[platform-swt-dev] Bumping minimum version of GTK3 to 3.14 in 4.11

[Eric Williams <ericwill@xxxxxxxxxx>]

Hello,

For the 4.11 release, I believe SWT will strongly benefit from moving to 
a minimum version of GTK3.14. Here are some specific details:

-CSS for backgrounds and foregrounds is 3.14+, no more GtkStyleContext 
background/foreground machinery

-no need to support pre-3.10 drawing model changes

-gtk-gradient CSS is gone in GTK4, we only use it for Combo on GTK3.12 
and below

-removal of non-Cairo setRegion() drawing as this is 3.8 and below

-removal of pre-GTK3.10 DnD logic

-removal of miscellaneous functions such as: GtkWidget opacity, 
GtkScrolledWindow add_with_viewport, etc.

-removal of several pre-GTK3.14 Table/Tree drawing hacks

-greatly allows for simplification of Cairo drawing in GC, as many of 
these operations are guarded with GTK3.14+ calls

-allows SWT to rely solely on GTK CSS theme parsing, no more 
GtkStyleContext lookups to get system colours


In summary, these changes would really simplify the codebase as almost 
all the items mentioned above are gone in GTK4. With the introduction of 
GTK4 guards it would be really beneficial if we could start to eliminate 
the GTK3 specific version guards. Furthermore, it is very hard to find a 
modern (supported) Linux distribution that ships with anything less than 
GTK3.14 anymore, and the disconnect between the 3.14- and 3.24 
methodologies is quite large.

If anyone has any concerns, please raise them.

Thanks,

--
Eric Williams
Software Engineer - Eclipse/SWT Team
Red Hat