Instead of fiddling around with scale in the iconhelper (and getting it
wrong), create a GtkScaler around the paintable that takes care of the
scaling.
That's kinda weird but allows us to delete the texture case from
GtkIconHelper and GTK_IMAGE_TEXTURE from the GtkImageType enum.
And it doesn't cause any other problems because the cell renderer
can't deal with paintables - otherwise it would mirror GtkImage and have
a "paintable" property instead.
If set, the image will draw its contents while keeping their aspect
ratio. That means empty areas show up on the top/bottom or left/right.
Also move the special-case snapshotting code for icons to
GtkIconHelper. That's where it belongs.
This only implements the vfuncs, but does not actually emit signals
yet.
It's also not useed for anything other than snapshot() so far, this
will come in later commits.
Instead of loading them into surfaces (which we want to get rid of), we
load into textures.
In fact, we introduce a new paintable subclass called a GtkScaler that
takes care of tracking scaling.
This also ideally gets rid of an extra conversion once renderers learn
to render textures directly.
This is in preparation for accepting the image type paintable.
It's a bit incovenient because we need more code to track width/height
ourselves (as the paintable no longer does it for us), but it's not too
hard.
GtkIconHelper does not track invalidations on the paintable.
Instead of looking at the icon size, look at the CSS value for
-gtk-icon-size. Set style classes depending on icon size instead.
Trivially change Adwaita and HighContrast to report the same values as
before.
Instead, add a function gtk_image_set_icon_size() for the cases where
overriding the icon size is necessary.
Treat icon sizes the same way as pixel sizes, too. So gtk_image_clear()
no longer unsets the icon size.
These are no longer used, instead we always covert to surface as
early as possible and drop the pixbuf.
This means we never store both the pixbuf and the surface at
for any longer time, which is wasteful. Also, its one step further
to drop GdkPixbufs from generic use in our APIs.
This patch makes that work using 1 of 2 options:
1. Add all missing enums to the switch statement
or
2. Cast the switch argument to a uint to avoid having to do that (mostly
for GdkEventType).
I even found a bug while doing that: clearing a GtkImage with a surface
did not notify thae surface property.
The reason for enabling this flag even though it is tedious at times is
that it is very useful when adding values to an enum, because it makes
GTK immediately warn about all the switch statements where this enum is
relevant.
And I expect changes to enums to be frequent during the GTK4 development
cycle.
It's not a GtkCssGadget anymore, it doesn't have any properties or
signals either and it's not public. Further, its lifetime is very clear
the way it's being used inside GTK+.
