[LAMW] Playing with the Alpha channel for fun using the CanvasES2
library.😀
lazarus / 43-Android

----------------------------------------------------------------------
José Hernández · 2025-09-03 19:09

Put one pixel via CanvasES2 like a pro (Part 2)

When I was analyzing how I could put a pixel using the CanvasES21GL
library, the Alpha Channel variable used to display the texture caught
my attention. I said to myself: If I'm going to be using the texturing
technique to simulate a ScreenBuffer, I might as well play with the
Alpha channel.

I really don't feel comfortable using black boxes, like this one, I
really don't know how it does it. Maybe using the GPU or something
else. I'm not sure. But it's there, whether I use it or not, I'm
forced to set it anyway.

From my point of view, I could use it for some very specific things,
and not abuse it. If I see that it is affecting performance, my first
option to fix it would be to not use it and use other techniques.

In this example, I'm going to play with the Alpha channel in two ways:
1. Create a gradient from a Start color to a End color.
2. Draw a donut with 25% transparency.

Here is the code:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
unit1; {$mode delphi} interface uses  {$IFDEF UNIX}{$IFDEF
UseCThreads}  cthreads,  {$ENDIF}{$ENDIF}  Classes, SysUtils,
AndroidWidget,  Laz_And_GLESv2_Canvas, Laz_And_GLESv2_Canvas_h; 
type   { TAndroidModule1 }   TAndroidModule1 = class(jForm)   
CanvasES21: jCanvasES2;    procedure AndroidModule1JNIPrompt(Sender:
TObject);    procedure CanvasES21GLCreate(Sender: TObject);   
procedure CanvasES21GLDraw(Sender: TObject);  private    {private
declarations}  public    {public declarations}    procedure
DeployBuffer(B: PDWord; T: TxgElement; W, H: Integer);    procedure
DrawTexture(T: TxgElement; A, x1, y1, x0, y0: Single);  end;  {
TMyOwnPrimitives }    TMyOwnPrimitives = class  private    Data:     
     PDWord;    Len:             Integer;     Alpha:           DWord; 
  Color:           DWord;    AlphaMater:      Single;    PencilColor:
   DWord;    BackgroundColor: DWord;     W,H,X:           Integer;   
Texture:         TxgElement;  public    constructor Create; virtual; 
 procedure Update;  virtual;    procedure UpdateColor;  virtual;   
procedure UpdateDimensions(Width, Height: Integer); virtual;   
procedure SetTheBufferUp;    procedure SetPencilColor(NewColor:
DWord);    procedure SetBackgroundColor(NewColor: Dword);    function
 GetWidth:   Integer;    function  GetHeight:  Integer;    function
 GetBuffer:  PDWord;    function  GetAlpha:   Single;    function
 GetTexture: TxgElement;     procedure MoveToInitialPoint;   
procedure MoveTo(NewX, Newy: Integer);    procedure
DrawHorizontal(Lenght: Integer);    procedure Clean;  end;   {
TChessBoard }   TChessBoard = class(TMyOwnPrimitives)     private    
 TotalSquaresByWidth:      Integer;       TotalSquaresByHeight:    
Integer;       LenghtOfSquareSide:       Integer;     
 DoubleSquareSize:         Integer;       Mask:                    
Integer;       Remainder:                Integer;     public     
 constructor Create; override;       procedure Update; override;     
 procedure UpdateDimensions(Width, Height: Integer); override;     
 procedure SetSquareSize(SquareSize: Integer);       procedure
DrawTwoSquareRows;       procedure DrawSquareRow;       procedure
DrawLine; virtual;       procedure DrawTwoSquares;       procedure
MoveToNextLine;       procedure WalkASquare;       procedure
GoASquareBack;   end;   { TGradiant }   TGradiant =
class(TChessBoard)     private       Gradiant:        DWord;     
 Numerator:       Integer;     public       constructor Create;
override;       procedure Update; override;       procedure
UpdateColor; override;       procedure DrawLine; override;     
 procedure CalculateGradiant;       procedure
DecrementGradianteAndNumerator;   end;   { TDonut }   TDonut =
class(TMyOwnPrimitives)    private      TheShorter, HoleRadius,
DonutRadius: Integer;    public      constructor Create; override;   
