如何防止彈出表單超出螢屏區域？

我正在使用 Forms 構建一個兩列自定義背景關系選單布局。
我將自定義背景關系選單形式的類命名為ContextMenu.

我創建了一個標志函式來檢查它是否在呼叫時超過了設備螢屏尺寸。
僅超出設備螢屏的長度或僅高度的單一情況有效。

但是，當涉及到超出設備螢屏的長度和高度時，它不知何故不起作用。我試圖在控制臺中列印值以進行檢查（示例）。列印的值是正確的，但由于某種原因，它沒有輸入它的switch大小寫。

我錯過了代碼中的任何地方嗎？

下面是標志功能。case 3不起作用（示例）。

//exceed screen flag function
private Point processContextMenuFormLocation(ContextMenu theContextMenu, int screenExceedFlag, Point mouseCoor)
{
    //local form coordinate
    int formXCoor;
    int formYCoor;

    switch (screenExceedFlag)
    {
        case 1: //if exceed right boundary
            formXCoor = (mouseCoor.X) - (contextMenuObj.Width); //move context menu to the left
            formYCoor = mouseCoor.Y; //no need changes
            //after exceedFlag, set where context menu position is
            theContextMenu.Location = new Point(formXCoor, formYCoor);
            break;
        case 2: //if exceed bottom boundary
            formXCoor = (mouseCoor.X); //no need changes
            formYCoor = (mouseCoor.Y) - (contextMenuObj.Height); //move context menu to the top
            theContextMenu.Location = new Point(formXCoor, formYCoor);
            break;
        case 3: //if exceed right & bottom boundary
            formXCoor = (mouseCoor.X) - (contextMenuObj.Width); //move context menu to the left
            formYCoor = (mouseCoor.Y) - (contextMenuObj.Height); //move context menu to the top
            theContextMenu.Location = new Point(formXCoor, formYCoor);
            break;
        case -1: //if exceeded nothing
            theContextMenu.Location = new Point(mouseCoor.X, mouseCoor.Y);
            break;
    }
    //return the new location of context menu
    return theContextMenu.Location;
}

下面是事件處理程式，它呼叫上述函式：

//mouse up event handler
private void richTextBox1_MouseUp(object sender, MouseEventArgs e)
{
    //set default CM closed so that won't open concurrently
    richContextStrip.Visible = false;

    if (e.Button == MouseButtons.Right)
    {
        IsKeyUp((int)MouseButtons.Right); //set rmbIsUp = true 

        //here because the rmb event handler is above this
        bool canDisplay = contextMenuDisplayFlag(ctrlIsDown, rmbIsUp); //get ctrl and rmb flag status 

        if (canDisplay)
        {
            //to process whether custom context menu was opened beyond screen area or not
            exceedScreenFlag = isBeyondScreen(Cursor.Position.X, Cursor.Position.Y, contextMenuObj.Width, contextMenuObj.Height);

            //obtain mouse coordinates
            Point theMouseCoor = new Point(Cursor.Position.X, Cursor.Position.Y);

            //exceed screen flag function
            Point formLocation = processContextMenuFormLocation(contextMenuObj, exceedScreenFlag, theMouseCoor);

            //center the cursor at context menu
            Point cursorLocation = processContextMenuCursorLocation(contextMenuObj, formLocation);

            displayCustomContextMenu(contextMenuObj, formLocation, cursorLocation);
            toolStripStatusLabel1.Text = "Custom context menu opened!";
        }
        else //if ctrl key is not pressed
        {
            richContextStrip.Visible = true;
            toolStripStatusLabel1.Text = "Default context menu opened!";
        }
    }
}

uj5u.com熱心網友回復：

您可能需要考慮當前滑鼠指標位置是由MouseEventArgs.Location. 您只需使用[Control].PointToScreen()方法將此值轉換為螢屏坐標。

然后將初始位置 - 加上您的彈出視窗的和 - 與 Screen.FromControl([Control]).WorkingArea 回傳的值進行Width比較，并驗證彈出視窗是否包含在此范圍內。 如果不是，則從左右邊界中減去彈出視窗和/或。Height
WidthHeightWorkingArea

像這樣：
_{請注意，這些措施不包括表單的不可見邊框。與螢屏兩側的距離為 14~16 像素。如果您喜歡更緊的位置，請調整它}

private void someControl_MouseUp(object sender, MouseEventArgs e)
{
    var f = new Form() { Width = 400, Height = 400, StartPosition = FormStartPosition.Manual };
    f.Location = SetPopupLocation(Screen.FromControl(this), f, (sender as Control).PointToScreen(e.Location));
    f.Show();
}

private Point SetPopupLocation(Screen screen, Form form, Point initPosition)
{
    var p = new Point();
    var wrkArea = screen.WorkingArea;
    p.X = wrkArea.Left   wrkArea.Width - (initPosition.X   form.Width);
    p.Y = wrkArea.Top   wrkArea.Height - (initPosition.Y   form.Height);
    p.X = p.X < 0 ? wrkArea.Width - form.Width : initPosition.X;
    p.Y = p.Y < 0 ? wrkArea.Height - form.Height : initPosition.Y;
    return p;
}

您的應用需要 DpiAware 才能接收可靠的測量值和坐標。請參閱將SetWindowPos 與多個監視器一起使用
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