Gtk: Consider font dpi when calculating device scale factor

Gtk: Consider font dpi when calculating device scale factor

Gtk2 did not have a global window scaling setting (so the only way to
scale up widgets was with a custom theme).  However, it did allow font
scaling with gdk-xft-dpi (backed by XSetting Xft/DPI).

Gtk3 adds (non-fractional) global window scaling with
gdk-window-scaling-factor (XSetting Gdk/WindowScalingFactor).  To
ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added in [1] that overrides gdk-xft-dpi: gdk-unscaled-dpi
(XSetting Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps like Chromium that still need it.

When modifying these settings, an invariant should be maintained:
gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.  Chromium
should have been able to keep using gdk-xft-dpi, but this invariant is
violated when changing the settings using gnome-tweak-tool, where I
have gdk-window-scaling-factor = 2, gdk-unscaled-dpi = 98304, and
gdk-xft-dpi = 98304 (gdk-xft-dpi should be 196608).

[2] changed Gtk builds to use the window scaling factor, which is
incorrect because it did not consider font scaling, making fractional
scaling impossible.

This CL takes gdk-unscaled-dpi into the calculation as well, and
continues to fallback on using gdk-xft-dpi if the other variables are
unavailable, which can happen on Gtk2.

[1] https://git.gnome.org/browse/gtk+/commit/?id=4b9c08f48d6f5be43b0795d3eee462d60b5f9e1f
[2] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org

Review-Url: https://codereview.chromium.org/2899943002
Cr-Commit-Position: refs/heads/master@{#473966}
Committed: https://chromium.googlesource.com/chromium/src/+/40910b90874699376e21625f26e580ff42541b1d

[Tom Anderson, 2017-05-23 01:27:53]

Description was changed from

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 only had one variable that represented font scaling: gdk-xft-dpi
(backed by XSettings Xft/DPI).

Gtk2 also did not have a global scale factor.  A custom theme was
needed if you wanted to scale up widgets.

Gtk3 adds global window scaling with gdk-window-scaling-factor
(XSettings Gdk/WindowScalingFactor), however it must be an integer.
To ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added to represent the unscaled font dpi: gdk-unscaled-dpi
(XSettings Gdk/UnscaledDPI).


* gdk-window-scaling-factor (XSettings Gdk/WindowScalingFactor):
  Integer scale factor for widgets.

* gdk-unscaled-dpi (XSettings Gdk/UnscaledDPI): Floating point scale
  factor applied to fonts (on top of gtk-window-scaling-factor).

* gtk-xft-dpi (XSettings Xft/DPI): Floating point scale factor applied
  to fonts.

Should be gtk-window-scaling-factor * gdk-unscaled-dpi



BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org
==========

to

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 only had one variable that represented font scaling: gdk-xft-dpi
(backed by XSettings Xft/DPI).

Gtk2 also did not have a global scale factor.  A custom theme was
needed if you wanted to scale up widgets.

Gtk3 adds global window scaling with gdk-window-scaling-factor
(XSettings Gdk/WindowScalingFactor), however it must be an integer.
To ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added to represent the unscaled font dpi: gdk-unscaled-dpi
(XSettings Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps that need it, like Chromium.  The invariant
should be gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.

Chromium should have been able to keep using gdk-xft-dpi, but this
invariant is violated on some environments (at least Ubuntu + GNOME +
X11), where I have gdk-window-scaling-factor = 2, gdk-unscaled-dpi =
98304, and gdk-xft-dpi = 98304.

[1] changed Gtk3 builds to use the window scaling factor, which is
incorrect because fractional scaling would not be possible.  It should
have taken into consideration gdk-unscaled-dpi as well.  This CL makes
that change, and continues to fallback on using gdk-xft-dpi if the
other variables are unavailable (eg. Gtk2).

[1] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org
==========

[Tom Anderson, 2017-05-23 02:10:33]

Description was changed from

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 only had one variable that represented font scaling: gdk-xft-dpi
(backed by XSettings Xft/DPI).

Gtk2 also did not have a global scale factor.  A custom theme was
needed if you wanted to scale up widgets.

Gtk3 adds global window scaling with gdk-window-scaling-factor
(XSettings Gdk/WindowScalingFactor), however it must be an integer.
To ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added to represent the unscaled font dpi: gdk-unscaled-dpi
(XSettings Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps that need it, like Chromium.  The invariant
should be gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.

Chromium should have been able to keep using gdk-xft-dpi, but this
invariant is violated on some environments (at least Ubuntu + GNOME +
X11), where I have gdk-window-scaling-factor = 2, gdk-unscaled-dpi =
98304, and gdk-xft-dpi = 98304.

[1] changed Gtk3 builds to use the window scaling factor, which is
incorrect because fractional scaling would not be possible.  It should
have taken into consideration gdk-unscaled-dpi as well.  This CL makes
that change, and continues to fallback on using gdk-xft-dpi if the
other variables are unavailable (eg. Gtk2).

[1] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org
==========

to

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 did not have a global window scaling setting (so the only way to
scale up widgets was with a custom theme).  However, it did allow font
scaling with gdk-xft-dpi (backed by XSetting Xft/DPI).

Gtk3 adds (non-fractional) global window scaling with
gdk-window-scaling-factor (XSetting Gdk/WindowScalingFactor).  To
ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added in [1] that overrides gdk-xft-dpi: gdk-unscaled-dpi
(XSetting Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps like Chromium that still need it.

