koreader/frontend/ui/widget/textwidget.lua

--[[--
A TextWidget puts a string on a single line.

Example:

    UIManager:show(TextWidget:new{
        text = "Make it so.",
        face = Font:getFace("cfont"),
        bold = true,
        fgcolor = Blitbuffer.COLOR_GREY,
    })

--]]

local Blitbuffer = require("ffi/blitbuffer")
local Geom = require("ui/geometry")
local Math = require("optmath")
local RenderText = require("ui/rendertext")
local Size = require("ui/size")
local Widget = require("ui/widget/widget")
local Screen = require("device").screen

local TextWidget = Widget:new{
    text = nil,
    face = nil,
    bold = nil,
    fgcolor = Blitbuffer.COLOR_BLACK,
    padding = Size.padding.small, -- should padding be function of face.size ?
    max_width = nil,
    _bb = nil,
    _length = 0,
    _height = 0,
    _baseline_h = 0,
    _maxlength = 1200,
}

--function TextWidget:_render()
    --local h = self.face.size * 1.3
    --self._bb = Blitbuffer.new(self._maxlength, h)
    --self._bb:fill(Blitbuffer.COLOR_WHITE)
    --self._length = RenderText:renderUtf8Text(self._bb, 0, h*0.8, self.face, self.text, true, self.bold)
--end

function TextWidget:updateSize()
    local tsize = RenderText:sizeUtf8Text(0, self.max_width and self.max_width or Screen:getWidth(), self.face, self.text, true, self.bold)
    if not tsize then
        self._length = 0
    else
        -- As text length includes last glyph pen "advance" (for positionning
        -- next char), it's best to use math.floor() instead of math.ceil()
        -- to get rid of a fraction of it in case this text is to be
        -- horizontally centered
        self._length = math.floor(tsize.x)
    end
    -- Used to be:
    --   self._height = math.ceil(self.face.size * 1.5)
    --   self._baseline_h = self._height*0.7
    -- But better compute baseline alignment from freetype font metrics
    -- to get better vertical centering of text in box
    -- (Freetype doc on this at https://www.freetype.org/freetype2/docs/tutorial/step2.html)
    local face_height, face_ascender = self.face.ftface:getHeightAndAscender()
    self._height = math.ceil(face_height) + 2*self.padding
    self._baseline_h = Math.round(face_ascender) + self.padding
    -- With our UI fonts, this usually gives 0.72 to 0.74, so text is aligned
    -- a bit lower than before with the hardcoded 0.7
    -- require("logger").warn("1.5*face.size:", self.face.size * 1.5, "face_height:", face_height, "self._height:", self._height)
    -- require("logger").warn("self._height ratio:", 1.0*self._baseline_h/self._height)
end

function TextWidget:getSize()
    --if not self._bb then
        --self:_render()
    --end
    --return { w = self._length, h = self._bb:getHeight() }
    self:updateSize()
    return Geom:new{
        w = self._length,
        h = self._height,
    }
end

function TextWidget:setText(text)
    self.text = text
    self:updateSize()
end

function TextWidget:paintTo(bb, x, y)
    --if not self._bb then
        --self:_render()
    --end
    --bb:blitFrom(self._bb, x, y, 0, 0, self._length, self._bb:getHeight())
    --@TODO Don't use kerning for monospaced fonts.    (houqp)
    if self.max_width and RenderText:sizeUtf8Text(0, Screen:getWidth(), self.face, self.text, true, self.bold).x > self.max_width then
        self.text = RenderText:truncateTextByWidth(self.text, self.face, self.max_width, true)
    end
    RenderText:renderUtf8Text(bb, x, y+self._baseline_h, self.face, self.text, true, self.bold,
                self.fgcolor, self.max_width and self.max_width or self.width)
end

function TextWidget:free()
    if self._bb then
        self._bb:free()
        self._bb = nil
    end
end

return TextWidget