src/selectionmode/backgroundcolorhelper.cpp

   1 /*
   2     This file is part of the KDE project
   3     SPDX-FileCopyrightText: 2022 Felix Ernst <felixernst@zohomail.eu>
   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
  27 void setBackgroundColorForWidget(QWidget *widget, QColor color)
  28 {
  29     QPalette palette;
  30     palette.setBrush(QPalette::Active,   QPalette::Window, color);
  31     palette.setBrush(QPalette::Inactive, QPalette::Window, color);
  32     palette.setBrush(QPalette::Disabled, QPalette::Window, color);
  33     widget->setAutoFillBackground(true);
  34     widget->setPalette(palette);
  35 }
  36
  37 void BackgroundColorHelper::controlBackgroundColor(QWidget *widget)
  38 {
  39     setBackgroundColorForWidget(widget, m_backgroundColor);
  40
  41     Q_ASSERT_X(std::find(m_colorControlledWidgets.begin(), m_colorControlledWidgets.end(), widget) == m_colorControlledWidgets.end(), "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 BackgroundColorHelper::BackgroundColorHelper()
  47 {
  48     updateBackgroundColor();
  49     QObject::connect(qApp, &QGuiApplication::paletteChanged, [=](){ slotPaletteChanged(); });
  50 }
  51
  52 void BackgroundColorHelper::slotPaletteChanged()
  53 {
  54     updateBackgroundColor();
  55     for (auto i = m_colorControlledWidgets.begin(); i != m_colorControlledWidgets.end(); ++i) {
  56         while (!*i) {
  57             i = m_colorControlledWidgets.erase(i);
  58             if (i == m_colorControlledWidgets.end()) {
  59                 return;
  60             }
  61         }
  62         setBackgroundColorForWidget(*i, m_backgroundColor);
  63     }
  64 }
  65
  66 void BackgroundColorHelper::updateBackgroundColor()
  67 {
  68     // We use colors from the color scheme for mixing so it fits the theme.
  69     const auto colorScheme = KColorScheme(QPalette::Normal, KColorScheme::Window);
  70     const auto activeBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::ActiveBackground).color();
  71     // We use the positive color for mixing so the end product doesn't look like a warning or error.
  72     const auto positiveBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::PositiveBackground).color();
  73
  74     // Make sure the new background color has a meaningfully different hue than the activeBackgroundColor.
  75     const int hueDifference = positiveBackgroundColor.hue() - activeBackgroundColor.hue();
  76     int newHue;
  77     if (std::abs(hueDifference) > 80) {
  78         newHue = (activeBackgroundColor.hue() + positiveBackgroundColor.hue()) / 2;
  79     } else {
  80         newHue = hueDifference > 0 ?
  81             activeBackgroundColor.hue() + 40 :
  82             activeBackgroundColor.hue() - 40;
  83         newHue %= 360; // hue needs to be between 0 and 359 per Qt documentation.
  84     }
  85
  86     m_backgroundColor = QColor::fromHsv(newHue,
  87                                         // Saturation should be closer to the saturation of the active color
  88                                         // because otherwise the selection mode color might overpower it.
  89                                         .7 * activeBackgroundColor.saturation() + .3 * positiveBackgroundColor.saturation(),
  90                                         (activeBackgroundColor.value() + positiveBackgroundColor.value()) / 2,
  91                                         (activeBackgroundColor.alpha() + positiveBackgroundColor.alpha()) / 2);
  92 }
  93
  94 BackgroundColorHelper *BackgroundColorHelper::s_instance = nullptr;