开价200元，寻求像Tshape的斜线图元：只有线条，不包含矩形区域。(200分)

想在TPanel上划斜线，不知用什么方法好：
1、用TShape划存在一个讨厌的矩形框，把其他元件给挡住了；
2、直接用 Lineto 划的又没有鼠标事件。
3、用两个 TShape + Lineto 画，用鼠标移动线条时，又存在分析鼠标位置，图元层次，
区域重画等诸多难题。
想了很久，也不得法。不知那位大师有这方面的高招，指引弟子早日走出迷途。
分不够可以加，需要 RMB 开个价。
Email: liyunhong2002@yahoo.com.cn

如果仅仅是在TPanel上画线，而不用进行编辑的话，可以考虑Canvas:
1.从TPanel继承一个控件（如TmyPanel）；
2.在TmyPanel中获得CM_MouseDown和CM_MouseUp消息，然后增加OnMouseDown和OnMouseUp事件；
3.继承父控件的Paint过程，增加OnPaint事件；
3.根据增加的鼠标事件，获得鼠标位置，在OnPaint事件中用Canvas画线。

关于直线的拾取

1: 判断鼠标位置是否在直线所在的矩形区域内, 如果在进行第二步, 否则false
2: 判断点到直线的距离是否小于一定的精度要求

请参考这个帖子（http://www.delphibbs.com/delphibbs/dispq.asp?lid=1661776）中我的控件，为了避免挡住其他的控件，对它进行了修改，附于下面。当然，还有一些代码你得自己完成。
unit LinLine;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls, CommCtrl;

type
TFrameType = (ftOuter,ftInner,ftMiddle);
TDragBox = (dbNone,dbDrag,dbPoint1,dbPoint2);
TOnPaintEvent = procedure (Sender: TObject; Canvas: TCanvas; Rect: TRect) of object;

TLinLine = class(TGraphicControl)
private
{ Private declarations }
FPoint1,FPoint2:TPoint;
FHasInit:Boolean;
FAutoForeGround: Boolean;
FReadOnly: Boolean;
FOnPaint: TOnPaintEvent;
FFrameType: TFrameType;
FAutoSize: Boolean;
FCaption: String;
FHideFrame: Boolean;
FFrameColor: TColor;
FBoxSize: Integer;
FBoxColor: TColor;
FActiveFrameColor: TColor;
FPassiveFrameColor: TColor;
FTextColor: TColor;
FDrawFrame: Boolean;
FDrawBoxes: Boolean;
FShowPos: Boolean;
FShowSize: Boolean;
FDragBox: TDragBox;
FPosX: Integer;
FPosY: Integer;
FHasFocus: Boolean;
procedure WMGetDlgCode(var Message: TWMGetDlgCode); message WM_GETDLGCODE;
procedure SetFocus(Value: Boolean);
procedure SetAutoSize(Value: Boolean);
procedure SetHideFrame(Value: Boolean);
procedure SetCaption(Value: String);
procedure SetFrameBox(PLeft,PTop,PWidth,PHeight: Integer);
procedure SetFrameType(Value: TFrameType);
procedure SetBoxSize(Value: Integer);
procedure SetBoxColor(Value: TColor);
procedure SetActiveFrameColor(Value: TColor);
procedure SetPassiveFrameColor(Value: TColor);
procedure SetTextColor(Value: TColor);
procedure SetDrawFrame(Value: Boolean);
procedure SetDrawBoxes(Value: Boolean);
procedure SetShowPos(Value: boolean);
procedure SetShowSize(Value: Boolean);
procedure WMLMouseDown(var Message: TMessage); message WM_LBUTTONDOWN;
procedure WMLMouseUp(var Message: TMessage); message WM_LBUTTONUP;
procedure MouseMove(Sender: TObject; Shift: TShiftState; X,Y: Integer);
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,Y: Integer);
function NearLine(X,Y: Integer):boolean;
protected
procedure paint; override;
public
procedure RemoveAllFocus;
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property AutoForeGround: Boolean read FAutoForeGround write FAutoForeGround;
property AutoSize: Boolean read FAutoSize write SetAutoSize;
property FrameType: TFrameType read FFrameType write SetFrameType;
property HidePassiveFrame: Boolean read FHideFrame write SetHideFrame;
property Caption: String read FCaption write SetCaption;
property BoxSize: Integer read FBoxSize write SetBoxSize;
property BoxColor: TColor read FBoxColor write SetBoxColor;
property ActiveFrameColor: TColor read FActiveFrameColor write SetActiveFrameColor;
property PassiveFrameColor: TColor read FPassiveFrameColor write SetPassiveFrameColor;
property DrawFrame: Boolean read FDrawFrame write SetDrawFrame;
property DrawBoxes: Boolean read FDrawBoxes write SetDrawBoxes;
property ShowPos: Boolean read FShowPos write SetShowPos;
property ShowSize: Boolean read FShowSize write SetShowSize;
property InfoTextColor: TColor read FTextColor write SetTextColor;
property Focus: Boolean read FHasFocus write SetFocus;
property Font;
property OnClick;
property PopupMenu;
property OnMouseDown;
property OnMouseMove;
property OnMouseUp;
property OnDblClick;
property OnStartDrag;
property OnDragOver;
property OnDragDrop;
property OnEndDrag;
property OnPaint: TOnPaintEvent read FOnPaint write FOnPaint;
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('DPD', [TLinLine]);
end;

