Qml Designer Theming: Fix background color

The background color for light theme is too dark. Instead of trying hard
to deduct that color mathematically, let's add a theme role for it.

Change-Id: I6a49d43e7e11c87427242819c67988b05b87518b
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

share/qtcreator/themes/dark.creatortheme

@@ -200,6 +200,7 @@ PaletteWindowTextDisabled=textDisabled
 PaletteBaseDisabled=backgroundColorDisabled
 PaletteTextDisabled=textDisabled
 
+QmlDesigner_BackgroundColor=ff3c3e40
 QmlDesigner_HighlightColor=ff46a2da
 
 [Flags]

share/qtcreator/themes/default.creatortheme

@@ -171,6 +171,7 @@ ProjectExplorer_TaskWarn_TextMarkColor=ffffa500
 ClangCodeModel_Error_TextMarkColor=ffff882f
 ClangCodeModel_Warning_TextMarkColor=ffc6c132
 
+QmlDesigner_BackgroundColor=ff4c4e50
 QmlDesigner_HighlightColor=ff46a2da
 
 [Flags]

share/qtcreator/themes/flat-dark.creatortheme

@@ -185,6 +185,7 @@ ProjectExplorer_TaskWarn_TextMarkColor=ffffff40
 ClangCodeModel_Error_TextMarkColor=ffff882f
 ClangCodeModel_Warning_TextMarkColor=ffceff40
 
+QmlDesigner_BackgroundColor=ff4c4e50
 QmlDesigner_HighlightColor=ff3f91c4
 
 PaletteWindow=normalBackground

share/qtcreator/themes/flat-light.creatortheme

@@ -182,6 +182,7 @@ ProjectExplorer_TaskWarn_TextMarkColor=ffffa500
 ClangCodeModel_Error_TextMarkColor=ffff882f
 ClangCodeModel_Warning_TextMarkColor=ffc6c132
 
+QmlDesigner_BackgroundColor=fff8f8f8
 QmlDesigner_HighlightColor=ff46a2da
 
 [Flags]

share/qtcreator/themes/flat.creatortheme

@@ -181,6 +181,7 @@ ProjectExplorer_TaskWarn_TextMarkColor=ffffa500
 ClangCodeModel_Error_TextMarkColor=ffff882f
 ClangCodeModel_Warning_TextMarkColor=ffc6c132
 
+QmlDesigner_BackgroundColor=ff4c4e50
 QmlDesigner_HighlightColor=ff46a2da
 
 [Flags]

src/libs/utils/theme/theme.h

@@ -282,6 +282,7 @@ public:
         ClangCodeModel_Warning_TextMarkColor,
 
         /* QmlDesigner */
+        QmlDesigner_BackgroundColor,
         QmlDesigner_HighlightColor
     };
 

src/plugins/qmldesigner/components/componentcore/theming.cpp

@@ -33,13 +33,6 @@
 
 namespace QmlDesigner {
 
-QColor midtone(const QColor &a, const QColor &b)
-{
-    QColor alphaB = b;
-    alphaB.setAlpha(128);
-    return Utils::StyleHelper::alphaBlendedColors(a ,alphaB);
-}
-
 void Theming::insertTheme(QQmlPropertyMap *map)
 {
     const QVariantHash creatorTheme = Utils::creatorTheme()->values();
@@ -47,6 +40,7 @@ void Theming::insertTheme(QQmlPropertyMap *map)
         map->insert(it.key(), it.value());
 
     /* Define QmlDesigner colors and remove alpha channels */
+    const QColor backgroundColor = Utils::creatorTheme()->color(Utils::Theme::QmlDesigner_BackgroundColor);
     const QColor panelStatusBarBackgroundColor = Utils::creatorTheme()->color(Utils::Theme::PanelStatusBarBackgroundColor);
     const QColor fancyToolButtonSelectedColor  = Utils::creatorTheme()->color(Utils::Theme::FancyToolButtonSelectedColor);
     const QColor darkerBackground = Utils::StyleHelper::alphaBlendedColors(panelStatusBarBackgroundColor, fancyToolButtonSelectedColor);
@@ -65,7 +59,7 @@ void Theming::insertTheme(QQmlPropertyMap *map)
     }
 
     map->insert("QmlDesignerBackgroundColorDarker", darkerBackground);
-    map->insert("QmlDesignerBackgroundColorDarkAlternate", midtone(panelStatusBarBackgroundColor, buttonColor));
+    map->insert("QmlDesignerBackgroundColorDarkAlternate", backgroundColor);
     map->insert("QmlDesignerTabLight", tabLight);
     map->insert("QmlDesignerTabDark", tabDark);
     map->insert("QmlDesignerButtonColor", buttonColor);