Develop Reference

Drawing an Arc with a linear gradient brush using Microsoft Maui Graphics

I'm having difficulty drawing a gradient colored arc with Microsoft Maui Graphics.
I'm using Windows Forms, Visual Studio Preview 5, and .NET Core 6.
Here is what I have tried:
using Microsoft.Maui.Graphics;
using Microsoft.Maui.Graphics.Skia;
using System;
using System.Windows.Forms;
namespace MauiWinForms {
public partial class Form1:Form {
public Form1() {
InitializeComponent();
}
private void skglControl1_PaintSurface(object sender, SkiaSharp.Views.Desktop.SKPaintGLSurfaceEventArgs e) {
ICanvas canvas = new SkiaCanvas() { Canvas = e.Surface.Canvas };
var canvasWidth = skglControl1.Width = 800;
var canvasHeight = skglControl1.Height = 800;
canvas.FillColor = Colors.LightGrey;
canvas.FillRectangle(0, 0, canvasWidth, canvasHeight);
canvas.StrokeColor = Colors.Red;
canvas.DrawRectangle(1, 1, 800-2, 800-2);
var centerX = canvasWidth / 2;
var centerY = canvasHeight / 2;
canvas.StrokeColor = Colors.Teal;
canvas.StrokeSize = 10;
var X = centerX - 200;
canvas.DrawArc(X, 0, 400, 400, 0, 90, false, false);
var linearGradientPaint = new LinearGradientPaint {
StartColor = Colors.White,
EndColor = Colors.Green,
StartPoint = new Point(0, 0),
EndPoint = new Point(1, 0)
};
var myRectangle = new RectangleF(X, 0, 410, 410);
canvas.SetFillPaint(linearGradientPaint, myRectangle);
canvas.DrawArc(X, 0, 400, 400, 0, -90, false, false);
}
private void skglControl1_SizeChanged(object sender, EventArgs e) => skglControl1.Invalidate();
}
}
And this is what I get:
As you can see, the linear gradient is not applied.
Any help will be greatly appreciated.
Charles

Object not shown on Canvas (WPF Application)

In this Application, i have a car class with a method called Spawn (which should draw the object on a Canvas which i defined in the XAML file). I call the Method in MainWindow, but when I run my program, there is no car being drawn onto the Canvas.
Here is the Spawn method:
public void Spawn(Canvas cvs)
{
cvs = new Canvas();
cvs.Children.Clear();
carBody.Width = 70;
carBody.Height = 120;
carBody.Background = new SolidColorBrush(Color);
Canvas.SetLeft(carBody, SpawnLocation.X);
Canvas.SetTop(carBody, SpawnLocation.Y);
Rectangle[] tires = new Rectangle[4];
Rectangle[] windows = new Rectangle[2];
Label lblBrand = new Label();
RotateTransform rotation = new RotateTransform();
// Reifen
tires[0] = new Rectangle()
{
Fill = Brushes.Black,
Width = 20,
Height = 30
};
Canvas.SetLeft(tires[0], -9);
Canvas.SetTop(tires[0], 18);
tires[1] = new Rectangle()
{
Fill = Brushes.Black,
Width = 20,
Height = 30
};
Canvas.SetLeft(tires[1], 61);
Canvas.SetTop(tires[1], 18);
tires[2] = new Rectangle()
{
Fill = Brushes.Black,
Width = 20,
Height = 30
};
Canvas.SetLeft(tires[2], -9);
Canvas.SetTop(tires[2], 80);
tires[3] = new Rectangle()
{
Fill = Brushes.Black,
Width = 20,
Height = 30
};
Canvas.SetLeft(tires[3], 61);
Canvas.SetTop(tires[3], 80);
// Fenster
windows[0] = new Rectangle() // Front
{
Fill = Brushes.White,
Width = 50,
Height = 40
};
Canvas.SetLeft(windows[0], 0);
Canvas.SetTop(windows[0], 0);
windows[1] = new Rectangle() // rear
{
Fill = Brushes.White,
Width = 50,
Height = 50
};
Canvas.SetLeft(windows[1], 0);
Canvas.SetTop(windows[1], 0);
// Label Automarke
lblBrand.Width = 40;
lblBrand.Height = 23;
lblBrand.Content = Brand;
// Add2Canvas
for (int i = 0; i < tires.Length; i++)
carBody.Children.Add(tires[i]);
for (int i = 0; i < windows.Length; i++)
carBody.Children.Add(windows[i]);
carBody.Children.Add(lblBrand);
if (Direction == "nord")
{
rotation.Angle = 0;
rotation.CenterX = SpawnLocation.X;
rotation.CenterY = SpawnLocation.Y;
carBody.RenderTransform = rotation;
}
else if (Direction == "süd")
{
rotation.Angle = 180;
rotation.CenterX = SpawnLocation.X;
rotation.CenterY = SpawnLocation.Y;
carBody.RenderTransform = rotation;
}
else if (Direction == "west")
{
rotation.Angle = 90;
rotation.CenterX = SpawnLocation.X;
rotation.CenterY = SpawnLocation.Y;
carBody.RenderTransform = rotation;
}
else if (Direction == "ost")
{
rotation.Angle = 270;
rotation.CenterX = SpawnLocation.X;
rotation.CenterY = SpawnLocation.Y;
carBody.RenderTransform = rotation;
}
cvs.Children.Add(carBody);
}
Calling the methodMainWindow:
Car car1;
public MainWindow()
{
InitializeComponent();
car1 = new Car("Audi", Colors.Red);
car1.Direction = "west";
car1.SpawnLocation = new Point(550, 340);
car1.Spawn(gameScreen);
}
Thanks in advance!

