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 <QtGlobal>
  15 #include <QWidget>
  16
  17 BackgroundColorHelper *BackgroundColorHelper::instance()
  18 {
  19     if (!s_instance) {
  20         s_instance = new BackgroundColorHelper;
  21     }
  22     return s_instance;
  23 }
  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(), "controlBackgroundColor",
  41                "Duplicate insertion is not necessary because the background color should already automatically update itself on paletteChanged");
  42     m_colorControlledWidgets.emplace_back(widget);
  43 }
  44
  45 BackgroundColorHelper::BackgroundColorHelper()
  46 {
  47     updateBackgroundColor();
  48     QObject::connect(qApp, &QGuiApplication::paletteChanged, [=](){ slotPaletteChanged(); });
  49 }
  50
  51 void BackgroundColorHelper::slotPaletteChanged()
  52 {
  53     updateBackgroundColor();
  54     for (auto i = m_colorControlledWidgets.begin(); i != m_colorControlledWidgets.end(); ++i) {
  55         if (!*i) {
  56             i = m_colorControlledWidgets.erase(i);
  57             continue;
  58         }
  59         setBackgroundColorForWidget(*i, m_backgroundColor);
  60     }
  61 }
  62
  63 void BackgroundColorHelper::updateBackgroundColor()
  64 {
  65     // We use colors from the color scheme for mixing so it fits the theme.
  66     const auto colorScheme = KColorScheme(QPalette::Normal, KColorScheme::Window);
  67     const auto activeBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::ActiveBackground).color();
  68     // We use the positive color for mixing so the end product doesn't look like a warning or error.
  69     const auto positiveBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::PositiveBackground).color();
  70
  71     // Make sure the new background color has a meaningfully different hue than the activeBackgroundColor.
  72     const int hueDifference = positiveBackgroundColor.hue() - activeBackgroundColor.hue();
  73     int newHue;
  74     if (std::abs(hueDifference) > 80) {
  75         newHue = (activeBackgroundColor.hue() + positiveBackgroundColor.hue()) / 2;
  76     } else {
  77         newHue = hueDifference > 0 ?
  78             activeBackgroundColor.hue() + 40 :
  79             activeBackgroundColor.hue() - 40;
  80         newHue %= 360; // hue needs to be between 0 and 359 per Qt documentation.
  81     }
  82
  83     m_backgroundColor = QColor::fromHsv(newHue,
  84                                         // Saturation should be closer to the active color because otherwise the selection mode color might overpower it.
  85                                         .7 * activeBackgroundColor.saturation() + .3 * positiveBackgroundColor.saturation(),
  86                                         (activeBackgroundColor.value() + positiveBackgroundColor.value()) / 2,
  87                                         (activeBackgroundColor.alpha() + positiveBackgroundColor.alpha()) / 2);
  88 }
  89
  90 BackgroundColorHelper *BackgroundColorHelper::s_instance = nullptr;