lighttroupe/luz-next

# encoding: UTF-8

#
# CairoFont uses Cairo and Pango to render text onto an Image (OpenGL surface)
#
class CairoFont
    #easy_accessor :font, :string

    CHARACTER_wIDTH = 64        # pixels
    CHARACTER_HEIGHT = 128        # pixels

    def render_to_image(string, font, width_in_characters, lines=1, text_align=:left)
        @canvas ||= CairoCanvas.new(CHARACTER_wIDTH * width_in_characters, CHARACTER_HEIGHT * lines)        # HACK: arbitrary pixel size
        @image ||= Image.new
        render(string, font, size=1.0, width_in_characters, lines, text_align)
        @image
    end

    LETTERS = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7','8','9','~','`','!','@','#','$','%','^','&','*','[',']','-','_','=','+','[','{',']','}',';',':',"'",'"',',','<','.','>','/','?','¡','¢','£','¥','§','©','®','¿','À','Á','Â','Ã','Ä','Å','Æ','Ç','È','É','Ê','Ë','Ì','Í','Î','Ï','Ð','Ñ','Ò','Ó','Ô','Õ','Ö','Ø','Ù','Ú','Û','Ü','Ý','ß','à','á','â','ã','ä','å','æ','ç','è','é','ê','ë','ì','í','î','ï','ð','ñ','ò','ó','ô','õ','ö','ø','ù','ú','û','ü','ý','ÿ']
    def self.renderable?(letter)
        LETTERS.include? letter
    end

private

    def render(string, font, font_size, width_in_characters, lines, text_align)
        #line_spacing = 1.0        # TODO ?
        border_left = 0.0
        border_top = 0.0

        vertical_scale = 0.78

        @canvas.using { |context|
            context.save
                clear_canvas(context)

                unless string.blank?
                    # color
                    context.set_source_rgba(1,1,1,1)
                    context.set_antialias(Cairo::ANTIALIAS_GRAY)        # or DEFAULT or GRAY or SUBPIXEL or NONE

                    # "layout" - a Pango plan for rendering
                    layout = context.create_pango_layout

                    #layout.spacing = line_spacing * Pango::SCALE                    # TODO: line spacing

                    # build Pango font description
                    font_description = Pango::FontDescription.new(font)

                    # sets height to full canvas height
                    font_description.absolute_size = @canvas.height * Pango::SCALE / lines        # * font_size
                    layout.font_description = font_description

                    # measure one "em"  https://en.wikipedia.org/wiki/Em_%28typography%29
                    layout.text = "M"
                    em_width, em_height = layout.pixel_size

                    layout.text = string        #.gsub("\n", " \n")        # TODO: document why ?!

                    logical_width_in_pixels = width_in_characters * em_width        # how big we pretend the canvas is
                    actual_width_in_pixels = @canvas.width

                    #puts "em_width => #{em_width}, em_height => #{em_height}"
                    #puts "logical_width_in_pixels=#{logical_width_in_pixels}, actual_width_in_pixels=#{actual_width_in_pixels}"

                    horizontal_scale = actual_width_in_pixels.to_f / logical_width_in_pixels.to_f

                    #puts "width_in_characters=#{width_in_characters}, horizontal_scale=#{horizontal_scale}"

                    # multi-line mode with word wrapping
                    if lines > 1
                        layout.wrap = Pango::WrapMode::WORD
                        layout.width = actual_width_in_pixels.to_f * Pango::SCALE / horizontal_scale        # wrap at this width (in pango units)
                        layout.alignment = symbol_to_pango_align(text_align)
                    end

                    context.translate(0.0, @canvas.height * (1.0 - vertical_scale) / 2.0)

                    case text_align
                    when :fill
                        # scale to fill horizontally
                        layout_width, layout_height = layout.pixel_size
                        context.scale(@canvas.width / layout_width.to_f, vertical_scale)
                    when :left, nil        # default
                        # font is 1 tall, width is approx how many chars we can show
                        context.scale(horizontal_scale, vertical_scale)
                        #layout.ellipsize = Pango::ELLIPSIZE_END
                    when :center
                        # Center layout assumes the string is smaller than the container
                        layout_width, layout_height = layout.pixel_size
                        free_space = (@canvas.width.to_f - (layout_width.to_f * horizontal_scale))        # NOTE: using final, post-scaled text width
                        context.move_to((free_space / 2.0), 0.0) if lines == 1
                        context.scale(horizontal_scale, vertical_scale)
                    when :right
                        layout_width, layout_height = layout.pixel_size
                        free_space = (@canvas.width.to_f - (layout_width.to_f * horizontal_scale))        # NOTE: using final, post-scaled text width
                        context.move_to(free_space, 0.0) if lines == 1
                        context.scale(horizontal_scale, vertical_scale)
                    else
                        raise "text_align = #{text_align}"
                    end

                    #puts "layout_width = #{layout_width}, layout_height = #{layout_height}"
                    #context.scale(1, @canvas.height / layout_height)
                    context.show_pango_layout(layout)
                end
            context.restore
        }
        @image.from_bgra8(@canvas.string_data, @canvas.width, @canvas.height)
    end

    def clear_canvas(context)
        context.set_source_rgba(0.0, 0.0, 0.0, 0.0)        # NOTE: alpha 0.0
        context.set_operator(:source)
        context.paint
    end

    def symbol_to_pango_align(sym)
        {:left => Pango::Alignment::LEFT, :center => Pango::Alignment::CENTER, :right => Pango::Alignment::RIGHT}[sym] || Pango::Alignment::LEFT
    end
end

#font_description = font
#weight = Cairo::FONT_WEIGHT_NORMAL
#if font =~ / Bold/
    #font = font.gsub(' Bold', '')
    #weight = Pango::WEIGHT_BOLD
#end

#slant = Cairo::FONT_SLANT_NORMAL
#if font =~ / Italic/
    #font = font.gsub(' Italic', '')
    #style = Pango::STYLE_ITALIC
#end