Re: Scintilla GTK 4 port

Sergey Bugaev:

> Between these two, GTK behaves closer to Cocoa, in that
> application/widget level coordinates are in logical pixels/units,
> which are then scaled inside the toolkit to get to physical/device
> pixels. This way, most of the application code never has to care about
> the details of scaling (other than shipping icons with a larger
> resolution etc).

Since Windows allows fractional scaling, I'd say that GTK4 is more
similar to Windows than Cocoa.

To minimize difficulties now and with applying future changes, it
could help to make this platform layer behave as much as possible like
Windows. Windows is the most popular platform for Scintilla,
accounting for most of the users and developers with Linux and macOS
minorities. Linux is further split into GTK and Qt, wxWidgets, Tk, and
other toolkits.

To avoid seams, the scale of the drawing context could be changed to
ensure that Scintilla is again addressing whole pixels. That would
then need to be balanced by changing font creation to invert that
scale so text appears the expected size.

> Yes, so we of course have to keep compatibility with applications
> forcing specific colors and fonts, if they do.
>
> The issue with this (as it's always the case when a specific color is
> provided instead of going through the style sheet mechanism) is that
> it won't (without additional work on each application's side) follow
> system settings like dark mode, accent color, high contrast.

Applications and users really do implement detailed control over
styling with themes and complex style configuration dialogs. This is
one of the main reasons that applications choose Scintilla. There are
often between 20 and 100 individual styles set by a language mode with
many distinct colours.

> GtkSourceView has pairs of light/dark styles for this, and uses the
> accent color for selection.

Using the accent colour for selection is currently possible on Cocoa.
It is a bit more complex there as Cocoa allows the user to set
different accent and selection colours.

Selection background colors on Cocoa go through the elements system
which also allows the application to override the colours if desired.
See SC_ELEMENT_SELECTION_BACK and ScintillaCocoa::UpdateBaseElements
which is responsible for reflecting user preferences and changes to
these.

There are 5 selection background colours currently defined by
Scintilla to allow differentiating additional (and secondary)
selections and to choose a different appearance when the window does
not have focus.

> There are libraries in the platform whose API was not designed with
> introspection and language bindings in mind, and this is seen as a
> deficiency.

There is a lot of code in the gtk4 directory to support introspection
and wrapping the API: 130K for enumerations in ScintillaEnums.[ch] and
around 22K for a partial API wrapper.

For Qt there are separate directories for ScintillaEditBase and
ScintillaEdit (which includes an API wrapper) so that it was easier to
understand and modify the base functionality.

> I just tried building this on Ubuntu 25.10, using their provided
> toolchain, and the packages you listed, and I only get some
> "-Wincompatible-pointer-types" warnings (when building the demo, not

The actual failure was not finding the scintilla library and that was
due to building inside the ScintillaDemo directory instead of gtk4. It
is working now.

> fill out more metadata for the project (see gi-docgen doc page [3])
> such as authors and license.

There should also be a mention of the license in the source code
files. All source code distributed with Scintilla uses
https://www.scintilla.org/License.txt . It is OK to add additional
license possibilities (as Sun did for files in the cocoa directory)
but everything (distributed from scintilla.org) must also allow use
with the main license.

Neil

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