Enhance readability of sorted columns in high contrast mode (white text on black background). Check brightness and decide for a brighter or darker background color as needed. See issue #1366.

source/const.inc

@@ -196,7 +196,8 @@ const
   DEFAULT_FIELDCOLOR_DATETIME = $00000080; // clMaroon
   DEFAULT_FIELDCOLOR_ENUM = $00008080; // clOlive
   DEFAULT_FIELDCOLOR_SET = $00808000; // clTeal
-  COLORSHIFT_NULLFIELDS = 45; // Percentage of brightness to add to normal field colors for NULL values
+  COLORSHIFT_NULLFIELDS = 70; // Shift brightness to add to normal field colors for NULL values
+  COLORSHIFT_SORTCOLUMNS = 12; // Shift brightness to add to normal field colors for NULL values
 
   REGNAME_FIELDEDITOR_BINARY = 'FieldEditor_Binary';
   REGNAME_FIELDEDITOR_DATETIME = 'FieldEditor_Datetime';
@@ -261,8 +262,6 @@ const
   {PetaByte} NAME_PB = ' PB';
 
   // Used by ListViews and Grids
-  COLOR_SORTCOLUMN_ASC = $00F7F7F7; // light grey
-  COLOR_SORTCOLUMN_DESC = $00EEEEEE; // medium grey
   ORDER_ASC = 0;            // Used for tag-value of "Direction"-button
   ORDER_DESC = 1;           // dito
   TXT_ASC = 'ASC';          // Used for caption of "Direction"-button

source/helpers.pas

@@ -8,7 +8,7 @@ unit helpers;
 
 interface
 
-uses Classes, SysUtils, Graphics, db, clipbrd, dialogs,
+uses Classes, SysUtils, Graphics, GraphUtil, db, clipbrd, dialogs,
   forms, controls, ShellApi, checklst, windows,
   shlobj, ActiveX, WideStrUtils, VirtualTrees, SynRegExpr, Messages, WideStrings,
   TntCheckLst, Registry, SynEditHighlighter, mysql_connection, mysql_structures, DateUtils;
@@ -172,7 +172,7 @@ type
   function BinToWideHex(bin: string): WideString;
   procedure CheckHex(text: WideString; errorMessage: string);
   procedure FixVT(VT: TVirtualStringTree);
-  function ColorAdjustBrightness(Col: TColor; ShiftPercent: ShortInt): TColor;
+  function ColorAdjustBrightness(Col: TColor; Shift: SmallInt; BestFit: Boolean): TColor;
   function ComposeOrderClause(Cols: TOrderColArray): WideString;
   procedure OpenRegistry(Session: String = '');
   function GetRegValue( valueName: String; defaultValue: Integer; Session: String = '' ) : Integer; Overload;
@@ -187,6 +187,8 @@ type
   function DateBackFriendlyCaption(d: TDateTime): String;
   procedure InheritFont(AFont: TFont);
   function GetTableSize(Results: TMySQLQuery): Int64;
+  function GetLightness(AColor: TColor): Byte;
+
 var
   MainReg                    : TRegistry;
 
@@ -2641,26 +2643,20 @@ begin
 end;
 
 
-function ColorAdjustBrightness(Col: TColor; ShiftPercent: ShortInt): TColor;
+function ColorAdjustBrightness(Col: TColor; Shift: SmallInt; BestFit: Boolean): TColor;
 var
-  r, g, b, ShiftBytes: SmallInt;
+  Lightness: Byte;
 begin
-  // Split colors
-  r := GetRValue(Col);
-  g := GetGValue(Col);
-  b := GetBValue(Col);
-  // Convert percent value to bytes
-  ShiftBytes := Round(ShiftPercent * 255 / 100);
-  // Adjust single colors
-  r := r + ShiftBytes;
-  g := g + ShiftBytes;
-  b := b + ShiftBytes;
-  // Fix exceeded bounds
-  if r > 255 then r := 255 else if r < 0 then r := 0;
-  if g > 255 then g := 255 else if g < 0 then g := 0;
-  if b > 255 then b := 255 else if b < 0 then b := 0;
-  // Merge result
-  Result := RGB(r, g, b);
+  if BestFit then begin
+    // If base color is bright, make bg color darker (grey), and vice versa, so that
+    // colors work with high contrast mode for accessibility
+    Lightness := GetLightness(Col);
+    if (Lightness < 128) and (Shift < 0) then
+      Shift := Abs(Shift)
+    else if (Lightness > 128) and (Shift > 0) then
+      Shift := 0 - Abs(Shift);
+  end;
+  Result := ColorAdjustLuma(Col, Shift, true);
 end;
 
 
@@ -2901,6 +2897,21 @@ begin
 end;
 
 
+function GetLightness(AColor: TColor): Byte;
+var
+  R, G, B: Byte;
+  MaxValue, MinValue: Double;
+  Lightness: Double;
+begin
+  R := GetRValue(ColorToRGB(AColor));
+  G := GetGValue(ColorToRGB(AColor));
+  B := GetBValue(ColorToRGB(AColor));
+  MaxValue := Max(Max(R,G),B);
+  MinValue := Min(Min(R,G),B);
+  Lightness := (((MaxValue + MinValue) * 240) + 255 ) / 510;
+  Result := Round(Lightness);
+end;
+
 end.
 
 

source/main.pas

@@ -3178,9 +3178,10 @@ begin
   // Sorting color and title image
   for k:=0 to Length(FDataGridSort)-1 do begin
     if FDataGridSort[k].ColumnName = name then begin
+      col.Color := ColorAdjustBrightness(col.Color, COLORSHIFT_SORTCOLUMNS, True);
       case FDataGridSort[k].SortDirection of
-        ORDER_ASC:  begin col.Color := COLOR_SORTCOLUMN_ASC;  col.ImageIndex := 109; end;
-        ORDER_DESC: begin col.Color := COLOR_SORTCOLUMN_DESC; col.ImageIndex := 110; end;
+        ORDER_ASC:  col.ImageIndex := 109;
+        ORDER_DESC: col.ImageIndex := 110;
       end;
     end;
   end;
@@ -5387,18 +5388,16 @@ end;
 procedure TMainForm.vstAfterPaint(Sender: TBaseVirtualTree;
   TargetCanvas: TCanvas);
 var
-  i : Integer;
-  h : TVTHeader;
+  i: Integer;
+  h: TVTHeader;
+  NewColor: TColor;
 begin
   h := (Sender as TVirtualStringTree).Header;
-  for i := 0 to h.Columns.Count - 1 do
-  begin
+  for i:=0 to h.Columns.Count-1 do begin
+    NewColor := clWindow;
     if h.SortColumn = i then
-    case h.SortDirection of
-      sdAscending: h.Columns[i].Color := COLOR_SORTCOLUMN_ASC;
-      sdDescending: h.Columns[i].Color := COLOR_SORTCOLUMN_DESC;
-    end else
-      h.Columns[i].Color := clWindow;
+      NewColor := ColorAdjustBrightness(NewColor, COLORSHIFT_SORTCOLUMNS, True);
+    h.Columns[i].Color := NewColor;
   end;
 end;
 
@@ -6578,7 +6577,7 @@ var
   i: Integer;
 begin
   for i:=Low(DatatypeCategories) to High(DatatypeCategories) do
-    DatatypeCategories[i].NullColor := ColorAdjustBrightness(DatatypeCategories[i].Color, COLORSHIFT_NULLFIELDS);
+    DatatypeCategories[i].NullColor := ColorAdjustBrightness(DatatypeCategories[i].Color, COLORSHIFT_NULLFIELDS, False);
 end;