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Direct2D QPA: Pixel-align aliased drawing

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Aliased drawing has so far not been perfectly pixel aligned, resulting in
less than stellar output in some instances. Although a little hacky,
adding 0.5 to all coordinates when in aliased mode fixes things up nicely.
There doesn't appear to be a better way to get d2d to cooperate as we
would like it to.

Change-Id: I10ee494d2f576bfd0eca6d4429095a3726c0bf14
Reviewed-by: Risto Avila <risto.avila@digia.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
This commit is contained in:
Louai Al-Khanji 2014-04-29 16:14:19 +03:00 committed by The Qt Project
parent 090124eab6
commit 0edb21df15
1 changed files with 9 additions and 1 deletions
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10
src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
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@ -89,6 +89,11 @@ enum ClipType {
LayerClip
};
// Since d2d is a float-based system we need to be able to snap our drawing to whole pixels.
// Applying the magical aliasing offset to coordinates will do so, just make sure that
// aliased painting is turned on on the d2d device context.
static const qreal MAGICAL_ALIASING_OFFSET = 0.5;
#define D2D_TAG(tag) d->dc()->SetTags(tag, tag)
Q_GUI_EXPORT QImage qt_imageForBrush(int brushStyle, bool invert);
@ -184,8 +189,11 @@ public:
private:
D2D1_POINT_2F adjusted(const QPointF &point)
{
static const QPointF adjustment(MAGICAL_ALIASING_OFFSET,
MAGICAL_ALIASING_OFFSET);
if (m_roundCoordinates)
return to_d2d_point_2f(point.toPoint());
return to_d2d_point_2f(point + adjustment);
else
return to_d2d_point_2f(point);
}