[LAMW] DrawCircle using jCanvasES2

[Handoko]

This post is the answer for a request by a friend here.

Code: Pascal  [Select][+][-]

1. {Hint: save all files to location: /home/handoko/Desktop/GLES_Circle/GLES_Circle/jni }
2. unit unit1;
3.  
4. {$mode delphi}
5.  
6. interface
7.  
8. uses
9.   Classes, SysUtils, AndroidWidget, Laz_And_Controls, Laz_And_GLESv2_Canvas;
10.  
11. type
12.  
13.   { TAndroidModule1 }
14.  
15.   TAndroidModule1 = class(jForm)
16.     jCanvasES2_1: jCanvasES2;
17.     jTextView1: jTextView;
18.     jTimer1: jTimer;
19.     procedure AndroidModule1Destroy(Sender: TObject);
20.     procedure AndroidModule1JNIPrompt(Sender: TObject);
21.     procedure jCanvasES2_1GLCreate(Sender: TObject);
22.     procedure jCanvasES2_1GLDown(Sender: TObject; Touch: TMouch);
23.     procedure jCanvasES2_1GLDraw(Sender: TObject);
24.     procedure jCanvasES2_1GLUp(Sender: TObject; Touch: TMouch);
25.     procedure jTimer1Timer(Sender: TObject);
26.   private
27.     isPressing: Boolean;
28.     CircleX: Single;
29.     CircleY: Single;
30.     CircleR: Single;
31.   end;
32.  
33. var
34.   AndroidModule1: TAndroidModule1;
35.  
36. implementation
37.  
38. {$R *.lfm}
39.  
40. { TAndroidModule1 }
41.  
42. procedure TAndroidModule1.AndroidModule1JNIPrompt(Sender: TObject);
43. begin
44.   isPressing := False;
45.   jCanvasES2_1.Screen_Setup(jCanvasES2_1.Width, jCanvasES2_1.Height, xp2D);
46.   jTimer1.Enabled := True;
47. end;
48.  
49. procedure TAndroidModule1.AndroidModule1Destroy(Sender: TObject);
50. begin
51.   jTimer1.Enabled := False;
52. end;
53.  
54. procedure TAndroidModule1.jCanvasES2_1GLCreate(Sender: TObject);
55. begin
56.   jCanvasES2_1.Shader_Compile('simon_Vert', 'simon_Frag');
57.   jCanvasES2_1.Shader_Link;
58. end;
59.  
60. procedure TAndroidModule1.jCanvasES2_1GLDown(Sender: TObject; Touch: TMouch);
61. begin
62.   jTextView1.Visible := False;
63.   CircleX            := (Touch.Pt.X/jCanvasES2_1.Width*2) - 1;
64.   CircleY            := 1 - (Touch.Pt.Y/jCanvasES2_1.Height*2);
65.   CircleR            := 0.1;
66.   isPressing         := True;
67. end;
68.  
69. Procedure DrawCircleNew(XY: TXY; Z, L: Single; AColor: TRGBA; AWidth: Single = 0.3);
70. var
71.   i : Integer;
72. begin
73.   For i := 0 to 70 do
74.     AndroidModule1.jCanvasES2_1.DrawLine(
75.       _XYZ(cCircle[(i+0)*2]  *L+XY.X, cCircle[(i+0)*2+1]*L+XY.Y, Z),
76.       _XYZ(cCircle[(i+0)*2+2]*L+XY.X, cCircle[(i+0)*2+3]*L+XY.Y, Z),
77.       AColor, AWidth
78.       );
79.   AndroidModule1.jCanvasES2_1.DrawLine(
80.     _XYZ(cCircle[0]  *L+XY.X, cCircle[1]*L+XY.Y, Z),
81.     _XYZ(cCircle[142]*L+XY.X, cCircle[143]*L+XY.Y, Z),
82.     AColor, AWidth
83.     );
84. end;
85.  
86. procedure TAndroidModule1.jCanvasES2_1GLDraw(Sender: TObject);
87. begin
88.  
89.   jCanvasES2_1.MVP:= cID4x4;
90.   jCanvasES2_1.SetMVP(jCanvasES2_1.MVP);
91.   jCanvasES2_1.Screen_Clear(0, 0, 0, 1);
92.  
93.   if isPressing then
94.     DrawCircleNew(_XY(CircleX, CircleY), 0, CircleR, _RGBA(1, 0, 0, 0.1), 0.02);
95.  
96. end;
97.  
98. procedure TAndroidModule1.jCanvasES2_1GLUp(Sender: TObject; Touch: TMouch);
99. begin
100.   isPressing := False;
101. end;
102.  
103. procedure TAndroidModule1.jTimer1Timer(Sender: TObject);
104. begin
105.   CircleR := CircleR + 0.02;
106.   if CircleR > 0.8 then CircleR := 0.1;
107.   jCanvasES2_1.Refresh;
108. end;
109.  
110. end.

• jCanvasES2.DrawCircle has a serious bug, alternatively I wrote DrawCircleNew, see line #69. I will inform the developer of LAMW later.
• Previously I used DrawPolyFill to clear the OpenGL's screen. Now I use jCanvasES2.Screen_Clear (see line #91), which is much simpler.
• This code does not support device rotation, which I still unable to solve.
• The circle drawn actually is an ellipse because it does not calculate the aspect ratio of the jCanvasES.
• The circle drawn is not very smooth. This happens because the original author of DrawCircle uses only 72 points to construct the circle and the data are rounded to 2 digits only (which greatly reduces the accuracy).

Tested on Android 7.1.2 ARM device, binary compiled using Lazarus 1.8.4 64-bit Linux LAMW rev 754.

[Handoko]

And this is the apk: