我有一个 TForm，我将“位置”设置为 poMainFormCenter。
当我打开该表单时，它会正确显示在主表单的中心。
但是，在多个屏幕（2 个监视器）上，当我将应用程序放在辅助监视器中时，该窗体不会显示在主窗体的中心。
它仍显示在主监视器中，位于屏幕边缘。
我的应用程序没有什么花哨的，我只设置了 Position 属性。
有人知道怎么修这个东西吗？
我正在使用 Delphi 7 和 Windows XP SP3。
问问题
11885 次
6 回答
6
除了看鼠标之外，Jlouro 的想法是正确的。Screen.Monitors[] 包含每个屏幕的信息。
我有一个标准程序，它通过监视器列表并找出左上角的位置来决定将它放在哪个监视器上。虽然我的代码没有居中（我只是在确保窗口完全位于它出现的任何监视器之后），但想法保持不变。请注意，您必须考虑窗口不显示在任何监视器上的情况——我通过将其扔到第一个监视器来处理这种情况。（当保存的位置在一个不再存在的监视器上时，就会发生这种情况——要么被删除，要么在另一台机器上运行。）
自从我搞砸这个已经很长时间了，它并没有给我带来任何麻烦，所以我没有在比 XP/Delphi 7 更新的任何东西上测试它。
请注意，这只是为了确保表单是可见的并且完全在一台显示器上，不会尝试将其居中。
Function PointInBox(x, y, x1, y1, x2, y2 : Integer) : Boolean;
Begin
Result := (X >= X1) And (X <= X2) And (Y >= Y1) And (Y <= Y2);
End;
Function Overlapping(x11, y11, x12, y12, x21, y21, x22, y22 : Integer) : Boolean;
Var
tx1, ty1, tx2, ty2 : Integer;
Begin
Tx1 := Max(x11, x21);
Tx2 := Min(x12, x22);
Ty1 := Max(y11, y21);
Ty2 := Min(y12, y22);
Result := (Tx1 < Tx2) And (Ty1 < Ty2);
End;
Function GetWhere(Form : TForm) : Integer;
Var
Loop : Integer;
Where : Integer;
Begin
Where := -1;
For Loop := 1 to Screen.MonitorCount do
With Screen.Monitors[Loop - 1] do
If PointInBox(Form.Left, Form.Top, Left, Top, Left + Width - 1, Top + Height - 1) then
Where := Loop - 1;
If Where = -1 then // Top left corner is wild, check for anything
For Loop := 1 to Screen.MonitorCount do
With Screen.Monitors[Loop - 1] do
If Overlapping(Form.Left, Form.Top, Form.Left + Form.Width - 1, Form.Top + Form.Height - 1, Left, Top, Left + Width - 1, Top + Height - 1) then
Where := Loop - 1;
Result := Where;
End;
Procedure GetLimits(Where : Integer; var X, Y, WWidth, WHeight : Integer);
Var
R : TRect;
Begin
If Where < 0 then
Begin
SystemParametersInfo(Spi_GetWorkArea, 0, @R, 0);
X := R.Left;
Y := R.Top;
WWidth := R.Right - R.Left + 1;
WHeight := R.Bottom - R.Top + 1;
End
Else With Screen.Monitors[Where] do
Begin
X := Left;
Y := Top;
WWidth := Width;
WHeight := Height;
End;
End;
Procedure EnsureValidDisplay(Form : TForm);
Var
Left : Integer;
Top : Integer;
Width : Integer;
Height : Integer;
Where : WindowPlacement;
Begin
GetLimits(GetWhere(Form), Left, Top, Width, Height);
Where.Length := SizeOf(Where);
Where.Flags := 0;
GetWindowPlacement(Form.Handle, @Where);
If Form.Left < Left then
Where.rcNormalPosition.Left := Left
Else If Form.Left + Form.Width > Left + Width then
Where.rcNormalPosition.Left := Left + Width - Form.Width;
If Form.Top < Top then
Where.rcNormalPosition.Top := Top
Else If Form.Top + Form.Height > Top + Height then
Where.rcNormalPosition.Top := Top + Height - Form.Height;
If Form.Width > Width then
Where.rcNormalPosition.Right := Where.rcNormalPosition.Left + Width
Else
Where.rcNormalPosition.Right := Where.rcNormalPosition.Left + Form.Width;
If Form.Height > Height then
Where.rcNormalPosition.Bottom := Where.rcNormalPosition.Top + Height
Else
Where.rcNormalPosition.Bottom := Where.rcNormalPosition.Top + Form.Height;
SetWindowPlacement(Form.Handle, @Where);
End;
于 2012-04-10T17:31:19.457 回答
3
这里的其他答案都没有首先提到问题的原因，这是 VCL 中的一个错误。从我系统上的 forms.pas 中，为了简洁起见，做了一些删减：
procedure TCustomForm.CMShowingChanged(var Message: TMessage);
var
X, Y: Integer;
NewActiveWindow: HWnd;
CenterForm: TCustomForm;
begin
if (FPosition = poScreenCenter) or
((FPosition = poMainFormCenter) and (FormStyle = fsMDIChild)) then
begin
if FormStyle = fsMDIChild then
begin
X := (Application.MainForm.ClientWidth - Width) div 2;
Y := (Application.MainForm.ClientHeight - Height) div 2;
end else
begin
X := (Screen.Width - Width) div 2;
Y := (Screen.Height - Height) div 2;
