Implement resizing of individual windows in a layout

See the Layouts section in the README for details. Fixes #362

Note that it is only implemented for the Tall layout currently. Other
layouts to follow. The implementation might also be refined in the
future.

README.asciidoc

@@ -48,6 +48,7 @@
 :sc_seventh_window: pass:quotes[`ctrl+shift+7`]
 :sc_show_scrollback: pass:quotes[`ctrl+shift+h`]
 :sc_sixth_window: pass:quotes[`ctrl+shift+6`]
+:sc_start_resizing_window: pass:quotes[`ctrl+shift+r`]
 :sc_tenth_window: pass:quotes[`ctrl+shift+0`]
 :sc_third_window: pass:quotes[`ctrl+shift+3`]
 :sc_toggle_fullscreen: pass:quotes[`ctrl+shift+f11`]
@@ -343,6 +344,15 @@ You can switch between layouts using the {sc_next_layout} key combination. You c
 also create shortcuts to select particular layouts, and choose which layouts
 you want to enable/disable, see link:kitty/kitty.conf[kitty.conf] for examples.
 
+You can resize windows inside layouts. Press {sc_start_resizing_window} to
+enter resizing mode. Then use the `W/N` (Wider/Narrower) and `T/S`
+(Taller/Shorter) keys to change the window size.  Press the `0` key to rest the
+layout to default sizes. Any other key will exit resize mode.  In a given
+window layout only some operations may be possible for a particular window. For
+example, in the Tall layout you can make the first window wider/narrower, but
+not taller/shorter. Note that what you are resizing is actually not a window,
+but a row/column in the layout, all windows in that row/column will be resized.
+
 Some layouts take options to control their behavior. For example, the `fat` and `tall`
 layouts accept the `bias` option to control how the available space is split up. To specify the
 option, in kitty.conf use:
@@ -351,7 +361,7 @@ option, in kitty.conf use:
 enabled_layouts tall:bias=70
 ```
 
-this will make the tall window occupy `70%` of available width. `bias` can be
+This will make the tall window occupy `70%` of available width. `bias` can be
 any number between 10 and 90.
 
 Writing a new layout only requires about fifty lines of code, so if there is

kitty/boss.py

@@ -19,7 +19,8 @@ from .constants import (
     appname, config_dir, editor, set_boss, supports_primary_selection
 )
 from .fast_data_types import (
-    ChildMonitor, create_os_window, current_os_window, destroy_global_data,
+    GLFW_KEY_0, GLFW_KEY_W, GLFW_KEY_N, GLFW_KEY_S, ChildMonitor,
+    create_os_window, current_os_window, destroy_global_data,
     destroy_sprite_map, get_clipboard_string, glfw_post_empty_event,
     layout_sprite_map, mark_os_window_for_close, set_clipboard_string,
     set_dpi_from_os_window, set_in_sequence_mode, show_window,
@@ -413,6 +414,22 @@ class Boss:
             if matched_action is not None:
                 self.dispatch_action(matched_action)
 
+    def handle_resize_keypress(self, key, mods, os_window_id, tab_id, window_id):
+        tm = self.os_window_map.get(os_window_id)
+        if tm is None:
+            return
+        tab = tm.tab_for_id(tab_id)
+        if tab is None:
+            return
+        if key == GLFW_KEY_0:
+            tab.reset_window_sizes()
+            return
+        is_horizontal = key in (GLFW_KEY_W, GLFW_KEY_N)
+        increment = 0.05
+        if key in (GLFW_KEY_N, GLFW_KEY_S):
+            increment *= -1
+        tab.resize_window_by(window_id, increment, is_horizontal)
+
     def default_bg_changed_for(self, window_id):
         w = self.window_id_map.get(window_id)
         if w is not None:

kitty/glfw.c

@@ -765,6 +765,16 @@ os_window_swap_buffers(PyObject UNUSED *self, PyObject *args) {
     return NULL;
 }
 
+static PyObject*
+ring_bell(PyObject UNUSED *self, PyObject *args) {
+    id_type os_window_id;
+    if (!PyArg_ParseTuple(args, "K", &os_window_id)) return NULL;
+    OSWindow *w = os_window_for_kitty_window(os_window_id);
+    if (w && w->handle) {
+        glfwWindowBell(w->handle);
+    }
+    Py_RETURN_NONE;
+}