function between(PVal1,PVal2,PVal3: Integer):Boolean;
begin
if (PVal1 > PVal2) and (PVal1 < PVal3) then Result := True
else if (PVal1 > PVal3) and (PVal1 < PVal2) then result := True
else Result := False;
end;


constructor TLinLine.Create(AOwner: TComponent);
begin
inherited create(AOwner);
FBoxColor := clBlack;
FActiveFrameColor := clBlack;
FPassiveFrameColor := clGray;
FBoxSize := 5;
Height:=10; ////
Width:=20; ////
FHasInit:=false;
FDrawBoxes := True;
FDrawFrame := True;
FFrameType := ftOuter;
FAutoForeGround := True;
OnMouseMove := MouseMove;
end;

destructor TLinLine.Destroy;
begin
inherited Destroy;
end;

procedure TLinLine.Paint;
var
LHalfBox: Integer;
LRect,LClient: TRect;
Point1,Point2:Tpoint;

//StrTmp:string;
begin

if FAutoSize then SetBounds(Left,Top,Canvas.Textwidth(FCaption),Canvas.TextHeight(FCaption));
LRect := ClientRect;
if FFrameType = ftOuter then LHalfBox := 0
else if FFrameType = ftInner then LHalfBox := FBoxSize
else LHalfBox := (FBoxSize div 2);

if (not FHasInit) or (csDesigning in ComponentState) then
begin
FPoint1:=point(Left +FBoxSize ,top +FBoxSize );
FPoint2:=point(left+width -FBoxSize ,top+FBoxSize );
FHasInit:=true;
end;

//Calculate Client area that does not intercept the drag boxes;
LRect.Left := LRect.Left + LHalfBox + 1;
LRect.Right := LRect.Right - LHalfBox - 1;
LRect.Top := LRect.Top - LHalfBox;
LRect.Bottom := LRect.Bottom - LHalfBox - 1;

//client Area as defined by the frame drawn
LClient.Left := LHalfBox;
LClient.Top := LHalfBox;
LClient.right := width-1 - LHalfBox;
LClient.Bottom := Height - 1 - LHalfBox;

Point1:=ScreenToClient( Parent.ClientToScreen(FPoint1));
Point2:=ScreenToClient( Parent.ClientToScreen(FPoint2));
////MessageDlg(IntToStr(Point1.x)+':'+IntToStr(Point1.y)+':'+IntToStr(Point2.x)+':'+IntToStr(Point2.y), mtInformation, [mbOk], 0);

if assigned(FOnPaint) then FOnPaint(Self,Canvas,LClient);

