Re: [PATCH 2/2] drm/rect: Keep the clipped dst rectangle in place

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org,
	Benjamin Gaignard <benjamin.gaignard@st.com>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 2/2] drm/rect: Keep the clipped dst rectangle in place
Date: Fri, 22 Nov 2019 19:25:39 +0200	[thread overview]
Message-ID: <20191122172539.GP1208@intel.com> (raw)
In-Reply-To: <20191120171138.GI1208@intel.com>

On Wed, Nov 20, 2019 at 07:11:38PM +0200, Ville Syrjälä wrote:
> On Wed, Nov 20, 2019 at 05:43:40PM +0100, Daniel Vetter wrote:
> > On Wed, Nov 20, 2019 at 06:25:12PM +0200, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > Now that we've constrained the clipped source rectangle such
> > > that it can't have negative dimensions doing the same for the
> > > dst rectangle seems appropriate. Should at least result in
> > > the clipped src and dst rectangles being a bit more consistent
> > > with each other.
> > > 
> > > Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > selftests for this stuff? Looks like the prime example, write testcase
> > proving code is busted, fix it, everyone celebrate?
> 
> Yeah, seems like a good idea. Though I'll have to figure out if it's
> actually broken or not ;)

I *think* the only problem is that the clip can result in a visible
source rectangle when this happens. The dst rectangle will still
be correctly invisible so hopefully not a big deal. But I guess we
might as well fix it, and I can do a selftest which makes sure
both src and dst come out invisible.

> 
> Hmm. Ouch. There's seems to be a div by zero lurking in there if
> dst_w/h == 0. I wonder why nothing has hit that.

Definitely real. I'll fix it and toss in a selftest.

-- 
Ville Syrjälä
Intel
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