When modifying these settings, an invariant should be maintained:
gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.  Chromium
should have been able to keep using gdk-xft-dpi, but this invariant is
violated when changing the settings using gnome-tweak-tool, where I
have gdk-window-scaling-factor = 2, gdk-unscaled-dpi = 98304, and
gdk-xft-dpi = 98304 (gdk-xft-dpi should be 196608).

[2] changed Gtk builds to use the window scaling factor, which is
incorrect because it did not consider font scaling, making fractional
scaling impossible.

This CL takes gdk-unscaled-dpi into the calculation as well, and
continues to fallback on using gdk-xft-dpi if the other variables are
unavailable, which can happen on Gtk2.

[1]
https://git.gnome.org/browse/gtk+/commit/?id=4b9c08f48d6f5be43b0795d3eee462d6...
[2] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org
==========

[Tom Anderson, 2017-05-23 02:10:53]

The CQ bit was checked by thomasanderson@chromium.org to run a CQ dry run

[Tom Anderson, 2017-05-23 02:11:11]

erg ptal

[commit-bot: I haz the power, 2017-05-23 02:11:29]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-23 03:00:15]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-23 03:00:16]

Dry run: This issue passed the CQ dry run.

[Elliot Glaysher, 2017-05-23 17:21:07]

lgtm

[Tom Anderson, 2017-05-23 17:39:38]

The CQ bit was checked by thomasanderson@chromium.org

[commit-bot: I haz the power, 2017-05-23 17:40:19]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-23 17:45:50]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1495561178862300, "parent_rev":
"5b17d3a93fe37f7f62b9a70acc1fa0cac793e68b", "commit_rev":
"40910b90874699376e21625f26e580ff42541b1d"}

[commit-bot: I haz the power, 2017-05-23 17:46:01]

Description was changed from

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 did not have a global window scaling setting (so the only way to
scale up widgets was with a custom theme).  However, it did allow font
scaling with gdk-xft-dpi (backed by XSetting Xft/DPI).

Gtk3 adds (non-fractional) global window scaling with
gdk-window-scaling-factor (XSetting Gdk/WindowScalingFactor).  To
ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added in [1] that overrides gdk-xft-dpi: gdk-unscaled-dpi
(XSetting Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps like Chromium that still need it.

When modifying these settings, an invariant should be maintained:
gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.  Chromium
should have been able to keep using gdk-xft-dpi, but this invariant is
violated when changing the settings using gnome-tweak-tool, where I
have gdk-window-scaling-factor = 2, gdk-unscaled-dpi = 98304, and
gdk-xft-dpi = 98304 (gdk-xft-dpi should be 196608).

[2] changed Gtk builds to use the window scaling factor, which is
incorrect because it did not consider font scaling, making fractional
scaling impossible.

This CL takes gdk-unscaled-dpi into the calculation as well, and
continues to fallback on using gdk-xft-dpi if the other variables are
unavailable, which can happen on Gtk2.

[1]
https://git.gnome.org/browse/gtk+/commit/?id=4b9c08f48d6f5be43b0795d3eee462d6...
[2] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org
==========

to

==========
Gtk: Consider font dpi when calculating device scale factor

Gtk2 did not have a global window scaling setting (so the only way to
scale up widgets was with a custom theme).  However, it did allow font
scaling with gdk-xft-dpi (backed by XSetting Xft/DPI).

Gtk3 adds (non-fractional) global window scaling with
gdk-window-scaling-factor (XSetting Gdk/WindowScalingFactor).  To
ensure that fonts were not scaled up twice (once from
gdk-window-scaling-factor and once from gdk-xft-dpi), a new setting
was added in [1] that overrides gdk-xft-dpi: gdk-unscaled-dpi
(XSetting Gdk/UnscaledDPI).  gdk-xft-dpi was kept around for
compatibility with apps like Chromium that still need it.

When modifying these settings, an invariant should be maintained:
gdk-xft-dpi = gtk-window-scaling-factor * gdk-unscaled-dpi.  Chromium
should have been able to keep using gdk-xft-dpi, but this invariant is
violated when changing the settings using gnome-tweak-tool, where I
have gdk-window-scaling-factor = 2, gdk-unscaled-dpi = 98304, and
gdk-xft-dpi = 98304 (gdk-xft-dpi should be 196608).

[2] changed Gtk builds to use the window scaling factor, which is
incorrect because it did not consider font scaling, making fractional
scaling impossible.

This CL takes gdk-unscaled-dpi into the calculation as well, and
continues to fallback on using gdk-xft-dpi if the other variables are
unavailable, which can happen on Gtk2.

[1]
https://git.gnome.org/browse/gtk+/commit/?id=4b9c08f48d6f5be43b0795d3eee462d6...
[2] https://codereview.chromium.org/2869763004

BUG=723931
R=erg@chromium.org,chris.coulson@canonical.com
CC=oshima@chromium.org

Review-Url: https://codereview.chromium.org/2899943002
Cr-Commit-Position: refs/heads/master@{#473966}
Committed:
https://chromium.googlesource.com/chromium/src/+/40910b90874699376e21625f26e5...
==========

[commit-bot: I haz the power, 2017-05-23 17:46:02]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/40910b90874699376e21625f26e5...