 procedure Update; override;      procedure UpdateRadiusAndHole;     
procedure SetBackGroundTransparent;      procedure
SetPencilTransparent;      procedure MoveToTheCenter;      procedure
DrawFilledCircle(Radius: Integer);      procedure
WhichIsShorterBetweenHAndW;      procedure CirclePoints(Cx, Cy:
Integer); Virtual;  end;var  AndroidModule1: TAndroidModule1;  Layers:
Array[0..2] of TMyOwnPrimitives; const   FullyOpaque          =
$ff000000;   FullyTransparent     = $00000000;   PartiallyTransparent
= $80000000;    BlackColor   = $00000000;   WhiteColor   = $00bfbfbf; 
 GoldenBrown  = $001e5b89;   PrussianBlue = $00543500;   Olivine    
 = $0080c4b8;   PinkLavander = $00c1afdb;    FULLY_OPAQUE          =
 1.00;   PARTIALLY_TRANSPARENT =  0.25;   RightCorner           =
 1.00;   LeftCorner            = -1.00;   TopCorner             =
 1.00;   DownCorner            = -1.00;    Square32x32pixels = 5; 
 Square16x16pixels = 4;   Square64x64pixels = 6;  
 OneLevelOfTrransparency = $01000000;   DifferentLevelsOfTransparency
= 255;   implementation    {$R *.lfm}     { TAndroidModule1
} procedure TAndroidModule1.AndroidModule1JNIPrompt(Sender:
TObject);var i: Integer;begin  Layers[0]:= TChessBoard.Create; 
Layers[1]:= TGradiant.Create;  Layers[2]:= TDonut.Create;   for i:= 0
to High(Layers) do with Layers[i] do begin   
UpdateDimensions(CanvasES21.GetWidth, CanvasES21.GetHeight);   
SetTheBufferUp;    //Update;  end;end; procedure
TAndroidModule1.CanvasES21GLCreate(Sender: TObject);var i:
Integer;begin  CanvasES21.Shader_Compile('simon_Vert', 'simon_Frag'); 
CanvasES21.Shader_Link;   for i:= 0 to High(Layers) do
glGenTextures(1, @Layers[i].Texture.ID);end; procedure
TAndroidModule1.CanvasES21GLDraw(Sender: TObject);var i:
Integer;begin  CanvasES21.MVP:= cID4x4; 
CanvasES21.SetMVP(CanvasES21.MVP); 
CanvasES21.Screen_Setup(CanvasES21.GetWidth, CanvasES21.GetHeight); 
CanvasES21.Screen_Clear(0, 0, 0, 1);   for i:= 0 to High(Layers) do
with Layers[i] do begin    UpdateDimensions(CanvasES21.GetWidth,
CanvasES21.GetHeight);     Update;    DeployBuffer(GetBuffer,
GetTexture, GetWidth, GetHeight);    DrawTexture(GetTexture, GetAlpha,
RightCorner, TopCorner, LeftCorner, DownCorner);   end;end; procedure
TAndroidModule1.DeployBuffer(B: PDWord; T: TxgElement; W, H:
Integer);begin  glDisable      (GL_DEPTH_BUFFER_BIT);  glBindTexture
 (GL_TEXTURE_2D, T.ID);  glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MIN_FILTER, GL_NEAREST);  glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MAG_FILTER, GL_NEAREST);  glTexparameteri(GL_Texture_2D,
GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);  glTexparameteri(GL_Texture_2D,
GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);  glTexImage2D(GL_TEXTURE_2D, 0,
GL_RGBA, W, H, 0, GL_RGBA, GL_UNSIGNED_BYTE, B);end; procedure
TAndroidModule1.DrawTexture(T: TxgElement; A, x1, y1, x0, y0:
Single);begin  CanvasES21.DrawTexture(T, _xy4CW(x1,y0, x0,y0, x0,y1,
x1,y1), 0, A);end; { TMyOwnPrimitives } constructor
TMyOwnPrimitives.Create;begin  Data:= Nil;  Len:=0;  W:= 0; H:=0;
X:=0;   Alpha:= FullyOpaque;  AlphaMater:= FULLY_OPAQUE; 
SetBackgroundColor(BlackColor);end; procedure
TMyOwnPrimitives.Update;begin end; procedure
TMyOwnPrimitives.UpdateDimensions(Width, Height: Integer);begin  W:=
Width; H:= Height;end; procedure
TMyOwnPrimitives.SetTheBufferUp;begin  Len:= W*H;  GetMem(Data,
Len*SizeOf(DWord));end; procedure
TMyOwnPrimitives.SetPencilColor(NewColor: DWord);begin  PencilColor:=
NewColor;  UpdateColor;end; procedure
TMyOwnPrimitives.UpdateColor;begin  Color:= PencilColor or
Alpha;end; procedure TMyOwnPrimitives.SetBackgroundColor(NewColor:
Dword);begin  BackgroundColor:= NewColor or Alpha;end; function
TMyOwnPrimitives.GetWidth: Integer;begin  Result:= W;end; function
TMyOwnPrimitives.GetHeight: Integer;begin  Result:= H;end; function
TMyOwnPrimitives.GetBuffer: PDWord;begin  Result:= Data;end; function
TMyOwnPrimitives.GetAlpha: Single;begin  Result:=
AlphaMater;end; function TMyOwnPrimitives.GetTexture:
TxgElement;begin  Result:= Texture;end; procedure
