[SOLVED] Graph returns a SIGSEVG after calling custom 'Draw' function
lazarus / 39-Graphics

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mug33n · 2024-11-12 14:17

Hello, i have the problem with this code (it raises a SIGSEVG (see
problem.png) in Lazarus):

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 {$MODE
objfpc} {$H+} {$J-} {$R+} {$UNITPATH src}program Main; uses cthreads,
ptcGraph, ptcCrt, UMenu; var Menu: TMenu;   Mode, Driver:
SmallInt; begin   Mode := M800x600; Driver := D16Bit; 
 InitGraph(Driver, Mode, '');    Menu := TMenu.Init(3, 1, 'TEST');  
 Menu.Draw(16, 16, 16, White, ['WEE', 'WEE', 'WEE']);  
 CloseGraph;end. 
It says that the problem is a call for Menu.Draw from UMenu unit (see
reason.png).

The code of UMenu unit:
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 {$MODE
objfpc} {$H+} {$J-} {$R+}unit UMenu; interface   uses cthreads,
ptcGraph;    type TMenu = class         EntryCount, Font: SmallInt;  
     Title: String;         Texts: Array of String;         PosX,
PosY: Array of SmallInt;                  constructor Init(EC, F:
SmallInt; T: String = 'TEST');          procedure Draw(SX, SY, Step,
Color: SmallInt: ColorType; T: Array of String); 
 end; implementation   constructor TMenu.Init(EC, F: SmallInt; T:
String = 'TEST');   begin      if EC = 0 then EC := 1;      if F = 0
then F := 0;         EntryCount := EC; Font := F; Title := T;      
SetLength(Texts, EntryCount);      SetLength(PosX, EntryCount);
SetLength(PosY, EntryCount);   end;    procedure TMenu.Draw(SX, SY,
Step, Color: SmallInt; T: Array of String);   var I: Integer;        
  Temp: OutTextXYProc;    begin                if Length(T) = 0 then
RunError(10);      if (Length(T) > EntryCount) or (Length(T) <
EntryCount) then RunError(11);       { Set text color and font }     
SetColor(Color); SetTextStyle(Font, 0, 0);       { Display menu title
}                OutTextXY(SX, SY, Title);                 Inc(SY,
Step);       { Display menu entries }      for I := 1 to EntryCount
do      begin         PosX[I] := SX; PosY[I] := SY;         Texts[I]
:= T[I];                  OutTextXY(PosX[I], PosY[I], Texts[I]);     
   Inc(SY, Step);      end;   end;end. 
I use the following versions of software to build the project:
FPC version - 3.2.2 from Gentoo GNU/Linux official repository;
Lazarus version - 3.6, built from source code.

P.S. - Thanks to rvk for help.

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TRon · 2024-11-12 14:20

Hi mug33n,

You seem to be mixing old-style objects with a class.

Either tmenu is a class or an old style object.

try
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  type TMenu
= object // not class         EntryCount, Font: SmallInt;       
 Title: String;         Texts: Array of String;         PosX, PosY:
Array of SmallInt;                  constructor Init(EC, F: SmallInt;
T: String = 'TEST');          procedure Draw(SX, SY, Step, Color:
SmallInt: ColorType; T: Array of String);   end;

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rvk · 2024-11-12 14:31

Although I do have questions about the old-style object... why are you
using those????

The problem lies somewhere else.
You have several  Array of xx;

You do a SetLength on that Array.
After that you do a for loop with 1 to count.
But... array of x is always from index 0 !!!

So you need to do 0 to count - 1 (or access object[I - 1] instead of
object[ I ] )

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TRon · 2024-11-12 14:37

Ah yes rvk you are right.

As a quick dirty fix from
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 EntryCount
:= EC; Font := F; Title := T;...for I := 1 to EntryCount do to
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 EntryCount
:= EC+1; Font := F; Title := T;...for I := 1 to EntryCount-1 do 
Only for quick testing of course 

Better:
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 for i :=
low(your_array) to high(your_array)

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mug33n · 2024-11-12 15:04

Quote from: rvk
why are you using those????
Are You about usage of ptcGraph instead of other tools?

Quote from: rvkYou do a SetLength on that Array.
After that you do a for loop with 1 to count.
But... array of x is always from index 0 !!!

