Add vertical tab bars on the left and right

kitty/boss.py

@@ -2001,7 +2001,7 @@ def on_drop(self, os_window_id: int, drop: dict[str, bytes] | int, from_self: bo
                             window.on_drop(drop)
                             break
         elif tab_bar.left <= x < tab_bar.right and tab_bar.top <= y < tab_bar.bottom:
-            if (tab_id := tm.tab_bar.tab_id_at(x)) and (tab := self.tab_for_id(tab_id)) and (w := tab.active_window):
+            if (tab_id := tm.tab_bar.tab_id_at(x, y)) and (tab := self.tab_for_id(tab_id)) and (w := tab.active_window):
                 w.on_drop(drop)
 
     def on_drag_source_finished(

kitty/mouse.c

@@ -987,6 +987,8 @@ mouse_region(bool detect_borders, bool detect_title_bar) {
     const bool in_central = mouse_in_region(&central);
     if (!in_central) {
         if (
+                (tab_bar.left < central.left && w->mouse_x < central.left) ||
+                (tab_bar.right > central.right && w->mouse_x >= central.right) ||
                 (tab_bar.top < central.top && w->mouse_y < central.top) ||
                 (tab_bar.bottom > central.bottom && w->mouse_y >= central.bottom)
            ) ans.in_tab_bar = true;

kitty/options/definition.py

@@ -1616,18 +1616,22 @@
 
 opt('tab_bar_edge', 'bottom',
     option_type='tab_bar_edge', ctype='int',
-    long_text='The edge to show the tab bar on, :code:`top` or :code:`bottom`.'
+    long_text='The edge to show the tab bar on, :code:`top`, :code:`bottom`, :code:`left` or :code:`right`.'
     )
 
 opt('tab_bar_margin_width', '0.0',
     option_type='positive_float',
-    long_text='The margin to the left and right of the tab bar (in pts).'
+    long_text='''
+The margin perpendicular to the tab bar edge (in pts). For tab bars on the
+top or bottom this is the margin to the left and right. For tab bars on the
+left or right this is the margin above and below.
+'''
     )
 
 opt('tab_bar_margin_height', '0.0 0.0',
     option_type='tab_bar_margin_height', ctype='!tab_bar_margin_height',
     long_text='''
-The margin above and below the tab bar (in pts). The first number is the margin
+The margin along the tab bar edge (in pts). The first number is the margin
 between the edge of the OS Window and the tab bar. The second number is the
 margin between the tab bar and the contents of the current tab.
 '''
@@ -1675,11 +1679,12 @@
 are automatically restricted to work only on matching tabs.
 ''')
 
-opt('tab_bar_align', 'left',
-    choices=('left', 'center', 'right'),
+opt('tab_bar_align', 'start',
+    choices=('start', 'center', 'end', 'left', 'right'),
     long_text='''
-The horizontal alignment of the tab bar, can be one of: :code:`left`,
-:code:`center`, :code:`right`.
+The alignment of the tab bar, can be one of: :code:`start`, :code:`center`,
+:code:`end`, :code:`left`, :code:`right`. The values :code:`left` and
+:code:`right` are aliases for :code:`start` and :code:`end` respectively.
 '''
     )
 
@@ -1746,10 +1751,12 @@
     )
 
 opt('tab_title_max_length', '0',
-    option_type='positive_int',
+    option_type='positive_int', ctype='int',
     long_text='''
 The maximum number of cells that can be used to render the text in a tab.
-A value of zero means that no limit is applied.
+A value of zero means that no limit is applied. For vertical tab bars, kitty
+uses a default sidebar width sized for about twenty title cells when this is
+left unset.
 '''
     )
 

kitty/options/utils.py

@@ -751,7 +751,12 @@ def tab_separator(x: str) -> str:
 
 
 def tab_bar_edge(x: str) -> int:
-    return {'top': defines.TOP_EDGE, 'bottom': defines.BOTTOM_EDGE}.get(x.lower(), defines.BOTTOM_EDGE)
+    return {
+        'left': defines.LEFT_EDGE,
+        'top': defines.TOP_EDGE,
+        'right': defines.RIGHT_EDGE,
+        'bottom': defines.BOTTOM_EDGE,
+    }.get(x.lower(), defines.BOTTOM_EDGE)
 
 
 def tab_font_style(x: str) -> tuple[bool, bool]:

kitty/state.c

@@ -691,29 +691,76 @@ pyset_borders_rects(PyObject *self UNUSED, PyObject *args) {
 }
 