TMyOwnPrimitives.MoveToInitialPoint;begin  X:= 0;end; procedure
TMyOwnPrimitives.MoveTo(NewX, Newy: Integer);begin  X:= NewX +
W*NewY;end; procedure TMyOwnPrimitives.DrawHorizontal(Lenght:
Integer);begin  FillDWord(Data[X], Lenght, Color);  Inc(X,
Lenght);end; procedure TMyOwnPrimitives.Clean;begin  FillDWord(Data^,
Len, BackgroundColor);end; { TChessBoard } constructor
TChessBoard.Create;begin  inherited Create; 
SetSquareSize(Square32x32pixels); 
SetPencilColor(GoldenBrown);end; procedure
TChessBoard.SetSquareSize(SquareSize: Integer);begin 
DoubleSquareSize:= SquareSize + 1;  LenghtOfSquareSide:= 1 shl
SquareSize;  Mask:= (1 shl DoubleSquareSize) - 1;end; procedure
TChessBoard.UpdateDimensions(Width, Height: Integer);begin  inherited
UpdateDimensions(Width, Height);  TotalSquaresByHeight:= H shr
DoubleSquareSize;  TotalSquaresByWidth:=  W shr DoubleSquareSize; 
Remainder:=            W and Mask;end; procedure
TChessBoard.Update;var i: Integer;begin  Clean;  MoveToInitialPoint; 
for i:= 1 to TotalSquaresByHeight do DrawTwoSquareRows;end; procedure
TChessBoard.DrawTwoSquareRows;begin  DrawSquareRow;  WalkASquare; 
DrawSquareRow;  GoASquareBack;end; procedure
TChessBoard.DrawSquareRow;var i: Integer;begin  for i:= 1 to
LenghtOfSquareSide do DrawLine;end; procedure TChessBoard.DrawLine;var
i: Integer;begin  for i:= 1 to TotalSquaresByWidth do DrawTwoSquares; 
MoveToNextLine;end; procedure TChessBoard.DrawTwoSquares;begin 
DrawHorizontal(LenghtOfSquareSide);  WalkASquare;end; procedure
TChessBoard.MoveToNextLine;begin  Inc(X, Remainder);end; procedure
TChessBoard.WalkASquare;begin  Inc(X,
LenghtOfSquareSide);end; procedure TChessBoard.GoASquareBack;begin 
Dec(X, LenghtOfSquareSide);end; { TGradiant } constructor
TGradiant.Create;begin  inherited Create; 
SetPencilColor(PrussianBlue);end; procedure TGradiant.Update;begin 
Gradiant:= FullyOpaque;  inherited Update;end; procedure
TGradiant.UpdateColor;begin  Color:= PencilColor or
(Gradiant);end; procedure TGradiant.DrawLine;begin 
CalculateGradiant;  UpdateColor;  inherited DrawLine;end; procedure
TGradiant.CalculateGradiant;begin  If Numerator > H then
DecrementGradianteAndNumerator;  Inc(Numerator,
DifferentLevelsOfTransparency);end; procedure
TGradiant.DecrementGradianteAndNumerator;begin  Dec(Gradiant,
OneLevelOfTrransparency);  Dec(Numerator, H);end; { TDonut
} constructor TDonut.Create;begin  inherited Create;  AlphaMater:=
PARTIALLY_TRANSPARENT;end; procedure TDonut.Update;begin 
UpdateRadiusAndHole;  SetBackGroundTransparent;   MoveToTheCenter; 
SetPencilColor(PinkLavander);  DrawFilledCircle(DonutRadius);  
SetPencilTransparent;  DrawFilledCircle(HoleRadius);end; procedure
TDonut.UpdateRadiusAndHole;begin  WhichIsShorterBetweenHAndW; 
DonutRadius:= TheShorter shr 2;  HoleRadius:= DonutRadius -
(TheShorter shr 4);end; procedure
TDonut.SetBackGroundTransparent;begin  BackgroundColor:=
FullyTransparent;  Clean;end; procedure
TDonut.SetPencilTransparent;begin  Color:=
FullyTransparent;end; procedure TDonut.MoveToTheCenter;begin  MoveTo(W
shr 1, H shr 1);end; procedure
TDonut.WhichIsShorterBetweenHAndW;begin  if W > H then TheShorter:= H 
else TheShorter:= Wend; (*  Bresenham's Midpoint Circle
Algorithm*)procedure TDonut.DrawFilledCircle(Radius: Integer);var 
 CircleX, CircleY, d, deltaE, deltaSE: Integer;begin   CircleX:= 0; 
 CircleY:= Radius;   d:= 1 - Radius;   deltaE:= 3;   deltaSE:= 5
-(Radius shl 1);   CirclePoints(CircleX, CircleY);    while CircleY >
CircleX do begin     if d < 0 then begin       Inc(d, deltaE);     
 Inc(deltaE, 2);       Inc(deltaSE,2);       Inc(CircleX);     end
else begin       Inc(d, deltaSE);       Inc(deltaE,  2);     
 Inc(deltaSE, 4);       Inc(CircleX);       Dec(CircleY);     end;   
 CirclePoints(CircleX, CircleY);   end;end; procedure
TDonut.CirclePoints(Cx, Cy: Integer);var Wx, Wy: Integer;begin  Wx:=
W*Cx; Wy:= W*Cy;  FillDWord(Data[X-Cx+Wy], Cx shl 1, Color); 
FillDWord(Data[X-Cx-Wy], Cx shl 1, Color);  FillDWord(Data[X-Cy+Wx],
Cy shl 1, Color);  FillDWord(Data[X-Cy-Wx], Cy shl 1, Color);end; end.

