Note that you shouldn't use 2) or 3) for non-monospace fonts because of kerning.

font := StandardFonts defaultFont.
font widthOfString: 'eT'. "16"
font widthOfString: 'Te'. "15"

'eT' inject: 0 into: [ :width :c | width + (font getGlyphWidth: c) ]. "13.416015625"
'Te' inject: 0 into: [ :width :c | width + (font getGlyphWidth: c) ]. "13.416015625"

4) seems fine

font := StandardFonts defaultFont.
provider := CairoScaledFont fromFreetypeFont: font realFont.
width := [ :string |
converter := CairoUTF8Converter new.
converter convert: string from: 1 to: string size.
stringExtents := CairoTextExtents new.
provider getExtentsOf: converter buffer into: stringExtents.
stringExtents width ].

width value: 'eT'. "12.463638305664063"
width value: 'Te'. "12.561752319335938"


On Tue, Oct 27, 2015 at 12:27 PM, Yuriy Tymchuk <yuriy.tymchuk@me.com> wrote:
Hi Alex,

This is indeed a very useful information. You can also put it on StackOverflow, then it will be Googlable.

Cheers.
Uko



On 27 Oct 2015, at 12:02, Aliaksei Syrel <alex.syrel@gmail.com> wrote:

Hi

I'm sending it here so that it doesn't get lost.

There are multiple ways to measure string width. In the following examples performance will be tested measuring 10`000 times the width of the following string:

string := 'abcdefghijklmnopqrstuvwxyz 0123456789!@#$%^&*()_+'.

1) The most straightforward way is to send #widthOfString: to the font. Time to run gives around 250ms.
Resulting value is rounded to integer and seems to be not absolutely correct and precise.

2) More complex way is to go deeper on the level of glyphs and manually summarise the width of each character in the string sending #getGlyphWidth: character to the font. Time to run gives around 750ms.
Resulting value is float and looks like correct and precise value.

3) Even more complex is to use��CairoFontMetricsProvider instead of font's methods. The same as in 2nd case we measure each character. Time to run around 350ms.
Resulting value is exactly the same as in the 2nd case. With almost equal performance to 1st it is nice alternative.

4) One more way is to let native cairo to calculate everything for us. Calls happen through nativeboost. Time to run around 120ms.
As result it returns��CairoTextExtents which allows to calculate width and height with one call.

Cheers,
Alex