summaryrefslogtreecommitdiff
path: root/luaotfload-colors.lua
blob: ec076c2f0ed2bd4b3977f17efc706b3727cb543b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
if not modules then modules = { } end modules ['luaotfload-colors'] = {
    version   = 2.200,
    comment   = "companion to luaotfload.lua (font color)",
    author    = "Khaled Hosny, Elie Roux, Philipp Gesang",
    copyright = "Luaotfload Development Team",
    license   = "GNU GPL v2"
}

--[[doc--
buggy coloring with the pre_output_filter when expansion is enabled
    · tfmdata for different expansion values is split over different objects
    · in ``initializeexpansion()``, chr.expansion_factor is set, and only
      those characters that have it are affected
    · in constructors.scale: chr.expansion_factor = ve*1000 if commented out
      makes the bug vanish
--doc]]--


local color_callback = config.luaotfload.color_callback
if not color_callback then
    --- maybe this would be better as a method: "early" | "late"
    color_callback = "pre_linebreak_filter"
--  color_callback = "pre_output_filter" --- old behavior, breaks expansion
end


local newnode               = node.new
local nodetype              = node.id
local traverse_nodes        = node.traverse
local insert_node_before    = node.insert_before
local insert_node_after     = node.insert_after

local stringformat          = string.format
local stringgsub            = string.gsub
local stringfind            = string.find
local stringsub             = string.sub

local otffeatures           = fonts.constructors.newfeatures("otf")
local identifiers           = fonts.hashes.identifiers
local registerotffeature    = otffeatures.register

local add_color_callback --[[ this used to be a global‽ ]]

--[[doc--
This converts a single octet into a decimal with three digits of
precision. The optional second argument limits precision to a single
digit.
--doc]]--

--- string -> bool? -> string
local hex_to_dec = function (hex,one) --- one isn’t actually used anywhere ...
    if one then
        return stringformat("%.1g", tonumber(hex, 16)/255)
    else
        return stringformat("%.3g", tonumber(hex, 16)/255)
    end
end

--[[doc--
Color string validator / parser.
--doc]]--

local lpeg           = require"lpeg"
local lpegmatch      = lpeg.match
local C, Cg, Ct, P, R, S = lpeg.C, lpeg.Cg, lpeg.Ct, lpeg.P, lpeg.R, lpeg.S

local digit16        = R("09", "af", "AF")
local octet          = C(digit16 * digit16)

local p_rgb          = octet * octet * octet
local p_rgba         = p_rgb * octet
local valid_digits   = C(p_rgba + p_rgb) -- matches eight or six hex digits

local p_Crgb         = Cg(octet/hex_to_dec, "red") --- for captures
                     * Cg(octet/hex_to_dec, "green")
                     * Cg(octet/hex_to_dec, "blue")
local p_Crgba        = p_Crgb * Cg(octet/hex_to_dec, "alpha")
local extract_color  = Ct(p_Crgba + p_Crgb)

--- string -> (string | nil)
local sanitize_color_expression = function (digits)
    digits = tostring(digits)
    local sanitized = lpegmatch(valid_digits, digits)
    if not sanitized then
        luaotfload.warning(
            "“%s” is not a valid rgb[a] color expression", digits)
        return nil
    end
    return sanitized
end

--[[doc--
``setcolor`` modifies tfmdata.properties.color in place
--doc]]--

--- fontobj -> string -> unit
---
---         (where “string” is a rgb value as three octet
---         hexadecimal, with an optional fourth transparency
---         value)
---
local setcolor = function (tfmdata, value)
    local sanitized  = sanitize_color_expression(value)
    local properties = tfmdata.properties

    if sanitized then
        properties.color = sanitized
        add_color_callback()
    end
end

registerotffeature {
    name        = "color",
    description = "color",
    initializers = {
        base = setcolor,
        node = setcolor,
    }
}


--- something is carried around in ``res``
--- for later use by color_handler() --- but what?

local res --- <- state of what?

