DrawText API and Font Sizes

[Linkinfamous]

Ok. So I've managed to cobble together a ENUMLOGFONTEXDV, with a ENUMLOGFONTEX inside, which contains a LOGFONT with a Height of, say, 24. I then use SelectObject() to select the handle to that ENUMLOGFONTEXDV in my Graphics object, and use DrawText() to draw it. The unfortunate thing is that that 24 for, whatever reason, is in Pixels, and not in the format the is used for determining font sizes.

If i call Veranda and Georgia like this, they come out to the same size, when in Word, size 24 Veranda is larger than size 24 Georgia.

How do I calculate what values I should be using?

[azcodemonkey]

The height of the LOGFONT is in em's. Here's how you'd convert it to points.

// PointSize is given by you.
lfHeight = -MulDiv(PointSize, GetDeviceCaps(hDC, LOGPIXELSY), 72);

[Linkinfamous]

Thanks, but that still doesn't change my original problem. When I use the same Height for two different fonts that normally would come out at vastly different rendered sizes, they come out at the same height irregardless of what I do.

[azcodemonkey]

Verdana isn't bigger than Georgia at the same point size... the ascent for Verdana may be different, but they take up the same space in points. That's the point of the point measurement. 1/72 of an inch is 1pt. DPI is what causes scaling problems.

[Linkinfamous]

Yeah, I realize that now. I picked another font pair, with a vast obvious difference, and have the same problem.

If I call this with 50 for FontSize, I get 67, which I use for my LOGFONT's lfHeight.

MulDiv(FontSize, GetDeviceCaps(ptr1, 90), 72)

These are the two fonts I'm using,

and my results.

[azcodemonkey]

Yeah, that's a problem. lol! But you already knew that. Would you mind posting your code?

Actually, I think I have an idea. Is the rectangle you specify for DrawText the same for both? Regardless of the font size, when GDI paints, it will paint within the rect you give it.

[Linkinfamous]

Ok. Maybe I'm just getting my rectangle the wrong way.

			IntPtr ptr1 = graphics.GetHdc();
			SelectObject(ptr1, HandleToENUMLOGFONTEXDV);
			RECT r = new RECT();
			DrawText(ptr1, "Test1", 4, ref r, DT_CALCRECT | DT_LEFT | DT_SINGLELINE);

Shouldn't r now be the RECT I want to call DrawText again (but without DR_CALCRECT) with?

[azcodemonkey]

Hmmmm... Sorry, I'm a bit rusty with Win32. I hadn't noticed the DT_CALCRECT flag.

I believe your assertion is correct. If the rect needs resizing in any case, it won't draw the text but it will resize the rect. Give it a whirl. I don't have a sandbox to play in and doing all the imports for C# would take some time.

[Linkinfamous]

I just tried playing with the RECT. It only acts as a clipping region, it doesn't affect the size of the text in any way....Any more ideas?

[azcodemonkey]

  Dayon said:

....Any more ideas?

Use GDI+?

			using (Graphics g = Graphics.FromHwnd(this.Handle))
			{
				using (Font f1 = new Font("Blue Highway", 24f))
				{
					g.DrawString("Test!", f1, Brushes.Black, new PointF(25f, 25f));
				}

				using(Font f2 = new Font("Cargo Two SF", 24f))
				{
					g.DrawString("Test!", f2, Brushes.Black, new PointF(150f, 25f));
				}
			}

That drew the attachment:

[Winston]

Yeah, hmm i don't know why you needed to do pinvoking for something you could do in GDI+.

If you want to measure a string as well there's actually a MeasureString method in the Graphics object i believe.

[Linkinfamous]

As much as I'd like to, I can't exclude the use of PostScript fonts.....GDI+ doesn't support them.

Believe me. I feel sick every time I have to look at my gigantic Win32.cs file. :D

[Linkinfamous]

Got it.

I just had to make lfHeight negative, and voila, it works. Go figure.

[azcodemonkey]

  Dayon said:

Got it.

I just had to make lfHeight negative, and voila, it works. Go figure.

:pinch: wth? lol that's a wierd side effect.

[Linkinfamous]

  weenur said:

:pinch: wth? lol that's a wierd side effect.

Yeah, you threw a '-' in front of the MulDiv. I dropped it. (Stupid me.)

I found this on MSDN:

  Quote

lfHeight

Specifies the height, in logical units, of the font's character cell or character. The character height value (also known as the em height) is the character cell height value minus the internal-leading value. The font mapper interprets the value specified in lfHeight in the following manner.

Value Meaning

> 0 The font mapper transforms this value into device units and matches it against the cell height of the available fonts.

0 The font mapper uses a default height value when it searches for a match.

< 0 The font mapper transforms this value into device units and matches its absolute value against the character height of the available fonts.