nimcity/doc/part01/ch03.md

Глава 3. Рендеринг текста

Библиотека pixels может не только вызывать putPixel: она также предлагает минимальную процедуру drawText для вывода букв и слов на экран. Ее объявление выглядит так:

  proc drawText(x, y: int; text: string; size: int; color: Color)

We pass the following parameters to it:

x and y

The coordinates of a bottom-left corner of the text we want to draw

text

The text we want to render. It is of type string. We will look at strings in more depth in the next chapter, for now it is enough to know that string is a builtin type that is roughly a sequence of char, and a string literal can be written in double quotes, for example "like this".

size

This is a height of the text in pixels.

color

Similarly to the putPixel proc, we can define the color of the text we’re drawing.

The simplest way to call this proc is like this:

  drawText 30, 40, "Welcome to Nim!", 10, Yellow

Notice that we didn’t use the parentheses after the name of the function to enclose the list of arguments. This is equivalent to drawText(10, 10, "Welcome to Nim!", Yellow), either style can be used.

For the next more interesting example we need the dollar operator $ which can turn many types into its string representation, and the concatenation operator & which combines (“concatenates”) two strings into one:

 $12 == "12"   # convert an integer into a string
 "abc" & "def" == "abcdef" # concatenate two strings into one

The following example produces 3 lines of text:

 for i in 1..3:
   let texttodraw = "welcome to nim for the " & $i & "th time!"  1
   drawtext 10, i*10, texttodraw, 8, Yellow    2

• 1 Creates a string (concatenated from three separate strings) and assigns it to the local variable textToDraw.
• 2 Renders the text at position (10, i*10) where i is in one of the numbers in the 1..3 range, for each loop iteration.