----------------------------------------------------------------------
José Hernández · 2025-09-07 23:07

Playing more with the Alpha channel, we could use the code from this
thread:
https://forum.lazarus.freepascal.org/index.php?topic=44811.0

And improve it a bit: As the circle grows, it fades away like a ghost.

Enjoy reading the code:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
unit1; {$mode delphi} interface uses  {$IFDEF UNIX}{$IFDEF
UseCThreads}  cthreads,  {$ENDIF}{$ENDIF}  Classes, SysUtils,
AndroidWidget,  Laz_And_GLESv2_Canvas, Laz_And_GLESv2_Canvas_h,
Laz_And_Controls;  type   { TAndroidModule1 }   TAndroidModule1 =
class(jForm)    CanvasES21: jCanvasES2;    Timer1: jTimer;   
procedure AndroidModule1JNIPrompt(Sender: TObject);    procedure
CanvasES21GLCreate(Sender: TObject);    procedure
CanvasES21GLDown(Sender: TObject; Touch: TMouch);    procedure
CanvasES21GLDraw(Sender: TObject);    procedure CanvasES21GLUp(Sender:
TObject; Touch: TMouch);    procedure Timer1Timer(Sender: TObject); 
private    {private declarations}  public    {public declarations}   
procedure DeployBuffer(B: PDWord; T: TxgElement; W, H: Integer);   
procedure DrawTexture(T: TxgElement; A, x1, y1, x0, y0: Single); 
end;   { TMyOwnPrimitives }  TMyOwnPrimitives = class    private     
Data:            PDWord;      Len:             Integer;       Alpha: 
        DWord;      Color:           DWord;      AlphaMater:    
 Single;      PencilColor:     DWord;      BackgroundColor: DWord;   
  W,H,X:           Integer;      Texture:         TxgElement;      
TheDimensionsHaveChanged: Boolean;    public      constructor Create;
virtual;      procedure Update;  virtual;      procedure UpdateColor;
 virtual;      procedure UpdateDimensions(NewWidth, NewHeight:
Integer); virtual;      procedure SetTheBufferUp;      procedure
SetPencilColor(NewColor: DWord);      procedure
SetBackgroundColor(NewColor: Dword);      function  GetWidth:  
Integer;      function  GetHeight:  Integer;      function  GetBuffer:
 PDWord;      function  GetAlpha:   Single;      function  GetTexture:
TxgElement;       procedure MoveToInitialPoint;      procedure
MoveTo(NewX, Newy: Integer);      procedure DrawHorizontal(Lenght:
Integer);      procedure Clean;  end;     { TChessBoard }  
TChessBoard = class(TMyOwnPrimitives)     private     
 TotalSquaresByWidth:      Integer;       TotalSquaresByHeight:    
Integer;       LenghtOfSquareSide:       Integer;     
 DoubleSquareSize:         Integer;       Mask:                    
Integer;       Remainder:                Integer;     public     
 constructor Create; override;       procedure Update; override;     
 procedure UpdateDimensions(Width, Height: Integer); override;     
 procedure SetSquareSize(SquareSize: Integer);       procedure
DrawTwoSquareRows;       procedure DrawSquareRow;       procedure
DrawLine; virtual;       procedure DrawTwoSquares;       procedure
MoveToNextLine;       procedure WalkASquare;       procedure
GoASquareBack;   end;   { TGradiant }   TGradiant =
class(TChessBoard)     private       Gradiant:        DWord;     
 Numerator:       Integer;     public       constructor Create;
override;       procedure Update; override;       procedure
UpdateColor; override;       procedure DrawLine; override;     
 procedure CalculateGradiant;       procedure
DecrementGradianteAndNumerator;   end;     { TFilledCircle }  
TFilledCircle = class(TMyOwnPrimitives)    private      TheShorter:
Integer;      MaximumRadius, Radius: Integer;      ClippedRadius:
Integer;      Increment, InitialRadius: Integer;      Numerator:
Integer;    public      constructor Create; override;      procedure
Update; override;      procedure DrawExpandedCircle;      procedure
