How can I change font zoom progression in mintty

Question

ctrl+/- change font size on mintty terminal.

However, the steps in some place are quite large. Can I change the progression so I can fit to my window better?

Answer 1

Short answer: there’s no way to configure this behaviour without modifying the source.

Under the hood

Since mintty is free software (GPL), I checked out its source code from the mintty GitHub repository. It’s written in C and the code turns out to be fairly readable (I’m a sysadmin, not a programmer) and I’ve copied some of the relevant code here.

You can see from the following code in wininput.c that the zooming happens in discrete steps of 1 (increase the font size) or -1 (decrease) that are added to the current font size and that no configuration settings are used to control the size of the steps.

// Font zooming
if (cfg.zoom_shortcuts && mods == MDK_CTRL) {
  int zoom;
  switch (key) {
    when VK_OEM_PLUS or VK_ADD:       zoom = 1;
    when VK_OEM_MINUS or VK_SUBTRACT: zoom = -1;
    when '0' or VK_NUMPAD0:           zoom = 0;
    otherwise: goto not_zoom;
  }
  win_zoom_font(zoom);
  return 1;
  not_zoom:;
}

The relevant functions are defined in wintext.c:

void
win_set_font_size(int size)
{
  size = size ? sgn(font_size) * min(size, 72) : cfg.font.size;
  if (size != font_size) {
    win_init_fonts(size);
    win_adapt_term_size();
  }
}

void
win_zoom_font(int zoom)
{
  win_set_font_size(zoom ? max(1, abs(font_size) + zoom) : 0);
}

The win_adapt_term_size function ensures that the window size adapts to display the rows and lines in units of the new font size.

Note that sgn is a macro which returns the sign of a number (represented as an integer). From std.h:

#define sgn(x) ({ typeof(x) x_ = (x); (x_ > 0) - (x_ < 0); })

From config.c, we can see that the initial font size is taken from the FontHeight configured in ~/.minttyrc.

{"FontHeight", OPT_INT, offcfg(font.size)},

Font size appearance

How the differences in font size are displayed depends on the both the selected font and the font rendering software.

I’ve attached a screenshot showing how Lucida Console and Consolas are displayed at different font sizes in Windows 7 using DirectWrite, the newer font rendering API released with Windows 7 to replace the older GDI rendering engine.

As you can see, the variation in the rendered size of the font is not exactly linearly in proportion to the specified font size. I remember spending time choosing a font that displayed well at different sizes and Consolas (with ClearType enabled) gave me the best results.