.Shapes.Rectangle();
public int YPos;
public int XPos;
}
I think the important thing is that:
this.Children.Add(((Rect)rect).innerRectangle);
System.Windows.Controls.Canvas.SetTop(((Rect)rect).innerRectangle, ((Rect)rect).YPos);
System.Windows.Controls.Canvas.SetLeft(((Rect)rect).innerRectangle, ((Rect)rect).XPos);
Im using a own Class "Rect" because i need some extra properties which i removed from the shown code and I cant inherit from Rectangle.

I'm not entirely sure what you want your end result to look like, so I probably won't be able to suggest the exact solution you're after.
That said, the reason you're obtaining small points on your screen, rather than rectangles, is because the canvas is rendering the innerRectangle of your Rect object, at the specified coordinates, but you're never initialising setting the dimensions of that innerRectangle.
The dots you're seeing are those width/heightless rectangles, which are having the Black stroke rendered (the dot).
You can see what's going on if you try something along these lines:
public System.Windows.Shapes.Rectangle innerRectangle = new System.Windows.Shapes.Rectangle() { Width = 10, Height = 10 };

Can't paint 2 of the same control on winForm

I'm making a simple game in winform (tic-tac-toe), and I'm having some problem to paint block control.
Here is the class I made, that represent a block in the game (without game logic, is only UI).
public class UI_Block : Control
{
private Rectangle block;
private SIGNS sign;
public SIGNS Sign
{
get {return sign;}
set
{
if (sign == SIGNS.EMPTY)
sign = value;
}
}
public UI_Block( ) {
sign = SIGNS.EMPTY;
}
public void SetBlockOnBoard(int x, int y)
{
this.Location = new Point( x , y );
this.Size = new Size(Parent.Width /3, Parent.Height / 3);
block = new Rectangle(this.Location, this.Size);
}
public void DrawSign(Graphics g)
{
Pen myPen = new Pen(Color.Red);
if (sign == SIGNS.O)
{
drawO(g,new Pen(Brushes.Black));
}
if (sign == SIGNS.X)
{
drawX(g, new Pen(Brushes.Red));
}
}
protected override void OnPaint(PaintEventArgs e)
{
DrawSign(e.Graphics);
base.OnPaint(e);
}
//Draw X
private void drawX(Graphics g, Pen myPen)
{
//draw first daignol
Point daignolStart = new Point { X = this.Location.X , Y = this.Location.Y };
Point daignolEnd = new Point { X = this.Size.Width , Y = this.Size.Height };
g.DrawLine(myPen, daignolStart, daignolEnd);
//draw second daignol
daignolStart = new Point { X = Size.Width , Y = this.Location.Y };
daignolEnd = new Point { X = Location.X, Y = Size.Height };
g.DrawLine(myPen, daignolEnd, daignolStart);
}
//Draw O
private void drawO(Graphics g, Pen myPen)
{
g.DrawEllipse(myPen, block);
}
}
I added them both to the winForm class and to see how it looks like when I paint them:
public partial class Form1 : Form
{
UI.UI_Block block;
UI.UI_Block blockX;
public Form1()
{
InitializeComponent();
block = new UI.UI_Block();
blockX = new UI.UI_Block();
Controls.Add(block);
Controls.Add(blockX);
}
protected override void OnLoad(EventArgs e)
{
block. SetBlockOnBoard(0, 0);
blockX.SetBlockOnBoard(0, block.Height);
block.Sign = SIGNS.X;
blockX.Sign = SIGNS.O;
base.OnLoad(e);
}
protected override void OnPaint(PaintEventArgs e)
{
//block.DrawSign(e.Graphics);
//block.DrawSign(e.Graphics);
base.OnPaint(e);
}
}
I tried few things, like not using the onPaint event and I still get the same result.
Here what I see when I run it:
Any idea why I can't paint both of them?

You are not drawing the contents of your control in it's visible area, so it is drawing fine but you can't see it.
Every control has it's own coordinate space (client coords), which starts at 0,0 regardless of where it is positioned within the parent control. You are placing the control in it's parent correctly by setting its Location, but then you are also using the Location to offset the graphics, so they are essentially offset twice.
(If you make your control bigger you'll be able to see the X being drawn further down the screen)
To fix this, do all your drawing in the client coordinate space of your control, i.e. draw in the area (0, 0, width, height)
(P.S. You could just draw all 9 tiles in the parent control, which is a more efficient approach than creating 9 child controls. But what you are doing will work fine)

