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lcl: TGtk2WidgetSet.CreateEllipticRgn: using symmetrical coords with less edges for a smoother ellipsis

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mattias 2023-07-10 15:42:13 +02:00
parent 0cf38f57c7
commit 79cff8a8f3
1 changed files with 44 additions and 12 deletions
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56
lcl/interfaces/gtk2/gtk2winapi.inc
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@ -1304,26 +1304,58 @@ end;
function TGtk2WidgetSet.CreateEllipticRgn(X1, Y1, X2, Y2: Integer): HRGN;
var
points: array of TGdkPoint;
n_points: Integer;
i, Xc, Yc, a, b: Integer;
t: Double;
n_points, i, n4, aLeft, aRight, aTop, aBottom: Integer;
Xc, Yc, a, b, t: single;
AX, AY, BX, BY, CX, CY, Deviation: single;
GObject: PGdiObject;
RegionObj: PGdkRegion;
begin
a := (X2 - X1) div 2;
b := (Y2 - Y1) div 2;
Xc := X1 + a;
Yc := Y1 + b;
Xc:=single(X1+X2)/2;
Yc:=single(Y1+Y2)/2;
a:=single(X2-X1)/2;
b:=single(Y2-Y1)/2;
// Choose a large enough amount of points
n_points := Max(X2-X1,Y2-Y1) * 4;
n_points:=0;
repeat
inc(n_points,4);
t := single(1) / single(n_points) * 2 * Pi;
AX := a * cos(t);
AY := a * sin(t);
BX := a * cos(t/2);
BY := a * sin(t/2);
CX := (AX + a) /2;
CY := (AY + 0) /2;
Deviation := sqrt(sqr(BX-CX)+sqr(BY-CY));
until Deviation<0.4;
SetLength(points{%H-}, n_points);
// And fill them iterating through the ellipse
for i := 0 to n_points - 1 do
n4 := n_points div 4;
for i := 0 to n4 do
begin
t := (i / n_points) * 2 * Pi;
points[i].X := Round(Xc + a * cos(t));
points[i].Y := Round(Yc + b * sin(t));
t := single(i) / single(n_points) * 2 * Pi;
aRight := Round(Xc + a * cos(t));
aLeft := Trunc(2*Xc - aRight);
aTop := Round(Yc + b * sin(t));
aBottom := Trunc(2*Yc - aTop);
points[i].X := aRight;
points[i].Y := aTop;
if i>0 then
begin
points[n_points - i].X := aRight;
points[n_points - i].Y := aBottom;
end;
if i<n4 then
begin
points[2*n4 - i].X := aLeft;
points[2*n4 - i].Y := aTop;
if i>0 then
begin
points[2*n4 + i].X := aLeft;
points[2*n4 + i].Y := aBottom;
end;
end;
end;
GObject := NewGDIObject(gdiRegion);