how to draw using a while loop.

[Fouad Hanoun]

Hey guys, if i'm calculating a matrix that is supposed to change every second using a while loop and i'm using a painter in it and the pen changes colors depending on each value in the matrix, the problem is that when i run the program it doesn't draw continuously, but only the final result altho i put the code inside the paint event, in the dialog.cpp.

can anyone help?
i want to see the drawing at every loop at the while not at the end of it.

oh yes and one more thing, why is the code getting executed tons of times instead of just once? does the paint event loops? if yes how can i let it be executed just once?

Added after 33 minutes:


void Dialog::paintEvent(QPaintEvent *e)
{
QPainter painter(this);
QPen framepen(QColor::fromRgb(0,0,255,255));
QBrush brush(QColor::fromRgb(0,0,255,255));
framepen.setWidth(1);
float deltaX , deltaY, deltaT;
float D , vX, vY;
float m=9; //dim-1

deltaX=0.3;
deltaY=0.3;
deltaT=1;
vX=0.03;
vY=0;
D=0.01;
float deltaX2=deltaX*deltaX;
float deltaY2=deltaY*deltaY;
float alfa = vX * deltaT / deltaX;
float beta = vY * deltaT / deltaY;
float gamma = D * deltaT / deltaX2;
float etha = D * deltaT / deltaY2;

cout<<gamma + etha + alfa/2 + beta/2 <<endl;
//alfa 0.001 beta 0 gamma 0.0001 etha 0.0001
// il faut <0.5

Matricem C = Matricem(10,10);

//pour k = 0 (cas initial avec poluant sur 2,0 et 3,0)
float k =0;
for (float i=1; i<m+1; i++){ //0 a 9
for (float j=1; j<m+1; j++){
C(i,j) = 0;
}
}
C(3,1)=255;
C(4,1)=255;
//affiche(C);
//cout<<C;
//condition
//cout<<C;

// gamma + etha + 2*alfa*deltaT + 2*beta*deltaT < 0.25
// D * deltaT / deltaX2; + D * deltaT / deltaY2; + 2*vX * (deltaT / deltaX)*delta t ,2*vY * deltaT / deltaY;*delta t <0.25;
//prenons 100 incrementations de k
k=1;
// sans les bords
while (k< 3){
for (float i=2; i<m+1; i++){ // 1 a 8bb
for (float j=2; j<m+1; j++){ // 1 a 8
C(i,j) = C(i,j)*(1+alfa+beta-2*gamma-2*etha) + C(i+1,j)*(-alfa+gamma)
+C(i,j+1)*(-beta+etha) + gamma*C(i-1,j) + etha*C(i,j-1);
//C(i,j)=1;
}
}
//C(2,1) = C(2,1)*(1+alfa+beta-2*gamma-2*etha) + C(2+1,1)*(-alfa+gamma+etha)
//+C(2,1+1)*(-beta) + gamma*C(2-1,1) + etha*C(2,1-1);
//affiche(C);
// bord inferieur

for (float i=5; i<m+1; i++){ // colonne 1 a 8
C(i,1) = C(i,1)*(1+alfa-2*gamma-2*etha) + C(i+1,1)*(-alfa+gamma) //ligne 9
+ C(i-1,1)*(gamma) + 2*etha*C(i,2);
//C(2,1) = C(2,1)*(1+alfa-2*gamma-2*etha) + C(2+1,1)*(-alfa+gamma) //ligne 9
//+ C(2-1,1)*(gamma) + 2*etha*C(2,2);
//cout<<C(5,1)<<endl;
}
//cout<<C(5,1)<<endl;
//C(2,1) = C(2,1)*(1+alfa-2*gamma-2*etha) + C(2+1,1)*(-alfa+gamma) //ligne 9
//+ C(2-1,1)*(gamma) + 2*etha*C(2,2);
C(2,1) = C(2,1)*(1+alfa-2*gamma-2*etha) + C(2+1,1)*(-alfa+gamma) //ligne 9
+ C(2-1,1)*(gamma) + 2*etha*C(2,2);
//alfa 0.001 beta 0 gamma 0.0001 etha 0.0001
// bord superieur
//C(2-1,1)*(gamma)
//cout<<C(2,1)<<endl;
for (float i=2; i<m+1; i++){ //colonne x1 a 8
C(i,m+1) = C(i,m+1)*(1+alfa-2*gamma-2*etha) + C(i+1,m+1)*(-alfa+gamma) //ligne 9
+ C(i-1,m+1)*gamma + 2*etha*C(i,m);
}
for(float i=1;i<m+2;i++){
C(1,i)=0;
}
for(float j=1;j<m+2;j++){
C(m+1,j)=0;
}

