applications – I want to see line between two points (Only when touched with two fingers)

Just like pointer location feature, in developer option of android 10. It shows vertical and horizontal lines, I am willing to have direct line between two points, only when touched with two fingers, any where in any app.

Is it possible? Do we have any app?
I am ok even if i need to root my device.

Thanks in advance.

mail.app – How to prevent MacOS Mail autocomplete from inserting new line when accepting its suggestion?

When I compose an email in the stock Mail app, it shows potential words via autocomplete.

e.g. typing larg results in ‘large‘ popping up as a suggestion.

However, when I hit ENTER to select the word, it adds a carriage return/new line.

How can I turn this ‘additional newline’ behaviour off?

ag.algebraic geometry – Cubic surface in $mathbb{P}^3$ singular along a line

Maybe it is a stupid question but I’m not able to find the answer anywhere else.
My goal is to prove in an “algebraic geometry fashion” that $sqrt{n}$ is not a rational number for $n$ not a perfect square.

Thus suppose instead that $sqrt{n}=frac{p}{q}$ where $p,q in mathbb{Z}$. After some simple calculation we have $q^2n=p^2$. I can complete this equation in $mathbb{P}^3$ with homogeneous coordinates $(p,q,n,z)$ yielding $q^2n=p^2z$.

Now it is easy to check that the projective cubic surface $X=(q^2n-p^2z=0)$ is singular along the line $p=q=0$.
If this surface would be rational then it is possible to find a parametrization $varphi:mathbb{C}^2 rightarrow U$ where $U subset X$ is open such that $$varphi(x,y)=(varphi_1(x,y),varphi_2(x,y),varphi_3(x,y),1)$$ where each $varphi_i(x,y)$ is a rational function (I can eventually shrink $U$ such that does not contain the hyperplane at infinity).
If this holds then I can choose $x=frac{p}{q}$ and $y=frac{r}{s}$ and find infinite solutions to the problem.
This in some sense makes me thinking that $X$ is not rational, but I’m not able to prove it.

What is wrong with this idea? I’m not able to figure it out.

Thanks in advance.

Select to beginning/end of line in macVIM with cua-mode enabled

I am using the cua-mode from https://github.com/fabi1cazenave/cua-mode.vim/blob/master/plugin/cua-mode.vim . It works well for multi-line selections but does not have shift-command-[left|right]-arrow select on same line either to beginning or to end of line. Is there any additional set of vim commands that could be added to provide that feature?

command line – Unable to execute a “nonexistent” file

Screenshot...

If you can’t see the screenshot, I’m connected to my raspberry pi running Ubuntu Server. I followed the instructions and put the cloudflared file in /usr/local/bin. As I try to execute it from my home directory, it says the executable in /usr/local/bin does not exist!

However, it clearly knows the file exists because it sees the file in that directory. Otherwise, it would just say “command not found.” Yes, I have the correct architecture and yes, I added the executable permission. I can’t run it as ubuntu or root.

Need I say more?

Line Pay Simulation: How to fix the “Insufficient balance” error in the simulation

I have encountered a technical problem in simulation environment thanks to your help
I have called api from https://sandbox-api-pay.line.me/v2/payments/request this is Line Pay simulation environment, but I got an Insufficient balance error.
I am wondering why Insufficient balance error occurs in simulation environment
https://i.stack.imgur.com/YFxrf.png
Is there a way to fix the Insufficient Balance error in a simulation environment.
Sorry my english is not good.

command line – terminal can not open from desktop or power menu?

use to install python3.9 following the instructions of the next link (http://ubuntuhandbook.org/index.php/2020/10/python-3-9-0-released-install-ppa-ubuntu/)
unfortunately, I tried a non recommended field of code
(4.) (NOT Recommended) To use Python 3.9 as the default python3, run commands:
sudo update-alternatives –install /usr/bin/python3 python3 /usr/bin/python3.8 1
sudo update-alternatives –install /usr/bin/python3 python3 /usr/bin/python3.9 2
now i can’t run the terminal for either power menu or desktop, but its works from file.