Add support for the CSI t escape code to query window and cell sizes

graphics-protocol.asciidoc

@@ -56,6 +56,10 @@ print('number of columns: {}, number of rows: {}, screen width: {}, screen heigh
 Note that some terminals return `0` for the width and height values. Such terminals should be modified to return the correct values.
 Examples of terminals that return correct values: `kitty, xterm`
 
+You can also use the *CSI t* escape code to get the screen size. Send `<ESC>[14t` to *stdout* and kitty will reply on *stdin* with
+`<ESC>[4;<height>;<width>t` where *height* and *width* are the window size in pixels. This escape code is supported in many terminals,
+not just kitty.
+
 == The graphics escape code
 
 All graphics escape codes are of the form:

kitty/parser.c

@@ -694,6 +694,22 @@ dispatch_csi(Screen *screen, PyObject DUMP_UNUSED *dump_callback) {
             }
             REPORT_ERROR("Unknown CSI s sequence with start and end modifiers: '%c' '%c' and %u parameters", start_modifier, end_modifier, num_params);
             break;
+        case 't':
+            if (!start_modifier && !end_modifier && num_params == 1) {
+                switch(params[0]) {
+                    case 14:
+                    case 16:
+                    case 18:
+                        CALL_CSI_HANDLER1(screen_report_size, 0);
+                        break;
+                    default:
+                        REPORT_ERROR("Unknown CSI t sequences with parameter: '%u'", params[0]);
+                        break;
+                }
+                break;
+            }
+            REPORT_ERROR("Unknown CSI t sequence with start and end modifiers: '%c' '%c' and %u parameters", start_modifier, end_modifier, num_params);
+            break;
         case 'u':
             if (!start_modifier && !end_modifier && !num_params) {
                 REPORT_COMMAND(screen_restore_cursor);

kitty/screen.c

@@ -1113,6 +1113,34 @@ report_device_attributes(Screen *self, unsigned int mode, char start_modifier) {
     }
 }
 
+void
+screen_report_size(Screen *self, unsigned int which) {
+    char buf[32] = {0};
+    unsigned int code = 0;
+    unsigned int width = 0, height = 0;
+    switch(which) {
+        case 14:
+            code = 4;
+            width = self->cell_size.width * self->columns;
+            height = self->cell_size.height * self->lines;
+            break;
+        case 16:
+            code = 6;
+            width = self->cell_size.width;
+            height = self->cell_size.height;
+            break;
+        case 18:
+            code = 8;
+            width = self->columns;
+            height = self->lines;
+            break;
+    }
+    if (code) {
+        snprintf(buf, sizeof(buf), "%u;%u;%ut", code, height, width);
+        write_escape_code_to_child(self, CSI, buf);
+    }
+}
+
 void
 report_device_status(Screen *self, unsigned int which, bool private) {
     // We dont implement the private device status codes, since I haven't come

kitty/screen.h

@@ -172,6 +172,7 @@ void screen_handle_graphics_command(Screen *self, const GraphicsCommand *cmd, co
 bool screen_open_url(Screen*);
 void screen_dirty_sprite_positions(Screen *self);
 void screen_rescale_images(Screen *self);
+void screen_report_size(Screen *, unsigned int which);
 #define DECLARE_CH_SCREEN_HANDLER(name) void screen_##name(Screen *screen);
 DECLARE_CH_SCREEN_HANDLER(bell)
 DECLARE_CH_SCREEN_HANDLER(backspace)

kitty_tests/parser.py

@@ -160,6 +160,9 @@ class TestParser(BaseTest):
         pb('\033[?1$p', ('report_mode_status', 1, 1))
         self.ae(c.wtcbuf, b'\033[?1;2$y')
         pb('\033[2;4r', ('screen_set_margins', 2, 4))
+        c.clear()
+        pb('\033[14t', ('screen_report_size', 14))
+        self.ae(c.wtcbuf, b'\033[4;100;50t')
         self.ae(s.margin_top, 1), self.ae(s.margin_bottom, 3)
         pb('\033[r', ('screen_set_margins', 0, 0))
         self.ae(s.margin_top, 0), self.ae(s.margin_bottom, 4)