| Message ID | 20180412073148.17453-1-johan.helsing@qt.io |
|---|---|
| State | New |
| Series | "compositor-headless: Report a more realistic physical size" |
| Headers | show |
diff --git a/libweston/compositor-headless.c b/libweston/compositor-headless.c index 9307a36a..9f1a1a72 100644 --- a/libweston/compositor-headless.c +++ b/libweston/compositor-headless.c @@ -180,12 +180,19 @@ err_malloc: return -1; } +static int +physical_size_for_dpi(int pixels, int dpi) +{ + static const float mm_per_inch = 25.4; + return pixels * mm_per_inch / dpi; +} + static int headless_output_set_size(struct weston_output *base, int width, int height) { struct headless_output *output = to_headless_output(base); - int output_width, output_height; + int output_width, output_height, output_dpi; /* We can only be called once. */ assert(!output->base.current_mode); @@ -207,9 +214,10 @@ headless_output_set_size(struct weston_output *base, output->base.make = "weston"; output->base.model = "headless"; - /* XXX: Calculate proper size. */ - output->base.mm_width = width; - output->base.mm_height = height; + /* XXX: Make this configurable */ + output_dpi = 72 * output->base.scale; + output->base.mm_width = physical_size_for_dpi(output_width, output_dpi); + output->base.mm_height = physical_size_for_dpi(output_height, output_dpi); output->base.start_repaint_loop = headless_output_start_repaint_loop; output->base.repaint = headless_output_repaint;
On Thu, 12 Apr 2018 09:31:48 +0200 Johan Klokkhammer Helsing <johan.helsing@qt.io> wrote: > Some clients rely on the physical size to determine the physical DPI. With the > previous implementation, we would report 1px==1mm, which is a DPI of 25.4, > which is incredibly low. > > The problem is solved by setting a physical size so the DPI is close to 72 > instead. If the output is scaled, the DPI is set to the corresponding multiple > of 72. > > This makes the headless backend more usable for automated testing of DPI > sensitive functionality such as point sized fonts. > > Signed-off-by: Johan Klokkhammer Helsing <johan.helsing@qt.io> > --- > libweston/compositor-headless.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) Hi, this is a good idea, but could you rebase this patch to master? Thanks, pq > > diff --git a/libweston/compositor-headless.c b/libweston/compositor-headless.c > index 9307a36a..9f1a1a72 100644 > --- a/libweston/compositor-headless.c > +++ b/libweston/compositor-headless.c > @@ -180,12 +180,19 @@ err_malloc: > return -1; > } > > +static int > +physical_size_for_dpi(int pixels, int dpi) > +{ > + static const float mm_per_inch = 25.4; > + return pixels * mm_per_inch / dpi; > +} > + > static int > headless_output_set_size(struct weston_output *base, > int width, int height) > { > struct headless_output *output = to_headless_output(base); > - int output_width, output_height; > + int output_width, output_height, output_dpi; > > /* We can only be called once. */ > assert(!output->base.current_mode); > @@ -207,9 +214,10 @@ headless_output_set_size(struct weston_output *base, > output->base.make = "weston"; > output->base.model = "headless"; > > - /* XXX: Calculate proper size. */ > - output->base.mm_width = width; > - output->base.mm_height = height; > + /* XXX: Make this configurable */ > + output_dpi = 72 * output->base.scale; > + output->base.mm_width = physical_size_for_dpi(output_width, output_dpi); > + output->base.mm_height = physical_size_for_dpi(output_height, output_dpi); > > output->base.start_repaint_loop = headless_output_start_repaint_loop; > output->base.repaint = headless_output_repaint;
> On Thu, 12 Apr 2018 09:31:48 +0200 > Johan Klokkhammer Helsing <johan.helsing@qt.io> wrote: > > > Some clients rely on the physical size to determine the physical DPI. With the > > previous implementation, we would report 1px==1mm, which is a DPI of 25.4, > > which is incredibly low. > > > > The problem is solved by setting a physical size so the DPI is close to 72 > > instead. If the output is scaled, the DPI is set to the corresponding multiple > > of 72. > > > > This makes the headless backend more usable for automated testing of DPI > > sensitive functionality such as point sized fonts. > > > > Signed-off-by: Johan Klokkhammer Helsing <johan.helsing@qt.io> > > --- > > libweston/compositor-headless.c | 16 ++++++++++++---- > > 1 file changed, 12 insertions(+), 4 deletions(-) > > Hi, > > this