 // Boilerplate {{{
 
 static PyMethodDef module_methods[] = {
@@ -778,6 +788,7 @@ static PyMethodDef module_methods[] = {
     METHODB(glfw_window_hint, METH_VARARGS),
     METHODB(os_window_should_close, METH_VARARGS),
     METHODB(os_window_swap_buffers, METH_VARARGS),
+    METHODB(ring_bell, METH_VARARGS),
     METHODB(get_primary_selection, METH_NOARGS),
     METHODB(x11_display, METH_NOARGS),
     METHODB(x11_window_id, METH_O),

kitty/keys.c

@@ -81,10 +81,24 @@ is_ascii_control_char(char c) {
     return c == 0 || (1 <= c && c <= 31) || c == 127;
 }
 
+static inline bool
+handle_resize_key(int key, int action, int mods) {
+    if (action == GLFW_RELEASE) return true;
+    if (key == GLFW_KEY_T || key == GLFW_KEY_S || key == GLFW_KEY_W || key == GLFW_KEY_N || key == GLFW_KEY_0) {
+        call_boss(handle_resize_keypress, "iiKKK", key, mods, global_state.currently_resizing.os_window_id, global_state.currently_resizing.tab_id, global_state.currently_resizing.window_id);
+        return true;
+    }
+    return false;
+}
+
 void
 on_key_input(int key, int scancode, int action, int mods, const char* text, int state UNUSED) {
     Window *w = active_window();
     if (!w) return;
+    if (global_state.currently_resizing.os_window_id) {
+        if (handle_resize_key(key, action, mods)) return;
+        terminate_resize_mode();
+    }
     if (global_state.in_sequence_mode) {
         if (
             action != GLFW_RELEASE &&

kitty/kitty.conf

@@ -395,6 +395,8 @@ map kitty_mod+[        previous_window
 map kitty_mod+f        move_window_forward
 map kitty_mod+b        move_window_backward
 map kitty_mod+`        move_window_to_top
+map kitty_mod+r        start_resizing_window
+# Switching to a particular window
 map kitty_mod+1        first_window
 map kitty_mod+2        second_window
 map kitty_mod+3        third_window

kitty/layout.py

@@ -4,7 +4,7 @@
 
 from collections import namedtuple
 from functools import partial
-from itertools import islice
+from itertools import islice, repeat
 
 from .constants import WindowGeometry
 from .fast_data_types import (
@@ -42,8 +42,15 @@ def layout_dimension(start_at, length, cell_length, number_of_windows=1, border_
         inner_length = cells_in_window * cell_length
         return 2 * (border_length + margin_length) + inner_length
 
-    if bias is not None and number_of_windows > 1 and len(bias) == number_of_windows:
+    if bias is not None and number_of_windows > 1 and len(bias) == number_of_windows and cells_per_window > 5:
         cells_map = [int(b * number_of_cells) for b in bias]
+        while min(cells_map) < 5:
+            maxi, mini = map(cells_map.index, (max(cells_map), min(cells_map)))
+            if maxi == mini:
+                break
+            cells_map[mini] += 1
+            cells_map[maxi] -= 1
+
         extra = number_of_cells - sum(cells_map)
         if extra:
             cells_map[-1] += extra
@@ -90,6 +97,28 @@ class Layout:
         self.blank_rects = ()
         self.layout_opts = self.parse_layout_opts(layout_opts)
         self.full_name = self.name + ((':' + layout_opts) if layout_opts else '')
+        self.initialize_sub_class()
+
+    def initialize_sub_class(self):
+        pass
+
+    def apply_bias(self, idx, increment, num_windows, is_horizontal):
+        return False
+
+    def remove_all_biases(self):
+        return False
+
+    def modify_size_of_window(self, all_windows, window_id, increment, is_horizontal=True):
+        idx = idx_for_id(window_id, all_windows)
+        if idx is None:
+            return
+        w = all_windows[idx]
+        windows = process_overlaid_windows(all_windows)[1]
+        idx = idx_for_id(w.id, windows)
+        if idx is None:
+            idx = idx_for_id(w.overlay_window_id, windows)
+        if idx is not None:
+            return self.apply_bias(idx, increment, len(windows), is_horizontal)
 
     def parse_layout_opts(self, layout_opts):
         if not layout_opts:
