Resolves: tdf#104598 make bright theme shadow the same as it always was

The shadow color was originally set via StyleSettings::Set3DColors taking the
background color as the input, and doing DecreaseLuminance(64) on it to make
the shadow color

So, continue to follow that mode if the "dark shadow" is darker than the
foreground, and IncreaseLuminance the equal amount the other direction for dark
themes.

This way under a dark theme the problem of impossible to see rulers of
tdf#90214 is still fixed, while the bright theme colors are the same as they
always were, which avoid the wearing-on-the-nerves "regression" problem.

Change-Id: I33133ff180ecadce3a14ee45bd33db73c56c0225

2 files changed, 12 insertions, 16 deletions

diff --git a/vcl/unx/gtk/salnativewidgets-gtk.cxx b/vcl/unx/gtk/salnativewidgets-gtk.cxx
index 5e07ade6ea93..e8e8cdd81ef7 100644
--- a/vcl/unx/gtk/salnativewidgets-gtk.cxx
+++ b/vcl/unx/gtk/salnativewidgets-gtk.cxx
@@ -3943,14 +3943,12 @@ void GtkSalGraphics::updateSettings( AllSettings& rSettings )
     Color aDarkShadowColor = getColor( pStyle->fg[GTK_STATE_INSENSITIVE] );
     aStyleSet.SetDarkShadowColor( aDarkShadowColor );
 
-    int nRedDiff = aBackFieldColor.GetRed() - aDarkShadowColor.GetRed();
-    int nGreenDiff = aBackFieldColor.GetGreen() - aDarkShadowColor.GetGreen();
-    int nBlueDiff = aBackFieldColor.GetBlue() - aDarkShadowColor.GetBlue();
-
-    Color aShadowColor(aBackFieldColor.GetRed() + nRedDiff / 2,
-                       aBackFieldColor.GetGreen() + nGreenDiff / 2,
-                       aBackFieldColor.GetBlue() + nBlueDiff / 2);
-    aStyleSet.SetShadowColor( aShadowColor );
+    ::Color aShadowColor(aBackColor);
+    if (aDarkShadowColor.GetLuminance() > aBackColor.GetLuminance())
+        aShadowColor.IncreaseLuminance(64);
+    else
+        aShadowColor.DecreaseLuminance(64);
+    aStyleSet.SetShadowColor(aShadowColor);
 
     // highlighting colors
     Color aHighlightColor = getColor( pStyle->base[GTK_STATE_SELECTED] );
diff --git a/vcl/unx/gtk3/gtk3salnativewidgets-gtk.cxx b/vcl/unx/gtk3/gtk3salnativewidgets-gtk.cxx
index 48edf22f9d72..e036c207489f 100644
--- a/vcl/unx/gtk3/gtk3salnativewidgets-gtk.cxx
+++ b/vcl/unx/gtk3/gtk3salnativewidgets-gtk.cxx
@@ -2585,14 +2585,12 @@ void GtkSalGraphics::updateSettings( AllSettings& rSettings )
         ::Color aDarkShadowColor = getColor( color );
         aStyleSet.SetDarkShadowColor( aDarkShadowColor );
 
-        int nRedDiff = aBackFieldColor.GetRed() - aDarkShadowColor.GetRed();
-        int nGreenDiff = aBackFieldColor.GetGreen() - aDarkShadowColor.GetGreen();
-        int nBlueDiff = aBackFieldColor.GetBlue() - aDarkShadowColor.GetBlue();
-
-        ::Color aShadowColor(aBackFieldColor.GetRed() + nRedDiff / 2,
-                             aBackFieldColor.GetGreen() + nGreenDiff / 2,
-                             aBackFieldColor.GetBlue() + nBlueDiff / 2);
-        aStyleSet.SetShadowColor( aShadowColor );
+        ::Color aShadowColor(aBackColor);
+        if (aDarkShadowColor.GetLuminance() > aBackColor.GetLuminance())
+            aShadowColor.IncreaseLuminance(64);
+        else
+            aShadowColor.DecreaseLuminance(64);
+        aStyleSet.SetShadowColor(aShadowColor);
 
         g_object_unref( pCStyle );