//draw the frame
if (FHasFocus and DrawFrame) or (not FHasFocus and not FHideFrame) then begin
if FDrawFrame then begin
canvas.pen.color := FFrameColor;
Canvas.MoveTo(Point1.x,Point1.y+ LHalfBox);
Canvas.LineTo(Point2.x,Point2.y+ LHalfBox);
//Canvas.MoveTo(LClient.left,LClient.top);
//Canvas.LineTo(LClient.right,LClient.bottom);

end;
end;
//Draw the drag boxes
LHalfBox := (FBoxSize div 2);
if FDrawBoxes and (FHasFocus or (csDesigning in ComponentState)) then begin
Canvas.brush.color := FBoxColor;
Canvas.FillRect(rect(Point1.x - LHalfBox ,Point1.y - LHalfBox ,Point1.x + LHalfBox ,Point1.y + LHalfBox));
Canvas.FillRect(rect(Point2.x - LHalfBox ,Point2.y - LHalfBox ,Point2.x + LHalfBox ,Point2.y + LHalfBox));
end;

//Set the fixed font for the optional position information
Canvas.Font.Color := FTextColor;
Canvas.Brush.style := bsClear;
canvas.font.Name := 'MS Sans Serif';
canvas.font.Style := [];
canvas.font.height := 10;

if FShowPos and FHasFocus then begin
Canvas.Brush.style := bsClear;
Canvas.TextRect(LRect,FBoxSize+ 2,FBoxSize,'L:' + IntToStr(Left) + ' T:' + IntToStr(Top));
end;
if FShowSize and FHasFocus then begin
Canvas.TextRect(LRect,FBoxSize + 2,FBoxSize + (Canvas.font.Height * 1) + 3,'W:' + IntToStr(Width) + ' H:' + IntToStr(Height));
end;
Canvas.Font := Font;
Canvas.TextRect(LRect,(Width - Canvas.Textwidth(FCaption)) div 2,(Height - Canvas.TextHeight(FCaption)) div 2,FCaption);



//StrTmp:=IntToStr(Point1.x)+':'+IntToStr(Point1.y)+':'+IntToStr(Point2.x)+':'+IntToStr(Point2.y);
//Canvas.TextRect(LRect,2,2,Strtmp);

end;

procedure TLinLine.SetFrameType(Value: TFrameType);
begin
if FFrameType = Value then exit;
FFrameType := Value;
Invalidate;
end;

procedure TLinLine.SetBoxSize(Value: Integer);
begin
if Value = FBoxSize then exit;
if value < 2 then exit;
if value > 50 then exit;
FBoxSize := ((Value div 2) * 2) + 1; //保证是一个奇数
invalidate;
end;

procedure TLinLine.SetBoxColor(Value: Tcolor);
begin
if Value = FBoxColor then exit;
FBoxColor := Value;
invalidate;
end;

procedure TLinLine.SetActiveFrameColor(Value: Tcolor);
begin
if Value = FActiveFrameColor then exit;
FActiveFrameColor := Value;
invalidate;
end;

procedure TLinLine.SetPassiveFrameColor(Value: Tcolor);
begin
if Value = FPassiveFrameColor then exit;
FPassiveFrameColor := Value;
invalidate;
end;

procedure TLinLine.SetTextColor(Value: Tcolor);
begin
if Value = FTextColor then exit;
FTextColor := Value;
invalidate;
end;

procedure TLinLine.SetDrawFrame(Value: Boolean);
begin
if Value = FDrawFrame then exit;
FDrawFrame := Value;
invalidate;
end;


procedure TLinLine.SetDrawBoxes(Value: Boolean);
begin
if Value = FDrawBoxes then exit;
FDrawBoxes := Value;
invalidate;
end;

procedure TLinLine.SetShowPos(Value: boolean);
begin
if Value = FShowPos then exit;
FShowPos := Value;
invalidate;
end;

procedure TLinLine.SetShowSize(Value: Boolean);
begin
if Value = FShowSize then exit;
FShowSize := Value;
invalidate;
end;

procedure TLinLine.WMLMouseDown(var Message: TMessage);
begin
FPosX := Message.LParamLo;
FposY := Message.LParamHi;
if not NearLine(X,Y) then
begin
//向下层控件发送被点击的消息
end;
if FAutoForeGround then BringToFront;
if (Message.WParamLo <> 5) then begin
if FHasFocus =false then begin
RemoveAllFocus;
FHasFocus := True;
end;
end else //Shift按键被按下，要多选
FHasFocus := not FHasFocus;
if FHasFocus then begin
FFrameColor := FActiveFrameColor;
SetCapture(TForm(Parent).handle);
TForm(Parent).OnMouseMove := FormMouseMove;
end;
invalidate;
end;

