DelphiVCL TreeView OnCustomDrawItem

[shineworld 73]

I found an oddity in the "state" field of the OnCustomDrawItem event.
Basically instead of reporting the states of the VCL control passed by the related event all possible states are passed there:

function CustomDrawStateToPython(const ACustomDrawState: TCustomDrawState): PPyObject;

  procedure Append(const AList: PPyObject; const AString: string);
  var
    LItem: PPyObject;
  begin
    with GetPythonEngine do begin
      LItem := PyUnicodeFromString(AString);
      PyList_Append(AList, LItem);
      Py_XDecRef(LItem);
    end;
  end;

var
  LCompType: PTypeInfo;
  LMin: integer;
  LMax: integer;
  LState: integer;
begin
  Result := GetPythonEngine().PyList_New(0);
  LCompType := GetTypeData(TypeInfo(TCustomDrawState)).CompType^;
  LMin := LCompType^.TypeData^.MinValue;
  LMax := LCompType^.TypeData^.MaxValue;
  for LState := LMin to LMax do
    Append(Result, GetEnumName(LCompType, LState)); // <-- all enums are always set to state python attribute
end;

In my TreeView, when a node is selected, I've to change to white the font color otherwise text is hard to be sight:

 

Either I completely misunderstood the functionality of that function or there was an oversight.

Unfortunately Vcl.ComCtrls TCustomDrawItem is defined as a set with direct enumerators in the set so I didn't find

a direct method to do:

if CAST_TO_ENUM(LState) in TCustomDrawState then

but with a forcing and a pointer you still get something working:

function CustomDrawStateToPython(const ACustomDrawState: TCustomDrawState): PPyObject;

  procedure Append(const AList: PPyObject; const AString: string);
  var
    LItem: PPyObject;
  begin
    with GetPythonEngine do begin
      LItem := PyUnicodeFromString(AString);
      PyList_Append(AList, LItem);
      Py_XDecRef(LItem);
    end;
  end;

  function IsBitSet(Index: Integer; State: TCustomDrawState): Boolean;
  var
    P: PByte;
  begin
    if (Index < 0) or (Index >= SizeOf(TCustomDrawState) * 8) then Exit(False);
    P := @State;
    Result := (P^ and (1 shl Index)) <> 0;
  end;

var
  LCompType: PTypeInfo;
  LMin: integer;
  LMax: integer;
  LState: integer;
begin
  Result := GetPythonEngine().PyList_New(0);
  LCompType := GetTypeData(TypeInfo(TCustomDrawState)).CompType^;
  LMin := LCompType^.TypeData^.MinValue;
  LMax := LCompType^.TypeData^.MaxValue;
  for LState := LMin to LMax do
  begin
    if IsBitSet(LState, ACustomDrawState) then
      Append(Result, GetEnumName(LCompType, LState));
  end;
end;

I'm not so smart in these things so if some Delphi guru has a better solution I'm ready to fix the code.

Best regards.

[pyscripter 689]

A fix has been applied to P4D.  Please check.

[Remy Lebeau 1396]

4 hours ago, shineworld said:

Unfortunately Vcl.ComCtrls TCustomDrawItem is defined as a set with direct enumerators in the set so I didn't find

a direct method to do:

if CAST_TO_ENUM(LState) in TCustomDrawState then

 

FYI, in Delphi 12 Athens, TCustomDrawState now uses a new enum type TCustomDrawStateItem, so you can cast the values to that type, eg:

for LState := LMin to LMax do
begin
  if TCustomDrawStateItem(LState) in ACustomDrawState then
    Append(Result, GetEnumName(TypeInfo(TCustomDrawStateItem), LState));
end;

 

[shineworld 73]

14 hours ago, pyscripter said:

A fix has been applied to P4D.  Please check.

New commit fixes the issue and works perfectly.
 

Edited July 9 by shineworld