From e2a89fc2e07b0b063f166358cbf5a31f9e8ad3b0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Aur=C3=A9lien=20G=C3=A2teau?= Date: Thu, 21 Mar 2013 14:06:07 +0100 Subject: [PATCH] Fix transition between m_pixmap and m_hoverPixmap The default SourceOver composition mode of QPainter cannot be used to interpolate between two images, we must use intermediate buffers to perform the interpolation and blend the result on the widget. More details are available in the review request. REVIEW: 109614 FIXED-IN: 4.10.2 --- src/kitemviews/kstandarditemlistwidget.cpp | 47 +++++++++++++++++----- 1 file changed, 38 insertions(+), 9 deletions(-) diff --git a/src/kitemviews/kstandarditemlistwidget.cpp b/src/kitemviews/kstandarditemlistwidget.cpp index fcd0520457..6adb546332 100644 --- a/src/kitemviews/kstandarditemlistwidget.cpp +++ b/src/kitemviews/kstandarditemlistwidget.cpp @@ -249,17 +249,46 @@ void KStandardItemListWidget::paint(QPainter* painter, const QStyleOptionGraphic const KItemListStyleOption& itemListStyleOption = styleOption(); if (isHovered()) { - const qreal opacity = painter->opacity(); - // Blend the unhovered and hovered pixmap if the hovering - // animation is ongoing if (hoverOpacity() < 1.0) { - painter->setOpacity((1.0 - hoverOpacity()) * opacity); - drawPixmap(painter, m_pixmap); - } + /* + * Linear interpolation between m_pixmap and m_hoverPixmap. + * + * Note that this cannot be achieved by painting m_hoverPixmap over + * m_pixmap, even if the opacities are adjusted. For details see + * https://git.reviewboard.kde.org/r/109614/ + */ + // Paint pixmap1 so that pixmap1 = m_pixmap * (1.0 - hoverOpacity()) + QPixmap pixmap1(option->rect.size()); + pixmap1.fill(Qt::transparent); + { + QPainter p(&pixmap1); + p.setOpacity(1.0 - hoverOpacity()); + drawPixmap(&p, m_pixmap); + } - painter->setOpacity(hoverOpacity() * opacity); - drawPixmap(painter, m_hoverPixmap); - painter->setOpacity(opacity); + // Paint pixmap2 so that pixmap2 = m_hoverPixmap * hoverOpacity() + QPixmap pixmap2(option->rect.size()); + pixmap2.fill(Qt::transparent); + { + QPainter p(&pixmap2); + p.setOpacity(hoverOpacity()); + drawPixmap(&p, m_hoverPixmap); + } + + // Paint pixmap2 on pixmap1 using CompositionMode_Plus + // Now pixmap1 = pixmap2 + m_pixmap * (1.0 - hoverOpacity()) + // = m_hoverPixmap * hoverOpacity() + m_pixmap * (1.0 - hoverOpacity()) + { + QPainter p(&pixmap1); + p.setCompositionMode(QPainter::CompositionMode_Plus); + p.drawPixmap(0, 0, pixmap2); + } + + // Finally paint pixmap1 on the widget + painter->drawPixmap(0, 0, pixmap1); + } else { + drawPixmap(painter, m_hoverPixmap); + } } else { drawPixmap(painter, m_pixmap); }