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}

BUG=723931
TBR=erg@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2900133002
Cr-Commit-Position: refs/branch-heads/3071@{#674}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/5afa8d4f6e8ed276821ecaa4ec62b501e90d8d37

[Tom Anderson, 2017-05-23 18:12:03]

Landing this now (without merge approval) because I want this to make the last
beta release tomorrow so I can be sure the issue is fixed for all users

[Tom Anderson, 2017-05-23 18:12:06]

The CQ bit was checked by thomasanderson@chromium.org

[commit-bot: I haz the power, 2017-05-23 18:12:49]

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 18:15:38]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1495563126784990, "parent_rev":
"91754cf24203d703142138a81431cc178150014c", "commit_rev":
"5afa8d4f6e8ed276821ecaa4ec62b501e90d8d37"}

[commit-bot: I haz the power, 2017-05-23 18:15:49]

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
>
> Review-Url: https://codereview.chromium.org/2899943002
> Cr-Commit-Position: refs/heads/master@{#473966}

BUG=723931
TBR=erg@chromium.org
NOTRY=true
NOPRESUBMIT=true
==========

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}

BUG=723931
TBR=erg@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2900133002
Cr-Commit-Position: refs/branch-heads/3071@{#674}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/5afa8d4f6e8ed276821ecaa4ec62...
==========

[commit-bot: I haz the power, 2017-05-23 18:15:50]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/5afa8d4f6e8ed276821ecaa4ec62...