Get libAdwaita "patch" / libAdapta "fork" into their full potential

[billyswong]

Continuation of linuxmint/mint22.2-beta#51

Some clarification:

1. libAdwaita / libAdapta applications looking different from GTK3 applications is expected. I am not imagining they would be perfectly the same.
2. A lot of characteristics of Mint-X are not just aesthetic but also accessibility. Those characteristics are what I hope to regain in future libAdwaita "patch" / libAdapta "fork" improvement.

For characteristics in accessibility, I mean:

1. Buttons are 3D and look really like buttons.
2. Text boxes are also 3D and look carved in, no ambiguity between them and buttons.
3. Title bars or Header bars are 3D while other part of the window are flat gray, providing a visual hint that they are where one can drag the mouse and move the windows.
4. The window background color is in a stronger shade of gray, provides a lot better contrast between interactive region and non-interactive region of the GUI interface.
5. Paddings and margins are in general a lot thinner than Adwaita, allowing users with less than perfect eyesight to use larger UI texts without too much tedious scrolling back and forth, or be confused by .

Some Mint-Y users are comfortable with modern "flat" UI but find there too little distinction between active and inactive windows. It is an accessibility issue too. They came up with colored title bar + header bar hacks https://github.com/the-allanc/minty-color-titles Ideally we will need some way to let such hack work for libAdwaita / libAdapta too. (The minty-color-titles thing isn't just for Mint-Y. One may use it for Mint-X too.)

Ideally scrollbars in Mint-X shall retain their 3D look in libAdwaita applications too. But it is a lot less likely for one to fail to recognize a scrollbar just because it looks flat. So this is a far lower priority than other theme issue. Similar for the toggle buttons.

Summary:
Flat UI is difficult to navigate for some users. Let non-flat UI be possible for libAdwaita / libAdapta applications.

[mfreeman72]

I 100% concur with this. I have never liked flat themes, even though they seem to be the biggest fad right now. For me, themes are unusable unless there is at least some dimensionality to them. I don't like Mint-Y or L at all, because there's literally no visual difference between a button and a box.

That said, there is a sort of workaround for libadwaita. If you put export GTK_THEME= (do not put anything after the = sign) in either .profile or .xsessionrc, it will force the stylesheet of whatever system theme you're using onto libadwaita. This isn't perfect, however, as some libadwaita programs will have some odd formatting or color issues.

For example, if you use Nautilus instead of Nemo, its headerbar is a different size above the main part of the window than it is over the sidebar.

Another example is Gnome Crosswords. When using any of the Mint themes with it, the color it uses for the outline of the crossword puzzle will be the same color as the background, effectively making the puzzle invisible.

Another example is that in most programs, button placement will be right against the bottom edge of dialog windows, with no padding, which looks strange.

Now, I don't know if these things can be fixed by adjusting formatting and color values in the Mint themes. If that's possible, then this is completely solvable, and it becomes an easy, viable method for theming libadwaita without any hacks or forks. Or, if you just avoid programs that have these issues, this method can be used immediately.