Fading control in C#

I'm tring to build a Control derived class which supports an Opcacity property.
This control could host both text and image and will beable to fade them out and in.
Here is my code:
internal class FadeControl : Control
{
private int opacity = 100;
public FadeControl()
{
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
}
public int Opacity
{
get
{
return opacity;
}
set
{
if (value > 100) opacity = 100;
else if (value < 1) opacity = 1;
else opacity = value;
if (Parent != null)
Parent.Invalidate(Bounds, true);
}
}
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle = cp.ExStyle | 0x20;
return cp;
}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
//do nothing
}
protected override void OnMove(EventArgs e)
{
RecreateHandle();
}
protected override void OnPaint(PaintEventArgs e)
{
using (Graphics g = e.Graphics)
{
Rectangle bounds = new Rectangle(0, 0, Width - 1, Height - 1);
int alpha = (opacity * 255) / 100;
using (Brush bckColor = new SolidBrush(Color.FromArgb(alpha, BackColor)))
{
if (BackColor != Color.Transparent)
g.FillRectangle(bckColor, bounds);
}
ColorMatrix colorMatrix = new ColorMatrix();
colorMatrix.Matrix33 = (float)alpha / 255;
ImageAttributes imageAttr = new ImageAttributes();
imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
if (BackgroundImage != null)
g.DrawImage(BackgroundImage, bounds, 0, 0, Width, Height, GraphicsUnit.Pixel, imageAttr);
if (Text != string.Empty)
{
using (Brush txtBrush = new SolidBrush(Color.FromArgb(alpha, ForeColor)))
{
g.DrawString(Text, Font, txtBrush, 5, 5);
}
}
}
}
protected override void OnBackColorChanged(EventArgs e)
{
if (Parent != null)
Parent.Invalidate(Bounds, true);
base.OnBackColorChanged(e);
}
protected override void OnParentBackColorChanged(EventArgs e)
{
Invalidate();
base.OnParentBackColorChanged(e);
}
}
I've putted the control on a form which has a timer on it.
The timer set the control's opacity from 0 to 100 and back and its working well.
The problem I'm trying to solved is that the control flickers while changing its opacity.
Setting the control toControlStyles.DoubleBuffer will make the control invisible on the form.
Any advice will be welcome.

I was unable to use both a double buffer and WS_EX_TRANSPARENT (0x20) for the transparent background. So I decided to implement the transparent background by copying the content of the parent control and use double buffer to prevent flicker.
The following is the final source code, tested and working:
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;
internal class FadeControl : Control
{
private int opacity = 100;
private Bitmap backgroundBuffer;
private bool skipPaint;
public FadeControl()
{
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
SetStyle(ControlStyles.ResizeRedraw, true);
SetStyle(ControlStyles.DoubleBuffer |
ControlStyles.AllPaintingInWmPaint |
ControlStyles.UserPaint, true);
}
public int Opacity
{
get
{
return opacity;
}
set
{
if (value > 100) opacity = 100;
else if (value < 1) opacity = 1;
else opacity = value;
if (Parent != null)
Parent.Invalidate(Bounds, true);
}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
//do nothig
}
protected override void OnMove(EventArgs e)
{
RecreateHandle();
}
private void CreateBackgroundBuffer(Control parent)
{
int offsetX;
int offsetY;
GetOffsets(out offsetX, out offsetY, parent);
backgroundBuffer = new Bitmap(Width + offsetX, Height + offsetY);
}
protected override void OnResize(EventArgs e)
{
var parent = Parent;
if (parent != null)
{
CreateBackgroundBuffer(parent);
}
base.OnResize(e);
}
private void GetOffsets(out int offsetX, out int offsetY, Control parent)
{
var parentPosition = parent.PointToScreen(Point.Empty);
offsetY = Top + parentPosition.Y - parent.Top;
offsetX = Left + parentPosition.X - parent.Left;
}
private void UpdateBackgroundBuffer(int offsetX, int offsetY, Control parent)
{
if (backgroundBuffer == null)
{
CreateBackgroundBuffer(parent);
}
Rectangle parentBounds = new Rectangle(0, 0, Width + offsetX, Height + offsetY);
skipPaint = true;
parent.DrawToBitmap(backgroundBuffer, parentBounds);
skipPaint = false;
}
private void DrawBackground(Graphics graphics, Rectangle bounds)
{
int offsetX;
int offsetY;
var parent = Parent;
GetOffsets(out offsetX, out offsetY, parent);
UpdateBackgroundBuffer(offsetX, offsetY, parent);
graphics.DrawImage(backgroundBuffer, bounds, offsetX, offsetY, Width, Height, GraphicsUnit.Pixel);
}
private void Draw(Graphics graphics)
{
Rectangle bounds = new Rectangle(0, 0, Width, Height);
DrawBackground(graphics, bounds);
int alpha = (opacity * 255) / 100;
using (Brush bckColor = new SolidBrush(Color.FromArgb(alpha, BackColor)))
{
if (BackColor != Color.Transparent)
{
graphics.FillRectangle(bckColor, bounds);
}
}
ColorMatrix colorMatrix = new ColorMatrix();
colorMatrix.Matrix33 = (float)alpha / 255;
ImageAttributes imageAttr = new ImageAttributes();
imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
if (BackgroundImage != null)
{
graphics.DrawImage(BackgroundImage, bounds, 0, 0, Width, Height, GraphicsUnit.Pixel, imageAttr);
}
if (Text != string.Empty)
{
using (Brush txtBrush = new SolidBrush(Color.FromArgb(alpha, ForeColor)))
{
graphics.DrawString(Text, Font, txtBrush, 5, 5);
}
}
}
protected override void OnPaint(PaintEventArgs e)
{
if (!skipPaint)
{
Graphics graphics = e.Graphics;
Draw(graphics);
}
}
protected override void OnBackColorChanged(EventArgs e)
{
if (Parent != null)
{
Parent.Invalidate(Bounds, true);
}
base.OnBackColorChanged(e);
}
protected override void OnParentBackColorChanged(EventArgs e)
{
Invalidate();
base.OnParentBackColorChanged(e);
}
}
Note that the method CreateParams is no longer present, also I've changed the contructor.
The field skipPaint is to know when not to paint in order to be able to able to tell the parent to draw itself to a bitmap during OnPaint without having infinite recursion.
backgroundBuffer is not to implement double buffering, but to keep a copy of the contents of the parent without the control rendered. It is updated each paint, I know there are more efficient solutions...* yet this approach keeps it simple and shouldn't be a bottleneck unless you have too many of these controls on the same container.
*: A better solution would be to update it each time the parent invalidates. Futhermore shared it among all the FadeControls in the same parent.