On Fri, Mar 31, 2017 at 05:03:44PM +0200, Jean-Marc Lasgouttes wrote:
> commit da590925cd6749587b9f500ecdaa457e34bc0f4a
> Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
> Date: Fri Mar 31 16:56:06 2017 +0200
>
> Work around bug in QTextLine::xToCursor
>
> With RtL text, the method can be non-monotonic wrt x value (which is a
> Qt bug). To work around this, we check whether positions adjacent to
> those returned by xToCursor look better. Depending on whether the new
> x position is too small or too large, we look backward or forward for
> a better solution.
>
> The performance is probably not great, but this is only needed for
> user interactions, so the performance penalty should not be a problem.
>
> Fixes #10569.
> ---
> src/frontends/qt4/GuiFontMetrics.cpp | 29 +++++++++++++++++++++++++++--
> 1 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/src/frontends/qt4/GuiFontMetrics.cpp
> b/src/frontends/qt4/GuiFontMetrics.cpp
> index 33df3cf..585933a 100644
> --- a/src/frontends/qt4/GuiFontMetrics.cpp
> +++ b/src/frontends/qt4/GuiFontMetrics.cpp
> @@ -272,9 +272,34 @@ int GuiFontMetrics::x2pos(docstring const & s, int & x,
> bool const rtl,
> double const wordspacing) const
> {
> shared_ptr<QTextLayout const> tl = getTextLayout(s, rtl, wordspacing);
> - int const qpos = tl->lineForTextPosition(0).xToCursor(x);
> + QTextLine const & tline = tl->lineForTextPosition(0);
> + int qpos = tline.xToCursor(x);
> + int newx = static_cast<int>(tline.cursorToX(qpos));
> + // The value of qpos may be wrong in rtl text (see ticket #10569).
> + // To work around this, let's have a look at adjacent positions to
> + // see whether we find closer matches.
> + if (rtl && newx < x) {
> + while (qpos > 0) {
> + int const xm = static_cast<int>(tline.cursorToX(qpos -
> 1));
> + if (abs(xm - x) < abs(newx - x)) {
> + --qpos;
> + newx = xm;
> + } else
> + break;
> + }
> + } else if (rtl && newx > x) {
> + while (qpos < tline.textLength()) {
> + int const xp = static_cast<int>(tline.cursorToX(qpos +
> 1));
> + if (abs(xp - x) < abs(newx - x)) {
> + ++qpos;
> + newx = xp;
> + } else
> + break;
> + }
> + }
> // correct x value to the actual cursor position.
> - x = static_cast<int>(tl->lineForTextPosition(0).cursorToX(qpos));
> + x = newx;
> +
> /* Since QString is UTF-16 and docstring is UCS-4, the offsets may
> * not be the same when there are high-plan unicode characters
> * (bug #10443).What are your thoughts on using pro-processor directives to keep track of workarounds like this? For example, I really like the approach in docstream.cpp for "WORKAROUND_ICONV_BUG". Are there disadvantages to that approach? Scott
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