@@ -307,10 +336,59 @@ class Stack(Layout):
                 self.blank_rects = blank_rects_for_window(w)
 
 
+def safe_increment_bias(old_val, increment):
+    return max(0.1, min(old_val + increment, 0.9))
+
+
+def normalize_biases(biases):
+    s = sum(biases)
+    if s == 1:
+        return biases
+    return [x/s for x in biases]
+
+
+def distribute_indexed_bias(base_bias, index_bias_map):
+    if not index_bias_map:
+        return base_bias
+    ans = list(base_bias)
+    limit = len(ans)
+    for row, increment in index_bias_map.items():
+        if row >= limit or not increment:
+            continue
+        other_increment = -increment / (limit - 1)
+        ans = [safe_increment_bias(b, increment if i == row else other_increment) for i, b in enumerate(ans)]
+    return normalize_biases(ans)
+
+
 class Tall(Layout):
 
     name = 'tall'
 
+    def initialize_sub_class(self):
+        self.remove_all_biases()
+
+    def remove_all_biases(self):
+        self.x_bias = list(self.layout_opts['bias'])
+        self.biased_rows = {}
+        return True
+
+    def apply_bias(self, idx, increment, num_windows, is_horizontal):
+        if is_horizontal:
+            before = self.x_bias
+            if idx == 0:
+                self.x_bias = [safe_increment_bias(self.x_bias[0], increment), safe_increment_bias(self.x_bias[1], -increment)]
+            else:
+                self.x_bias = [safe_increment_bias(self.x_bias[0], -increment), safe_increment_bias(self.x_bias[1], increment)]
+            self.x_bias = normalize_biases(self.x_bias)
+            after = self.x_bias
+        else:
+            if idx == 0:
+                return False
+            idx -= 1
+            before = self.biased_rows.get(idx, 0)
+            self.biased_rows[idx] = after = before + increment
+        return before != after
+
     def parse_layout_opts(self, layout_opts):
         ans = Layout.parse_layout_opts(self, layout_opts)
         try:
@@ -328,12 +406,16 @@ class Tall(Layout):
             windows[0].set_geometry(0, wg)
             self.blank_rects = blank_rects_for_window(windows[0])
             return
-        xlayout = self.xlayout(2, bias=self.layout_opts['bias'])
+        xlayout = self.xlayout(2, bias=self.x_bias)
         xstart, xnum = next(xlayout)
         ystart, ynum = next(self.ylayout(1))
         windows[0].set_geometry(0, window_geometry(xstart, xnum, ystart, ynum))
         xstart, xnum = next(xlayout)
-        ylayout = self.ylayout(len(windows) - 1)
+        if len(windows) > 2:
+            y_bias = distribute_indexed_bias(list(repeat(1/(len(windows) - 1), len(windows) - 1)), self.biased_rows)
+        else:
+            y_bias = None
+        ylayout = self.ylayout(len(windows) - 1, bias=y_bias)
         for i, (w, (ystart, ynum)) in enumerate(zip(islice(windows, 1, None), ylayout)):
             w.set_geometry(i + 1, window_geometry(xstart, xnum, ystart, ynum))
             # right bottom blank rect

kitty/mouse.c

@@ -303,6 +303,7 @@ open_url(Window *w) {
 }
 
 HANDLER(handle_button_event) {
+    if (global_state.currently_resizing.os_window_id) { terminate_resize_mode(); }
     Tab *t = global_state.callback_os_window->tabs + global_state.callback_os_window->active_tab;
     bool is_release = !global_state.callback_os_window->mouse_button_pressed[button];
     if (window_idx != t->active_window) {

kitty/state.c

@@ -268,6 +268,14 @@ os_window_regions(OSWindow *os_window, Region *central, Region *tab_bar) {
     }
 }
 
+void
+terminate_resize_mode() {
+    global_state.currently_resizing.os_window_id = 0;
+    global_state.currently_resizing.tab_id = 0;
+    global_state.currently_resizing.window_id = 0;
+}
+
+
 
 // Python API {{{
 #define PYWRAP0(name) static PyObject* py##name(PYNOARG)
@@ -586,6 +594,14 @@ PYWRAP1(set_display_state) {
     Py_RETURN_NONE;
 }
 
+PYWRAP1(enter_resize_mode) {
+    global_state.currently_resizing.os_window_id = 0;
