Fix ghostty-org#4323: Ensure Kitty images scroll with text

[henriquevmac]

Previously, Kitty images did not scroll as shown in #4323 when the terminal was scrolled using ANSI commands (\033[xT for scrolling x down and \033[xS for scrolling x up).

This fix updates the insertLines and deleteLines methods in src/terminal/Terminal.zig to iterate over all kitty_images placements, updating their positions or deleting them if their top-left corner (the Pin position) scrolls off-screen.

Added four unit tests (two per method):

• One verifies that image positions update correctly when scrolled up or down.

• The other ensures images are deleted when they scroll out of view.

I ran some tests as shown in this video

The three scripts run where this:

• test_script:

#!/bin/sh

IMG="$(realpath $1)"

printf '\033[100S' # Scroll up by 100
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

printf '========= Image ============\n'
printf '\033_Gi=1,t=f,q=1,f=100,a=T,r=10,c=20;%s\033\\' "$(printf '%s' "$IMG" | base64 -w0)"
printf '<- image\n'
printf '1\n'
printf '2\n'
printf '3\n'

sleep 1

printf '\033[4T' # Scroll down by 4
sleep 1
printf '\033[4S' # Scroll up by 4
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

sleep 5

• test_script_out_bottom:

#!/bin/sh

IMG="$(realpath $1)"

printf '\033[100S' # Scroll up by 100
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

printf '========= Image ============\n'
printf '\033_Gi=1,t=f,q=1,f=100,a=T,r=10,c=20;%s\033\\' "$(printf '%s' "$IMG" | base64 -w0)"
printf '<- image\n'
printf '1\n'
printf '2\n'
printf '3\n'

sleep 1

printf '\033[100T' # Scroll down by 100
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

sleep 5

• test_script_out_top:

#!/bin/sh

IMG="$(realpath $1)"

printf '\033[100S' # Scroll up by 100
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

printf '========= Image ============\n'
printf '\033_Gi=1,t=f,q=1,f=100,a=T,r=10,c=20;%s\033\\' "$(printf '%s' "$IMG" | base64 -w0)"
printf '<- image\n'
printf '1\n'
printf '2\n'
printf '3\n'

sleep 1

printf '\033[4S' # Scroll up by 4
printf '\033[1d' # Move cursor to row 0
printf '\033[1G' # Move cursor to column 0

sleep 5

[qwerasd205]

Just taking a brief look at this, it seems like you're not accounting for left/right scrolling margins. I'll give this a more thorough review later today.

[qwerasd205]

I feel like this should probably account for all tracked pins, not just the ones used for image placements, since we also use tracked pins for, for example, selection endpoints - anything that needs to follow content uses a tracked pin.

Additionally, your pin adjustment logic doesn't account for the left/right scroll margin, as I noted before -- it should, and tests should be added for that as well.

(Side note: You'll find that all the existing tracked pin adjustment logic lives in PageList, and operations in Screen rely on the PageList operations behaving appropriately - so doing this all the way in Terminal is unfortunate, but it needs a refactor to avoid; as my note above insertLines explains, this operation really should belong to Screen not Terminal, but it's fine for now to do it here until that gets refactored.)

[henriquevmac]

So for the first point I should just have the loop iterate over all tracked pins instead of the pins related to images right?

And for the the left/right scroll margin I should implement something like page.moveCells is doing right now?

[qwerasd205]

Hi, sorry for the delay in getting back to you. Yes, iterate over all tracked pins (for examples search for pin_keys in PageList.zig), and account for the left/right scroll margins in the same way as is done when deciding how to move the cell contents in the insertLines/deleteLines functions.