Can you please publish this work somewhere so somebody else can use it? Or consider writing a blog about it? I think that would be a great way to help out. Also which compositor did you use? If it wasn't Weston then that could be a problem, if you want to have a chance for this to be stable in Wayland then usually you'd start with a working patch to Weston. If you don't want to do that work then maybe you can send your patches to someone who is able to modify them and get them working in Weston or KDE, or anything else really.
Edit: Also I'd like to give some feedback.
"a way to have the compositor notify the application which dpis it should render at (because it’d be multiple)."
Right, so that's one additional message. I assume by multiple you mean the case when you have multiple monitors at different scales.
"a way for applications to tag each buffer it renders with the DPI it’s rendered at, so the compositor can show the right buffer natively on the right screen."
I think this would be one or two additional messages. But I'm actually confused by why you would do this because it seems like it would still cause performance issues, if you're now rendering every program two or more times every frame. I think you may want to save this for an "accuracy mode" or something, and normally have it so only the max DPI applies.
"it even makes sense to provide a clip mask telling which part of the window each DPI should be rendered for"
This won't work in Wayland because the client never clips windows, it just redraws the whole window each time.
"What’s more complicated is handling situations where compositors don’t support this, or only support parts of it. That whole backwards compatibility part is more work than getting the whole feature built and shipped, and it’s entirely unnecessary. "
I don't see how that's complicated or why it's more work, programs would just work as they do now, i.e. you just assume those programs always have a DPI of 96 * buffer_scale.
Also depending on how you design this, you may have to consider how this would interact with OpenGL and Vulkan, and maybe consider the possibility of creating additional extensions there in order to handle this. But that may or may not be necessary, I'm not sure.
> I think this would be one or two additional messages. But I'm actually confused by why you would do this because it seems like it would still cause performance issues, if you're now rendering every program two or more times every frame. I think you may want to save this for an "accuracy mode" or something, and normally have it so only the max DPI applies.
Some compositor/toolkit combinations today render at both 1x and 2x, or similar scales, if multi-monitor setups are used.
Now, to improve that situation, you’d need to render at each of the scales of the monitors the window is on right now instead.
To improve performance of that, sending a clip mask from compositor to toolkit to say "hey, only render the left half at 2x, right half at 1x" makes sense, if the toolkit decides to support it, that’d improve performance at no cost.
> or only support parts of it
What if the compositor sends the info about each monitor’s DPI, but doesn’t support the dpi-tagged buffers, instead only supporting viewport-tagged or integer-scale-tagged buffers?
Edit: Also I'd like to give some feedback.
"a way to have the compositor notify the application which dpis it should render at (because it’d be multiple)."
Right, so that's one additional message. I assume by multiple you mean the case when you have multiple monitors at different scales.
"a way for applications to tag each buffer it renders with the DPI it’s rendered at, so the compositor can show the right buffer natively on the right screen."
I think this would be one or two additional messages. But I'm actually confused by why you would do this because it seems like it would still cause performance issues, if you're now rendering every program two or more times every frame. I think you may want to save this for an "accuracy mode" or something, and normally have it so only the max DPI applies.
"it even makes sense to provide a clip mask telling which part of the window each DPI should be rendered for"
This won't work in Wayland because the client never clips windows, it just redraws the whole window each time.
"What’s more complicated is handling situations where compositors don’t support this, or only support parts of it. That whole backwards compatibility part is more work than getting the whole feature built and shipped, and it’s entirely unnecessary. "
I don't see how that's complicated or why it's more work, programs would just work as they do now, i.e. you just assume those programs always have a DPI of 96 * buffer_scale.
Also depending on how you design this, you may have to consider how this would interact with OpenGL and Vulkan, and maybe consider the possibility of creating additional extensions there in order to handle this. But that may or may not be necessary, I'm not sure.