QRect rect10(10,60,50,50); //2eme ligne 1ere colonne

painter.drawRect(rect10);
painter.fillRect(rect10,brush);


QRect rect11(60,60,50,50); //2eme ligne 2eme colonne
framepen.setColor(QColor::fromRgb(0,C(2,9),255-C(2,9),255));
brush.setColor(QColor::fromRgb(0,C(2,9),255-C(2,9),255));
painter.drawRect(rect11);
painter.fillRect(rect11,brush);

QRect rect12(110,60,50,50); //2eme ligne 3eme colonne
framepen.setColor(QColor::fromRgb(0,C(3,9),255-C(3,9),255));
brush.setColor(QColor::fromRgb(0,C(3,9),255-C(3,9),255));
painter.drawRect(rect12);
painter.fillRect(rect12,brush);

QRect rect13(160,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(4,9),255-C(4,9),255));
brush.setColor(QColor::fromRgb(0,C(4,9),255-C(4,9),255));
painter.drawRect(rect13);
painter.fillRect(rect13,brush);

QRect rect14(210,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(5,9),255-C(5,9),255));
brush.setColor(QColor::fromRgb(0,C(5,9),255-C(5,9),255));
painter.drawRect(rect14);
painter.fillRect(rect14,brush);

QRect rect15(260,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(6,9),255-C(6,9),255));
brush.setColor(QColor::fromRgb(0,C(6,9),255-C(6,9),255));
painter.drawRect(rect15);
painter.fillRect(rect15,brush);

QRect rect16(310,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(7,9),255-C(7,9),255));
brush.setColor(QColor::fromRgb(0,C(7,9),255-C(7,9),255));
painter.drawRect(rect16);
painter.fillRect(rect16,brush);

QRect rect17(360,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(8,9),255-C(8,9),255));
brush.setColor(QColor::fromRgb(0,C(8,9),255-C(8,9),255));
painter.drawRect(rect17);
painter.fillRect(rect17,brush);

QRect rect18(410,60,50,50);
framepen.setColor(QColor::fromRgb(0,C(9,9),255-C(9,9),255));
brush.setColor(QColor::fromRgb(0,C(9,9),255-C(9,9),255));
painter.drawRect(rect18);
painter.fillRect(rect18,brush);

QRect rect19(460,60,50,50);
framepen.setColor(QColor::fromRgb(0,0,255,255));
brush.setColor(QColor::fromRgb(0,0,255,255));
painter.drawRect(rect19);
painter.fillRect(rect19,brush);






QRect rect20(10,110,50,50);
framepen.setColor(QColor::fromRgb(0,0,255,255));
brush.setColor(QColor::fromRgb(0,0,255,255));
painter.drawRect(rect20);
painter.fillRect(rect20,brush);

QRect rect21(60,110,50,50);
framepen.setColor(QColor::fromRgb(0,C(2,8),255-C(2,8),255));
brush.setColor(QColor::fromRgb(0,C(2,8),255-C(2,8),255));
painter.drawRect(rect21);
painter.fillRect(rect21,brush);


update();

k++;
}
}



i have 100 rectangle so i only posted 10 of them... i hope you understand what i'm trying to do and what my problem is...

it's failing with rgb error out of range while the biggest value of my matrix is 255.. so i am not going past that.

[anda_skoa]

If you don't return from paintEvent, then there is no time for Qt to update the widget's content with what you have just drawn.

So if "drawing in a loop" means you are drawing different things in each interation, then you don't use an actual loop, but return after each "iteration" and schedule another paint by calling QWidget::update().
The latter potentially delayed with a timer, there is a limit of what a human eye can still see regarding frame rate.

Cheers,
_

P.S.: when you post code, wrap it in
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