DrawACircleWhereTheFingerTouches;      procedure UpdateRadius;     
procedure DecreaseTheOpacity;      procedure
DecreaseNumeratorAndAlpha;      function TheAlphaChannelIsTooLow:
Boolean;      procedure ResetOpacityAndRadius;      procedure
ResetRadius;      procedure SetBackGroundTransparent;      procedure
SetPencilTransparent;      procedure GetClippedRadius;      function
 TheRadiusExceedsTheTopSide: Boolean;      function
 TheRadiusExceedsTheLeftSide: Boolean;      function
 TheRadiusExceedsTheBottomSide: Boolean;      function
 TheRadiusExceedsTheRightSide: Boolean;      procedure
ClipTheTopSide;      procedure ClipTheLeftSide;      procedure
ClipTheBottomSide;      procedure ClipTheRightSide;      procedure
DrawFilledCircle(Radius: Integer);      procedure
WhichIsShorterBetweenHAndW;      procedure CirclePoints(Cx, Cy:
Integer); Virtual;  end;   { TBanner }   TBanner =
class(TMyOwnPrimitives)    private      Text: String;      T,
Remainder: Integer;    public      constructor Create; override;     
procedure Update; override;      procedure ResetTextIndex;     
procedure DrawBanner;      procedure DrawBannerLine;      procedure
NextBannerLine;      procedure PutTextPixel;      procedure
NextTextPixel;      procedure CalculateRemainder;  end; var 
AndroidModule1: TAndroidModule1;  Layers: Array[0..3] of
TMyOwnPrimitives;  isPressing: Boolean = False;  FingerX: Integer =
100;  FingerY: Integer = 100;   TextBanner: String =      '          
                 00                                                  
                      00                             00        0     
          00                              '    + '0000000            
        00          00000                                            
             00                 00000                 0              
 00                              '    + '   0                        
00         0                                                         
     00                00                     0                 00   
                         '    + '   0    0000   0    0   0000 000000 
  00       0000 0 00  0000   0000   00000       0000   00000    00000
    0000      0       0 00 00  0000  0   0000       00000  0 00 0000
 00  00   0 00000 '    + '   0   00  00  0    0  00    00   0      00
   00    00   00  00 00  00  00  00         00  00  00  0   00       
00    00       00   00  0     0  00  00     0   00  00      00  0  000
 0 00  00'    + '   0   0    00 0    0  0     00   0       000  00   
00   0    0 0    0  0   00         00  0   00 00   00         00    00
      0    00 00     0  0    0    00   00  0       00  0  000 00 0  
00'    + '   0   0    00 0    0  0     00   0         00 00     0  
 000000 000000  0   00      00000  0   00 00   00      00000    00   
  0    00 00     0  000000    00   00  0    00000  00 0 0 00 0   00' 
 + '   0   0    00 0    0  0     00   0          0 00     0    0    
 0       0   00     00  00  0   00 00   00     00  00     0       0  
 00 00     0  0         00   00  0   00  00   000 000  0   00'    + '
 0   00  00  00  00  00    00   0          0  00    0    00     00   
 0   00     0   00  0   00  0   00     0   00     00      0    00  0 
  0  00         0   00  0   0   00   00  000  0   00'    + '   0  
 0000    00000   0000 00   0     00000    0000 0     00000  00000  0 
00     000000  0   00   00000     000000      00000  0    00  0000  0
 00000      00000  0    00000   00   00  0   00'; const   FullyOpaque
        = $ff000000;   FullyTransparent     = $00000000; 
 PartiallyTransparent = $80000000;    BlackColor   = $00000000; 
 WhiteColor   = $00bfbfbf;   GoldenBrown  = $001e5b89;   PrussianBlue
