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Draw right-to-left text string-wise using Qt

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We rely on Qt built-in unicode support for handling Arabic and Hebrew
compose characters. This allows to avoid to use our homegrown
machinery.

This  should provide a nice speedup at a low cost and
will eventually allow us to get rid of:
 * most of our Arabic/Hebrew machinery in Encodings.cpp,
 * Paragraph::transformChar,
 * and probably more.
This commit is contained in:
Jean-Marc Lasgouttes 2014-04-10 16:37:21 +02:00
parent b8170e0e01
commit ea1a5cb80e
7 changed files with 91 additions and 143 deletions
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25
00README_STR_METRICS_BRANCH
View File

@ -11,7 +11,7 @@ what we have with force_paint_single_char. Moreover there has been
some code factorization in TextMetrics, where the same row-breaking
algorithm was basically implemented 3 times.
Currently everything is supposed to work for LTR text, and RTL text
Currently everything is supposed to work for LTR text, and RtL text
should work too except possibly metrics with Arabic and Hebrew fonts.
When KEEP_OLD_METRICS_CODE is defined in TextMetrics.cpp, the new code
@ -40,13 +40,14 @@ What is done:
lyxrc.force_paint_single_char is false. In this case, remove also
useless workarounds which disable kerning and ligatures.
* when lyxrc.force_paint_single_char is false, draw also RtL text
string-wise. This both speed-up drawing and prepare for code
removal, since we now rely on Qt to do things we use to do by
ourselves (see isArabic* and isHebrew* code in Encodings.cpp).
Next steps:
* check what happens with Arabic and/or Hebrew text. There may be some
problems related to compose characters. Investigate whether RtL
strings could be drawn on a string-wise basis.
* investigate whether strings could be cut at separators in RowPainter
only in justified text. This would speed-up painting in other cases
by lowering the number of strings to draw.
@ -76,18 +77,18 @@ Steps for later (aka out of the scope of this branch):
Known bugs:
* there are still difference in what breaks words. In particular,
RowPainter breaks strings at: selection end, spell-checking
extremities. This seems to be harmless.
* when clicking in the right margin, getPosNearX does not return
the same value as before. I am not sure whether this is important.
* When selecting text, the display seems to move around. This is
because partly selected words are drawn in two parts, and in case
like "ef|fort" or "V|AN", there are some ligature or kerning effects
that change the display. I am not sure yet how to fix that.
* there are other differences in what breaks words. In particular,
RowPainter breaks strings at spell-checking extremities. This seems
to be harmless.
* when clicking in the right margin, getPosNearX does not return
the same value as before. I am not sure whether this is important.
Other differences in behavior (aka bug fixes):

6
src/Encoding.cpp
View File

@ -711,6 +711,12 @@ docstring Encodings::fromLaTeXCommand(docstring const & cmd, int cmdtype,
}
bool Encodings::isHebrewChar(char_type c)
{
return c >= 0x0590 && c <= 0x05ff;
}
bool Encodings::isHebrewComposeChar(char_type c)
{
return c <= 0x05c2 && c >= 0x05b0 && c != 0x05be && c != 0x05c0;

2
src/Encoding.h
View File

@ -269,6 +269,8 @@ public:
///
static bool isHebrewComposeChar(char_type c);
///
static bool isHebrewChar(char_type c);
///
static bool isArabicComposeChar(char_type c);
///
static bool isArabicSpecialChar(char_type c);