So you need to do 0 to count - 1 (or access object[I - 1] instead of
object[ I ] )
I tried to do that by replacing 47th line in UMenu on this one (i'm
not sure what i understand this part of Your answer correctly), but it
still fails with SIGSEGV:
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 for I := 0
to EntryCount do

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rvk · 2024-11-12 15:13

Quote from: mug33n on November 12, 2024, 04:04:23 pmQuote from: rvk
why are you using those????
Are You about usage of ptcGraph instead of other tools?No, I'm talking
about the contructor Init(). I haven't seen that since my good ol'
Borland Pascal years.

Quote from: mug33n on November 12, 2024, 04:04:23 pmQuote from: rvkYou
do a SetLength on that Array.
After that you do a for loop with 1 to count.
But... array of x is always from index 0 !!!

So you need to do 0 to count - 1 (or access object[I - 1] instead of
object[ I ] )
I tried to do that by replacing 47th line in UMenu on this one (i'm
not sure what i understand this part of Your answer correctly), but it
still fails with SIGSEGV:
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 for I := 0
to EntryCount doYou can't go to EntryCount. If you use Array of X you
end up with an array [0..EntryCount - 1] !!
So you can't loop to EntryCount but you need to loop to EntryCount -
1.

But you then also need to make sure you fill those correctly.

You could go the 'dirty' way TRon already mentioned and do SetLength (
EntryCount + 1).
But that will give you Array[ 0 .. EntryCount ] and then you have a 0
entry which you don't use.
For testing this is fine but it's best you learn how to use dynamic
arrays and you need to know they start on 0 up to (and NOT including)
the count you gave.

SetLength(Count) reserves Count elements.
That's [0 .. Count - 1] (you see that?)

Doing SetLength(Count + 1) will reserve Count + 1 elements.
And then you have [0 .. Count ] (and you can use that [ Count ] but
have a  [ 0 ] which you don't use.

That's how dynamic arrays work

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TRon · 2024-11-12 15:15

A slightly other approach (I tried to stay in line with your original
as much as possible) as there were many other small things not exactly
right.

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 program
Main; {$MODE objfpc} {$H+} {$J-} {$R+} uses  {$ifdef linux} 
cthreads,  {$endif}  ptcgraph, ptccrt, umenu; var  Menu   : TMenu; 
Mode   : SmallInt;  Driver : SmallInt; begin   Mode   := M800x600; 
 Driver := D16Bit;   InitGraph(Driver, Mode, '');    Menu.Init(3, 1,
'TEST');    Menu.Draw(16, 16, 16, White, ['WEE', 'WEE', 'WEE']); 
 repeat   until keypressed;    CloseGraph;end. 
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 unit
UMenu; {$MODE objfpc} {$H+} {$J-} {$R+} interface uses  {$ifdef
linux}  cthreads,  {$endif}  ptcGraph; type  TMenuItem = record    //
if wanted/required add fields xpos and ypos here as well.    FTitle :
string;  end;   TMenu = object // class    FFont : SmallInt;   
FTitle: String;    FMenuItems : array of TMenuItem;    constructor
Init(EC, F: SmallInt; const T: String = 'TEST');    procedure Draw(SX,
SY, Step, Color: SmallInt; T: Array of String); 
end; implementation constructor TMenu.Init(EC, F: SmallInt; const T:
String = 'TEST');begin  SetLength(FMenuItems, EC);  FFont  := F; 
FTitle := T;end;  procedure TMenu.Draw(SX, SY, Step, Color: SmallInt;
T: Array of String);var  i : integer;  Title: string;begin  // copy
title  i := low(FMenuItems);  for Title in T do  begin    if i <
length(FMenuItems)      then FMenuItems[i].FTitle := Title      else
break;    inc(i);  end;    { Set text color and font } 
SetColor(Color);  SetTextStyle(FFont, 0, 0);   { Display menu title } 
OutTextXY(SX, SY, FTitle);    { Display menu entries }  for I :=
low(FMenuItems) to high(FMenuItems) do  begin    Inc(SY, step);   
OutTextXY(SX, SY, FMenuItems[I].FTitle);  end;end; end.

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mug33n · 2024-11-12 15:53

Quote from: rvk on November 12, 2024, 04:13:37 pmNo, I'm talking about
the contructor Init().

I use because it seems more familiar (?) for me then Create.

Quote from: rvk on November 12, 2024, 04:13:37 pmSo you can't loop to
EntryCount but you need to loop to EntryCount - 1.
Thank You!