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Subject: Re: Soft Scrolling & CPU usage
From: Linus Nielsen Feltzing (
Date: 2003-01-03 wrote:
> ok - if I see right, if just one line of text is scrolled with 10Hz, the
> whole lcd_framebuffer being copied to GDRAM over and over again, i.e. a complete
> display refresh (lcd_update) is being done, which isn`t necessary

What makes you think that is updates the entire display?

This is the update part of the scroll thread:

             lcd_clearrect(xpos, ypos, LCD_WIDTH - xmargin, h);
             lcd_putsxyofs(xpos, ypos, s->offset, s->line);
             lcd_update_rect(xpos, ypos, LCD_WIDTH - xmargin, h);

> There already is a routine lcd_update_rect() for just updating a fraction of
> the display.
> Does someone know, why it isn`t being used for scrolling ?

It is used. See the code above.


Page was last modified "Jan 10 2012" The Rockbox Crew