170
src/rowpainter.cpp
View File

@ -161,72 +161,7 @@ void RowPainter::paintInset(Inset const * inset, pos_type const pos)
}
void RowPainter::paintHebrewComposeChar(pos_type & vpos, FontInfo const & font)
{
pos_type pos = bidi_.vis2log(vpos);
docstring str;
// first char
char_type c = par_.getChar(pos);
str += c;
++vpos;
int const width = theFontMetrics(font).width(c);
int dx = 0;
for (pos_type i = pos - 1; i >= 0; --i) {
c = par_.getChar(i);
if (!Encodings::isHebrewComposeChar(c)) {
if (isPrintableNonspace(c)) {
int const width2 = pm_.singleWidth(i,
text_metrics_.displayFont(pit_, i));
dx = (c == 0x05e8 || // resh
c == 0x05d3) // dalet
? width2 - width
: (width2 - width) / 2;
}
break;
}
}
// Draw nikud
pi_.pain.text(int(x_) + dx, yo_, str, font);
}
void RowPainter::paintArabicComposeChar(pos_type & vpos, FontInfo const & font)
{
pos_type pos = bidi_.vis2log(vpos);
docstring str;
// first char
char_type c = par_.getChar(pos);
c = par_.transformChar(c, pos);
str += c;
++vpos;
int const width = theFontMetrics(font).width(c);
int dx = 0;
for (pos_type i = pos - 1; i >= 0; --i) {
c = par_.getChar(i);
if (!Encodings::isArabicComposeChar(c)) {
if (isPrintableNonspace(c)) {
int const width2 = pm_.singleWidth(i,
text_metrics_.displayFont(pit_, i));
dx = (width2 - width) / 2;
}
break;
}
}
// Draw nikud
pi_.pain.text(int(x_) + dx, yo_, str, font);
}
void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
bool hebrew, bool arabic)
void RowPainter::paintChars(pos_type & vpos, Font const & font)
{
// This method takes up 70% of time when typing
pos_type pos = bidi_.vis2log(vpos);
@ -236,15 +171,21 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
str.reserve(100);
str.push_back(prev_char);
// special case for arabic
string const & lang = font.language()->lang();
bool const swap_paren = lang == "arabic_arabtex"
|| lang == "arabic_arabi"
|| lang == "farsi";
// FIXME: Why only round brackets and why the difference to
// Hebrew? See also Paragraph::getUChar
if (arabic) {
if (swap_paren) {
char_type c = str[0];
if (c == '(')
c = ')';
else if (c == ')')
c = '(';
str[0] = par_.transformChar(c, pos);
str[0] = c;
}
pos_type const end = row_.endpos();
@ -260,6 +201,12 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
bool const spell_state =
lyxrc.spellcheck_continuously && par_.isMisspelled(pos);
// are we building a RtL string?
//FIXME: I would like to use the new isRTL() from textutils.h,
// but it does not give the same results for some reason I do
// not understand.
bool const rtl = Encodings::isArabicChar(str[0]) || Encodings::isHebrewChar(str[0]);
// collect as much similar chars as we can
for (++vpos ; vpos < end ; ++vpos) {
if (lyxrc.force_paint_single_char)
@ -287,48 +234,27 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
char_type c = par_.getChar(pos);
//FIXME: I would like to use the new isRTL() from textutils.h,
// but it does not give the same results for some reason I do
// not understand.
bool const new_rtl = Encodings::isArabicChar(c) || Encodings::isHebrewChar(c);
if (new_rtl != rtl)
// String direction has changed
break;
if (c == '\t')
break;
if (!isPrintableNonspace(c))
break;
/* Because we do our own bidi, at this point the strings are
* already in visual order. However, Qt also applies its own
* bidi algorithm to strings that it paints to the screen.
* Therefore, if we were to paint Hebrew/Arabic words as a
* single string, the letters in the words would get reversed
* again. In order to avoid that, we don't collect Hebrew/
* Arabic characters, but rather paint them one at a time.
* See also http://thread.gmane.org/gmane.editors.lyx.devel/79740
*/
if (hebrew)
break;
/* FIXME: these checks are irrelevant, since 'arabic' and
* 'hebrew' alone are already going to trigger a break.
* However, this should not be removed completely, because
* if an alternative solution is found which allows grouping
* of arabic and hebrew characters, then these breaks may have
* to be re-applied.
if (arabic && Encodings::isArabicComposeChar(c))
break;
if (hebrew && Encodings::isHebrewComposeChar(c))
break;
*/
// FIXME: Why only round brackets and why the difference to
// Hebrew? See also Paragraph::getUChar
if (arabic) {
if (swap_paren) {
if (c == '(')
c = ')';
else if (c == ')')
c = '(';
c = par_.transformChar(c, pos);
/* see comment in hebrew, explaining why we break */
break;
}
str.push_back(c);
@ -337,15 +263,27 @@ void RowPainter::paintChars(pos_type & vpos, FontInfo const & font,
docstring s(&str[0], str.size());
/* Because we do our own bidi, at this point the strings are
* already in visual order. However, Qt also applies its own
* bidi algorithm to strings that it paints to the screen.
* Therefore, if we were to paint Hebrew/Arabic words as a
* single string, the letters in the words would get reversed
* again. In order to avoid that, we reverse the string in advance.
* See also http://thread.gmane.org/gmane.editors.lyx.devel/79740
* for an earlier thread on the subject
*/
if (rtl)
reverse(s.begin(), s.end());
if (s[0] == '\t')
s.replace(0,1,from_ascii(" "));
if (!selection && !change_running.changed()) {
x_ += pi_.pain.text(int(x_), yo_, s, font);
x_ += pi_.pain.text(int(x_), yo_, s, font.fontInfo());
return;
}
FontInfo copy = font;
FontInfo copy = font.fontInfo();
if (change_running.changed())
copy.setPaintColor(change_running.color());
else if (selection)
@ -394,36 +332,14 @@ void RowPainter::paintMisspelledMark(double orig_x, bool changed)
void RowPainter::paintFromPos(pos_type & vpos, bool changed)
{
pos_type const pos = bidi_.vis2log(vpos);
Font const orig_font = text_metrics_.displayFont(pit_, pos);
Font const font = text_metrics_.displayFont(pit_, pos);
double const orig_x = x_;
// usual characters, no insets
char_type const c = par_.getChar(pos);
paintChars(vpos, font);
paintForeignMark(orig_x, font.language());
// special case languages
string const & lang = orig_font.language()->lang();
bool const hebrew = lang == "hebrew";
bool const arabic = lang == "arabic_arabtex" || lang == "arabic_arabi" ||
lang == "farsi";
// spelling correct?
bool const misspelled =
lyxrc.spellcheck_continuously && par_.isMisspelled(pos);
// draw as many chars as we can
if ((!hebrew && !arabic)
|| (hebrew && !Encodings::isHebrewComposeChar(c))
|| (arabic && !Encodings::isArabicComposeChar(c))) {
paintChars(vpos, orig_font.fontInfo(), hebrew, arabic);
} else if (hebrew) {
paintHebrewComposeChar(vpos, orig_font.fontInfo());
} else if (arabic) {
paintArabicComposeChar(vpos, orig_font.fontInfo());
}
paintForeignMark(orig_x, orig_font.language());
if (lyxrc.spellcheck_continuously && misspelled) {
// Paint the spelling mark if needed.
if (lyxrc.spellcheck_continuously && par_.isMisspelled(pos)) {
// check for cursor position
// don't draw misspelled marker for words at cursor position
// we don't want to disturb the process of text editing

