From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <1055b16f0605011057h1ef7acdbra2fdb6e4bb646f20@mail.gmail.com> Date: Mon, 1 May 2006 13:57:56 -0400 From: "Artem Letko" To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu> Subject: Re: [9fans] nvidia scrolling performance In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <28c4986548f732f8d3648e3df15865c7@quanstro.net> Topicbox-Message-UUID: 4c2dc866-ead1-11e9-9d60-3106f5b1d025 what if we use hardware to do blits with alpha? -art On 5/1/06, Russ Cox wrote: > > why does the framebuffer need to be consulted when the background is a = known, > > solid color? > > the underlying operation is just plain draw, > and drawing text corresponds to drawing > solid black through the font (as a mask) > onto the destination image. if the mask has > fractional alpha, that requires reading the > destination image to do the mixing. > > the destination image might in this case > be a known solid color, but in general it > need not be. > > you could address this by adding a fourth argument > to memdraw and then using it inside devdraw > to specify a "read from this instead of the destination" > image. it's not clear to me that this is worth the bother, > and it makes the interface less clean. you'd also have > to redo libframe to use stringbg everywhere. > > russ > >