Fixed it! I initialized the argmument of my Spawn method, it now works after I deleted it.
My method looked like this first:
public void Spawn(Canvas cvs)
{
cvs = new Canvas();
cvs.Children.Clear();
carBody.Width = 70;
I initialized my the Argument, but since i don't wanna create a new Canvas, i deleted these two first lines of my method.
public void Spawn(Canvas cvs)
{
carBody.Width = 70;
carBody.Height = 120;
carBody.Background = new SolidColorBrush(Color);
Now its working fine.

How to make an image(or a rectangle) follow a Spline

I have a project that I need to make an image follow a spline.
I build the spline using Graphics.DrawCurve through an array of Points.
I'm trying to use PointAnimationUsingPath but I can't seem to get it to work. Apparently it doesn't work in C# with Windows form.
Can someone give me a light on how to do this?
Thank you All.
-----EDIT-----
Change to a WPF UserControl as recommend in comments.
Still need some help as the shape does not move exactly following the dots, below my code:
public partial class SplineBox : UserControl
{
Point[] finalPoint;
public SplineBox()
{
InitializeComponent();
}
public void MoveShape(Point[] _path)
{
// Create a NameScope for the page so that
// we can use Storyboards.
NameScope.SetNameScope(this, new NameScope());
// Create the EllipseGeometry to animate.
EllipseGeometry animatedEllipseGeometry =
new EllipseGeometry(new Point(10, 100), 15, 15);
// Register the EllipseGeometry's name with
// the page so that it can be targeted by a
// storyboard.
this.RegisterName("AnimatedEllipseGeometry", animatedEllipseGeometry);
// Create a Path element to display the geometry.
Path ellipsePath = new Path();
ellipsePath.Data = animatedEllipseGeometry;
ellipsePath.Fill = Brushes.Blue;
ellipsePath.Margin = new Thickness(15);
SplineCanvas.Children.Add(ellipsePath);
this.Content = SplineCanvas;
// Create the animation path.
PathGeometry animationPath = new PathGeometry();
PathFigure pFigure = new PathFigure();
pFigure.StartPoint = _path[0];
PolyBezierSegment pBezierSegment = new PolyBezierSegment();
for (int p = 1; p < _path.Length; p++)
{
pBezierSegment.Points.Add(_path[p]);
}
pFigure.Segments.Add(pBezierSegment);
animationPath.Figures.Add(pFigure);
// Freeze the PathGeometry for performance benefits.
animationPath.Freeze();
// Create a PointAnimationgUsingPath to move
// the EllipseGeometry along the animation path.
PointAnimationUsingPath centerPointAnimation = new PointAnimationUsingPath();
centerPointAnimation.PathGeometry = animationPath;
centerPointAnimation.Duration = TimeSpan.FromSeconds(5);
centerPointAnimation.RepeatBehavior = RepeatBehavior.Forever;
// Set the animation to target the Center property
// of the EllipseGeometry named "AnimatedEllipseGeometry".
Storyboard.SetTargetName(centerPointAnimation, "AnimatedEllipseGeometry");
Storyboard.SetTargetProperty(centerPointAnimation,
new PropertyPath(EllipseGeometry.CenterProperty));
// Create a Storyboard to contain and apply the animation.
Storyboard pathAnimationStoryboard = new Storyboard();
pathAnimationStoryboard.RepeatBehavior = RepeatBehavior.Forever;
pathAnimationStoryboard.AutoReverse = true;
pathAnimationStoryboard.Children.Add(centerPointAnimation);
// Start the Storyboard when ellipsePath is loaded.
ellipsePath.Loaded += delegate (object sender, RoutedEventArgs e)
{
// Start the storyboard.
pathAnimationStoryboard.Begin(this);
};
}
public void Paint(ScreenObject _spline)
{
List<Point> points = new List<Point>();
if (true)
{
var spline = _spline;
foreach (System.Windows.Point point in spline.SplineAnchors)
{
Point tempP = new Point((int)point.X, (int)point.Y);
points.Add(tempP);
}
finalPoint = points.ToArray();
//Pen pen = new Pen(Color.FromArgb(255, 0, 0, 255), 1);
//e.Graphics.DrawCurve(pen, finalPoint);
foreach (Point p in finalPoint)
{
// Create a red Ellipse.
Ellipse myEllipse = new Ellipse();
// Create a SolidColorBrush with a red color to fill the
// Ellipse with.
SolidColorBrush mySolidColorBrush = new SolidColorBrush();
// Describes the brush's color using RGB values.
// Each value has a range of 0-255.
mySolidColorBrush.Color = Color.FromArgb(255, 100, 255, 0);
myEllipse.Fill = mySolidColorBrush;
myEllipse.StrokeThickness = 2;
myEllipse.Stroke = Brushes.Black;
// Set the width and height of the Ellipse.
myEllipse.Width = 10;
myEllipse.Height = 10;
myEllipse.Margin = new Thickness(p.X - 5, p.Y - 5, 0, 0);
//e.Graphics.DrawRectangle(pen, new Rectangle(p.X - 5, p.Y - 5, 10, 10));
//e.Graphics.FillRectangle(Brushes.Red, new Rectangle(p.X - 5, p.Y - 5, 10, 10));
SplineCanvas.Children.Add(myEllipse);
}
}
}
}

