マウスで移動するカーソルの X 位置に垂直線を描画しようとしています。この行は、フォームのすべてのコンポーネントの「上」に描画する必要があります。これを実現するために、 https ://stackoverflow.com/a/4481835 で提供されているコードを使用しています。
完全な形式のコードは次のとおりです。
unit UDemo;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, AdvSmoothTimeLine, ImgList, StdCtrls, ComCtrls, ExtCtrls,
System.ImageList, Vcl.AppEvnts;
type
TForm235 = class(TForm)
ImageList1: TImageList;
Panel1: TPanel;
DateTimePicker1: TDateTimePicker;
Edit1: TEdit;
Button1: TButton;
ComboBox1: TComboBox;
ApplicationEvents1: TApplicationEvents;
Button2: TButton;
Panel2: TPanel;
Panel3: TPanel;
Panel4: TPanel;
Panel5: TPanel;
Panel6: TPanel;
Panel7: TPanel;
Panel8: TPanel;
Panel9: TPanel;
Panel10: TPanel;
Panel11: TPanel;
Panel12: TPanel;
procedure FormCreate(Sender: TObject);
procedure ApplicationEvents1Message(var Msg: tagMSG; var Handled: Boolean);
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
private
{ Private declarations }
FSelecting : Boolean;
FSelectRect : TRect;
FFixedLineX : Integer;
FDragLineX : Integer;
FMousePt, FOldPt: TPoint;
procedure WM_PAINT(var Msg: TWmPaint); message WM_PAINT;
public
{ Public declarations }
end;
var
Form235: TForm235;
implementation
{$R *.dfm}
procedure TForm235.ApplicationEvents1Message(var Msg: tagMSG;
var Handled: Boolean);
var
R: TRect;
Pt: TPoint;
begin
if Msg.message = WM_MOUSEMOVE then begin
// assume no drawing (will test later against the point).
// also, below RedrawWindow will cause an immediate WM_PAINT, this will
// provide a hint to the paint handler to not to draw anything yet.
FMousePt := Point(-1, -1);
// first, if there's already a previous rectangle, invalidate it to clear
if (FOldPt.X > 0) and (FOldPt.Y > 0) then begin
R := Rect(FOldPt.X -1, 0, FOldPt.X + 1, self.Height);
InvalidateRect(Handle, @R, True);
// invalidate childs
// the pointer could be on one window yet parts of the rectangle could be
// on a child or/and a parent, better let Windows handle it all
RedrawWindow(Handle, @R, 0, RDW_INVALIDATE or RDW_UPDATENOW or RDW_ALLCHILDREN);
end;
// is the message window our form?
if Msg.hwnd = Handle then
// then save the bottom-right coordinates
FMousePt := SmallPointToPoint(TSmallPoint(Msg.lParam))
else begin
// is the message window one of our child windows?
if GetAncestor(Msg.hwnd, GA_ROOT) = Handle then begin
// then convert to form's client coordinates
Pt := SmallPointToPoint(TSmallPoint(Msg.lParam));
windows.ClientToScreen(Msg.hwnd, Pt);
FMousePt := ScreenToClient(Pt);
end;
end;
// will we draw? (test against the point)
if PtInRect(ClientRect, FMousePt) then begin
R := Rect(FMousePt.X - 1, 0, FMousePt.X +1, self.Height);
InvalidateRect(Handle, @R, False);
end;
end;
end;
procedure TForm235.WM_PAINT(var Msg: TWmPaint);
var
DC: HDC;
Rgn: HRGN;
begin
inherited;
if (FMousePt.X > 0) and (FMousePt.Y > 0) then begin
// save where we draw, we'll need to erase before we draw an other one
FOldPt := FMousePt;
// get a dc that could draw on child windows
DC := GetDCEx(Handle, 0, DCX_PARENTCLIP);
// don't draw on borders & caption
Rgn := CreateRectRgn(ClientRect.Left, ClientRect.Top,
ClientRect.Right, ClientRect.Bottom);
SelectClipRgn(DC, Rgn);
DeleteObject(Rgn);
// draw a red rectangle
SelectObject(DC, GetStockObject(DC_BRUSH));
SetDCBrushColor(DC, ColorToRGB(clBlack));
FillRect(DC, Rect(FMousePt.X - 1, 0, FMousePt.X +1, self.Height ), 0);
ReleaseDC(Handle, DC);
end;
end;
procedure TForm235.FormCreate(Sender: TObject);
begin
FSelectRect := TRect.Create(TPoint.Create(self.Left, self.Top));
end;
procedure TForm235.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
FSelectRect.Bottom := self.Height;
FSelectRect.Right := X;
FDragLineX := X;
self.Repaint;
end;
end.
1つのことを除いて、私が望んでいたように機能します。マウスを左右に動かしたり (X 位置を変更したり) すると、線が常に画面から描画されたり、描画されなかったりするため、ちらつきます。比較的速く移動すると、行がカーソルの「遅れ」に気付くこともあります。
この視覚効果を改善する方法を知っている人はいますか? 別の技術/アルゴリズム? どこかに専用コンポーネント？