Question

我正在编写一个自定义控件，它只是一个非客户区域的容器。在该非客户区域内，有一个小区域是一个按钮，其余区域是透明的。图纸不是一个精确的矩形。

到目前为止，我已经中途工作了。问题是它不会预先计算非客户区域，除非我做一个小的调整，比如重新调整它。

我已经跟踪了许多描述如何实现这一目标的资源。我处理WM_NCCALCSIZE的实施与＆＃34;工作＆＃34;或多或少相同。我找到的例子。但是，当首次创建控件时，它根本不会计算。当我在我的消息处理程序（WMNCCalcSize）中放置一个断点时，根据我发现的示例，我应该首先检查Msg.CalcValidRects，并且只进行我的计算如果是True。但是在调试运行时时，它是False，因此计算没有完成。

在设计时，如果我重新调整控件的大小，那么它决定正确计算。它仍然不完美（这段代码仍在使用中），但在我调整它之前，似乎并没有设置非客户区域。此外，在运行时，如果我调整代码中的大小，它仍然无法计算。

顶部的图像是最初创建/显示表单的时间。第二个是在我重新调整它的大小之后。注意测试按钮，它对齐alLeft。所以最初，它消耗了应该是非客户的区域。

如果我将支票if Msg.CalcValidRects then begin注释掉，那么它会正确计算。但是我看到每个例子都在做这个检查，我很确定它是需要的。

我做错了什么以及如何让它一直计算非客户区域？

unit FloatBar;

interface

uses
  System.Classes, System.SysUtils, System.Types,
  Vcl.Controls, Vcl.Graphics, Vcl.Forms,
  Winapi.Windows, Winapi.Messages;

type
  TFloatBar = class(TCustomControl)
  private
    FCollapsed: Boolean;
    FBtnHeight: Integer;
    FBtnWidth: Integer;
    procedure RepaintBorder;
    procedure PaintBorder;
    procedure SetCollapsed(const Value: Boolean);
    function BtnRect: TRect;
    procedure SetBtnHeight(const Value: Integer);
    procedure SetBtnWidth(const Value: Integer);
    function TransRect: TRect;
  protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
    procedure WMNCPaint(var Message: TWMNCPaint); message WM_NCPAINT;
    procedure WMNCHitTest(var Message: TWMNCHitTest); message WM_NCHITTEST;
    procedure WMNCCalcSize(var Msg: TWMNCCalcSize); message WM_NCCALCSIZE;
    procedure Paint; override;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure Repaint; override;
    procedure Invalidate; override;
  published
    property BtnWidth: Integer read FBtnWidth write SetBtnWidth;
    property BtnHeight: Integer read FBtnHeight write SetBtnHeight;
    property Collapsed: Boolean read FCollapsed write SetCollapsed;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Float Bar', [TFloatBar]);
end;

{ TFloatBar }

constructor TFloatBar.Create(AOwner: TComponent);
begin
  inherited;
  ControlStyle:= [csAcceptsControls,
    csCaptureMouse,
    csDesignInteractive,
    csClickEvents,
    csReplicatable,
    csNoStdEvents
    ];
  Width:= 400;
  Height:= 60;
  FBtnWidth:= 50;
  FBtnHeight:= 20;
  FCollapsed:= False;
end;

procedure TFloatBar.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  with Params.WindowClass do
    Style := Style and not (CS_HREDRAW or CS_VREDRAW);
end;

destructor TFloatBar.Destroy;
begin

  inherited;
end;

procedure TFloatBar.Invalidate;
begin
  inherited;
  RepaintBorder;
end;

procedure TFloatBar.Repaint;
begin
  inherited Repaint;
  RepaintBorder;
end;

procedure TFloatBar.RepaintBorder;
begin
  if Visible and HandleAllocated then
    Perform(WM_NCPAINT, 0, 0);
end;

procedure TFloatBar.SetBtnHeight(const Value: Integer);
begin
  FBtnHeight := Value;
  Invalidate;
end;

procedure TFloatBar.SetBtnWidth(const Value: Integer);
begin
  FBtnWidth := Value;
  Invalidate;
end;

procedure TFloatBar.SetCollapsed(const Value: Boolean);
begin
  FCollapsed := Value;
  Invalidate;
end;

procedure TFloatBar.WMNCPaint(var Message: TWMNCPaint);
begin
  inherited;
  PaintBorder;
end;

procedure TFloatBar.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
  Message.Result := 1;
end;

procedure TFloatBar.WMNCCalcSize(var Msg: TWMNCCalcSize);
var
  lpncsp: PNCCalcSizeParams;
begin
  if Msg.CalcValidRects then begin            //<------ HERE --------
    lpncsp := Msg.CalcSize_Params;
    if lpncsp = nil then Exit;
    lpncsp.rgrc[0].Bottom:= lpncsp.rgrc[0].Bottom-FBtnHeight;
    Msg.Result := 0;
  end;
  inherited;
end;

