diff options
author | Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io> | 2021-01-15 09:11:07 +0100 |
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committer | Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io> | 2021-01-25 15:56:50 +0100 |
commit | d79a9b1a4f694a227ce62ccab9b44685a9755916 (patch) | |
tree | e943780120ee3abcf987ecd0c05440f9ed5a9b7b /src/gui/painting/qpaintengine_raster.cpp | |
parent | 80e87ca05c2b421dbca9fc8f9a8f290a3eabc206 (diff) |
Implement vertical subpixel positioning where available
For some use cases, vertical subpixel positioning may be
useful, as it allows you to vertically align text with
other painting primitives. This does impose an overhead,
so we make it opt-int with a render hint on the painter.
Note that this is only supported on Freetype currently.
It might be possible to support on older macOS versions,
prior to Mojave (which has disabled subpixel positioning
entirely), but since it would have limited usefulness
and Freetype is cross-platform anyway, I skipped that.
Note: This drive-by-fixes an issue with subpixel
positioning where glyphs would always be offset by 1/64,
because we added the aliasing offset *after* we had
determined the closest subpixel position. The idea of
this, as far as I can understand, is rather to snap to
nearest subpixel position upwards, not to add an offset
to all glyphs, so it should be added before finding the
correct position. It had a subtle visual effect when
animating the position. It might be that we could get
rid of it entirely, as I haven't been able to reproduce
any issues with that, but I have moved it instead, to
match what I believe the intention was.
[ChangeLog][QtGui][Text] Added render hint flag
QPainter::VerticalSubpixelPositioning which will position
text at subpixel positions vertically whenever supported.
In absence of this, text position will be rounded
vertically as before.
Fixes: QTBUG-35682
Change-Id: I8ce7a72a64e5a0924dac7c244e3e07c2938bfd09
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Diffstat (limited to 'src/gui/painting/qpaintengine_raster.cpp')
-rw-r--r-- | src/gui/painting/qpaintengine_raster.cpp | 26 |
1 files changed, 20 insertions, 6 deletions
diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp index ca1c4f831e..26f8de5b8b 100644 --- a/src/gui/painting/qpaintengine_raster.cpp +++ b/src/gui/painting/qpaintengine_raster.cpp @@ -1,6 +1,6 @@ /**************************************************************************** ** -** Copyright (C) 2016 The Qt Company Ltd. +** Copyright (C) 2021 The Qt Company Ltd. ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the QtGui module of the Qt Toolkit. @@ -2812,6 +2812,9 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs, Q_D(QRasterPaintEngine); QRasterPaintEngineState *s = state(); + bool verticalSubPixelPositions = fontEngine->supportsVerticalSubPixelPositions() + && (s->renderHints & QPainter::VerticalSubpixelPositioning) != 0; + if (fontEngine->hasInternalCaching()) { QFontEngine::GlyphFormat neededFormat = painter()->device()->devType() == QInternal::Widget @@ -2822,7 +2825,9 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs, neededFormat = QFontEngine::Format_Mono; for (int i = 0; i < numGlyphs; i++) { - QFixed spp = fontEngine->subPixelPositionForX(positions[i].x); + QFixedPoint spp = fontEngine->subPixelPositionFor(positions[i]); + if (!verticalSubPixelPositions) + spp.y = 0; const QFontEngine::Glyph *alphaMap = fontEngine->glyphData(glyphs[i], spp, neededFormat, s->matrix); if (!alphaMap) @@ -2847,9 +2852,13 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs, Q_UNREACHABLE(); }; + QFixed y = verticalSubPixelPositions + ? qFloor(positions[i].y) + : qRound(positions[i].y); + alphaPenBlt(alphaMap->data, bytesPerLine, depth, qFloor(positions[i].x) + alphaMap->x, - qRound(positions[i].y) - alphaMap->y, + qFloor(y) - alphaMap->y, alphaMap->width, alphaMap->height, fontEngine->expectsGammaCorrectedBlending()); } @@ -2864,7 +2873,7 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs, fontEngine->setGlyphCache(nullptr, cache); } - cache->populate(fontEngine, numGlyphs, glyphs, positions); + cache->populate(fontEngine, numGlyphs, glyphs, positions, s->renderHints); cache->fillInPendingGlyphs(); const QImage &image = cache->image(); @@ -2881,15 +2890,20 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs, int margin = fontEngine->glyphMargin(glyphFormat); const uchar *bits = image.bits(); for (int i=0; i<numGlyphs; ++i) { + QFixedPoint subPixelPosition = fontEngine->subPixelPositionFor(positions[i]); + if (!verticalSubPixelPositions) + subPixelPosition.y = 0; - QFixed subPixelPosition = fontEngine->subPixelPositionForX(positions[i].x); QTextureGlyphCache::GlyphAndSubPixelPosition glyph(glyphs[i], subPixelPosition); const QTextureGlyphCache::Coord &c = cache->coords[glyph]; if (c.isNull()) continue; int x = qFloor(positions[i].x) + c.baseLineX - margin; - int y = qRound(positions[i].y) - c.baseLineY - margin; + int y = (verticalSubPixelPositions + ? qFloor(positions[i].y) + : qRound(positions[i].y)); + y -= c.baseLineY + margin; // printf("drawing [%d %d %d %d] baseline [%d %d], glyph: %d, to: %d %d, pos: %d %d\n", // c.x, c.y, |