--- float -> unit
local function pageresources(alpha)
    local res2
    if not res then
       res = "/TransGs1<</ca 1/CA 1>>"
    end
    res2 = stringformat("/TransGs%s<</ca %s/CA %s>>",
                        alpha, alpha, alpha)
    res  = stringformat("%s%s",
                        res,
                        stringfind(res, res2) and "" or res2)
end

--- we store results of below color handler as tuples of
--- push/pop strings
local color_cache = { } --- (string, (string * string)) hash_t

--- string -> (string * string)
local hex_to_rgba = function (digits)
    if not digits then
        return
    end

    --- this is called like a thousand times, so some
    --- memoizing is in order.
    local cached = color_cache[digits]
    if not cached then
        local push, pop
        local rgb = lpegmatch(extract_color, digits)
        if rgb.alpha then
            pageresources(rgb.alpha)
            push = stringformat(
                        "/TransGs%g gs %s %s %s rg",
                        rgb.alpha,
                        rgb.red,
                        rgb.green,
                        rgb.blue)
            pop  = "0 g /TransGs1 gs"
        else
            push = stringformat(
                        "%s %s %s rg",
                        rgb.red,
                        rgb.green,
                        rgb.blue)
            pop  = "0 g"
        end
        color_cache[digits] = { push, pop }
        return push, pop
    end

    return cached[1], cached[2]
end

--- Luatex internal types

local glyph_t           = nodetype("glyph")
local hlist_t           = nodetype("hlist")
local vlist_t           = nodetype("vlist")
local whatsit_t         = nodetype("whatsit")
local page_insert_t     = nodetype("page_insert")
local sub_box_t         = nodetype("sub_box")

--- node -> nil | -1 | color‽
local lookup_next_color
lookup_next_color = function (head) --- paragraph material
    for n in traverse_nodes(head) do
        local n_id = n.id

        if n_id == glyph_t then
            local n_font
            if  identifiers[n_font]
            and identifiers[n_font].properties
            and identifiers[n_font].properties.color
            then
                return identifiers[n.font].properties.color
            else
                return -1
            end

        elseif n_id == vlist_t or n_id == hlist_t or n_id == sub_box_t then
            local r = lookup_next_color(n.list)
            if r then
                return r
            end

        elseif n_id == whatsit_t or n_id == page_insert_t then
            return -1
        end
    end
    return nil
end

--[[doc--
While the second argument and second returned value are apparently
always nil when the function is called, they temporarily take string
values during the node list traversal.
--doc]]--

local cnt = 0
--- node -> string -> int -> (node * string)
local node_colorize
node_colorize = function (head, current_color, next_color)
    for n in traverse_nodes(head) do
        local n_id      = n.id
        local nextnode  = n.next

        if n_id == hlist_t or n_id == vlist_t or n_id == sub_box_t then
            local next_color_in = lookup_next_color(nextnode) or next_color
            n.list, current_color = node_colorize(n.list, current_color, next_color_in)

        elseif n_id == glyph_t then
            cnt = cnt + 1
            local tfmdata = identifiers[n.font]

            --- colorization is restricted to those fonts
            --- that received the “color” property upon
            --- loading (see ``setcolor()`` above)
            if tfmdata and tfmdata.properties  and tfmdata.properties.color then
                local font_color = tfmdata.properties.color
--                luaotfload.info(
--                    "n: %d; %s; %d %s, %s",
--                    cnt, utf.char(n.char), n.font, "<TRUE>", font_color)
                if font_color ~= current_color then
                    local pushcolor = hex_to_rgba(font_color)
                    local push      = newnode(whatsit_t, 8)
                    push.mode       = 1
                    push.data       = pushcolor
                    head            = insert_node_before(head, n, push)
                    current_color   = font_color
                end
                local next_color_in = lookup_next_color (nextnode) or next_color
                if next_color_in ~= font_color then
                    local _, popcolor = hex_to_rgba(font_color)
                    local pop         = newnode(whatsit_t, 8)
                    pop.mode          = 1
                    pop.data          = popcolor
                    head              = insert_node_after(head, n, pop)
                    current_color     = nil
                end

--            else
--                luaotfload.info(
--                    "n: %d; %s; %d %s",
--                    cnt, utf.char(n.char), n.font, "<FALSE>")
            end
        end
    end
    return head, current_color
end

--- node -> node
local color_handler = function (head)
    -- check if our page resources existed in the previous run
    -- and remove it to avoid duplicating it later
    if res then
        local r = "/ExtGState<<" .. res .. ">>"
        tex.pdfpageresources = stringgsub(tex.pdfpageresources, r, "")
    end
    local new_head = node_colorize(head, nil, nil)
    -- now append our page resources
    if res and stringfind(res, "%S") then -- test for non-empty string
        local r = "/ExtGState<<" .. res .. ">>"
        tex.pdfpageresources = tex.pdfpageresources..r
    end
    return new_head
end

local color_callback_activated = 0

--- unit -> unit
add_color_callback = function ( )
    if color_callback_activated == 0 then
        luatexbase.add_to_callback(color_callback,
                                   color_handler,
                                   "luaotfload.color_handler")
        color_callback_activated = 1
    end
end

-- vim:tw=71:sw=4:ts=4:expandtab