I have been upgrading or migrating our software from XP OS to be able to compile and run under Windows 7. Our software is starting to show issues that we didn't notice under Windows XP. Currently, I am dealing with a user defined control flickering on a TForm. It seems to flicker every now and then not always, but when it flickers it is very noticeable. I have set DoubleBuffered for the TForm and TTrendChart Class, but it is not helping.
This a user-defined control of TCustomPanel. It is supposed to display a Live Trendchart on a TForm.
Any help will be appreciated. Thank you.
Answer:
This a user-defined control of TCustomPanel. It is supposed to display a Live Trendchart on a TForm.
TTrendChart = class(TCustomPanel)
private
fCount:integer;
fColors:array[0..7] of TColor;
fNames:array[0..7] of string;
fMinText:string16;
fMaxText:string16;
fShowNames:Boolean;
fMaxTextWidth:integer;
data:TList;
Indexer:integer;
chartRect:TRect;
fWidth:integer;
fHeight:integer;
firstTime:Boolean;
function GetColors(Index:integer):TColor;
procedure SetColors(Index:integer; const value :TColor);
function GetNames(Index:integer):string;
procedure SetNames(Index:integer; const value: string);
procedure SetCount(const value : integer);
procedure rShowNames(const value : Boolean);
procedure SetMaxText(const value:string16);
procedure SetMinText(const value:string16);
procedure RecalcChartRect;
protected
procedure Resize; override;
procedure Paint; override;
public
constructor Create(AOwner : TComponent); override;
destructor Destroy; override;
procedure PlotPoints(p1,p2,p3,p4,p5,p6,p7,p8:real);
procedure ClearChart;
procedure Print;
property TrendColors[Index:integer]: TColor read GetColors write SetColors;
property TrendNames[index:integer]: string read GetNames write SetNames;
published
property TrendCount: Integer read fCount write SetCount default 8;
property ShowNames: Boolean read fShowNames write rShowNames default true;
property MaxText:string16 read fMaxText write SetMaxText;
property MinText:string16 read fMinText write SetMinText;
property Align;
property Alignment;
property BevelInner;
property BevelOuter;
property BevelWidth;
property DragCursor;
property DragMode;
property Enabled;
property Caption;
property Color;
property Ctl3D;
property Font;
property Locked;
property ParentColor;
property ParentCtl3D;
property ParentFont;
property ParentShowHint;
property PopupMenu;
property ShowHint;
property TabOrder;
property TabStop;
property Visible;
property OnClick;
property OnDblClick;
property OnDragDrop;
property OnDragOver;
property OnEndDrag;
property OnEnter;
property OnExit;
property OnMouseDown;
property OnMouseUp;
property OnMouseMove;
property OnResize;
end; constructor TTrendChart.Create(AOwner:TComponent);
var
i:integer;
tp:TTrendPoints;
begin
inherited Create(AOwner);
Parent := TWinControl(AOwner);
fCount := 8;
fShowNames := true;
Caption := '';
fMaxText := '100';
fMinText := '0';
fMaxTextWidth := Canvas.TextWidth('Bar 0');
firstTime := true;
BevelInner := bvLowered;
data := TList.Create;
Indexer := 0;
RecalcChartRect;
DoubleBuffered:=true;
for i := 0 to 10 do
begin
tp := TTrendPoints.Create(0.0 + 0.1 * fWidth,0.0,0.0,0.0,0.0,0.0,0.0,0.0);
data.Add(tp);
end;
for i := 0 to 7 do
begin
case i of
0: fColors[i] := clMaroon;
1: fColors[i] := clGreen;
2: fColors[i] := clOlive;
3: fColors[i] := clNavy;
4: fColors[i] := clPurple;
5: fColors[i] := clFuchsia;
6: fColors[i] := clLime;
7: fColors[i] := clBlue;
end;
fNames[i] := Format('Line %d',[i]);
end;
end;
Here is how it is painted on the Form: procedure TTrendChart.Paint;
var
oldColor:TColor;
dataPt:TTrendPoints;
i,j:integer;
curx:integer;
count,step:integer;
r:TRect;
begin
inherited Paint;
oldcolor := Canvas.Pen.Color;
Canvas.Brush.Color:=clWhite;
r.Left:=chartRect.Left-25;
r.Right:=chartRect.Right+11;
r.Top:=chartRect.Top-11;
r.Bottom:=chartRect.Bottom+22;
Canvas.FillRect(r);
if FirstTime then
begin
count := Indexer - 1;
end
else
count := data.Count - 2;
{ Draw minute lines }
Canvas.Pen.Color := clBtnShadow;
i := chartRect.left + 60;
while i < chartRect.Right do
begin
Canvas.Moveto(i, chartRect.top);
Canvas.LineTo(i, chartRect.bottom);
i := i + 60;
end;
{ Draw value lines }
step := (chartRect.bottom - chartRect.top) div 5;
if step > 0 then
begin
i := chartRect.bottom - step;
while i > (chartRect.top + step - 1) do
begin
Canvas.Moveto(chartRect.left,i);
Canvas.LineTo(chartRect.right,i);
i := i - step;
end;
end;
{ Draw Pens }
for j := 0 to fCount - 1 do
begin
Canvas.Pen.Color := fColors[j];
dataPt := TTrendPoints(data.Items[0]);
Canvas.MoveTo(chartRect.left,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
for i := 1 to count do
begin
dataPt := TTrendPoints(data.Items[i]);
if i <> Indexer then
begin
Canvas.LineTo(chartRect.left+i,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
end
else
begin
Canvas.MoveTo(chartRect.left+i,PinValue(round(chartRect.bottom - (fHeight * dataPt.pnts[j] / 100.0)),
chartRect.top,chartRect.bottom));
end;
end;
end;
r := chartRect;
InflateRect(r,1,1);
Canvas.Pen.Color := clBtnShadow;
Canvas.moveto(r.left,r.top);
Canvas.lineto(r.right,r.top);
Canvas.lineto(r.right,r.bottom);
Canvas.lineto(r.left,r.bottom);
Canvas.lineto(r.left,r.top);
{ draw index line }
// Canvas.Pen.Color := clWhite;
Canvas.Pen.Color := clBlack;
Canvas.MoveTo(chartRect.Left + Indexer,chartRect.top);
Canvas.LineTo(chartRect.left + Indexer, chartRect.bottom+1);
Canvas.Pen.Color := oldcolor;
Canvas.Font.COlor := clBlack;
Canvas.TextOut(chartRect.left-Canvas.TextWidth(string(fMinText))-2,chartRect.Bottom-8,string(fMinText));
Canvas.TextOut(chartRect.left-Canvas.TextWIdth(string(fMaxText))-2,chartRect.top-8,string(fMaxText));
if fShowNames then
begin
curx := 32;
for i := 0 to fCount - 1 do
begin
Canvas.Font.Color := fColors[i];
Canvas.TextOut(curx,chartRect.bottom+4,fNames[i]);
curx := curx + fMaxTextWidth + 16;
end;
end;
end;
Here is how one would use it: TrendChart := TTrendChart.Create(form);
Any help will be appreciated. Thank you.
Answer:
ControlStyle := ControlStyle + [csOpaque]; 
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