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 using namespace SelectionMode;
  18
  19 BackgroundColorHelper *BackgroundColorHelper::instance()
  20 {
  21     if (!s_instance) {
  22         s_instance = new BackgroundColorHelper;
  23     }
  24     return s_instance;
  25 }
  26
  27
  28 void setBackgroundColorForWidget(QWidget *widget, QColor color)
  29 {
  30     QPalette palette;
  31     palette.setBrush(QPalette::Active,   QPalette::Window, color);
  32     palette.setBrush(QPalette::Inactive, QPalette::Window, color);
  33     palette.setBrush(QPalette::Disabled, QPalette::Window, color);
  34     widget->setAutoFillBackground(true);
  35     widget->setPalette(palette);
  36 }
  37
  38 void BackgroundColorHelper::controlBackgroundColor(QWidget *widget)
  39 {
  40     setBackgroundColorForWidget(widget, m_backgroundColor);
  41
  42     Q_ASSERT_X(std::find(m_colorControlledWidgets.begin(), m_colorControlledWidgets.end(), widget) == m_colorControlledWidgets.end(), "controlBackgroundColor",
  43                "Duplicate insertion is not necessary because the background color should already automatically update itself on paletteChanged");
  44     m_colorControlledWidgets.emplace_back(widget);
  45 }
  46
  47 BackgroundColorHelper::BackgroundColorHelper()
  48 {
  49     updateBackgroundColor();
  50     QObject::connect(qApp, &QGuiApplication::paletteChanged, [=](){ slotPaletteChanged(); });
  51 }
  52
  53 void BackgroundColorHelper::slotPaletteChanged()
  54 {
  55     updateBackgroundColor();
  56     for (auto i = m_colorControlledWidgets.begin(); i != m_colorControlledWidgets.end(); ++i) {
  57         while (!*i) {
  58             i = m_colorControlledWidgets.erase(i);
  59             if (i == m_colorControlledWidgets.end()) {
  60                 break;
  61             }
  62         }
  63         setBackgroundColorForWidget(*i, m_backgroundColor);
  64     }
  65 }
  66
  67 void BackgroundColorHelper::updateBackgroundColor()
  68 {
  69     // We use colors from the color scheme for mixing so it fits the theme.
  70     const auto colorScheme = KColorScheme(QPalette::Normal, KColorScheme::Window);
  71     const auto activeBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::ActiveBackground).color();
  72     // We use the positive color for mixing so the end product doesn't look like a warning or error.
  73     const auto positiveBackgroundColor = colorScheme.background(KColorScheme::BackgroundRole::PositiveBackground).color();
  74
  75     // Make sure the new background color has a meaningfully different hue than the activeBackgroundColor.
  76     const int hueDifference = positiveBackgroundColor.hue() - activeBackgroundColor.hue();
  77     int newHue;
  78     if (std::abs(hueDifference) > 80) {
  79         newHue = (activeBackgroundColor.hue() + positiveBackgroundColor.hue()) / 2;
  80     } else {
  81         newHue = hueDifference > 0 ?
  82             activeBackgroundColor.hue() + 40 :
  83             activeBackgroundColor.hue() - 40;
  84         newHue %= 360; // hue needs to be between 0 and 359 per Qt documentation.
  85     }
  86
  87     m_backgroundColor = QColor::fromHsv(newHue,
  88                                         // Saturation should be closer to the saturation of the active color
  89                                         // because otherwise the selection mode color might overpower it.
  90                                         .7 * activeBackgroundColor.saturation() + .3 * positiveBackgroundColor.saturation(),
  91                                         (activeBackgroundColor.value() + positiveBackgroundColor.value()) / 2,
  92                                         (activeBackgroundColor.alpha() + positiveBackgroundColor.alpha()) / 2);
  93 }
  94
  95 BackgroundColorHelper *BackgroundColorHelper::s_instance = nullptr;