= $00543500;   Olivine      = $0080c4b8;   PinkLavander = $00c1afdb;  
 FULLY_OPAQUE          =  1.00;   PARTIALLY_TRANSPARENT =  0.25; 
 RightCorner           =  1.00;   LeftCorner            = -1.00; 
 TopCorner             =  1.00;   DownCorner            = -1.00;  
 Square32x32pixels = 5;   Square16x16pixels = 4;   Square64x64pixels =
6;    OneLevelOfTrransparency   = $01000000; 
 EightLevelOfTrransparency = $08000000; 
 DifferentLevelsOfTransparency = 255;   Infinite = $7fffffff;  
 _120FPS = 8;   _60FPS = 17;   _50FPS = 20;   _30FPS = 33;   _25FPS =
40;    HeightBanner = 10;   WidthBanner = 196;   implementation    {$R
*.lfm}     { TAndroidModule1 } procedure
TAndroidModule1.Timer1Timer(Sender: TObject);begin 
CanvasES21.Refresh;end; procedure
TAndroidModule1.AndroidModule1JNIPrompt(Sender: TObject);var i:
Integer;begin  Layers[0]:= TChessBoard.Create;  Layers[1]:=
TGradiant.Create;  Layers[2]:= TBanner.Create;  Layers[3]:=
TFilledCircle.Create;   for i:= 0 to High(Layers) do with Layers[i] do
begin    UpdateDimensions(CanvasES21.GetWidth, CanvasES21.GetHeight); 
  SetTheBufferUp;  end;   Timer1.Interval:= _50FPS;  Timer1.Enabled:=
True;end; procedure TAndroidModule1.CanvasES21GLCreate(Sender:
TObject);var i: Integer;begin  CanvasES21.Shader_Compile('simon_Vert',
'simon_Frag');  CanvasES21.Shader_Link;   for i:= 0 to High(Layers) do
glGenTextures(1, @Layers[i].Texture.ID);end; procedure
TAndroidModule1.CanvasES21GLDown(Sender: TObject; Touch:
TMouch);begin  isPressing:= True;  FingerX:= round(Touch.Pt.X); 
FingerY:= round(Touch.Pt.Y);end; procedure
TAndroidModule1.CanvasES21GLDraw(Sender: TObject);var i:
Integer;begin  CanvasES21.MVP:= cID4x4; 
CanvasES21.SetMVP(CanvasES21.MVP); 
CanvasES21.Screen_Setup(CanvasES21.GetWidth, CanvasES21.GetHeight);  
for i:= 0 to High(Layers) do with Layers[i] do begin   
UpdateDimensions(CanvasES21.GetWidth, CanvasES21.GetHeight);   
Update;    DeployBuffer(GetBuffer, GetTexture, GetWidth, GetHeight); 
 DrawTexture(GetTexture, GetAlpha, RightCorner, TopCorner, LeftCorner,
DownCorner);   end;end; procedure
TAndroidModule1.CanvasES21GLUp(Sender: TObject; Touch: TMouch);begin 
isPressing:= False;  Touch.Pt.X:= Touch.Pt.X;end; procedure
TAndroidModule1.DeployBuffer(B: PDWord; T: TxgElement; W, H:
Integer);begin  glDisable      (GL_DEPTH_BUFFER_BIT);  glBindTexture
 (GL_TEXTURE_2D, T.ID);  glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MIN_FILTER, GL_NEAREST);  glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MAG_FILTER, GL_NEAREST);  glTexparameteri(GL_Texture_2D,
GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);  glTexparameteri(GL_Texture_2D,
GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);  glTexImage2D(GL_TEXTURE_2D, 0,
GL_RGBA, W, H, 0, GL_RGBA, GL_UNSIGNED_BYTE, B);end; procedure
TAndroidModule1.DrawTexture(T: TxgElement; A, x1, y1, x0, y0:
Single);begin  CanvasES21.DrawTexture(T, _xy4CW(x1,y0, x0,y0, x0,y1,
x1,y1), 0, A);end; { TMyOwnPrimitives } constructor
TMyOwnPrimitives.Create;begin  Data:= Nil;  Len:=0;  W:= 0; H:=0;
X:=0;   Alpha:= FullyOpaque;  AlphaMater:= FULLY_OPAQUE; 
SetBackgroundColor(BlackColor);  TheDimensionsHaveChanged:=
True;end; procedure TMyOwnPrimitives.Update;begin end; procedure
TMyOwnPrimitives.UpdateDimensions(NewWidth, NewHeight: Integer);begin 
TheDimensionsHaveChanged:= ((W xor NewWidth) or (H xor NewHeight)) <>
0;  W:= NewWidth; H:= NewHeight;end;  procedure
TMyOwnPrimitives.SetTheBufferUp;begin  Len:= W*H;  GetMem(Data,
Len*SizeOf(DWord));end; procedure
TMyOwnPrimitives.SetPencilColor(NewColor: DWord);begin  PencilColor:=
NewColor;  UpdateColor;end; procedure
TMyOwnPrimitives.UpdateColor;begin  Color:= PencilColor or
Alpha;end; procedure TMyOwnPrimitives.SetBackgroundColor(NewColor:
Dword);begin  BackgroundColor:= NewColor or Alpha;end; function
TMyOwnPrimitives.GetWidth: Integer;begin  Result:= W;end; function
TMyOwnPrimitives.GetHeight: Integer;begin  Result:= H;end; function
TMyOwnPrimitives.GetBuffer: PDWord;begin  Result:= Data;end; function
TMyOwnPrimitives.GetAlpha: Single;begin  Result:=
AlphaMater;end; function TMyOwnPrimitives.GetTexture:
TxgElement;begin  Result:= Texture;end; procedure
TMyOwnPrimitives.MoveToInitialPoint;begin  X:= 0;end; procedure
TMyOwnPrimitives.MoveTo(NewX, Newy: Integer);begin  X:= NewX +
W*NewY;end; procedure TMyOwnPrimitives.DrawHorizontal(Lenght:
Integer);begin  FillDWord(Data[X], Lenght, Color);  Inc(X,
Lenght);end; procedure TMyOwnPrimitives.Clean;begin  FillDWord(Data^,
Len, BackgroundColor);end; { TChessBoard } constructor
TChessBoard.Create;begin  inherited Create; 
SetSquareSize(Square32x32pixels); 
SetPencilColor(GoldenBrown);end; procedure
TChessBoard.SetSquareSize(SquareSize: Integer);begin 
DoubleSquareSize:= SquareSize + 1;  LenghtOfSquareSide:= 1 shl
SquareSize;  Mask:= (1 shl DoubleSquareSize) - 1;end; procedure
TChessBoard.UpdateDimensions(Width, Height: Integer);begin  inherited
UpdateDimensions(Width, Height);  TotalSquaresByHeight:= H shr
DoubleSquareSize;  TotalSquaresByWidth:=  W shr DoubleSquareSize; 
Remainder:=            W and Mask;end; procedure
TChessBoard.Update;var i: Integer;begin  Clean;  MoveToInitialPoint; 
for i:= 1 to TotalSquaresByHeight do DrawTwoSquareRows;end; procedure
TChessBoard.DrawTwoSquareRows;begin  DrawSquareRow;  WalkASquare; 
DrawSquareRow;  GoASquareBack;end; procedure
TChessBoard.DrawSquareRow;var i: Integer;begin  for i:= 1 to
LenghtOfSquareSide do DrawLine;end; procedure TChessBoard.DrawLine;var
i: Integer;begin  for i:= 1 to TotalSquaresByWidth do DrawTwoSquares; 
MoveToNextLine;end; procedure TChessBoard.DrawTwoSquares;begin 
DrawHorizontal(LenghtOfSquareSide);  WalkASquare;end; procedure
TChessBoard.MoveToNextLine;begin  Inc(X, Remainder);end; procedure
TChessBoard.WalkASquare;begin  Inc(X,
LenghtOfSquareSide);end; procedure TChessBoard.GoASquareBack;begin 
Dec(X, LenghtOfSquareSide);end; { TGradiant } constructor
TGradiant.Create;begin  inherited Create; 
SetPencilColor(PrussianBlue);end; procedure TGradiant.Update;begin 
Gradiant:= FullyOpaque;  inherited Update;end; procedure
TGradiant.UpdateColor;begin  Color:= PencilColor or
(Gradiant);end; procedure TGradiant.DrawLine;begin 
CalculateGradiant;  UpdateColor;  inherited DrawLine;end; procedure
TGradiant.CalculateGradiant;begin  If Numerator > H then
DecrementGradianteAndNumerator;  Inc(Numerator,
DifferentLevelsOfTransparency);end; procedure
TGradiant.DecrementGradianteAndNumerator;begin  Dec(Gradiant,
OneLevelOfTrransparency);  Dec(Numerator, H);end; { TFilledCircle
} constructor TFilledCircle.Create;begin  inherited Create; 
ClippedRadius:= Infinite;end; procedure TFilledCircle.Update;begin 
UpdateRadius;  SetBackGroundTransparent;   if isPressing then
DrawExpandedCircle  else ResetOpacityAndRadius;end; procedure
TFilledCircle.DrawExpandedCircle;begin  Inc(Radius, Increment);  
GetClippedRadius;  if Radius > ClippedRadius then
ResetOpacityAndRadius;   DrawACircleWhereTheFingerTouches;  
DecreaseTheOpacity;end; procedure TFilledCircle.UpdateRadius;begin 
WhichIsShorterBetweenHAndW;  InitialRadius:=  TheShorter shr 3; 
MaximumRadius:=  TheShorter shr 2 + InitialRadius;  Increment:=    
 TheShorter shr 7;end; procedure
TFilledCircle.DrawACircleWhereTheFingerTouches;begin  MoveTo(FingerX,
FingerY);  SetPencilColor(PinkLavander); 
DrawFilledCircle(Radius);end; procedure
TFilledCircle.DecreaseTheOpacity;begin  while Numerator >
InitialRadius do DecreaseNumeratorAndAlpha;  Inc(Numerator,