function TFloatBar.BtnRect: TRect;
begin
  //Return a rect where the non-client collapse button is to be...
  Result:= Rect(ClientWidth-FBtnWidth, ClientHeight, ClientWidth, ClientHeight+FBtnHeight);
end;

function TFloatBar.TransRect: TRect;
begin
  //Return a rect where the non-client transparent area is to be...
  Result:= Rect(0, ClientHeight, ClientWidth, ClientHeight+FBtnHeight);
end;

procedure TFloatBar.WMNCHitTest(var Message: TWMNCHitTest);
var
  P: TPoint;
  C: TCursor;
begin
  C:= crDefault; //TODO: Find a way to change cursor elsewhere...
  P:= Point(Message.XPos, Message.YPos);
  if PtInRect(BtnRect, P) then begin
    Message.Result:= HTCLIENT;
    C:= crHandPoint;
  end else
  if PtInRect(TransRect, P) then
    Message.Result:= HTTRANSPARENT
  else
    inherited;
  Screen.Cursor:= C;
end;

procedure TFloatBar.Paint;
begin
  inherited;

  //Paint Background
  Canvas.Brush.Style:= bsSolid;
  Canvas.Pen.Style:= psClear;
  Canvas.Brush.Color:= Color;
  Canvas.FillRect(Canvas.ClipRect);

  Canvas.Pen.Style:= psSolid;
  Canvas.Pen.Width:= 3;
  Canvas.Brush.Style:= bsClear;
  Canvas.Pen.Color:= clBlue;

  Canvas.MoveTo(0, 0);
  Canvas.LineTo(ClientWidth, 0); //Top
  Canvas.LineTo(ClientWidth, ClientHeight+FBtnHeight); //Right
  Canvas.LineTo(ClientWidth-FBtnWidth, ClientHeight+FBtnHeight); //Bottom of Button
  Canvas.LineTo(ClientWidth-FBtnWidth, ClientHeight); //Left of Button
  Canvas.LineTo(0, ClientHeight); //Bottom
  Canvas.LineTo(0, 0);

end;

procedure TFloatBar.PaintBorder;
begin
  Canvas.Handle:= GetWindowDC(Handle);
  try

    //TODO: Paint "transparent" area by painting parent...


    //Paint NC button background
    Canvas.Brush.Style:= bsSolid;
    Canvas.Pen.Style:= psClear;
    Canvas.Brush.Color:= Color;
    Canvas.Rectangle(ClientWidth-FBtnWidth, ClientHeight, ClientWidth, ClientHeight+FBtnHeight);

    //Paint NC button border
    Canvas.Pen.Style:= psSolid;
    Canvas.Pen.Width:= 3;
    Canvas.Brush.Style:= bsClear;
    Canvas.Pen.Color:= clBlue;
    Canvas.MoveTo(ClientWidth, ClientHeight);
    Canvas.LineTo(ClientWidth, ClientHeight+FBtnHeight);
    Canvas.LineTo(ClientWidth-FBtnWidth, ClientHeight+FBtnHeight);
    Canvas.LineTo(ClientWidth-FBtnWidth, ClientHeight);

    //Paint NC Button Chevron      //TODO: Calculate chevron size/position
    if FCollapsed then begin
      Canvas.MoveTo(ClientWidth-30, ClientHeight+7);
      Canvas.LineTo(ClientWidth-25, ClientHeight+13);
      Canvas.LineTo(ClientWidth-20, ClientHeight+7);
    end else begin
      Canvas.MoveTo(ClientWidth-30, ClientHeight+13);
      Canvas.LineTo(ClientWidth-25, ClientHeight+7);
      Canvas.LineTo(ClientWidth-20, ClientHeight+13);
    end;
  finally
    ReleaseDC(Handle, Canvas.Handle);
  end;
end;

end.

Answer 1

......我应该先检查一下Msg.CalcValidRects，然后再做我的计算是否为True。

你错了。该消息的机制有点复杂，documentation可能会稍微混淆，试图解释消息操作的两种不同模式（wParam是或否）。与您的案例相关的部分是lParam的第二段：

如果wParam FALSE ，则lParam指向 RECT 结构。进入时，结构包含窗口的建议窗口矩形。上退出时，结构应该包含屏幕坐标相应的窗口客户区。

您会在VCL中找到这个简单表单的大量用法示例，其中wParam根本未经过检查，例如TToolWindow.WMNCCalcSize，TCustomCategoryPanel.WMNCCalcSize等。

（请注意，当NCCALCSIZE_PARAMS.rgrc为false时，wParam甚至不是矩形数组，但由于您在假定的第一个矩形上运行，所以你很好。）

具有非客户区域的自定义控制 - 最初不会计算

1 个答案: