src/selectionmode/backgroundcolorhelper.cpp

   1 /*
   2     This file is part of the KDE project
   3     SPDX-FileCopyrightText: 2022 Felix Ernst <felixernst@kde.org>
   4
   5     SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
   6 */
   7
   8 #include "backgroundcolorhelper.h"
   9
  10 #include <KColorScheme>
  11
  12 #include <QGuiApplication>
  13 #include <QPalette>
  14 #include <QWidget>
  15
  16 using namespace SelectionMode;
  17
  18 BackgroundColorHelper *BackgroundColorHelper::instance()
  19 {
  20     if (!s_instance) {
  21         s_instance = new BackgroundColorHelper;
  22     }
  23     return s_instance;
  24 }
  25
  26 void setBackgroundColorForWidget(QWidget *widget, QColor color)
  27 {
  28     QPalette palette;
  29     palette.setBrush(QPalette::Active, QPalette::Window, color);
  30     palette.setBrush(QPalette::Inactive, QPalette::Window, color);
  31     palette.setBrush(QPalette::Disabled, QPalette::Window, color);
  32     widget->setAutoFillBackground(true);
  33     widget->setPalette(palette);
  34 }
  35
  36 void BackgroundColorHelper::controlBackgroundColor(QWidget *widget)
  37 {
  38     setBackgroundColorForWidget(widget, m_backgroundColor);
  39
  40     Q_ASSERT_X(std::find(m_colorControlledWidgets.begin(), m_colorControlledWidgets.end(), widget) == m_colorControlledWidgets.end(),
  41                "controlBackgroundColor",
  42                "Duplicate insertion is not necessary because the background color should already automatically update itself on paletteChanged");
  43     m_colorControlledWidgets.emplace_back(widget);
  44 }
  45
  46 bool BackgroundColorHelper::eventFilter(QObject *obj, QEvent *event)
  47 {
  48     Q_UNUSED(obj);
  49     if (event->type() == QEvent::ApplicationPaletteChange) {
  50         slotPaletteChanged();
  51     }
  52     return false;
  53 }
  54
  55 BackgroundColorHelper::BackgroundColorHelper()
  56 {
  57     updateBackgroundColor();
  58     qApp->installEventFilter(this);
  59 }
  60
  61 void BackgroundColorHelper::slotPaletteChanged()
  62 {
  63     updateBackgroundColor();
  64     for (auto i = m_colorControlledWidgets.begin(); i != m_colorControlledWidgets.end(); ++i) {
  65         while (!*i) {
  66             i = m_colorControlledWidgets.erase(i);
  67             if (i == m_colorControlledWidgets.end()) {
  68                 return;
  69             }
  70         }
  71         setBackgroundColorForWidget(*i, m_backgroundColor);
  72     }
  73 }
  74
  75 void BackgroundColorHelper::updateBackgroundColor()
  76 {
  77     // We use colors from the color scheme for mixing so it fits the theme.
  78     const auto colorScheme = KColorScheme(QPalette::Normal, KColorScheme::Window);
  79     const auto activeBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::ActiveBackground).color();
  80     // We use the positive color for mixing so the end product doesn't look like a warning or error.
  81     const auto positiveBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::PositiveBackground).color();
  82
  83     // Make sure the new background color has a meaningfully different hue than the activeBackgroundColor.
  84     const int hueDifference = positiveBackgroundColor.hue() - activeBackgroundColor.hue();
  85     int newHue;
  86     if (std::abs(hueDifference) > 80) {
  87         newHue = (activeBackgroundColor.hue() + positiveBackgroundColor.hue()) / 2;
  88     } else {
  89         newHue = hueDifference > 0 ? activeBackgroundColor.hue() + 40 : activeBackgroundColor.hue() - 40;
  90         newHue %= 360; // hue needs to be between 0 and 359 per Qt documentation.
  91     }
  92
  93     m_backgroundColor = QColor::fromHsv(newHue,
  94                                         // Saturation should be closer to the saturation of the active color
  95                                         // because otherwise the selection mode color might overpower it.
  96                                         .7 * activeBackgroundColor.saturation() + .3 * positiveBackgroundColor.saturation(),
  97                                         (activeBackgroundColor.value() + positiveBackgroundColor.value()) / 2,
  98                                         (activeBackgroundColor.alpha() + positiveBackgroundColor.alpha()) / 2);
  99 }
 100
 101 BackgroundColorHelper *BackgroundColorHelper::s_instance = nullptr;
 102
 103 #include "moc_backgroundcolorhelper.cpp"