5
src/rowpainter.h
View File

@ -61,10 +61,7 @@ private:
void paintSeparator(double orig_x, double width, FontInfo const & font);
void paintForeignMark(double orig_x, Language const * lang, int desc = 0);
void paintMisspelledMark(double orig_x, bool changed);
void paintHebrewComposeChar(pos_type & vpos, FontInfo const & font);
void paintArabicComposeChar(pos_type & vpos, FontInfo const & font);
void paintChars(pos_type & vpos, FontInfo const & font,
bool hebrew, bool arabic);
void paintChars(pos_type & vpos, Font const & font);
int paintAppendixStart(int y);
void paintFromPos(pos_type & vpos, bool changed);
void paintInset(Inset const * inset, pos_type const pos);

23
src/support/lstrings.cpp
View File

@ -161,6 +161,29 @@ bool isNumber(char_type c)
}
bool isRTL(char_type c)
{
if (!is_utf16(c))
// assume that no non-utf16 character is right-to-left
// c outside the UCS4 range is catched as well
return false;
QChar::Direction direction = ucs4_to_qchar(c).direction();
/**
* See for example:
* http://en.wikipedia.org/wiki/Template:Bidi_Class_%28Unicode%29.
* Here we only handle the easy cases:
* * R: Hebrew alphabet and related punctuation
* * AL: Arabic, Thaana and Syriac alphabets, and most
* punctuation specific to those scripts
*
* FIXME: testing show that this does not work (see
* RowPainter::paintChars), but my knowledge of unicode is too
* poor to understand why.
*/
return direction == QChar::DirR || direction ==QChar::DirAL;
}
bool isDigitASCII(char_type c)
{
return '0' <= c && c <= '9';

3
src/support/textutils.h
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@ -44,6 +44,9 @@ bool isSpace(char_type c);
/// return true if a unicode char is a numeral.
bool isNumber(char_type c);
/// return true is a unicode char uses a right-to-left direction for layout
bool isRTL(char_type c);
/// return whether \p c is a digit in the ASCII range
bool isDigitASCII(char_type c);