フォームの枠(サイズ変更可能なウィンドウ枠)の幅と高さを取得する - C#

サイズ変更可能なウィンドウ枠の幅と高さを取得するコードを紹介します。

概要

フォームのWidthやHeightプロパティに値を入力した場合、フォームの枠の幅を含めたサイズがWidthやHeightプロパティに入力したサイズとなります。(下図参照)

そのため、内部のサイズを指定したサイズにする場合は、ウィンドウの枠の幅を取得する必要があります。

対処法

今回はサイズ変更可能なウィンドウフォームの枠の幅を取得します。
ウィンドウ枠の幅を取得するには、Windows APIのGetSystemMetrics関数を用います。引数に、SM_CXSIZEFRAMEを与えるとサイズ変更可能なウィンドウ枠の幅（左右:垂直枠の幅）を取得でき、SM_CYSIZEFRAMEを与えるとサイズ変更可能なウィンドウ枠の幅（上下:水平枠くの高さ）を取得できます。

実装例

コード

namespace App
{
  public partial class FormMain : Form
  {
    [DllImport("user32.dll")]
    static extern int GetSystemMetrics(SystemMetric smIndex);
    public enum SystemMetric : int
    {
      SM_CXSCREEN = 0,
      SM_CYSCREEN = 1,
      SM_CYVSCROLL = 2,
      SM_CXVSCROLL = 3,
      SM_CYCAPTION = 4,
      SM_CXBORDER = 5,
      SM_CYBORDER = 6,
      SM_CXDLGFRAME = 7,
      SM_CYDLGFRAME = 8,
      SM_CYVTHUMB = 9,
      SM_CXHTHUMB = 10,
      SM_CXICON = 11,
      SM_CYICON = 12,
      SM_CXCURSOR = 13,
      SM_CYCURSOR = 14,
      SM_CYMENU = 15,
      SM_CXFULLSCREEN = 16,
      SM_CYFULLSCREEN = 17,
      SM_CYKANJIWINDOW = 18,
      SM_MOUSEWHEELPRESENT = 75,
      SM_CYHSCROLL = 20,
      SM_CXHSCROLL = 21,
      SM_DEBUG = 22,
      SM_SWAPBUTTON = 23,
      SM_RESERVED1 = 24,
      SM_RESERVED2 = 25,
      SM_RESERVED3 = 26,
      SM_RESERVED4 = 27,
      SM_CXMIN = 28,
      SM_CYMIN = 29,
      SM_CXSIZE = 30,
      SM_CYSIZE = 31,
      SM_CXFRAME = 32,
      SM_CYFRAME = 33,
      SM_CXMINTRACK = 34,
      SM_CYMINTRACK = 35,
      SM_CXDOUBLECLK = 36,
      SM_CYDOUBLECLK = 37,
      SM_CXICONSPACING = 38,
      SM_CYICONSPACING = 39,
      SM_MENUDROPALIGNMENT = 40,
      SM_PENWINDOWS = 41,
      SM_DBCSENABLED = 42,
      SM_CMOUSEBUTTONS = 43,
      SM_CXFIXEDFRAME = SM_CXDLGFRAME,
      SM_CYFIXEDFRAME = SM_CYDLGFRAME,
      SM_CXSIZEFRAME = SM_CXFRAME,
      SM_CYSIZEFRAME = SM_CYFRAME,
      SM_SECURE = 44,
      SM_CXEDGE = 45,
      SM_CYEDGE = 46,
      SM_CXMINSPACING = 47,
      SM_CYMINSPACING = 48,
      SM_CXSMICON = 49,
      SM_CYSMICON = 50,
      SM_CYSMCAPTION = 51,
      SM_CXSMSIZE = 52,
      SM_CYSMSIZE = 53,
      SM_CXMENUSIZE = 54,
      SM_CYMENUSIZE = 55,
      SM_ARRANGE = 56,
      SM_CXMINIMIZED = 57,
      SM_CYMINIMIZED = 58,
      SM_CXMAXTRACK = 59,
      SM_CYMAXTRACK = 60,
      SM_CXMAXIMIZED = 61,
      SM_CYMAXIMIZED = 62,
      SM_NETWORK = 63,
      SM_CLEANBOOT = 67,
      SM_CXDRAG = 68,
      SM_CYDRAG = 69,
      SM_SHOWSOUNDS = 70,
      SM_CXMENUCHECK = 71,
      SM_CYMENUCHECK = 72,
      SM_SLOWMACHINE = 73,
      SM_MIDEASTENABLED = 74,
      SM_MOUSEPRESENT = 19,
      SM_XVIRTUALSCREEN = 76,
      SM_YVIRTUALSCREEN = 77,
      SM_CXVIRTUALSCREEN = 78,
      SM_CYVIRTUALSCREEN = 79,
      SM_CMONITORS = 80,
      SM_SAMEDISPLAYFORMAT = 81,
      SM_IMMENABLED = 82,
      SM_CXFOCUSBORDER = 83,
      SM_CYFOCUSBORDER = 84,
      SM_TABLETPC = 86,
      SM_MEDIACENTER = 87,
      SM_CMETRICS_OTHER = 76,
      SM_CMETRICS_2000 = 83,
      SM_CMETRICS_NT = 88,
      SM_REMOTESESSION = 0x1000,
      SM_SHUTTINGDOWN = 0x2000,
      SM_REMOTECONTROL = 0x2001,
    }

    const int Inner_Width=200;
    const int Inner_Height=180;

    private void Form1_Load(object sender, EventArgs e)
    {
      int cxb = GetSystemMetrics(SystemMetric.SM_CXSIZEFRAME);
      int cyb = GetSystemMetrics(SystemMetric.SM_CYSIZEFRAME);
      this.Width = Inner_Width +  cxb*2;
      this.Height = Inner_Height +  cyb * 2;
    }
  }
}