var rangeHeight=cas.height-topOffset-bottomOffset-arrowHeight;
时间: 2024-06-06 22:11:24 浏览: 11
As an AI language model, I do not have enough context to provide a complete answer to this question. However, based on the given code snippet, it seems that a variable named "rangeHeight" is being declared and initialized with a value that is calculated by subtracting the top offset, bottom offset, and arrow height from the height of a canvas element (represented by the variable "cas"). The resulting value represents the available height range for a specific UI element.
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context.lineTo(cas.width-rightOffset-arrowHeight,y-arrowWidth/2);
This line of code is used in a JavaScript canvas drawing context to draw a line that starts from the current point and ends at a specified point on the canvas.
The canvas width is subtracted by the value of rightOffset and arrowHeight, and the resulting value is used as the x-coordinate of the endpoint of the line. The y-coordinate of the endpoint is calculated by subtracting half the value of arrowWidth from the value of y.
This code is typically used to draw an arrow on a canvas element. The arrow points towards the right side of the canvas, and its size and position can be adjusted by changing the values of rightOffset, arrowHeight, and arrowWidth.
winform 滚动条重绘
在 WinForm 中,滚动条的重绘可以通过以下两种方式实现:
1. 重写滚动条的 OnPaint 方法
在滚动条控件的子类中,可以重写 OnPaint 方法,实现自定义的滚动条绘制。在 OnPaint 方法中,可以使用 Graphics 对象绘制滚动条的背景、滑块和箭头等元素。
以下是一个示例:
```csharp
public class CustomScrollBar : VScrollBar
{
protected override void OnPaint(PaintEventArgs e)
{
// 调用基类的 OnPaint 方法,绘制默认的滚动条
base.OnPaint(e);
// 绘制自定义的滚动条
Graphics g = e.Graphics;
Rectangle trackBounds = this.TrackRectangle;
Rectangle thumbBounds = this.ThumbRectangle;
// 绘制滚动条的背景
g.FillRectangle(Brushes.Gray, trackBounds);
// 绘制滑块
g.FillRectangle(Brushes.White, thumbBounds);
// 绘制箭头
int arrowWidth = thumbBounds.Width / 2;
int arrowHeight = thumbBounds.Height / 2;
int arrowX = thumbBounds.X + (thumbBounds.Width - arrowWidth) / 2;
int arrowUpY = thumbBounds.Y - arrowHeight;
int arrowDownY = thumbBounds.Y + thumbBounds.Height;
Point[] arrowUpPoints = new Point[]
{
new Point(arrowX, arrowUpY),
new Point(arrowX + arrowWidth, arrowUpY),
new Point(arrowX + arrowWidth / 2, thumbBounds.Y)
};
Point[] arrowDownPoints = new Point[]
{
new Point(arrowX, arrowDownY),
new Point(arrowX + arrowWidth, arrowDownY),
new Point(arrowX + arrowWidth / 2, thumbBounds.Bottom)
};
g.FillPolygon(Brushes.Black, arrowUpPoints);
g.FillPolygon(Brushes.Black, arrowDownPoints);
}
}
```
2. 使用滚动条控件的自定义绘制事件
在滚动条控件的事件中,有一个 DrawTrackBar 和 DrawArrowButton 事件,可以用于自定义滚动条的绘制。这两个事件分别在绘制滑块轨道和箭头按钮时触发,可以在事件中使用 Graphics 对象绘制自定义的元素。
以下是一个示例:
```csharp
public class CustomScrollBar : VScrollBar
{
public CustomScrollBar()
{
this.DrawMode = ScrollBarDrawModes.OwnerDrawAll;
}
protected override void OnHandleCreated(EventArgs e)
{
base.OnHandleCreated(e);
// 注册自定义绘制事件
if (this.DesignMode == false)
{
this.DrawTrackBar += CustomScrollBar_DrawTrackBar;
this.DrawArrowButton += CustomScrollBar_DrawArrowButton;
}
}
private void CustomScrollBar_DrawTrackBar(object sender, DrawScrollBarEventArgs e)
{
Graphics g = e.Graphics;
Rectangle trackBounds = e.ScrollBar.TrackRectangle;
Rectangle thumbBounds = e.ScrollBar.ThumbRectangle;
// 绘制滚动条的背景
g.FillRectangle(Brushes.Gray, trackBounds);
// 绘制滑块
g.FillRectangle(Brushes.White, thumbBounds);
}
private void CustomScrollBar_DrawArrowButton(object sender, DrawScrollBarEventArgs e)
{
Graphics g = e.Graphics;
Rectangle arrowBounds = e.ScrollBar.ArrowRectangle;
// 绘制箭头
int arrowWidth = arrowBounds.Width / 2;
int arrowHeight = arrowBounds.Height / 2;
int arrowX = arrowBounds.X + (arrowBounds.Width - arrowWidth) / 2;
int arrowUpY = arrowBounds.Y - arrowHeight;
int arrowDownY = arrowBounds.Y + arrowBounds.Height;
Point[] arrowUpPoints = new Point[]
{
new Point(arrowX, arrowUpY),
new Point(arrowX + arrowWidth, arrowUpY),
new Point(arrowX + arrowWidth / 2, arrowBounds.Y)
};
Point[] arrowDownPoints = new Point[]
{
new Point(arrowX, arrowDownY),
new Point(arrowX + arrowWidth, arrowDownY),
new Point(arrowX + arrowWidth / 2, arrowBounds.Bottom)
};
g.FillPolygon(Brushes.Black, arrowUpPoints);
g.FillPolygon(Brushes.Black, arrowDownPoints);
}
}
```