Font size super tiny and unchangeable when connecting a display with the setting "optimize for <external display>" on macOS

[terlar]

When connecting a new display to a computer running macOS 10.13.6 and selecting in the display menu that the screen should be optimized for the external display and not the built-in one.

E.g.

The font renders super tiny and is unchangeable. The keybindings for decreasing/increasing/resetting size does nothing as well as manually running something like:

kitty @ set-font-size 20.0

Assuming this could be some GL releated rendering issue I started kitty with debug-gl flag, but that doesn't output any extra information. However I see errors mentioning Cocoa: Failed to find a screen for monitor which potentially could be related. I don't see that when I select the other option and optimize for the Built-in Retina Display.

$ kitty --debug-gl                                                                                                                                                                                                                                                                                                                       (14.53s) 
[282 17:21:50.250056] Failed to set locale with LANG: en_SE.UTF-8
GL version string: '4.1 INTEL-10.36.19' Detected version: 4.1
[282 17:22:13.334988] [glfw error 65544]: Cocoa: Failed to find a screen for monitor
[282 17:22:18.640242] [glfw error 65544]: Cocoa: Failed to find a screen for monitor

Anything else that could be done to debug this further to get to the bottom of this? Restarting kitty makes the terminal be in a workable state again, until you disconnect and reconnect the external display again, then the same behavior is experienced.

[kovidgoyal]

Do the font size bindings you are using work normally? And before using kitty @ did you enable remote control?

[terlar]

Yes, the bindings normally work, and as soon as I disconnect the screen or change to optimize for built-in screen they start working again. And yes, I enabled the remote control. Sorry for missing out on this information in my first description.

[kovidgoyal]

try using an outrageously large number for the font size, like 200 or 2000 (I suspect what is happening is the DPI used when the external monitor is connected is some invalid value)

[terlar]

Good theory, I haven't thought about that. However seems that is not the case. I tried with 0.0, 1.0, 200, 2000 and 20000. None of them affect the font-size in any way. However as soon as I disconnect the display or change to optimize for the Built-in Retina Display I get that font-change that I set.

[kovidgoyal]

well in that case you will need to debug, font size calculations are basically a function of the specified size in pts and the DPI. look in update_os_window_viewport() in glfw.c and check what DPI value is being set.

Then the cell size calculation is in calc_cell_metrics() in fonts.c

[kovidgoyal]

no followup

[terlar]

Sorry, I wasn't sure about how to run a debugger or similar with the c code. I will look into it when I have some free time and get back to you at that time. Thanks for the help and instructions

[kovidgoyal]

you dont need to run a debugger, just insert some printf() statements to print out the values. You can see the output of the printf() statements by running kitty from within another terminal. And you can build kityt from source by following the instructions on the kitty website.

[terlar]

Thank you for the instructions, this was easier than I thought.

I did the following operations:

1. Open kitty
2. Zoom in
3. Zoom out
4. Connect remote screen
5. Zoom in
6. Zoom out
7. Disconnect remote screen

This was the following output:

cell height: 42, cell width: 14, baseline: 30
X DPI: 144.000000, Y DPI: 144.000000
cell height: 48, cell width: 16, baseline: 35
cell height: 42, cell width: 14, baseline: 30
[293 12:11:10.538417] [glfw error 65544]: Cocoa: Failed to find a screen for monitor
X DPI: 144.000000, Y DPI: 144.000000
cell height: 18, cell width: 6, baseline: 12
cell height: 18, cell width: 6, baseline: 12
cell height: 18, cell width: 6, baseline: 12
X DPI: 0.000000, Y DPI: 0.000000
cell height: 42, cell width: 14, baseline: 30

Seems that when the screen is connected the cell height and cell width stays the same. Another curious thing is also that the DPI X/Y says 0 when the screen is disconnected. Not sure if this tells you anything, I will continue explore a bit. If you have some pointers to more information that could be useful I could also present that.

[kovidgoyal]

can you post the diff to show me exactly what you are printing.

[terlar]

diff --git a/kitty/fonts.c b/kitty/fonts.c
index 80323759..f9065132 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -407,6 +407,7 @@ calc_cell_metrics(FontGroup *fg) {
         underline_position += MIN(cell_height - 1, (unsigned)line_height_adjustment / 2);
     }
     sprite_tracker_set_layout(&fg->sprite_tracker, cell_width, cell_height);
+    printf("cell height: %d, cell width: %d, baseline: %d\n", cell_height, cell_width, baseline);
     fg->cell_width = cell_width; fg->cell_height = cell_height;
     fg->baseline = baseline; fg->underline_position = underline_position; fg->underline_thickness 
= underline_thickness;
     free(fg->canvas);
diff --git a/kitty/glfw.c b/kitty/glfw.c
index 74063c3e..eaa3b305 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -36,6 +36,7 @@ update_os_window_viewport(OSWindow *window, bool notify_boss) {
     window->viewport_y_ratio = (double)window->viewport_height / (double)h;
     double xdpi = window->logical_dpi_x, ydpi = window->logical_dpi_y;
     set_os_window_dpi(window);
+    printf("X DPI: %f, Y DPI: %f\n", xdpi, ydpi);
     bool dpi_changed = (xr != 0.0 && xr != window->viewport_x_ratio) || (yr != 0.0 && yr != window
->viewport_y_ratio) || (xdpi != window->logical_dpi_x) || (ydpi != window->logical_dpi_y);
 
     window->viewport_size_dirty = true;

[kovidgoyal]

If the cell height calculation is resulting in the same cell height values with different font sizes, then something very strange is going on. Look in font_group_for() in fonts.c to see exactly what pt sz and dpi values are being used to create the font group that is then used in calc_cell_metrics()