procedure TLinLine.WMLMouseUp(var Message: TMessage);
begin
releaseCapture;
FPosX := -1;
FPosY := -1;
FDragBox := dbNone;
invalidate
end;

procedure TLinLine.FormMouseMove(Sender: TObject; Shift: TShiftState; X,Y: Integer);
var
LPoint: TPoint;
begin
//Translate coodinates to object
LPoint := ScreenToClient( Tform(Parent).ClientToScreen(point(X,Y)));
MouseMove(Sender,Shift,LPoint.X,Lpoint.Y);
end;

procedure TLinLine.MouseMove(Sender: TObject; Shift: TShiftState; X,Y: Integer);
var
Point1, Point2: TPoint;
HalfBoxSize,Temp:integer;
begin
//Prepare some variables
HalfBoxSize:=FBoxSize div 2;
Point1:=ScreenToClient( parent.ClientToScreen(FPoint1));
Point2:=ScreenToClient( parent.ClientToScreen(FPoint2));

if not (ssLeft in Shift) then begin
FDragBox := dbNone;
//Check if cursor is over any of the most left boxes
if (between(X,Point1.x - HalfBoxSize,Point1.x + HalfBoxSize) and between(Y,Point1.y - HalfBoxSize,Point1.y + HalfBoxSize)) then begin Cursor := crSizeALL; FDragBox := dbPoint1; end
else if (between(X,Point2.x - HalfBoxSize,Point2.x + HalfBoxSize) and between(Y,Point2.y - HalfBoxSize,Point2.y + HalfBoxSize)) then begin Cursor := crSizeALL; FDragBox := dbPoint2; end
else if (between(X,0,width) and between(Y,0,Height) ) or (FHasFocus and (ssShift in shift))then begin Cursor := crDefault; FDragBox := dbDrag; end; //用点到直线的距离来解决拖动问题
end else begin
//Make size changes if clicked
if (FPosX >= 0) and (FPosY >= 0 ) then begin
if FDragBox = dbPoint1 then begin
Point1.x:=X;Point1.y:= Y ;
FPoint1:=parent.ScreenToClient( ClientToScreen(Point1));
Temp:=Point1.x;
if Point2.x<Point1.x then begin
Point1.X:=Point2.x;
Point2.X:=Temp;
end;
Temp:=point1.Y;
if Point2.y<Point1.y then begin
Point1.Y:=Point2.y;
Point2.Y:=Temp;
end;

Point1:=parent.ScreenToClient( ClientToScreen(Point1));
Point2:=parent.ScreenToClient( ClientToScreen(Point2));
SetFrameBox(Point1.X - HalfBoxSize,Point1.Y - HalfBoxSize,Point2.X - Point1.X + FBoxSize,Point2.Y - Point1.Y + FBoxSize);
end else if FDragBox = dbPoint2 then begin
Point2.x:=X ;Point2.y:=Y ;
FPoint2:=parent.ScreenToClient( ClientToScreen(Point2));
Temp:=Point1.x;
if Point2.x<Point1.x then begin
Point1.X:=Point2.x;
Point2.X:=Temp;
end;
Temp:=point1.Y;
if Point2.y<Point1.y then begin
Point1.Y:=Point2.y;
Point2.Y:=Temp;
end;

Point1:=parent.ScreenToClient( ClientToScreen(Point1));
Point2:=parent.ScreenToClient( ClientToScreen(Point2));
SetFrameBox(Point1.X - HalfBoxSize,Point1.Y - HalfBoxSize,Point2.X - Point1.X + FBoxSize,Point2.Y - Point1.Y + FBoxSize);
end else if FDragBox = dbDrag then begin
FPoint1.X:=FPoint1.X+ X - FPosX;
FPoint1.Y:=FPoint1.Y+ Y - FPosY;
FPoint2.X:=FPoint2.X+ X - FPosX;
FPoint2.Y:=FPoint2.Y+ Y - FPosY;
SetFrameBox(Left - (FPosX - X),Top - (FPosY - Y),Width,Height);
invalidate;
end;
end;
end;
end;