+    global_state.currently_resizing.tab_id = 0;
+    global_state.currently_resizing.window_id = 0;
+    PA("|KKK", &global_state.currently_resizing.os_window_id, &global_state.currently_resizing.tab_id, &global_state.currently_resizing.window_id);
+    Py_RETURN_NONE;
+}
+
 THREE_ID_OBJ(update_window_title)
 THREE_ID(remove_window)
 PYWRAP1(resolve_key_mods) { int mods; PA("ii", &kitty_mod, &mods); return PyLong_FromLong(resolve_mods(mods)); }
@@ -632,6 +648,7 @@ static PyMethodDef module_methods[] = {
     MW(update_window_visibility, METH_VARARGS),
     MW(set_boss, METH_O),
     MW(set_display_state, METH_VARARGS),
+    MW(enter_resize_mode, METH_VARARGS),
     MW(destroy_global_data, METH_NOARGS),
 
     {NULL, NULL, 0, NULL}        /* Sentinel */

kitty/state.h

@@ -137,6 +137,9 @@ typedef struct {
     bool debug_gl, debug_font_fallback;
     bool has_pending_resizes;
     bool in_sequence_mode;
+    struct {
+        id_type os_window_id, tab_id, window_id;
+    } currently_resizing;
 } GlobalState;
 
 extern GlobalState global_state;
@@ -183,3 +186,4 @@ void free_texture(uint32_t*);
 void send_image_to_gpu(uint32_t*, const void*, int32_t, int32_t, bool, bool);
 void send_sprite_to_gpu(unsigned int, unsigned int, unsigned int, pixel*);
 void set_titlebar_color(OSWindow *w, color_type color);
+void terminate_resize_mode();

kitty/tabs.py

@@ -12,8 +12,9 @@ from .config import build_ansi_color_table
 from .constants import WindowGeometry, appname, get_boss, is_macos, is_wayland
 from .fast_data_types import (
     DECAWM, Screen, add_tab, glfw_post_empty_event, mark_tab_bar_dirty,
-    next_window_id, pt_to_px, remove_tab, remove_window, set_active_tab,
+    next_window_id, pt_to_px, remove_tab, remove_window, ring_bell,
-    set_tab_bar_render_data, swap_tabs, viewport_for_window, x11_window_id
+    set_active_tab, set_tab_bar_render_data, swap_tabs, viewport_for_window,
+    x11_window_id
 )
 from .layout import Rect, create_layout_object_for, evict_cached_layouts
 from .session import resolved_shell
@@ -162,6 +163,16 @@ class Tab:  # {{{
         self.current_layout = self.create_layout_object(layout_name)
         self.relayout()
 
+    def resize_window_by(self, window_id, increment, is_horizontal):
+        if self.current_layout.modify_size_of_window(self.windows, window_id, increment, is_horizontal):
+            self.relayout()
+        else:
+            ring_bell(self.os_window_id)
+
+    def reset_window_sizes(self):
+        if self.current_layout.remove_all_biases():
+            self.relayout()
+
     def launch_child(self, use_shell=False, cmd=None, stdin=None, cwd_from=None, cwd=None, env=None):
         if cmd is None:
             if use_shell:

kitty/window.py

@@ -17,10 +17,10 @@ from .fast_data_types import (
     BLIT_PROGRAM, CELL_BG_PROGRAM, CELL_FG_PROGRAM, CELL_PROGRAM,
     CELL_SPECIAL_PROGRAM, CSI, CURSOR_PROGRAM, DCS, GRAPHICS_PREMULT_PROGRAM,
     GRAPHICS_PROGRAM, OSC, SCROLL_FULL, SCROLL_LINE, SCROLL_PAGE, Screen,
-    add_window, compile_program, get_clipboard_string, glfw_post_empty_event,
+    add_window, compile_program, enter_resize_mode, get_clipboard_string,
-    init_cell_program, init_cursor_program, set_clipboard_string,
+    glfw_post_empty_event, init_cell_program, init_cursor_program,
-    set_titlebar_color, set_window_render_data, update_window_title,
+    set_clipboard_string, set_titlebar_color, set_window_render_data,
-    update_window_visibility, viewport_for_window
+    update_window_title, update_window_visibility, viewport_for_window
 )
 from .keys import keyboard_mode_name
 from .rgb import to_color
@@ -193,6 +193,9 @@ class Window:
             return True
         self.write_to_child(text)
 
+    def start_resizing_window(self):
+        enter_resize_mode(self.os_window_id, self.tab_id, self.id)
+
     def write_to_child(self, data):
         if data:
             if get_boss().child_monitor.needs_write(self.id, data) is not True: