ta/monitor ordering

[ThomasAdam]

• WIP
• WIP: Monitor ordering

[somiaj]

The order only seems to be set at the initialization stage, if I run xrandr --output DP-2 --left-of DP-4 to change my monitor order, the variables are not updated, and now 1 is my left monitor and 0 is my right monitor. But if I then restart fvwm3, the order is updated.

Now that I see what you are doing with this, I think my lexographic order approach would be worthwhile. If the monitors are all in the same line, you'll get the same result here, but there will also be a predictable order for other setups as well. (well I'm assuming in a line means the top coordinate is all the same, with different sized monitors lined up along the bottom, which I think is a very odd setup, it would be different).

[ThomasAdam]

Hey @somiaj

Yeah -- there's definitely some rough edges which I've yet to deal with, such as recreating the ordering should the layout change while FVWM is running.

I completely agree about your lexicographical approach -- I'm just not too sure how best to implement it.

[somiaj]

@ThomasAdam point me to which part of the code assigns the order, I might be able to come up with something, should be just a simple sort, and since the number of monitors will always be small, a standard sort algorithm should do the trick.

[somiaj]

@ThomasAdam It seems like qsort in <stdlib.h> will do the job. Here is some pseudo code that I hope is enough for you to understand and maybe implement.

First you need a compare function, such as:

int mon_compare(const void *m1, const void *m2)
{
	const struct monitor *mon1 = m1;
	const struct monitor *mon2 = m2;

	if (mon1->si->y == mon2->si->y) {
		return mon2->si->x - mon1->si->x;
	} else {
		return mon2->si->y - mon1->si->y;
	}
}

Then just put all of the monitors into an array, mon_array, and call qsort:

qsort(mon_array, number_of_monitors, sizeof(monitor), mon_compare);

The array will be sorted, then just number the monitors based on their position in the array:

for (int i = 0; i < number_of_monitors; i++) {
	mon_array[i]->si->number = i;
}

My c knowledge is still very basic, and just following examples, so I'm sure this will need to be adjusted.

[somiaj]

My quick tests (with only two monitors) seem to show it works. I even tested my optimization suggestion and I get the exact same result. It still doesn't update the ordering on monitor changes, I have to restart fvwm to get the ordering to update.

[ThomasAdam]

It still doesn't update the ordering on monitor changes, I have to restart fvwm to get the ordering to update.

Really? I'm moving the ordering of screens around using xrandr, and they update just fine, without restarting fvwm.

What am I missing?

[somiaj]

Seems to work now!!