Changing background color

[jonashn]

Not sure if this is the right forum..

I've just begun to experiment with plugin-writing, and i've tried to change the background color like this:

Code: [Select]

unsigned int a,b,c=0;
 Â   for(a=0;a<=255;a++)
 Â   {
 Â       for(b=0;b<=255;b++)
 Â       {
 Â           for(c=0;c<=255;c++)
 Â           {
 Â                   rb->lcd_set_background(LCD_RGBPACK(a,b,c));
 Â                   rb->lcd_clear_display();
 Â                   rb->lcd_update();
 Â           }
 Â       }
 Â   
 Â   }    

BUT it doesn't work. What is wrong?

[Job Van Dam]

I know absolutely no C, I know PHP though.

Shouldn't you clear_display then set_background? It seems like your setting the background then clearing it therefore getting rid of what you just did.

Aren't the loops just going to make the screen white?

You're also going to be updating the screen 255 times, is that normal?

Something tells me I'm in way over my head here...... I'm sorry.

[stripwax]

jonashn - are you running this in the sim or the real target?  if in the sim, it's (possible) that it executes the nested loops so quickly you don't actually see the background colour changing - as prev post says you just end up with white.  You could try doing an  rb->sleep(HZ/10)  to put a 1/10 sec pause in there each time round.

[stripwax]

other alternative of course is that it's so slow you don't see it doing anything  ..  to loop through all colours would take 16million lcd updates and at 50fps that's nearly 4 days  
If you do += 32 instead of ++ you ought to see something happen.
What target by the way?

[jonashn]

What target by the way?

Ipod Video.

And first i tried without clear_display, but that didn't worked.

And in the wiki it's quite unclear about _when_ it is required to lcd_update().

Job Van Dam> http://www.rockbox.org/twiki/bin/view/Main/HowtoWritePlugins says:  

rb->lcd_clear_display();
This will clear the display, writing the background colour to the entire screen. Again, no input required, so it can just be called as is.

So when playing with background color like this i surely have to clear_display.

And for example

Code: [Select]

    rb->lcd_set_backdrop(NULL);
 Â   rb->lcd_clear_display();
 Â   unsigned int a,b,c=0;
 Â   for(a=0;a<=255;a+=32)
 Â   {
 Â       for(b=0;b<=255;b+=32)
 Â       {
 Â           for(c=0;c<=255;c+=32)
 Â           {
 Â                   rb->lcd_set_background(LCD_RGBPACK(a,b,c));
 Â                   rb->lcd_clear_display();
 Â                   rb->sleep(HZ/10);
 Â           }
 Â       }
 Â   
 Â   }

Also won't work. It even don't clear the backdrop, altrough my rb->lcd_set_backdrop(NULL);

[linuxstb]

Your first attempt looks correct to me, but as others have said, looping through all 14 million colours will take a while...

Can you post the entire source to your plugin?  Maybe something else is causing it to fail.

[jonashn]

It's just the helloworld plugin with the background-changer code added:

Code: [Select]

#include "plugin.h"

PLUGIN_HEADER
static struct plugin_api* rb;


enum plugin_status plugin_start(struct plugin_api* api, void* parameter)
{
    (void)parameter;
    rb = api;

    rb->lcd_set_backdrop(NULL);
    rb->lcd_clear_display();
    unsigned int a,b,c=0;
    for(a=0;a<=255;a+=32)
    {
        for(b=0;b<=255;b+=32)
        {
            for(c=0;c<=255;c+=32)
            {
                    rb->lcd_set_background(LCD_RGBPACK(a,b,c));
                    rb->lcd_clear_display();
                    rb->sleep(HZ/10);
            }
        }
    
    }

    return PLUGIN_OK;
}

[linuxstb]

You need a call to rb->lcd_update() in there (e.g. just before the rb->sleep() call).

[jonashn]

Thanks linuxstb! That works.

[stripwax]

Thanks linuxstb! That works.

Wait .. what?  The original code did have the lcd_update  ..   so how come the original post complained it didn't work?  

[jonashn]

No idea:D