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How to create a TScrollBox with an own background Turn on/off line numbers in source code. Switch to Orginial background IDE or DSP color Comment or reply to this aritlce/tip for discussion. Bookmark this article to my favorite article(s). Print this article
28-Aug-02
Category
VCL-General
Language
Delphi 2.x
Views
93
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Publisher:
DSP, Administrator
Reference URL:
DKB
			Author: Tomas Rutkauskas

How to create a TScrollBox with an own background

Answer:

1   unit NScroll;
2   
3   interface
4   
5   uses
6     SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms;
7   
8   type
9     TMyScrollBox = class(TScrollBox)
10    private
11      FNHBitmap: TBitmap;
12      FNHCanvas: TCanvas;
13      procedure WMPaint(var message: TWMPaint); message WM_PAINT;
14      procedure SetBitmap(Value: TBitmap);
15    protected
16      procedure Painting;
17      procedure PaintWindow(DC: HDC); override;
18    published
19      property BackBitmap: TBitmap read FNHBitmap write SetBitmap;
20    public
21      constructor Create(Owner: TComponent); override;
22      destructor Destroy; override;
23    end;
24  
25  procedure register;
26  
27  implementation
28  
29  constructor TMyScrollBox.Create(Owner: TComponent);
30  begin
31    inherited Create(Owner);
32    FNHBitmap := TBitmap.Create;
33    FNHCanvas := TControlCanvas.Create;
34    TControlCanvas(FNHCanvas).Control := Self;
35  end;
36  
37  destructor TMyScrollBox.Destroy;
38  begin
39    FNHBitmap.Destroy;
40    FNHCanvas.Destroy;
41    inherited Destroy;
42  end;
43  
44  procedure TMyScrollBox.SetBitmap(Value: TBitmap);
45  begin
46    FNHBitmap.Assign(Value);
47    invalidate;
48  end;
49  
50  procedure TMyScrollBox.WMPaint(var message: TWMPaint);
51  begin
52    PaintHandler(message);
53  end;
54  
55  procedure TMyScrollBox.PaintWindow(DC: HDC);
56  begin
57    FNHCanvas.Handle := DC;
58    try
59      Painting;
60    finally
61      FNHCanvas.Handle := 0;
62    end;
63  end;
64  
65  procedure TMyScrollBox.Painting;
66  var
67    FDrawHeight, FDrawWidth: Integer;
68    Row, Column, xl, xt, xw, xh: Integer;
69    xdl, xdt: Integer;
70    xRect: TRect;
71    i: integer;
72    xhdl: Word;
73  begin
74    if (FNHBitmap.width <> 0) and (FNHBitmap.Height <> 0) then
75    begin
76      xRect := ClientRect;
77      FDrawHeight := xRect.Bottom - xRect.Top;
78      FDrawWidth := xRect.Right - xRect.Left;
79      xdl := (HorzScrollBar.Position mod FNHBitmap.Width);
80      xdt := (VertScrollBar.Position mod FNHBitmap.Height);
81      for Row := 0 to (FDrawHeight div FNHBitmap.Height) + 1 do
82      begin
83        for Column := 0 to (FDrawWidth div FNHBitmap.Width) + 1 do
84        begin
85          xl := Column * FNHBitmap.Width + xRect.Left - xdl;
86          xt := Row * FNHBitmap.Height + xRect.Top - xdt;
87          xw := FNHBitmap.Width;
88          if (FDrawWidth - xl + xRect.Left) < xw then
89            xw := (FDrawWidth - xl + xRect.Top);
90          xh := FNHBitmap.Height;
91          if (FDrawHeight - xt + xRect.Top) < xh then
92            xh := (FDrawHeight - xt + xRect.Top);
93          FNHCanvas.CopyRect(Rect(xl, xt, xl + xw, xt + xh), FNHBitmap.Canvas, 
94  Rect(0, 0, xw, xh));
95        end;
96      end;
97    end;
98  end;
99  
100 procedure register;
101 begin
102   RegisterComponents('Samples', [TMyScrollBox]);
103 end;
104 
105 end.


			
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