标签文字显得太低

Question

I want to display two numbers in a full-screen manner,
above each other,
as regardless of actual screen size as possible.

        //getting screen size and setting window to maximized
        Rectangle screenEdge = Screen.PrimaryScreen.Bounds;
        this.Width = screenEdge.Width;
        this.Height = screenEdge.Height;
        this.FormBorderStyle = FormBorderStyle.FixedToolWindow;
        this.WindowState = FormWindowState.Maximized;

        //using 90% of width and 40% (times two) of height
        int lWidth = (int)(this.Width * 0.9);
        int lHeight = (int)(this.Height * 0.4);

        //horiz. spacing: remainder, divided up for left and right
        int lLeft = ( this.Width - lWidth ) / 2;
        //vert. spacing: remainder divided for top, bottom and between
        int lTop = ( this.Height - (2 * lHeight)) / 3 ;

        //the labels holding the numbers
        lSoll = new Label();
        lIst = new Label();

        //setting label lSoll to calc'd dimensions, adding & aligning text
        lSoll.Left = lLeft;
        lSoll.Width = lWidth;
        lSoll.Top = lTop;
        lSoll.Height = lHeight;
        Font sollFont = new Font(FontFamily.GenericSansSerif, lSoll.Height);
        Font sFSized = new Font(sollFont.FontFamily, lSoll.Height);
        lSoll.Font = sFSized;
        lSoll.TextAlign = ContentAlignment.MiddleCenter;
        lSoll.ForeColor = Color.Blue;
        lSoll.BackColor = Color.White;
        updateSollText(42);

        //same as above, just a bit lower
        lIst.Left = lLeft;
        lIst.Width = lWidth;
        lIst.Top = lTop * 2 + lSoll.Height;
        lIst.Height = lHeight;
        Font istFont = new Font(FontFamily.GenericSansSerif, lIst.Height);
        Font iFSized = new Font(istFont.FontFamily, lIst.Height);
        lIst.Font = iFSized;
        lIst.TextAlign = ContentAlignment.TopCenter;
        lIst.ForeColor = Color.Red;
        lIst.BackColor = Color.White;
        updateIstText(39);

Issue with this code (besides clumsyness):
The text on the labels is displayed partly below the labels' lower bounds, ie invisible, see screenshot at the bottom.
I double checked my calculations and found that other than a rounding error of 1 pt (tops) it all should work.
I also tried making the fontsize less than label height, which helped a little but was certainly not a fix.
I actually though the textalign should cover this, because that is what it is for.
Also chaning the height-comp(low middle top) of textalign did not change anything, whereas left / center / right do make the difference expected

What could be causing this?

Answer 1

The default unit of measurement for a font is points, not pixels. For example, with a default DPI setting of 96, a 9 point font takes up 9 * 96 / 72 = 12 pixels. So the font you ask for is too big and doesn't fit.

The workaround is simple, you can specify the unit of measurement you prefer with a Font constructor overload that takes a GraphicsUnit argument. Fix:

 Font sollFont = new Font(FontFamily.GenericSansSerif, lSoll.Height, GraphicsUnit.Pixel);
 Font sFSized = new Font(sollFont.FontFamily, lSoll.Height, GraphicsUnit.Pixel);