Comments (17)
rodrigocfd
commented on May 24, 2024
1
Yeah, I just did this. This kind of undocumented behavior is really hard to work with.
Thank you very much for your help.
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rodrigocfd
commented on May 24, 2024
1
@michidk I changed this function to return an iterator, so the loop work is done internally. If you're still interested, I'd be glad to hear if it works for you.
New docs with example can be found here.
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rodrigocfd
commented on May 24, 2024
As far as I could investigate, the enumeration ends when EnumDisplayDevices returns zero and GetLastError returns ERROR_PROC_NOT_FOUND, therefore the foolproof implementation has to consider this. The check is necessary to rule out legitimate errors.
I changed the implementation to reflect this. Please let me know if this worked for you.
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michidk
commented on May 24, 2024
Wow that was quick :D. I am not too familiar with winapi error handling stuff, but if I adjusted my code like mentioned in the example:
/// Returns a list of all displays.
pub fn discover_displays() -> Result<DisplaySet> {
let mut result = Vec::<Display>::new();
let mut dev_num: u32 = 0;
let mut display_device = DISPLAY_DEVICE::default();
loop {
let has_more = EnumDisplayDevices(
None,
dev_num,
&mut display_device,
EDD::GET_DEVICE_INTERFACE_NAME,
)?;
if has_more {
result.push(Display::from_winsafe(dev_num, &display_device)?);
dev_num += 1;
} else {
break;
}
}
Ok(DisplaySet { displays: result })
}Then the fn returns early with the following Err: "[0x00cb 203] The system could not find the environment option that was entered.".
The following works fine:
let has_more = EnumDisplayDevices(
...
); // no `?`
if has_more.is_ok() { // `is_ok()` instead
result.push(Display::from_winsafe(dev_num, &display_device)?);
dev_num += 1;
} else {
break;
}This might have to do with the fact that I have one display that is active: false?
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rodrigocfd
commented on May 24, 2024
Indeed, it seems that a display with active: false returns an error for that specific index, and since this is meaningful to you, you'll have to treat that error specifically, and turn the active into some sort of flag. Maybe something like this:
{
use winsafe as w;
let mut dev_num: u32 = 0;
let mut display_device = w::DISPLAY_DEVICE::default();
loop {
let (is_good, is_active) = match w::EnumDisplayDevices(
None,
dev_num,
&mut display_device,
w::co::EDD::GET_DEVICE_INTERFACE_NAME,
) {
Ok(r) => (r, true), // active
Err(e) => match e {
w::co::ERROR::ENVVAR_NOT_FOUND => (true, false), // inactive
_ => panic!("Actual error!"),
}
};
if is_good {
// result.push(Display::from_winsafe(dev_num, &display_device)?);
println!("{}, active: {}", display_device.DeviceName(), is_active);
dev_num += 1;
} else {
break;
}
}
}from winsafe.
michidk
commented on May 24, 2024
When I run your code, I get an infinite loop, because is_good is always true.
But it should stop after there is no display anymore right? I have three active displays and one inactive. This means it should iterate five times, and since the fifth display does not exist an error ("The system could not find the environment option that was entered.") will be thrown and the code should break. This is not the case with the code you just posted.
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michidk
commented on May 24, 2024
I only have three displays attached to the four DisplayPort ports on my GPU (maybe the fourth one is also some kind of virtual display output device).
This is how the API calls look in APIMonitor:
While all other displays have the active flag there, my fourth "display" shows this flag:
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rodrigocfd
commented on May 24, 2024
This is very unsettling... please run the code below and post back the results:
{
use winsafe as w;
for n in 0..8 {
let mut dide = w::DISPLAY_DEVICE::default();
let ret = w::EnumDisplayDevices(
None, n, &mut dide, w::co::EDD::GET_DEVICE_INTERFACE_NAME);
match ret {
Ok(b) => println!("{} Ok {}", n, b),
Err(e) => println!("{} Err {}", n, e),
}
}
}from winsafe.
michidk
commented on May 24, 2024
Results in an infinite loop with the following output
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
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rodrigocfd
commented on May 24, 2024
It's just a for iterating from 0 to 7... it can't be an infinite loop.
Are you running this code inside something else?
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michidk
commented on May 24, 2024
Agh sorry. Wanted to get back to you ASAP and got sloppy: I had another loop {} around this from code before. This code actually doesn't loop. Output is just:
0 Ok true
1 Ok true
2 Ok true
3 Ok true
4 Err [0x00cb 203] The system could not find the environment option that was entered.
5 Err [0x00cb 203] The system could not find the environment option that was entered.
6 Err [0x00cb 203] The system could not find the environment option that was entered.
7 Err [0x00cb 203] The system could not find the environment option that was entered.
The code snippet you posted earlier (before the last one) still leads to endless looping.
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rodrigocfd
commented on May 24, 2024
What about this example in the docs? Does it still loop?
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michidk
commented on May 24, 2024
No, it does not loop on the latest commit. However, an error is thrown:
0: \\.\DISPLAY1 - NVIDIA GeForce GTX 1080
1: \\.\DISPLAY2 - NVIDIA GeForce GTX 1080
2: \\.\DISPLAY3 - NVIDIA GeForce GTX 1080
3: \\.\DISPLAY4 - NVIDIA GeForce GTX 1080
Error:
0: [0x00cb 203] The system could not find the environment option that was entered.
0:
Location:
src\display.rs:462
The error occurs on the following line:
let is_good = EnumDisplayDevices(None, dev_num, &mut dide, co::EDD::NoValue)?;
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rodrigocfd
commented on May 24, 2024
This means that when the loop ends, GetLastError returns code 203, which should be the stop condition.
However... on my computer, it returns code 127 instead. That's odd.
I'm on Windows 10 x64, what's yours?
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michidk
commented on May 24, 2024
Win 10 Pro x64
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rodrigocfd
commented on May 24, 2024
OK, so I completely removed the internal error checking, and the zero is always considered the "done" state now.
Let me know if this works for you.
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michidk
commented on May 24, 2024
Output now is:
0: \\.\DISPLAY1 - NVIDIA GeForce GTX 1080
1: \\.\DISPLAY2 - NVIDIA GeForce GTX 1080
2: \\.\DISPLAY3 - NVIDIA GeForce GTX 1080
3: \\.\DISPLAY4 - NVIDIA GeForce GTX 1080
So it works!
We could also handle just 127 as well as 203 as codes for Ok(false).
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