soumya92/barista

// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package pango

import (
    "fmt"
    "image/color"
    "strconv"

    "github.com/lucasb-eyer/go-colorful"
)

func (n *Node) setAttr(name, value string) *Node {
    if n.content == "" {
        // Convert a placeholder wrapper to a full span tag.
        n.content = "span"
        n.attributes = map[string]string{}
    }
    if value == "" {
        delete(n.attributes, name)
    } else {
        n.attributes[name] = value
    }
    return n
}

func colorAndAlpha(value color.Color) (color, alpha string) {
    if value == nil {
        return "", ""
    }
    _, _, _, a := value.RGBA()
    if a == 0 {
        return "", "0"
    }
    if a < 0xffff {
        alpha = strconv.Itoa(int(a))
    }
    cful, _ := colorful.MakeColor(value)
    color = cful.Hex()
    return color, alpha
}

// Font sets the font face.
func (n *Node) Font(face string) *Node {
    return n.setAttr("face", face)
}

// Size sets the font size, in points.
func (n *Node) Size(size float64) *Node {
    // Pango size is 1/1024ths of a point.
    return n.setAttr("size", strconv.Itoa(int(size*1024)))
}

// Keyword sizes supported in Pango.
//go:generate ruby kwattrs.rb --name=size XXSmall:xx-small XSmall:x-small Small Medium Large XLarge:x-large XXLarge:xx-large

// Smaller decreases the font size of the contents
// by wrapping them in <small>...</small>
func (n *Node) Smaller() *Node {
    n.children = []*Node{&Node{
        nodeType: ntSizer,
        content:  "small",
        children: n.children,
    }}
    return n
}

// Larger increases the font size of the contents
// by wrapping them in <big>...</big>
func (n *Node) Larger() *Node {
    n.children = []*Node{&Node{
        nodeType: ntSizer,
        content:  "big",
        children: n.children,
    }}
    return n
}

// Font styles supported in Pango.
//go:generate ruby kwattrs.rb --name=style StyleNormal:normal Oblique Italic

// Weight sets the font weight in numeric form.
func (n *Node) Weight(weight int) *Node {
    return n.setAttr("weight", strconv.Itoa(weight))
}

// Keyword weights supported in Pango.
//go:generate ruby kwattrs.rb --name=weight UltraLight Light WeightNormal:normal Bold UltraBold Heavy

// Pango font variants.
//go:generate ruby kwattrs.rb --name=variant VariantNormal:normal SmallCaps

// Pango font stretch keywords.
//go:generate ruby kwattrs.rb --name=stretch UltraCondensed ExtraCondensed Condensed SemiCondensed StretchNormal:normal SemiExpanded Expanded ExtraExpanded UltraExpanded

// Color applies a foreground color and alpha.
func (n *Node) Color(c color.Color) *Node {
    col, alpha := colorAndAlpha(c)
    n.setAttr("alpha", alpha)
    return n.setAttr("color", col)
}

// Alpha applies just a foreground alpha, keeping the default text colour.
func (n *Node) Alpha(alpha float64) *Node {
    return n.setAttr("alpha", fmt.Sprintf("%.0f", 65535.0*alpha))
}

// Background applies a background color and alpha.
func (n *Node) Background(c color.Color) *Node {
    col, alpha := colorAndAlpha(c)
    n.setAttr("background_alpha", alpha)
    return n.setAttr("background", col)
}

// Pango underline keywords.
//go:generate ruby kwattrs.rb --name=underline UnderlineNone:none UnderlineSingle:single UnderlineDouble:double UnderlineLow:low UnderlineError:error

// UnderlineColor applies an underline color.
func (n *Node) UnderlineColor(c color.Color) *Node {
    col, _ := colorAndAlpha(c)
    return n.setAttr("underline_color", col)
}

// Rise sets the font "rise" in pango units.
// Negative for subscript, positive for superscript.
func (n *Node) Rise(rise int) *Node {
    return n.setAttr("rise", strconv.Itoa(rise))
}

// Whether to strike through the text.
//go:generate ruby kwattrs.rb --name=strikethrough Strikethrough:true NoStrikethrough:false

// StrikethroughColor applies a strikethrough color.
func (n *Node) StrikethroughColor(c color.Color) *Node {
    col, _ := colorAndAlpha(c)
    return n.setAttr("strikethrough_color", col)
}

// LetterSpacing sets the letter spacing, in points.
func (n *Node) LetterSpacing(spacing float64) *Node {
    // Pango spacing is 1/1024ths of a point.
    return n.setAttr("letter_spacing", strconv.Itoa(int(spacing*1024)))
}