[gimp/gimp-2-10] Issue 6210: Subpixel font rendering system settings should only apply…

[Jehan <jehanp src gnome org>]

commit 9b871067207166bea1648fa1907402c1dd043bc4
Author: Jehan <jehan girinstud io>
Date:   Tue Apr 20 18:26:15 2021 +0200

    Issue 6210: Subpixel font rendering system settings should only apply…
    
    … to GIMP not text layer rendering in image
    
    Patch was merged n Cairo today, wouhou!
    https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/114
    If not mistaken, the fix should then appear in Cairo 1.17.6 or 1.18.0
    (whatever comes next). As we are obviously not going to bump the Cairo
    dependency so early, let's just add the patch, at the very least to be
    used for our official builds. Also this way, we won't forget about this
    issue in the future when we need to bump Cairo.
    
    (cherry picked from commit 5f61d845704452adba3eb6e332db1c7a0977dd33)

 build/patches/cairo-mr114-gimp-issue-6210.patch | 44 +++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
---
diff --git a/build/patches/cairo-mr114-gimp-issue-6210.patch b/build/patches/cairo-mr114-gimp-issue-6210.patch
new file mode 100644
index 0000000000..8ea8e36ed4
--- /dev/null
+++ b/build/patches/cairo-mr114-gimp-issue-6210.patch
@@ -0,0 +1,44 @@
+From 4f4d89506f58a64b4829b1bb239bab9e46d63727 Mon Sep 17 00:00:00 2001
+From: Jehan <jehan girinstud io>
+Date: Tue, 19 Jan 2021 12:42:31 +0100
+Subject: [PATCH] src: do not override explicitly requested grayscale
+ antialiasing.
+
+If CAIRO_ANTIALIAS_DEFAULT is selected and system is set to subpixel, it
+is perfectly normal to switch to CAIRO_ANTIALIAS_SUBPIXEL.
+But when the calling application specifically requested
+CAIRO_ANTIALIAS_GRAY then Cairo should honor the request.
+
+This is an issue we have had for years in GIMP, where text on images
+would render differently depending on the system the file is opened on.
+This is obviously not right as a graphics work should be system
+independant and allow the creator to decide if one wants a text to have
+grayscale or subpixel rendering (a settings which would stick when
+sharing the work file). Cairo should not override this.
+The CAIRO_ANTIALIAS_DEFAULT settings exists exactly for this (when we
+want Cairo to choose for us, in a system-dependant way); other settings
+are when we need system independance.
+
+Thanks to Adam Fontenot for initial investigations and tests on this and
+other contributors before this.
+---
+ src/cairo-ft-font.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/src/cairo-ft-font.c b/src/cairo-ft-font.c
+index d2221edec..1f5befec3 100644
+--- a/src/cairo-ft-font.c
++++ b/src/cairo-ft-font.c
+@@ -1945,8 +1945,7 @@ _cairo_ft_options_merge (cairo_ft_options_t *options,
+     }
+ 
+     if (other->base.antialias == CAIRO_ANTIALIAS_SUBPIXEL &&
+-      (options->base.antialias == CAIRO_ANTIALIAS_DEFAULT ||
+-       options->base.antialias == CAIRO_ANTIALIAS_GRAY)) {
++      options->base.antialias == CAIRO_ANTIALIAS_DEFAULT) {
+       options->base.antialias = CAIRO_ANTIALIAS_SUBPIXEL;
+       options->base.subpixel_order = other->base.subpixel_order;
+     }
+-- 
+GitLab
+