我在一个相当大的应用程序中自定义绘制了我的标题栏,它有多种形式,并决定尝试通过自己处理一些消息并在处理 WM_NCPAINT 时将绘图以老式方式进行。
这幅画本身进展顺利,基本上可以工作。一件不起作用的事情是绘制 TMainMenu。要么我有默认的 WM_NCACTIVATE 处理程序在绘制之前绘制整个非客户区(我必须在我的 WM_NCPAINT 处理程序中执行 WM_NCACTIVATE 消息),这会导致闪烁,这似乎无济于事。或者我可以尝试让 WM_NCPAINT 的默认处理程序仅绘制包含 TMainMenu 的 Rect,这会产生平滑的结果,但不会重新绘制菜单。
我的问题是:
- 当我自己处理 WM_NCPAINT 时,如何才能有一个 TMainMenu 并且只重绘一个 TMainmenu?
我已经尝试了几次,我认为我走在正确的道路上,但正在碰壁;我对自己在做什么没有足够的了解,似乎也找不到关于它的明确文档。我的代码中最重要的部分是:
RedrawWindow(Handle, nil, MenuRegion, RDW_INVALIDATE or RDW_FRAME or RDW_NOERASE or RDW_ALLCHILDREN or RDW_UPDATENOW);
我认为这正是问题所在。(或者更确切地说,是我计算“MenuRegion”的代码。我只是不知道它是否出错是因为我使用了错误的坐标系,或者是因为我正在以完全错误的方式处理这个问题。
这是我的代码的简化版本,它将在 delphi (xe3) 中“按原样”编译和运行:
unit Unit3;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Menus;
type
TForm3 = class(TForm)
private
FDrawMenu: Boolean;
function CalcFrameRegion: HRGN;
function CalcMenuRegion: HRGN;
procedure DrawMenu;
procedure FormFrame(minimal: Boolean = false);
procedure WMNCActivate(var message: TWMNCActivate); message WM_NCACTIVATE;
procedure WMNCPaint(var message: TMessage); message WM_NCPAINT;
procedure WMSIZE(var message : TWMSIZE); message WM_SIZE;
constructor Create(AOwner: TComponent); override;
public
{ Public declarations }
end;
var
Form3: TForm3;
implementation
{$R *.dfm}
{ TForm3 }
function TForm3.CalcFrameRegion: HRGN;
var
YCaption, YFrame, XFrame: Integer;
begin
YCaption := GetSystemMetrics(SM_CYCaption);
YFrame := GetSystemMetrics(SM_CYFRAME);
XFrame := GetSystemMetrics(SM_CXFRAME);
Result := CreateRectRgn(0, 0, YCaption + YFrame, Width);
Result := Result + CreateRectRgn(0, 0, Height, XFrame);
Result := Result + CreateRectRgn(0, Height - YFrame, Width, Height);
Result := Result + CreateRectRgn(Width - XFrame, 0, Width, Height);
end;
function TForm3.CalcMenuRegion: HRGN;
var
XFrame, YFrame, YCaption, YMenu: Integer;
begin
XFrame := GetSystemMetrics(SM_CXFRAME);
YFrame := GetSystemMetrics(SM_CYFRAME);
YCaption := GetSystemMetrics(SM_CYCAPTION);
YMenu := GetSystemMetrics(SM_CYMENU);
Result := CreateRectRgn(XFrame, YFrame + YCaption, Width - XFrame, YFrame + YCaption + YMenu);
end;
constructor TForm3.Create(AOwner: TComponent);
var
testItem: TMenuItem;
begin
inherited;
// Creating a MainMenu and attatching it to the form.
Menu := TMainMenu.Create(self);
// The menu need san item.
testItem := TMenuItem.Create(Menu);
testItem.Caption := 'test';
Menu.Items.Add(testItem);
FDrawMenu := false;
end;
procedure TForm3.FormFrame(minimal: Boolean);
var
YCaption, YFrame, XFrame: Integer;
begin
YCaption := GetSystemMetrics(SM_CYCaption);
YFrame := GetSystemMetrics(SM_CYFRAME);
XFrame := GetSystemMetrics(SM_CXFRAME);
Canvas.Handle := GetWindowDC(Handle);
Canvas.Pen.Style := psClear;
Canvas.Brush.Style := bsSolid;
Canvas.Brush.Color := clRed;
if not minimal then begin
Canvas.Rectangle(0, 0, Width + 1, YCaption + YFRame + 1);
Canvas.Rectangle(0, YCaption + YFRame, XFrame + 1, Height + 1);
Canvas.Rectangle(XFrame, Height - YFrame, Width + 1, Height + 1);
Canvas.Rectangle(Width - XFrame, YCaption + YFRame, Width + 1, Height - YFrame + 1);
end;
end;
procedure TForm3.DrawMenu;
var
MenuRegion: HRGN;
begin
if Assigned(Menu) then begin
MenuRegion := CalcMenuRegion;
FDrawMenu := true; // Make sure the inherited handler gets called.
// Force a redraw of the region defined by MenuRegion.
RedrawWindow(Handle, nil, MenuRegion,
RDW_INVALIDATE or RDW_FRAME or RDW_NOERASE or RDW_ALLCHILDREN or RDW_UPDATENOW);
FDrawMenu := false; // Use the FormFrame function again.
end;
end;
procedure TForm3.WMNCActivate(var message: TWMNCActivate);
begin
FormFrame;
message.Result := 1; // This makes sure the message gets handled properly.
end;
procedure TForm3.WMNCPaint(var message: TMessage);
begin
if FDrawMenu then
inherited // Gets called when the Menu has to be drawn.
else
FormFrame; // Gets called in all other cases.
end;
procedure TForm3.WMSIZE(var message: TWMSIZE);
begin
inherited;
DrawMenu;
end;
end.