fusioncontrast-qt6.diff

Description: Fix dreadful contrast of the Qt Fusion style in various places.
We can't use a proxy style for this stuff because for some reason that destroys
the layout for everything in Windows set to Chinese. I guess it has some special
hacks that only work if the style is set directly.

Tool bar extension arrows are black by default, which means they're virtually
invisible in dark styles. We load bespoke theme icons if we can find them.

Checkbox outlines have completely garbage contrast in dark styles. We detect
that and increase the lightness on them in that case.

Contrast on sunken buttons is really bad in dark themes and worse in darker
ones. We adjust those pretty hard to be actually visible.

--- a/src/widgets/styles/qcommonstyle.cpp
+++ b/src/widgets/styles/qcommonstyle.cpp
@@ -5796,6 +5796,10 @@
                 return QIcon::fromTheme(themeName);
             break;
         }
+        case QStyle::SP_ToolBarHorizontalExtensionButton:
+            return QIcon::fromTheme(rtl(option) ? "toolbar-ext-h-rtl-drawpile"_L1 : "toolbar-ext-h-drawpile"_L1);
+        case QStyle::SP_ToolBarVerticalExtensionButton:
+            return QIcon::fromTheme("toolbar-ext-v-drawpile"_L1);
         default:
             break;
         }
--- a/src/widgets/styles/qfusionstyle.cpp
+++ b/src/widgets/styles/qfusionstyle.cpp
@@ -634,7 +634,8 @@
             gradient.setColorAt(1, (state & State_Sunken) ? pressedColor : option->palette.base().color());

             painter->setBrush((state & State_Sunken) ? QBrush(pressedColor) : gradient);
-            painter->setPen(QPen(outline.lighter(110)));
+            bool dark = option->palette.color(QPalette::Window).lightness() < 128;
+            painter->setPen(QPen(outline.lighter(dark ? 170 : 110)));

             if (option->state & State_HasFocus && option->state & State_KeyboardFocusChange)
                 painter->setPen(QPen(highlightedOutline));
@@ -808,7 +809,12 @@

         QLinearGradient gradient = qt_fusion_gradient(rect, (isEnabled && option->state & State_MouseOver ) ? buttonColor : buttonColor.darker(104));
         p->setPen(Qt::transparent);
-        p->setBrush(isDown ? QBrush(buttonColor.darker(110)) : gradient);
+        if(isDown) {
+            int lightness = option->palette.color(QPalette::Window).lightness();
+            p->setBrush(QBrush(buttonColor.darker(lightness > 127 ? 110 : lightness > 63 ? 140 : 180)));
+        } else {
+            p->setBrush(QBrush(gradient));
+        }
         p->drawRoundedRect(r, 2.0, 2.0);
         p->setBrush(Qt::NoBrush);