function TLinLine.NearLine(X,Y: Integer):boolean;
begin
result := (self.Canvas.Pixels(X,Y)= self.FFrameColor) or (self.Canvas.Pixels(X-1,Y)= self.FFrameColor) or (self.Canvas.Pixels(X,Y -1)= self.FFrameColor) or (self.Canvas.Pixels(X+1,Y)= self.FFrameColor)or (self.Canvas.Pixels(X,Y+1)= self.FFrameColor) then

end;


procedure TLinLine.SetFrameBox(PLeft,PTop,PWidth,PHeight: Integer);
begin
if (PWidth < FBoxSize) or (PHeight < FBoxSize) then exit;
SetBounds(PLeft,PTop,PWidth,PHeight);
end;

procedure TLinLine.WMGetDlgCode(var Message: TWMGetDlgCode);
begin
inherited;
Message.Result := DLGC_WANTARROWS;
end;

procedure TLinLine.SetCaption(Value: String);
begin
if Value = FCaption then exit;
FCaption := Value;
invalidate;
end;

procedure TLinLine.SetHideFrame(Value: Boolean);
begin
if Value = FHideFrame then exit;
FHideFrame := Value;
Invalidate;
end;

procedure TLinLine.SetAutoSize(Value: Boolean);
begin
if Value = FAutoSize then exit;
FAutoSize := Value;
invalidate;
end;

procedure TLinLine.RemoveAllFocus;
//var
// i: Integer;
// LRectBox: TLinLine;
begin
SendMessage (parent.Handle, WM_RBUTTONDOWN,0, MakeLong (0, 0));
application.ProcessMessages;
application.ProcessMessages;
// for i := 0 to Owner.ComponentCount - 1 do begin
// if Owner.Components is TLinLine then begin
// LRectBox := TLinLine(Owner.Components);
// if LRectBox.FHasFocus then begin
// LRectBox.FHasFocus := False;
// LRectBox.Invalidate;
// end;
// end;
// end;
end;

procedure TLinLine.SetFocus(Value: Boolean);
begin
if Value = FHasFocus then exit;
FHasFocus := Value;
invalidate;
end;


end.

{*******************************************************
TZWShape
ver : 1.0
description : This is a shape like component that can
be moved and has bitmap background.
It's free to use this component, but if
you do some changes to it, please send the
new version to me.

Copyright (c) 2002 zhuwei <zw84611@sina.com>
*******************************************************}

unit ZWShape;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ExtCtrls;

type
TZWShape = class(TShape)
private
{ Private declarations }
old_x,old_y: integer;
can_move: boolean;
PicLeft,PicTop,TexLeft,TexTop: integer;
//ImgRect: TRect;

FPicture: TPicture;
FNumber: Cardinal;
FTouch: TNotifyEvent;

procedure SetPicture(Value: TPicture);
procedure SetNumber(Value: Cardinal);
//procedure WMEraseBkgnd(var Msg: TMessage); message WM_ERASEBKGND;
//procedure WMSize(var Msg: TWMSize); message WM_SIZE;
protected
{ Protected declarations }
procedure Paint; override;

public
{ Public declarations }
TextX, TextY: integer;
//Ctr: Ctr_T;
neighbor_x,neighbor_y:integer;
constructor Create(AOwner: TComponent);override;
destructor Destroy;override;
procedure MouseDown(Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);override;
procedure MouseUp(Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);override;
procedure MouseMove(Shift: TShiftState; X,
Y: Integer); override;
function CenterX:integer;
function CenterY:integer;
published
{ Published declarations }
property Picture: TPicture read FPicture write SetPicture;
property Number: Cardinal read FNumber write SetNumber default 0;
property OnTouch : TNotifyEvent read FTouch write FTouch;
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('220', [TZWShape]);
end;

constructor TZWShape.Create(AOwner: TComponent);
begin

inherited Create(AOwner);
can_move := false;
FPicture := TPicture.Create;
//Shape := stCircle;
Canvas.Font.Color := ClWhite;
Canvas.Font.Style := Canvas.Font.Style + [fsBold];
TextX := 0;
TextY := 0;
TexLeft := width div 2 - Canvas.Font.Height div 2 + TextX;
TexTop := height div 2 - Canvas.Font.Size div 2 + TextY;

