Using classes to encapsulate data

[TBMan]

I coded a simple file listing dialog using ptcgraph. I want to wrap the entire code that the dialog box uses - the file list data types, the painting procedures the whole thing. I don't want any external records used except my "trect" which just defines a rectangle. I think using a class is best? I've never used them before (but I do ok with objects).

Basically what I want to do is create the dialog and then have a boolean "rundialog(filemask, returnfilename)" function that returns true if a filename is selected (passed back by rundialog).

Do I have the right idea?

[cdbc]

Hi
If you're comfortable with Objects then you might have a look in unit 'UDialogs', which is the dialog section of 'FreeVision', good inspiration in there.
Otherwise you might take a look at Lazarus' 'Dialogs' unit, which implements the LCL-Dialogs...
Your description sounds a lot like the standard dialog in Lazarus, e.g:

Code: Pascal  [Select][+][-]

1. OpenDialog1.Directory:= '/home/youser/tmp/'; // or maybe '~/tmp/';
2. if OpenDialog1.execute then begin
3.   fs:= TFilestream.Create(OpenDialog1.Filename,fmOpenRead or fmShareDenyNone);
4.   try
5.     /// use the filestream ///
6.   finally fs.Free; end;
7. end;

Regards Benny

[Warfley]

Why not just use a unit? Units are perfectly well suited for encapsulating functionality. They have two sections, the interface is what is visible to the outside, and the implementation is only visible inside the unit.

Code: Pascal  [Select][+][-]

1. unit MyDialog;
2.  
3. {$Mode ObjFPC}{$H+}
4.  
5. interface
6.  
7. uses ...;
8.  
9. function runDialog(const fileMask: String; out returnFilename: String): Boolean;
10.  
11. implementation
12.  
13. procedure DrawDialog(...)...
14.  
15. procedure OtherHelperFunc(...)...
16.  
17. function runDialog(const fileMask: String; out returnFilename: String): Boolean;
18. begin
19.   // Implement and use the helper functions defined above
20. end;

[TBMan]

Why not just use a unit? Units are perfectly well suited for encapsulating functionality. They have two sections, the interface is what is visible to the outside, and the implementation is only visible inside the unit.
....

Yes, thanks. I did use a unit, but in case I develop other class based GUI elements I wanted the list dialog variables to be self contained. I finished it this morning, here's a short video and the class declaration code:

https://youtu.be/MC-tlEiMX2Y

Code: Pascal  [Select][+][-]

1. type
2.   LGC_FileDialog = class
3.   private
4.   const
5.     MaxItems = 300;  // limit for file list - needs more error checking
6.     Maxbuttons = 2;
7.     max = 14;
8.     ev_ok = 1000;
9.     ev_cancel = 2000;
10.  
11.   type
12.     buttonType = record
13.       event: integer;
14.       Rect: Trect;
15.       Txt: string;
16.     end;
17.  
18.     ItemType = record
19.       Id: integer;
20.       Info: string;
21.     end;
22.  
23.     ListType = record
24.       List: array[1..maxitems] of itemtype;
25.       Items: integer;
26.     end;
27.  
28.     ContentType = record
29.       IdRef: integer;  // reference to List item
30.       Rect: Trect;
31.     end;
32.   var
33.     bitmap: pointer;
34.     sz: longint;
35.  
36.     uprect, downrect, scrollrect, ScrollButton, outerRect,
37.     DisplayRect: Trect;
38.  
39.     ScrollButtonSize: integer;
40.     Contents: array[1..Max] of ContentType;
41.     ListContents: ListType;
42.  
43.     EventCode: integer;
44.     EndResult: boolean;
45.     Buttons: array[1..2] of buttontype;
46.     ScrollPercentage: double;
47.     Rowlimit, ScrollDownLimit: integer;
48.     changed: boolean;
49.     mx, my, mb: longint;
50.     key: char;
51.     x, y, spot, xx, yy, w, d: integer;
52.     currentrow: integer;
53.  
54.  
55.   public
56.   var
57.     ErrorCode, Steelblue, Gray: integer;
58.     constructor Create(xxx, yyy: integer; Fmask: string);
59.     destructor Destroy; override;
60.     procedure drawbutton(IB: integer; Up: boolean);
61.     procedure SetButtons;
62.     procedure UpDateScroll;
63.     procedure highlight(fc, bc: integer; Yes: boolean);
64.     procedure scrolldisplay(startRow, Endrow: integer);
65.     function createList(filemask: string): boolean;
66.     function run(var returnstring: string): boolean;
67.     procedure paint;
68.     procedure scrollbuttonactive(TheRect: Trect);
69.   end;
70.  
71.  

And it gets called as (after graph mode initialized by PTCGraph):

Code: Pascal  [Select][+][-]

1. filedialog := lgc_filedialog.create(400,200,'*.arr');
2.  if filedialog.errorcode=0 then
3.   begin
4.   if filedialog.run(ts) then
5.    begin
6.      setcolor(white);
7.      outtextxy(400,100,'Returned file name:'+ts);
8.    end;
9.   end
10.   ELSE
11.      BEGIN
12.      SETCOLOR(15);
13.      outtextxy(600,100,'ERROR!');
14.  
15.      end;
16.  
17.  filedialog.destroy;                
18.  

In the video I'm showing the scroll action using the scroll button controls, but you can also click on
the list to select a item as well. I'm just going to group my variables by type in the code and it's done.)
I'm happy with how it came out, but now I want to be able to change directories within the dialog as well
to add full functionality. For my game asset tools though it's fine as I stay in one folder for each project usually.

I'll probably have to add a file attrib field to the "itemtype" record and then if it isn't "archive" then change directories and  rebuild the list.....  or something like that

I also modified it now to allow me to change all the colors used by the filedialog so I can change palettes from the default ptcgraph palette.