I have been noticing over the last couple of releases that sometimes,
when I open up a file, and it comes up with the Serial monitor window
open, and then I click to close that Serial monitor it leaves the
Serial monitor in a strange state. Where the Monitor window looks closed, but leaves the are still in a region of the main window that you can resize...
Note: I have mine configured for monitor on right side...
In this state clicking on the serial monitor icon on the far right does not
appear to do anything.
But if I move the mouse to the area below it that used to have the show/hide
monitor button, it shows the select like mouse cursor and if I click it,
I get back to the state:
Just as another confirmation I started to run into this issue today running 2.3.7 nightly from 4/10/2025. In addition I am experiencing the original window goes all black as I mentioned in another thread. With me I usually have use task manager to kill the ide and restart it.
For me, the fault only occurs if I close Serial Monitor while the window is still loading. If the situation is the same for you, then it should be fairly easy to avoid until such time as the bug is fixed.
Note that if you only want to collapse the right hand panel (as opposed to terminating the Serial Monitor process), then you can do that by clicking the magnifying glass in the activity bar on the right side of the Arduino IDE window. Note that this icon has a different behavior from the magnifying glass icon on the right side of the toolbar. The icon on the toolbar does the following things:
Terminate Serial Monitor
Collapse the right hand panel
The icon on the activity bar does the following things:
Collapse the right hand panel
From my tests, the bug is specific to the toolbar icon. The fault does not occur if I use the activity bar icon to collapse the panel, even if I do that while the window is loading.
@ptillisch - I am not sure that is the only way that this problem manifests itself.
Maybe it is indirectly.
A reasonable percentage of the times I have seen this, is I start up Arduino, it brings up the
last sketch it thinks I was using. I want a different one, so I open up one, that is usually
in the recent list. It comes up with the Serial Monitor Window open. I try to do an
upload and it fails. I figure maybe it is because the Serial monitor is open
and it fails... (I have found that there are times if the Serial Monitor is open in multiple
sketch windows, it often fails to get the comm port... And I have run into this...
But maybe, the other window was hung waiting for startup to complete (usually with the
downloading teensy package... or maybe if I told the other window to update multiple boards and or libraries or ???.
Sorry I know this is not completely clear. But my guess is that they are all related to the
case you found, just different triggers.
I agree with @KurtE - it seems to happening at different points. I will try to be more observant when it happens. I have gotten into the habit of closing the serial port.
But to be honest it is annoying enough and happens enough that I am thinking about downgrading to 2.3.4
In general, the most important thing is to have a procedure by which the developers and beta testers can reliably reproduce the fault. So even if maybe there are other conditions under which it occurs, it is likely that they are all caused by the same bug, and will all be resolved by the same bug fix. So when I managed to find a procedure by which the fault could be reliably reproduced, I considered that sufficient to make the report actionable.
However, if you do find a different procedure by which the fault can be reproduced, please do let us know. There is always the possibility that different bugs can have the same symptoms, and that the fix for one bug will not also fix another bug that produces the same symptoms under different conditions. So it would be good to test using each of the known reproduction procedures before considering the fault to be comprehensively resolved.
