（七十五）c#Winform自定义控件-控件水印组件

前提

入行已经7,8年了，一直想做一套漂亮点的自定义控件，于是就有了本系列文章。

github：https://github.com/kwwwvagaa/netwinformcontrol

码云：

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nuget

install-package hzh_controls

目录

用处及效果

此效果只是牛刀小试，需要注意的是，像textbox这样的控件并不起作用，请注意。

你可以向目标控件绘图，画任何你想画的东西

准备工作

没什么可准备的

开始

添加一个类graphicaloverlay ，继承component

代码比较少，一次全上了，主要就是用控件的paint事件搞事情，逻辑比较简单

  1 using system;
  2 using system.componentmodel;
  3 using system.drawing;
  4 using system.windows.forms;
  5 
  6 namespace hzh_controls.controls
  7 {
  8     [defaultevent("paint")]
  9     public partial class graphicaloverlay : component
 10     {
 11         public event eventhandler<painteventargs> paint;
 12         
 13         public graphicaloverlay()
 14         {
 15             initializecomponent();
 16         }
 17 
 18         public graphicaloverlay(icontainer container)
 19         {
 20             container.add(this);
 21 
 22             initializecomponent();
 23         }
 24         private control owner;      
 25         public control owner
 26         {
 27             get { return owner; }
 28             set
 29             {
 30                 // the owner form cannot be set to null.
 31                 if (value == null)
 32                     throw new argumentnullexception();
 33 
 34                 // the owner form can only be set once.
 35                 if (owner != null)
 36                     throw new invalidoperationexception();
 37 
 38                 // save the form for future reference.
 39                 owner = value;
 40 
 41                 // handle the form's resize event.
 42                 owner.resize += new eventhandler(form_resize);
 43 
 44                 // handle the paint event for each of the controls in the form's hierarchy.
 45                 connectpainteventhandlers(owner);
 46             }
 47         }
 48 
 49         private void form_resize(object sender, eventargs e)
 50         {
 51             owner.invalidate(true);
 52         }
 53 
 54         private void connectpainteventhandlers(control control)
 55         {
 56             // connect the paint event handler for this control.
 57             // remove the existing handler first (if one exists) and replace it.
 58             control.paint -= new painteventhandler(control_paint);
 59             control.paint += new painteventhandler(control_paint);
 60 
 61             control.controladded -= new controleventhandler(control_controladded);
 62             control.controladded += new controleventhandler(control_controladded);
 63 
 64             // recurse the hierarchy.
 65             foreach (control child in control.controls)
 66                 connectpainteventhandlers(child);
 67         }
 68 
 69         private void control_controladded(object sender, controleventargs e)
 70         {
 71             // connect the paint event handler for the new control.
 72             connectpainteventhandlers(e.control);
 73         }
 74 
 75         private void control_paint(object sender, painteventargs e)
 76         {
 77             // as each control on the form is repainted, this handler is called.
 78 
 79             control control = sender as control;
 80             point location;
 81 
 82             // determine the location of the control's client area relative to the form's client area.
 83             if (control == owner)
 84                 // the form's client area is already form-relative.
 85                 location = control.location;
 86             else
 87             {
 88                 // the control may be in a hierarchy, so convert to screen coordinates and then back to form coordinates.
 89                 location = owner.pointtoclient(control.parent.pointtoscreen(control.location));
 90 
 91                 // if the control has a border shift the location of the control's client area.
 92                 location += new size((control.width - control.clientsize.width) / 2, (control.height - control.clientsize.height) / 2);
 93             }
 94 
 95             // translate the location so that we can use form-relative coordinates to draw on the control.
 96             if (control != owner)
 97                 e.graphics.translatetransform(-location.x, -location.y);
 98 
 99             // fire a paint event.
100             onpaint(sender, e);
101         }
102 
103         private void onpaint(object sender, painteventargs e)
104         {
105             // fire a paint event.
106             // the paint event will be handled in form1.graphicaloverlay1_paint().
107 
108             if (paint != null)
109                 paint(sender, e);
110         }
111     }
112 }
113 
114 namespace system.windows.forms
115 {
116     using system.drawing;
117 
118     public static class extensions
119     {
120         public static rectangle coordinates(this control control)
121         {
122             // extend system.windows.forms.control to have a coordinates property.
123             // the coordinates property contains the control's form-relative location.
124             rectangle coordinates;
125             form form = (form)control.toplevelcontrol;
126 
127             if (control == form)
128                 coordinates = form.clientrectangle;
129             else
130                 coordinates = form.rectangletoclient(control.parent.rectangletoscreen(control.bounds));
131 
132             return coordinates;
133         }
134     }
135 }

 

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