WPF DocumentViewer show document as byte array

This might be a silly question, but I was wondering if it's possible to display a document in WPF's DocumentViewer control from a byte array.
If not, could someone provide an example of how the control is normally used to display a document? I can't seem to find a decent example.

It is about arranging different UIElements:
FixedDocument fixedDocument = new FixedDocument();
DocumentViewer dv = new DocumentViewer() { Document = fixedDocument };
this.Content = dv;
var page1 = new FixedPage() { Width = 600, Height = 800 };
PageContent page1Content = new PageContent() { Child = page1 };
var sp = new StackPanel();
sp.Children.Add(new TextBlock
{
Text = "Title",
FontSize = 30,
Margin = new Thickness(100, 50, 0, 70)
});
sp.Children.Add(new TextBlock
{
Text = "The quick brown fox jumps over the lazy dog...",
FontSize = 15,
Margin = new Thickness(10, 0, 0, 10)
});
Rectangle rect = new Rectangle();
rect.Width = 150;
rect.Height = 150;
rect.Fill = Brushes.Black;
sp.Children.Add(new Rectangle
{
Width = 150,
Height = 150,
Fill = Brushes.Black
});
page1.Children.Add(sp);
fixedDocument.Pages.Add(page1Content);

C# Xamarin avoiding code repetition

I am making a basic note taking app using C# in Xamarin Studio and have been following along with a course online.
Problem is that the code examples provided contain a lot of repetitive code which is making updating the app increasingly hard.
I labelled the relevant code below which is pertinent to two very similar classes, EditNoteViewController.cs and AddNoteViewController.cs, how can I extract the code out so that I can call it just once?
Alternatively I am looking at extracting it all into one class and having a conditional flow rendering different attributes based on whether the user is creating or updating a note.
EditNoteController.cs
using System;
using UIKit;
namespace NoteTaker.iOS
{
public class EditNoteViewController : UIViewController
{
Note note;
public EditNoteViewController (Note _note)
{
note = _note;
}
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255); // Repeated code. Also used in MainViewController.cs
this.Title = "Edit Note";
this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };
this.NavigationController.NavigationBar.TintColor = UIColor.White;
this.View.BackgroundColor = UIColor.White;
var titleEntryBox = new UITextField () {
Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45), // Repeated code
BackgroundColor = UIColor.LightGray,
TextColor = UIColor.Black,
Text = note.title
};
var descriptionLabel = new UILabel () {
Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
Text = "Description",
};
var descriptionEntryBox = new UITextView () {
Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100), // Repeated code
BackgroundColor = UIColor.LightGray,
TextColor = UIColor.Black,
Text = note.description
};
var updateButton = new UIButton () {
Frame = new CoreGraphics.CGRect (10, 340, 120, 45)
}; // Repeated code
updateButton.SetTitle ("Update", UIControlState.Normal);
updateButton.BackgroundColor = UIColor.FromRGB (255, 0, 255);
updateButton.SetTitleColor (UIColor.White, UIControlState.Normal);
this.View.Add (titleEntryBox);
this.View.Add (descriptionLabel);
this.View.Add (descriptionEntryBox);
this.View.Add (updateButton);
updateButton.TouchUpInside += (sender, e) => {
if (titleEntryBox.Text.Length < 4)
return;
var noteToUpdate = new Note () {
ID = note.ID,
title = titleEntryBox.Text,
description = descriptionEntryBox.Text,
dateCreated = DateTime.Now
};
Database.updateNote (noteToUpdate);
this.NavigationController.PopViewController (true);
};
}
}
}
AddNoteViewController.cs
using System;
using UIKit;
namespace NoteTaker.iOS
{
public class AddNoteViewController : UIViewController
{
public AddNoteViewController ()
{
}
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255);
