workspace/kwin/effects/shadow_helper.h

   1 /********************************************************************
   2 KWin - the KDE window manager
   3 This file is part of the KDE project.
   4
   5 Copyright (C) 2008 Louai Al-Khanji <louai.khanji@gmail.com>
   6
   7 This program is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2 of the License, or
  10 (at your option) any later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 *********************************************************************/
  20
  21 // This contains code shared by the shadow effect and shadow effect configurator
  22 // Mark all functions static so the symbols are not exported!
  23
  24 #ifndef KWIN_SHADOW_HELPER_H
  25 #define KWIN_SHADOW_HELPER_H
  26
  27 #include <KColorScheme>
  28 #include <KColorUtils>
  29
  30 static const int MAX_ITERS = 10; // should be enough
  31 static const qreal LUMA_THRESHOLD = 0.05;
  32 static const qreal MINIMUM_CONTRAST = 3.0;
  33
  34 static bool contrastTooLow(const QColor& one, const QColor& two)
  35     {
  36     return KColorUtils::contrastRatio(one, two) < MINIMUM_CONTRAST;
  37     }
  38
  39 static QColor schemeShadowColor()
  40     {
  41     QPalette palette;
  42     QColor shadowColor;
  43     QPalette::ColorRole shadowRole;
  44     QColor windowColor;
  45
  46     windowColor = palette.color(QPalette::Window);
  47
  48     if (KColorUtils::luma(windowColor) >= LUMA_THRESHOLD)
  49         shadowRole = QPalette::Shadow;
  50     else
  51         shadowRole = QPalette::Light;
  52
  53     shadowColor = palette.color(shadowRole);
  54
  55     // Some styles might set a weird shadow or light color. Make sure we
  56     // do not end up looping forever or we might lock up the desktop!!
  57     int iters = 0;
  58     while (contrastTooLow(shadowColor, windowColor) && iters < MAX_ITERS)
  59         {
  60         iters++;
  61         if (shadowRole == QPalette::Shadow)
  62             shadowColor = KColorUtils::darken(shadowColor);
  63         else
  64             shadowColor = KColorUtils::lighten(shadowColor);
  65         }
  66
  67     return shadowColor;
  68     }
  69
  70 #endif // KWIN_SHADOW_HELPER_H