is a good idea, but could you rebase this patch to master? > > > Thanks, > pq Hi, Would it make sense to change the protocol to allow compositors to send a zero physical size in case it isn't relevant? > > > > diff --git a/libweston/compositor-headless.c b/libweston/compositor-headless.c > > index 9307a36a..9f1a1a72 100644 > > --- a/libweston/compositor-headless.c > > +++ b/libweston/compositor-headless.c > > @@ -180,12 +180,19 @@ err_malloc: > > return -1; > > } > > > > +static int > > +physical_size_for_dpi(int pixels, int dpi) > > +{ > > + static const float mm_per_inch = 25.4; > > + return pixels * mm_per_inch / dpi; > > +} > > + > > static int > > headless_output_set_size(struct weston_output *base, > > int width, int height) > > { > > struct headless_output *output = to_headless_output(base); > > - int output_width, output_height; > > + int output_width, output_height, output_dpi; > > > > /* We can only be called once. */ > > assert(!output->base.current_mode); > > @@ -207,9 +214,10 @@ headless_output_set_size(struct weston_output *base, > > output->base.make = "weston"; > > output->base.model = "headless"; > > > > - /* XXX: Calculate proper size. */ > > - output->base.mm_width = width; > > - output->base.mm_height = height; > > + /* XXX: Make this configurable */ > > + output_dpi = 72 * output->base.scale; > > + output->base.mm_width = physical_size_for_dpi(output_width, output_dpi); > > + output->base.mm_height = physical_size_for_dpi(output_height, output_dpi); > > > > output->base.start_repaint_loop = headless_output_start_repaint_loop; > > output->base.repaint = headless_output_repaint; > > _______________________________________________ > wayland-devel mailing list > wayland-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/wayland-devel
On Mon, 02 Jul 2018 10:29:48 -0400 Simon Ser <contact@emersion.fr> wrote: > > On Thu, 12 Apr 2018 09:31:48 +0200 > > Johan Klokkhammer Helsing <johan.helsing@qt.io> wrote: > > > > > Some clients rely on the physical size to determine the physical DPI. With the > > > previous implementation, we would report 1px==1mm, which is a DPI of 25.4, > > > which is incredibly low. > > > > > > The problem is solved by setting a physical size so the DPI is close to 72 > > > instead. If the output is scaled, the DPI is set to the corresponding multiple > > > of 72. > > > > > > This makes the headless backend more usable for automated testing of DPI > > > sensitive functionality such as point sized fonts. > > > > > > Signed-off-by: Johan Klokkhammer Helsing <johan.helsing@qt.io> > > > --- > > > libweston/compositor-headless.c | 16 ++++++++++++---- > > > 1 file changed, 12 insertions(+), 4 deletions(-) > > > > Hi, > > > > this is a good idea, but could you rebase this patch to master? > > > > > > Thanks, > > pq > > Hi, > > Would it make sense to change the protocol to allow compositors to send a zero > physical size in case it isn't relevant? I think it's often full of lies anyway, because usually the reported numbers come directly from EDID. I've heard rumours of something like width=16 height=9 (mm? cm?) etc. when the physical size is unknowable (e.g. a projector) but they still want to send the aspect ratio. If existing toolkits can cope with it, zero would be fine. Whether they do, I really don't know. Something about aspect ratio might need to be taken into account though. We've never really had non-square pixels, so the assumption of square pixels is probably used throughout the stack. If output information implied non-square pixels, does it mean client pixels will be shown equally non-square or are they scaled assuming they are originally square? OTOH, headless reporting a sensible fake size for a fake output is still a good idea in my opinion. Thanks, pq
Some clients rely on the physical size to determine the physical DPI. With the previous implementation, we would report 1px==1mm, which is a DPI of 25.4, which is incredibly low. The problem is solved by setting a physical size so the DPI is close to 72 instead. If the output is scaled, the DPI is set to the corresponding multiple of 72. This makes the headless backend more usable for automated testing of DPI sensitive functionality such as point sized fonts. Signed-off-by: Johan Klokkhammer Helsing <johan.helsing@qt.io> --- libweston/compositor-headless.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)