Question

Im setting up a progress bar as follows :

void CProgressBar::add(int ammount)
{
    mProgress += ammount;
}

float CProgressBar::get()
{
    float pr = (float)mProgress * 100.0f / (float)mMax;
    return pr;
}

And now here is the problem.I’m trying to render a small surface although it doesn’t properly fill it because i can’t
figure out how to scale properly the value :

/*
    Progress bar box has size of 128x16
    |-----------|
    |-----------|
*/
float progress = progressBar->get();
float scale = 4.0f; //Here i have it hardcoded although i have to make this generic

progress *= scale;
graphics->color(prgColor);
graphics->renderQd(CRect(x,y,progress,height));

So im kindly asking for some help on the matter…

Answer 1

You have to linearly interpolate between the width of the rectangle with 0% progress and the width of the rectangle with 100% progress. E.G:

float width_0 = 0.f; // or any other number of pixels
float width_100 = 250.f; // or any other number of pixels

The interpolation works as follows:

float interpolated_width = (width_100 - width_0) * progress + width_0;

Important: progress has to be in the range of 0 to 1! So you might want to change the CProgressBar::get() function or divide by 100 first.

Now you can just render the rectangle with the new width:

graphics->renderQd(CRect(x,y,interpolated_width,height));