Register and use my own ColorToIdent/IdentToColor

Question

In my Delphi IDE package, I have my own list of colors with corresponding color names.

When I register my package to Delphi, the colors are shown in the property editor's list, along with all predefined colors:

When I assign my color to a control, that color value is saved with its color name in the .dfm file.

But, when I run my program, an Application Error is shown:

Error reading Form1.Color: invalid property value

I have added a call to register my own color conversion functions in the initialization section of my TSColor unit, but I don't get any debugger dots for those lines.

It works, if I add the call from the initialization section of the current project's source (.dpr), so the reason for the error is that the initialization section of my TSColor unit is never executed. Why is that?

I could add the initialization call to the project source of each project, but I would prefer that this call is made automatically as soon as I use TSColors in any of my project's units.

What controls whether or not the initialization section of a unit is compiled/executed?

Here are some excerpts of my `TSColors.pas unit:

My self-defined colors:

const
    TSColorCount = 4;
    clTSRed = TColor($005652EE); //5657327
    clTSYellow = TColor($0080FFFE); //8454143
    clTSGreen = TColor($004BF562); //4978017
    clTSGray = TColor($00BCBCBD); //12369084
    TSColorMap: array[0..TSColorCount - 1] of TIdentMapEntry = (
        (Value: clTSRed; Name: 'clTSRed'),
        (Value: clTSYellow; Name: 'clTSYellow'),
        (Value: clTSGreen; Name: 'clTSGreen'),
        (Value: clTSGray; Name: 'clTSGray')
 )

I have my own corresponding functions to convert color names to color values and vice versa:

function TSColorToIdent(Color: Longint; var Ident: string): Boolean;
var
    I: Integer;
begin
    for I := Low(TSColorMap) to High(TSColorMap) do
        if TSColorMap[I].Value = Color then
        begin
            Result := True;
            Ident := TSColorMap[I].Name;
            Exit;
        end;
    Result := ColorToIdent(Color, Ident); //No Color found. Do the original conversion.
end;

function TSIdentToColor(const Ident: string; var Color: Longint): Boolean;
var
    I: Integer;
begin
    Result := IdentToColor(Ident, Color);//first call Delphi original.
    if not Result then //if Ident is no known Delphi color name, check my list.
        for I := Low(TSColorMap) to High(TSColorMap) do 
            if SameText(TSColorMap[I].Name, Ident) then
            begin
                Result := True;
                Color := TSColorMap[I].Value;
                Exit;
            end;
end;

I have functions to register my own color conversions and to reset to Delphi's original:

procedure UnregisterCurrentColorConst;
var
    Int2ID: TIntToIdent;
    ID2Int: TIdentToInt;
begin
    Int2ID := FindIntToIdent(TypeInfo(TColor));
    ID2Int := FindIdentToInt(TypeInfo(TColor));
    if Assigned(Int2ID) then
        UnregisterIntegerConsts(TypeInfo(TColor), ID2Int, Int2ID);
end;

procedure RegisterTSColorIdent;
begin
    UnregisterCurrentColorConst;
    RegisterIntegerConsts(TypeInfo(TColor), TSIdentToColor, TSColorToIdent);
end;

procedure UnregisterTSColorIdent;
begin
    UnregisterCurrentColorConst;
    RegisterIntegerConsts(TypeInfo(TColor), IdentToColor, ColorToIdent);
end;

The initialization sections in that unit:

initialization
    RegisterTSColorIdent; //this line is never called.

finalization
    UnregisterTSColorIdent;

Answer 1

As you noted in comments, your unit's initialization section was after the end. of the unit, which is why the initialization was not executing.

I just want to point out that there are some other issues with your code:

• There is no guarantee that the VCL's ColorToIdent()/IdentToColor() functions are the ones your registration is replacing. There could be other packages installed that register their own color conversion functions. So, when registering your functions, you should first find the current registered functions and save them before you overwrite them, and then you can use them inside your functions as fallbacks for values that don't exist in your array.

• you don't need to unregister the current registered conversion functions for TColor. The RTL's integer conversion system allows multiple pairs of functions to be registered for the same type. The last registered pair will be the active pair used by the RTL at runtime. So simply unregister your own functions to restore the priority of the previous function pair.

• you can use the RTL's IdentToInt() /IntToIdent() functions to simplify your conversion functions.

With that said, try something more like this:

unit TSColors;

interface

uses
  Vcl.Graphics;

const
  clTSRed = TColor($005652EE); //5657327
  clTSYellow = TColor($0080FFFE); //8454143
  clTSGreen = TColor($004BF562); //4978017
  clTSGray = TColor($00BCBCBD); //12369084

function TSColorToIdent(Color: Longint; var Ident: string): Boolean;
function TSIdentToColor(const Ident: string; var Color: Longint): Boolean;

implementation

uses
  System.Classes;

const
  TSColorMap: array[0..3] of TIdentMapEntry = (
    (Value: clTSRed; Name: 'clTSRed'),
    (Value: clTSYellow; Name: 'clTSYellow'),
    (Value: clTSGreen; Name: 'clTSGreen'),
    (Value: clTSGray; Name: 'clTSGray')
  );

var
  Int2ID: TIntToIdent;
  ID2Int: TIdentToInt;

function TSColorToIdent(Color: Longint; var Ident: string): Boolean;
begin
  Result := IntToIdent(Color, Ident, TSColorMap);
  if (not Result) and Assigned(Int2ID) then
    Result := Int2ID(Color, Ident);
end;

function TSIdentToColor(const Ident: string; var Color: Longint): Boolean;
begin
  Result := IdentToInt(Ident, Color, TSColorMap);
  if (not Result) and Assigned(ID2Int) then
    Result := ID2Int(Ident, Color);
end;

procedure RegisterTSColorIdent;
begin
  Int2ID := FindIntToIdent(TypeInfo(TColor));
  ID2Int := FindIdentToInt(TypeInfo(TColor));
  RegisterIntegerConsts(TypeInfo(TColor), TSIdentToColor, TSColorToIdent);
end;
    
procedure UnregisterTSColorIdent;
begin
  UnregisterIntegerConsts(TypeInfo(TColor), TSIdentToColor, TSColorToIdent);
end;

initialization
  RegisterTSColorIdent;
    
finalization
  UnregisterTSColorIdent;

end.