Comment by badsectoracula | Hacker News Reader

Comment by badsectoracula | Hacker News Reader

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> The "Wayland Way" is for the compoisitor to relay information (monitor-reported scale, etc) to the client, and have the client figure out how to scale itself correctly.

FWIW this is also the "Xorg Way" (RandR provides all the necessary information), it is just that clients do not bother.

Ideally the window manager would use the information provided by RandR to set up default scale levels for each monitor and then send notifications to the applications whenever the window changes monitor to alter their scale levels (this would also allow for custom per-window scale level that is applied on top of the per-monitor scale level in case someone wants to scale up/down a specific window - e.g. scaling up some notepad-like editor for a screencast).

This does require each client (and toolkit) to support arbitrary scaling... and window managers to agree on such a message, though i do remember an email about this topic being posted on Xorg mailing list some time ago. AFAIK Qt should already provide the necessary functionality for this.

> FWIW this is also the "Xorg Way" (RandR provides all the necessary information), it is just that clients do not bother.

One of the differences is, that Wayland surfaces do have scale property. So compositor knows, when clients do not bother, and can do scaling for them. Under X11, some clients do bother, some don't, and the compositor doesn't know which are which.

Right now there isn't any protocol for doing what i described, however this information could easily be added. EWM (or something like it) needs to be extended for scaling support. Applications could do the scaling themselves as they detect their toplevel windows be moved around, but i'm not aware of any application doing that and it'd be fighting the window manager so it isn't a good idea anyway.

But the X server already provides all the necessary information and mechanism for implementing this, it is the clients that need to use it: the window managers need to implement some way to inform toplevel windows that they need to change scale (e.g. via a custom message), applications need to inform the window manager and the compositor that they support such scaling messages (e.g. via a window attribute) and compositors need to be able to scale windows that do not support this scaling (this will probably need a special window manager <-> compositor protocol for compositors that are independent from the window manager while still allowing the window manager to handle scaling without having to also be a compositor).

> But the X server already provides all the necessary information and mechanism for implementing this,

X server provides that at the display level, not at the screen level. If you do that at display level, you cannot move windows between displays, the application has to destroy and recreate them (out of all applications, only emacs can do that). If you want to use then per screen, how it is done today, then screens must have identical density.

> the window managers need to implement some way to inform toplevel windows that they need to change scale (e.g. via a custom message), applications need to inform the window manager and the compositor that they support such scaling messages (e.g. via a window attribute) and compositors need to be able to scale windows that do not support this scaling (this will probably need a special window manager <-> compositor protocol for compositors that are independent from the window manager while still allowing the window manager to handle scaling without having to also be a compositor).

Defining the protocol would be the easier part; persuading application authors to support it would be the hard part. They would ignore it for years to come. And that's for applications that are maintained or can be updated.

So when you have to make changes, you might as well as change the protocol and adjust for achieving multiple additional objectives - which is exactly what Wayland did.

What you are describing is not enough, the X server or the X compositor would still need to scale windows up/down if they don't support scaling or if you want to have fractional scaling. It's not something a old-style window manager can do -- There is just no real "Xorg way" on how to do this right now.

This is only needed if a program doesn't support scaling itself and is something that a compositor can support. In addition there is a branch by Keith Packard for having server-side window scaling that could also be used for this and work independent of any window manager (though a compositor can also be made to work with any window manager - for example there are people using a compositor with Window Maker even though WM doesn't support composition).

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