QFont::fromString() of Qt 5.x and Qt <= 6.10 rejects the >= 19 field
descriptions QFont::toString() emits since Qt 6.11, silently leaving a
broken font at every read site. Add QETUtils::fontFromString(): try the
native parser first, and on failure re-compose the legacy 10/11 field
form from the known Qt 6.11 field layout (OpenType weight mapped back
to the legacy scale) so no font information stored in existing files is
lost. Also salvage the 21 field double-serialized descriptions left
behind by some historical builds (a complete legacy description
embedded as the family name of a second one) by taking the embedded
leading description, matching what the lenient parser of Qt 6.11+
resolves them to. All font read sites now go through the helper; on
failure the default font of the caller is left untouched instead of a
cleared family.
Verified end to end on a Qt 5.15 build: a project whose 53 font
attributes were rewritten into the 19 field Qt 6.11 format loads and
autosaves byte-identical to the original legacy file (family, sizes,
bold/italic/underline, style name all preserved), and a mixed file
containing the exact 21 field string from the issue comes back
normalized as "Caladea,9,-1,5,75,1,0,0,0,0,Bold Italic".
See issue #553.
QFont::toString() is not stable across Qt versions: Qt 6.11 switched to
a 19-field format carrying OpenType weights, which QFont::fromString()
of Qt 5.x and Qt <= 6.10 rejects, leaving a broken font. Projects saved
by a Qt 6.11+ build were therefore unreadable by older builds.
Add QETUtils::fontToString() composing the legacy 10/11-field
description (weight mapped back to the legacy scale with the same
closest-match table Qt uses when parsing) and use it at every site that
stores a font description in a project, element, table config or
settings file. Every Qt version from 5.15 through 6.12-beta parses this
form correctly, so files stay readable by every QET build in
circulation.
See issue #553.
Dieter Mayer