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PDF text selection: fix/tweak spacing between words/boxes

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We may get multiple boxes when selecting texts, one for each
word, and we have to add spaces between the extracted words
ourselves. Previously, we were only adding a space if the
last char of previous word was ASCII, so missing spaces
after accents or greek words.
Try to do better by measuring the distances between boxes
and comparing to box heights, with a few heuristics.
This commit is contained in:
poire-z
2021-07-18 19:56:17 +02:00
parent 63e800e3b3
commit eeb09d2150
2 changed files with 61 additions and 12 deletions
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59
frontend/document/koptinterface.lua
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@@ -875,6 +875,7 @@ Get text and text boxes between `pos0` and `pos1`.
--]]
function KoptInterface:getTextFromBoxes(boxes, pos0, pos1)
if not pos0 or not pos1 or #boxes == 0 then return {} end
local isCJKChar = require("util").isCJKChar
local line_text = ""
local line_boxes = {}
local i_start, j_start = getWordBoxIndices(boxes, pos0)
@@ -888,18 +889,62 @@ function KoptInterface:getTextFromBoxes(boxes, pos0, pos1)
-- insert line words
local j0 = i > i_start and 1 or j_start
local j1 = i < i_stop and #boxes[i] or j_stop
local line_first_word_seen = false
local prev_word
local prev_word_end_x
for j = j0, j1 do
local word = boxes[i][j].word
if word then
-- if last character of this word is an ascii char then append a space
local space = (word:match("[%z\194-\244][\128-\191]*$") or j == j1)
and "" or " "
line_text = line_text..word..space
if not line_first_word_seen then
line_first_word_seen = true
if #line_text > 0 then
if line_text:sub(-1) == "-" then
-- Previous line ended with a minus.
-- Assume it's some hyphenation and discard it.
line_text = line_text:sub(1, -2)
elseif line_text:sub(-2, -1) == "\xC2\xAD" then
-- Previous line ended with a hyphen.
-- Assume it's some hyphenation and discard it.
line_text = line_text:sub(1, -3)
else
-- No hyphenation, add a space (might be not welcome
-- with CJK text, but well...)
line_text = line_text .. " "
end
end
end
local box = boxes[i][j]
if prev_word then
-- A box should have been made for each word, so assume
-- we want a space between them, with some exceptions
local add_space = true
local box_height = box.y1 - box.y0
local dist_from_prev_word = box.x0 - prev_word_end_x
if prev_word:sub(-1, -1) == " " or word:sub(1, 1) == " " then
-- Already a space between these words
add_space = false
elseif dist_from_prev_word < box_height * 0.03 then
-- If the space between previous word box and this word box
-- is smaller than 5% of box height, assume these boxes
-- should be stuck
add_space = false
elseif dist_from_prev_word < box_height * 0.8 then
if isCJKChar(prev_word:sub(-3, -1)) and isCJKChar(word:sub(1, 3)) then
-- Two CJK chars whose spacing is not large enough
-- (we checked the 3 UTF8 bytes that CJK chars must be,
-- no need to split into unicode codepoints)
add_space = false
end
end
if add_space then
word = " " .. word
end
end
line_text = line_text .. word
prev_word = word
prev_word_end_x = box.x1
end
end
-- append a space at the end of the line unless its a hyphenated word
line_text = line_text .. " "
line_text = line_text:gsub("- $", "")
-- insert line box
local lb = boxes[i]
if i > i_start and i < i_stop then