Can I modified the border of a cell in the TValueListEditor?
lazarus / 31-LCL

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EganSolo · 2021-02-18 07:34

I'm trying to draw a red segment over the top border of a cell in a
TValueListEditor. Below is my code. VLE is the name of the
TValueListEditor:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Procedure
TForm1.VLEDrawCell(Sender: TObject; aCol, aRow: Integer; aRect: TRect;
aState: TGridDrawState);With VLE.Canvas dobegin      Pen.Color :=
clRed;      Pen.Width := 1;      Line(aRect.Left, aRect.Top,aRect.Left
+ 10 , aRect.Top);end; I'm expecting this code to draw a red segment
over the top border of the cell, but instead, it's drawing it below
it. It would seem that aRect parameter does not contain the border. I
tried the following:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Procedure
TForm1.VLEDrawCell(Sender: TObject; aCol, aRow: Integer; aRect: TRect;
aState: TGridDrawState);//VLE is a variable of type TValueListEditor,
declared in the main form. //this code is contained in the OnDrawCell
event handler of VLE.With VLE.Canvas dobegin      Pen.Color := clRed; 
    Pen.Width := 1;      Line(aRect.Left, aRect.Top-1,aRect.Left + 10
, aRect.Top-1);end; 
The segment vanishes. I think the overall code of TDrawString clips
anything outside of TRect.

There is no event handler exposed in TValueListEditor to handle the
drawing of the border. The paint method in TCustomGrid doesn't show
any obvious hook. Any nudge in the right direction would be welcome!

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EganSolo · 2021-02-18 07:53

Okay, I think I answered my own question 

In the Grids unit, the code for TCustomGrid.DrawllCell looks like so:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i //Code
starts on line 10,539procedure TCustomDrawGrid.DrawCell(aCol,aRow:
Integer; aRect: TRect;  aState:TGridDrawState);var  OldDefaultDrawing:
boolean;begin  if Assigned(OnDrawCell) and not(CsDesigning in
ComponentState) then begin    PrepareCanvas(aCol, aRow, aState);    if
DefaultDrawing then      DefaultDrawCell(aCol, aRow, aRect, aState); 
 OnDrawCell(Self,aCol,aRow,aRect,aState)  end else begin   
OldDefaultDrawing:=FDefaultDrawing;    FDefaultDrawing:=True;    try 
   PrepareCanvas(aCol, aRow, aState);    finally     
FDefaultDrawing:=OldDefaultDrawing;    end;   
DefaultDrawCell(aCol,aRow,aRect,aState);  end; 
DrawCellGrid(aCol,aRow,aRect,State); //<==== Code responsible for
drawing the grid.end; 
TCustomGrid.DrawCellGrid (which is DrawCell is calling) has no hook
for an event to be handled. Here's its code, taken from line 4,448

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TCustomGrid.DrawCellGrid(aCol,aRow: Integer; aRect: TRect; aState:
TGridDrawState);var  dv,dh: Boolean;begin   with Canvas do begin    
// fixed cells    if (gdFixed in aState) then begin      Dv :=
goFixedVertLine in Options;      Dh := goFixedHorzLine in Options;   
 Pen.Style := psSolid;      if FGridLineWidth > 0 then       
Pen.Width := 1      else        Pen.Width := 0;      if not FFlat then
begin        if FTitleStyle=tsNative then          exit        else  
    if FGridLineWidth > 0 then begin          if gdPushed in aState
then            Pen.Color := cl3DShadow          else           
Pen.Color := cl3DHilight;          if UseRightToLeftAlignment then
begin            //the light still on the left but need to new x     
     MoveTo(aRect.Right, aRect.Top);            LineTo(aRect.Left + 1,
aRect.Top);            LineTo(aRect.Left + 1, aRect.Bottom);         
end else begin            MoveTo(aRect.Right - 1, aRect.Top);        
  LineTo(aRect.Left, aRect.Top);            LineTo(aRect.Left,
aRect.Bottom);          end;          if FTitleStyle=tsStandard then
begin            // more contrast            if gdPushed in aState
then              Pen.Color := cl3DHilight            else           
 Pen.Color := cl3DShadow;            if UseRightToLeftAlignment then
begin              MoveTo(aRect.Left+2, aRect.Bottom-2);             
LineTo(aRect.Right, aRect.Bottom-2);              LineTo(aRect.Right,
aRect.Top);            end else begin             
MoveTo(aRect.Left+1, aRect.Bottom-2);             
LineTo(aRect.Right-2, aRect.Bottom-2);             
LineTo(aRect.Right-2, aRect.Top);            end;          end;      
end;        Pen.Color := cl3DDKShadow;      end else begin       
Pen.Color := FFixedGridLineColor;      end;    end else begin      Dv
:= goVertLine in Options;      Dh := goHorzLine in Options;     
Pen.Style := fGridLineStyle;      Pen.Color := fGridLineColor;     
Pen.Width := fGridLineWidth;    end;     // non-fixed cells    if
fGridLineWidth > 0 then begin   //<=== That's the part I'm interested
in. the border of non-fixed cells.      if Dh then begin       
MoveTo(aRect.Left, aRect.Bottom - 1);        LineTo(aRect.Right,
aRect.Bottom - 1);      end;      if Dv then begin        if
UseRightToLeftAlignment then begin          MoveTo(aRect.Left,
aRect.Top);          LineTo(aRect.Left, aRect.Bottom);        end else
begin          MoveTo(aRect.Right - 1, aRect.Top);         
LineTo(aRect.Right - 1, aRect.Bottom);        end;      end;    end;  
end; // with canvas,rectend; 
It looks like the way to go would be to create my own descendant class
of TValueListEditor (there is no TCustomValueListEditor) and override
this method.