 
+static unsigned
+vertical_tab_bar_cols(const OSWindow *os_window, long margin_outer, long margin_inner) {
+    unsigned cell_width = MAX(1u, os_window->fonts_data->fcm.cell_width);
+    long available_width = (long)os_window->viewport_width - margin_outer - margin_inner;
+    if (available_width <= 0) return 0;
+    unsigned available_cols = MAX(1u, (unsigned)available_width / cell_width);
+    unsigned title_cols = OPT(tab_title_max_length) > 0 ? (unsigned)OPT(tab_title_max_length) : 20u;
+    unsigned desired_cols = title_cols + 8u;
+    unsigned soft_max = available_cols / 3u;
+    if (soft_max < 6u) soft_max = available_cols;
+    return MAX(1u, MIN(available_cols, MIN(desired_cols, MAX(1u, soft_max))));
+}
+
 void
 os_window_regions(const OSWindow *os_window, Region *central, Region *tab_bar) {
     if (!OPT(tab_bar_hidden) && os_window->num_tabs && !os_window->has_too_few_tabs) {
         long margin_outer = pt_to_px_for_os_window(OPT(tab_bar_margin_height.outer), os_window);
         long margin_inner = pt_to_px_for_os_window(OPT(tab_bar_margin_height.inner), os_window);
         central->left = 0; central->right = os_window->viewport_width;
-        unsigned tab_bar_height = os_window->fonts_data->fcm.cell_height + margin_inner + margin_outer;
+        central->top = 0; central->bottom = os_window->viewport_height;
         switch(OPT(tab_bar_edge)) {
-            case TOP_EDGE:
+            case TOP_EDGE: {
+                unsigned tab_bar_height = os_window->fonts_data->fcm.cell_height + margin_inner + margin_outer;
                 central->top = tab_bar_height;
                 central->bottom = os_window->viewport_height;
                 central->top = MIN(central->top, central->bottom);
                 tab_bar->top = margin_outer;
+                tab_bar->left = central->left; tab_bar->right = central->right;
+                tab_bar->bottom = tab_bar->top + os_window->fonts_data->fcm.cell_height;
+                break;
+            }
+            case LEFT_EDGE: {
+                unsigned left_cols = vertical_tab_bar_cols(os_window, margin_outer, margin_inner);
+                if (!left_cols) {
+                    zero_at_ptr(tab_bar);
+                    return;
+                }
+                unsigned left_width = left_cols * os_window->fonts_data->fcm.cell_width;
+                central->left = MIN((long)(left_width + margin_inner + margin_outer), (long)central->right);
+                tab_bar->left = margin_outer;
+                tab_bar->right = tab_bar->left + left_width;
+                tab_bar->top = central->top;
+                tab_bar->bottom = central->bottom;
                 break;
-            default:
+            }
+            case RIGHT_EDGE: {
+                unsigned right_cols = vertical_tab_bar_cols(os_window, margin_outer, margin_inner);
+                if (!right_cols) {
+                    zero_at_ptr(tab_bar);
+                    return;
+                }
+                unsigned right_width = right_cols * os_window->fonts_data->fcm.cell_width;
+                central->right = MAX(0, (long)os_window->viewport_width - (long)(right_width + margin_inner + margin_outer));
+                tab_bar->left = central->right + margin_inner;
+                tab_bar->right = tab_bar->left + right_width;
+                tab_bar->top = central->top;
+                tab_bar->bottom = central->bottom;
+                break;
+            }
+            default: {
+                unsigned tab_bar_height = os_window->fonts_data->fcm.cell_height + margin_inner + margin_outer;
                 central->top = 0;
                 long bottom = os_window->viewport_height - tab_bar_height;
                 central->bottom = MAX(0, bottom);
                 tab_bar->top = central->bottom + margin_inner;
+                tab_bar->left = central->left; tab_bar->right = central->right;
+                tab_bar->bottom = tab_bar->top + os_window->fonts_data->fcm.cell_height;
                 break;
+            }
         }
-        tab_bar->left = central->left; tab_bar->right = central->right;
-        tab_bar->bottom = tab_bar->top + os_window->fonts_data->fcm.cell_height;
     } else {
         zero_at_ptr(tab_bar);
         central->left = 0; central->top = 0; central->right = os_window->viewport_width;

kitty/state.h

@@ -110,6 +110,7 @@ typedef struct Options {
     bool dynamic_background_opacity;
     float inactive_text_alpha;
     Edge tab_bar_edge;
+    int tab_title_max_length;
     DisableLigature disable_ligatures;
     bool force_ltr;
     bool resize_in_steps;