end;


procedure TZWShape.MouseDown(Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
begin
old_x := x;
old_y := y;
can_move := true;
cursor := crSizeAll;
if assigned(OnMouseDown) then OnMouseDown(self,Button,shift,x,y);
end;

procedure TZWShape.MouseUp(Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
begin

can_move := false;
cursor := crDefault;;
if assigned(OnMouseUp) then OnMouseUp(self,Button,shift,x,y);

end;

procedure TZWShape.MouseMove(Shift: TShiftState; X,
Y: Integer);
{var TemShape: TZWShape;
i: integer;}
begin
cursor := crSizeAll;
if can_move then
begin
Left := Left+x-old_x;
Top := Top+y-old_y;
end;
if assigned(OnMouseMove) then OnMouseMove(self,shift,x,y);

end;

procedure TZWShape.Paint;
var
SavedBrushStyle : TBrushStyle;
SavedBrushColor: TColor;
begin
SavedBrushStyle := Canvas.Brush.Style;
SavedBrushColor := Canvas.Brush.Color;
try
Canvas.Brush.Style := bsFDiagonal; //注意这样就能画出斜线！
Canvas.Brush.Color := RGB(50,190,60); //clGreen;
Canvas.Pen.Color := Parent.Color; //这样就能去掉边框
Canvas.Rectangle(ClientRect); //画出来

if assigned(FPicture) then
begin
//Canvas.StretchDraw(ImageRect,FPicture.Graphic);
Canvas.Draw(PicLeft,PicTop,Fpicture.Bitmap);

Canvas.TextOut(TexLeft,TexTop,inttostr(FNumber));
//if assigned(OnTouch) then OnTouch(self);
end;
finally
Canvas.Brush.Style := SavedBrushStyle;
Canvas.Brush.Color := SavedBrushColor;
end;
end;

{procedure TZWShape.WMSize(var Msg: TWMSize);
begin
inherited;
DeleteObject(FHRgn);
FHRgn := CreateEllipticRgn(ClientRect.Left, ClientRect.Top,
ClientRect.Right, ClientRect.Bottom);
SetWindowRgn(Handle, FHRgn, True);
end;}

procedure TZWShape.SetPicture(Value: TPicture);
begin

FPicture.Assign(Value);

//set transparent
Fpicture.Bitmap.TransparentMode := tmAuto;
Fpicture.Bitmap.TransparentColor := Fpicture.BitMap.canvas.pixels[5,5];
Fpicture.Bitmap.Transparent := true;

PicLeft := width div 2 - Value.Bitmap.Width div 2;
PicTop := height div 2 - Value.Bitmap.Height div 2;

TexLeft := width div 2 - Canvas.Font.Height div 2 + TextX;
TexTop := height div 2 - Canvas.Font.Size div 2 + TextY;

invalidate;

end;

procedure TZWShape.SetNumber(Value: Cardinal);
begin
FNumber := value;
end;

{procedure TZWShape.WMEraseBkgnd(var Msg: TMessage);
begin

inherited;
if assigned(OnTouch) then OnTouch(self);
end;}

function TZWShape.CenterX:integer;
begin
Result:=left + (width div 2);
end;

function TZWShape.CenterY:integer;
begin
Result:=top + (height div 2);
end;

destructor TZWShape.Destroy;
begin
FPicture.Free;
inherited Destroy;
end;

end.

Canvas.Pen.Color := Parent.Color; //这样就能去掉边框
zw84611: 这个不好,不知你用没用过VB,它那个线条的Parent可能是窗体,
但它在最上层,所以它下面的可能会有其它的控件,你那个颜色不就不能隐藏了吗?
最好是透明的了,呵呵,

to arhaha，zw84611:
谢谢您们，我试过了，还是有矩形区域，该区域虽然没有把其他控件挡住
却把其他控件的鼠标事件挡住了，可我只要一条线。不知怎么办。

up

To: LiGen
看到“//向下层控件发送被点击的消息”了么？
这儿就是要处理没有点中直线（但鼠标仍在直线矩形区内）要做的事，
处理好了，就可以克服这个问题了。