this.Title = "New Note";
this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };
this.NavigationController.NavigationBar.TintColor = UIColor.White;
this.View.BackgroundColor = UIColor.White;
var titleEntryBox = new UITextField () {
Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45),
BackgroundColor = UIColor.LightGray,
Placeholder = "Enter title...",
TextColor = UIColor.Black
};
var descriptionLabel = new UILabel () {
Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
Text = "Enter description below"
};
var descriptionEntryBox = new UITextView () {
Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100),
BackgroundColor = UIColor.LightGray,
TextColor = UIColor.Black
};
var saveButton = new UIButton () {
Frame = new CoreGraphics.CGRect (10, 340, 120, 45)
};
saveButton.SetTitle ("Save Note", UIControlState.Normal);
saveButton.BackgroundColor = UIColor.FromRGB (255, 0, 255);
saveButton.SetTitleColor (UIColor.White, UIControlState.Normal);
this.View.Add (titleEntryBox);
this.View.Add (descriptionLabel);
this.View.Add (descriptionEntryBox);
this.View.Add (saveButton);
saveButton.TouchUpInside += (sender, e) => {
if (titleEntryBox.Text.Length < 4)
return;
var noteToSave = new Note () {
title = titleEntryBox.Text,
description = descriptionEntryBox.Text,
dateCreated = DateTime.Now
};
Database.InsertNote (noteToSave);
titleEntryBox.Text = "";
descriptionEntryBox.Text = "";
};
}
}
}

There are lots of different ways to approach a problem like this; this is just a simple example - passing a null into the controller will cause it to "Add", otherwise it will act as an "Edit" page
public class NoteViewController : UIViewController
{
Note note;
public NoteViewController (Note _note)
{
note = _note;
}
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
this.NavigationController.NavigationBar.BarTintColor = UIColor.FromRGB (255, 0, 255); // Repeated code. Also used in MainViewController.cs
this.Title = note == null ? "Add Note" : "Edit Note";
this.NavigationController.NavigationBar.TitleTextAttributes = new UIStringAttributes () { ForegroundColor = UIColor.White };
this.NavigationController.NavigationBar.TintColor = UIColor.White;
this.View.BackgroundColor = UIColor.White;
var titleEntryBox = new UITextField () {
Frame = new CoreGraphics.CGRect (0, 100, View.Bounds.Width, 45), // Repeated code
BackgroundColor = UIColor.LightGray,
TextColor = UIColor.Black,
Text = note == null ? string.Empty : note.title
};
var descriptionLabel = new UILabel () {
Frame = new CoreGraphics.CGRect (10, 180, 250, 35),
Text = "Description",
};
var descriptionEntryBox = new UITextView () {
Frame = new CoreGraphics.CGRect (0, 220, View.Bounds.Width, 100), // Repeated code
BackgroundColor = UIColor.LightGray,
TextColor = UIColor.Black,
Text = note == null ? string.Empty : note.description
};
var button = new UIButton () {
Frame = new CoreGraphics.CGRect (10, 340, 120, 45)
}; // Repeated code
if (note == null) {
button.SetTitle ("Add", UIControlState.Normal);
} else {
button.SetTitle ("Update", UIControlState.Normal);
}
button.BackgroundColor = UIColor.FromRGB (255, 0, 255);
button.SetTitleColor (UIColor.White, UIControlState.Normal);
this.View.Add (titleEntryBox);
this.View.Add (descriptionLabel);
this.View.Add (descriptionEntryBox);
this.View.Add (button);
button.TouchUpInside += (sender, e) => {
if (note == null) {
var noteToSave = new Note () {
title = titleEntryBox.Text,
description = descriptionEntryBox.Text,
dateCreated = DateTime.Now
};
Database.InsertNote (noteToSave);
titleEntryBox.Text = "";
descriptionEntryBox.Text = "";
} else {
if (titleEntryBox.Text.Length < 4)
return;
var noteToUpdate = new Note () {
ID = note.ID,
title = titleEntryBox.Text,
description = descriptionEntryBox.Text,
dateCreated = DateTime.Now
};
Database.updateNote (noteToUpdate);
this.NavigationController.PopViewController (true);
}
};
}
}