InitialRadius);end; procedure
TFilledCircle.DecreaseNumeratorAndAlpha;begin  Dec(Numerator,
InitialRadius);  if TheAlphaChannelIsTooLow then Alpha:= 0  else
Dec(Alpha, EightLevelOfTrransparency);end; function
TFilledCircle.TheAlphaChannelIsTooLow: Boolean;begin  Result:= Alpha
<= EightLevelOfTrransparency;end; procedure
TFilledCircle.GetClippedRadius;begin  ClippedRadius:= MaximumRadius; 
if TheRadiusExceedsTheTopSide    then ClipTheTopSide;  if
TheRadiusExceedsTheLeftSide   then ClipTheLeftSide;  if
TheRadiusExceedsTheBottomSide then ClipTheBottomSide;  if
TheRadiusExceedsTheRightSide  then ClipTheRightSide;end; function
TFilledCircle.TheRadiusExceedsTheTopSide: Boolean;begin  Result:=
FingerY < ClippedRadius;end; function
TFilledCircle.TheRadiusExceedsTheLeftSide: Boolean;begin  Result:=
FingerX < ClippedRadius;end; function
TFilledCircle.TheRadiusExceedsTheBottomSide: Boolean;begin  Result:=
(H - FingerY) < ClippedRadius;end; function
TFilledCircle.TheRadiusExceedsTheRightSide: Boolean;begin  Result:= (W
- FingerX) < ClippedRadius;end; procedure
TFilledCircle.ClipTheTopSide;begin  ClippedRadius:=
FingerY;end; procedure TFilledCircle.ClipTheLeftSide;begin 
ClippedRadius:= FingerX;end; procedure
TFilledCircle.ClipTheBottomSide;begin  ClippedRadius:= H -
FingerY;end; procedure TFilledCircle.ClipTheRightSide;begin 
ClippedRadius:= W - FingerX;end; procedure
TFilledCircle.ResetOpacityAndRadius;begin  Alpha:= FullyOpaque; 
Numerator:= DifferentLevelsOfTransparency;  ResetRadius;end; procedure
TFilledCircle.ResetRadius;begin  if InitialRadius > ClippedRadius then
Radius:= ClippedRadius  else Radius:= InitialRadius;end; procedure
TFilledCircle.WhichIsShorterBetweenHAndW;begin  if W > H then
TheShorter:= H  else TheShorter:= W;end;procedure
TFilledCircle.SetBackGroundTransparent;begin  BackgroundColor:=
FullyTransparent;  Clean;end; procedure
TFilledCircle.SetPencilTransparent;begin  Color:=
FullyTransparent;end; procedure TFilledCircle.DrawFilledCircle(Radius:
Integer);var  CircleX, CircleY, d, deltaE, deltaSE: Integer;begin 
CircleX:= 0;  CircleY:= Radius;  d:= 1 - Radius;  deltaE:= 3; 
deltaSE:= 5 -(Radius shl 1);  CirclePoints(CircleX, CircleY);   while
CircleY > CircleX do begin   if d < 0 then begin     Inc(d, deltaE); 
  Inc(deltaE, 2);     Inc(deltaSE,2);     Inc(CircleX);   end else
begin     Inc(d, deltaSE);     Inc(deltaE,  2);     Inc(deltaSE, 4); 
  Inc(CircleX);     Dec(CircleY);   end;   CirclePoints(CircleX,
CircleY);  end;end; procedure TFilledCircle.CirclePoints(Cx, Cy:
Integer);var Wx, Wy: Integer;begin  Wx:= W*Cx; Wy:= W*Cy; 
FillDWord(Data[X-Cx+Wy], Cx shl 1, Color);  FillDWord(Data[X-Cx-Wy],
Cx shl 1, Color);  FillDWord(Data[X-Cy+Wx], Cy shl 1, Color); 
FillDWord(Data[X-Cy-Wx], Cy shl 1, Color);end; { TBanner } constructor
TBanner.Create;begin  inherited Create;  Text:= TextBanner; 
SetPencilColor(WhiteColor);  BackgroundColor:=
FullyTransparent;end; procedure TBanner.Update;begin  Clean; 
ResetTextIndex;  MoveTo(50, 50);  DrawBanner;end; procedure
TBanner.ResetTextIndex;begin  T:= 1;end; procedure
TBanner.DrawBanner;var i: Integer;begin  CalculateRemainder;  for i:=1
to HeightBanner do DrawBannerLine;end; procedure
TBanner.DrawBannerLine;var i: Integer;begin  for i:= 1 to WidthBanner
do PutTextPixel;  NextBannerLine;end; procedure
TBanner.PutTextPixel;begin  if Text[T] = '0' then begin    Data[X]:=
Color;    Data[X+1]:= Color;    Data[X+W]:= Color;    Data[X+W+1]:=
Color;  end;  NextTextPixel;end; procedure
TBanner.NextBannerLine;begin  Inc(X, Remainder);end; procedure
TBanner.NextTextPixel;begin  Inc(T);  Inc(X, 2);end; procedure
TBanner.CalculateRemainder;begin  Remainder:= 3*W -
2*WidthBanner;end; end.