end;
if X < 0 then X := 0;
if Y < 0 then Y := 0;
SetBounds(X, Y, Width, Height);
if Visible then SetWindowToMonitor;
end
else if FPosition in [poMainFormCenter, poOwnerFormCenter] then
begin
CenterForm := Application.MainForm;
if (FPosition = poOwnerFormCenter) and (Owner is TCustomForm) then
CenterForm := TCustomForm(Owner);
if Assigned(CenterForm) then
begin
X := ((CenterForm.Width - Width) div 2) + CenterForm.Left;
Y := ((CenterForm.Height - Height) div 2) + CenterForm.Top;
end else
begin
X := (Screen.Width - Width) div 2;
Y := (Screen.Height - Height) div 2;
end;
if X < 0 then X := 0;
if Y < 0 then Y := 0;
SetBounds(X, Y, Width, Height);
if Visible then SetWindowToMonitor;
end
else if FPosition = poDesktopCenter then
begin
if FormStyle = fsMDIChild then
begin
X := (Application.MainForm.ClientWidth - Width) div 2;
Y := (Application.MainForm.ClientHeight - Height) div 2;
end else
begin
X := (Screen.DesktopWidth - Width) div 2;
Y := (Screen.DesktopHeight - Height) div 2;
end;
if X < 0 then X := 0;
if Y < 0 then Y := 0;
SetBounds(X, Y, Width, Height);
end;
这个错误的关键似乎是以下片段，在函数中重复了几次：
if X < 0 then X := 0;
if Y < 0 then Y := 0;
So, if you try to center the form on a monitor to the left or above the primary monitor (remember that origin is at upper-left corner of primary monitor), it will get snapped to the primary monitor from this check. It seems that this code wasn't updated when VCL was updated to support multiple monitors. Which is amusing, since two lines later are calls to SetWindowToMonitor.
The code was probably there from when only single monitors were supported in Windows 95 / Windows NT 4.0. In a single-monitor environment, negative coordinates are always off-screen, and it makes sense to snap to onscreen coordinates, which are always positive. However, the code fails miserably in the presence of multiple monitors, which allows for negative onscreen coordinates.
Working around this bug is left as an exercise to the reader. There are a number of possible solutions.
于 2013-05-01T20:12:43.393 回答
2
我在创建事件中使用它：
C_FollowMouse :BOOLEAN=TRUE; // Global Const - Follow mouse. Opens App in the monitor where the mouse is.
C_Monitor :BYTE=0; // Default Monitor
Procedure TfrmMain.ScreenPOS;
Var pt:tpoint;
_lMonitor :BYTE;
Begin
if NOT Screen.MonitorCount > 1 then Begin
Position := poScreenCenter;
Exit;
End;
_lMonitor := C_Monitor;
if C_FollowMouse then Begin
_lMonitor := 0;
getcursorpos(pt);
if pt.X < 0 then
_lMonitor := 1;
End;
Left:= Screen.Monitors[_lMonitor].Left + Round( (Screen.Monitors[_lMonitor].Width - Width ) / 2);
Top:=Screen.Monitors[_lMonitor].Top + Round( (Screen.Monitors[_lMonitor].Height - Height ) / 2)
End;
刚刚用2台显示器测试过。是我的全部。如果您有更多，请发回更改。
于 2012-04-10T15:18:31.683 回答
2
我可以通过在 OnActivate 表单上使用以下代码来解决此问题：
Self.Left := MainForm.Left + ((MainForm.Width div 2) - (Self.Width div 2)); Self.Top := MainForm.Top + ((MainForm.Height div 2) - (Self.Height div 2));
MainForm 是应用程序的“主要”形式。
于 2012-04-19T13:56:35.043 回答
0
Hey David you can use poOwnerFormCenter Instead of poMainFormCenter. It will Solve your problem. Read this post.
于 2015-06-04T09:58:59.737 回答
0
I know this is an old thread but I was just trying to fix this problem with regards to modal dialog forms and found the following to work (after reading the above post by James Johnson)
On OnActivate:
X := (Application.MainForm.ClientWidth - Width) div 2;
Y := (Application.MainForm.ClientHeight - Height) div 2;
self.SetBounds(x,y,self.width,self.height);
于 2020-02-27T10:49:49.987 回答