From 2acc883b3a339b716da9249a1366b08225acbd8a Mon Sep 17 00:00:00 2001 From: Gunnar Sletta Date: Thu, 11 Feb 2010 15:16:44 +0100 Subject: document the slowness of QPixmap::hasAlpha() Reviewed-by: Kim --- src/gui/image/qpixmap.cpp | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/src/gui/image/qpixmap.cpp b/src/gui/image/qpixmap.cpp index d1e5c40..1df7946 100644 --- a/src/gui/image/qpixmap.cpp +++ b/src/gui/image/qpixmap.cpp @@ -1670,10 +1670,9 @@ QPixmap QPixmap::transformed(const QMatrix &matrix, Qt::TransformationMode mode) \o The hasAlphaChannel() returns true if the pixmap has a format that - respects the alpha channel, otherwise returns false, while the - hasAlpha() function returns true if the pixmap has an alpha - channel \e or a mask (otherwise false). The mask() function returns - the mask as a QBitmap object, which can be set using setMask(). + respects the alpha channel, otherwise returns false. The hasAlpha(), + setMask() and mask() functions are legacy and should not be used. + They are potentially very slow. The createHeuristicMask() function creates and returns a 1-bpp heuristic mask (i.e. a QBitmap) for this pixmap. It works by @@ -1760,6 +1759,8 @@ QPixmap QPixmap::transformed(const QMatrix &matrix, Qt::TransformationMode mode) Returns true if this pixmap has an alpha channel, \e or has a mask, otherwise returns false. + \warning This is potentially an expensive operation. + \sa hasAlphaChannel(), mask() */ bool QPixmap::hasAlpha() const -- cgit v0.12