void DaoxCanvas_Rotate( int x, int y )
{
DaoxMatrix3D rotate = {1.0,0.0,0.0,0.0,1.0,0.0};
DaoxAABBox2D box = daox_current_canvas->viewport;
DaoxVector2D start, end, center = {0.0,0.0};
double W2 = 0.5 * window_width;
double H2 = 0.5 * window_height;
double area, cosine, sine;
start.x = last_x - W2;
start.y = last_y - H2;
end.x = x - W2;
end.y = y - H2;
area = DaoxTriangle_Area( center, start, end );
cosine = DaoxTriangle_AngleCosine( center, start, end );
sine = sqrt( 1.0 - cosine * cosine );
rotate.A11 = rotate.A22 = cosine;
if( area < 0.0 ){
rotate.A12 = - sine;
rotate.A21 = sine;
}else{
rotate.A12 = sine;
rotate.A21 = - sine;
}
DaoxMatrix3D_Multiply( & daox_current_canvas->transform, rotate );
Done:
last_x = x;
last_y = y;
}
void DaoxWindow_RotateCanvas( DaoxWindow *self, DaoxCanvas *canvas, int x, int y )
{
DaoxMatrix3D rotate = {1.0,0.0,0.0,0.0,1.0,0.0};
DaoxVector2D start, end, center = {0.0,0.0};
double W2 = 0.5 * self->width;
double H2 = 0.5 * self->height;
double area, cosine, sine;
start.x = self->cursorPosX - W2;
start.y = self->cursorPosY - H2;
end.x = x - W2;
end.y = y - H2;
area = DaoxTriangle_Area( center, start, end );
cosine = DaoxTriangle_AngleCosine( center, start, end );
sine = sqrt( 1.0 - cosine * cosine );
rotate.A11 = rotate.A22 = cosine;
if( area < 0.0 ){
rotate.A12 = - sine;
rotate.A21 = sine;
}else{
rotate.A12 = sine;
rotate.A21 = - sine;
}
DaoxMatrix3D_Multiply( & canvas->transform, rotate );
}
