Finish implementing resize by increment

docs/changelog.rst

@@ -16,6 +16,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Fix :opt:`background_opacity` incorrectly applying to selected text and
   reverse video text (:iss:`2177`)
 
+- Add a :opt:`resize_in_steps` option that can be used resize the OS window
+  in steps as large as the cells (:pull:`2131`)
+
 0.15.0 [2019-11-27]
 --------------------
 

kitty/config_data.py

@@ -649,6 +649,13 @@ A value of :code:`blank` means draw a blank window.
 A value of :code:`size` means show the window size in cells.
 '''))
 
+o('resize_in_steps', False, long_text=_('''
+Resize the OS window in steps as large as the cells, instead of with the usual pixel accuracy.
+Combined with an :opt:`initial_window_width` and :opt:`initial_window_height` in number of cells,
+this option can be used to keep the margins as small as possible when resizing the OS window.
+Note that this does not currently work on Wayland.
+'''))
+
 # }}}
 
 g('tabbar')   # {{{

kitty/glfw.c

@@ -625,7 +625,7 @@ create_os_window(PyObject UNUSED *self, PyObject *args) {
     w->fonts_data = fonts_data;
     w->shown_once = true;
     w->last_focused_counter = ++focus_counter;
-    glfwSetWindowSizeIncrements(glfw_window, fonts_data->cell_width, fonts_data->cell_height);
+    if (OPT(resize_in_steps)) glfwSetWindowSizeIncrements(glfw_window, fonts_data->cell_width, fonts_data->cell_height);
 #ifdef __APPLE__
     if (OPT(macos_option_as_alt)) glfwSetCocoaTextInputFilter(glfw_window, filter_option);
     glfwSetCocoaToggleFullscreenIntercept(glfw_window, intercept_cocoa_fullscreen);

kitty/state.c

@@ -522,6 +522,7 @@ PYWRAP1(set_options) {
     S(tab_bar_min_tabs, PyLong_AsUnsignedLong);
     S(disable_ligatures, PyLong_AsLong);
     S(resize_draw_strategy, PyLong_AsLong);
+    S(resize_in_steps, PyObject_IsTrue);
     S(pointer_shape_when_grabbed, pointer_shape);
 
     GA(tab_bar_style);
@@ -781,6 +782,7 @@ PYWRAP1(os_window_font_size) {
                     resize_screen(os_window, w->render_data.screen, true);
                 }
             }
+            if (OPT(resize_in_steps)) glfwSetWindowSizeIncrements(os_window->handle, os_window->fonts_data->cell_width, os_window->fonts_data->cell_height);
         }
         return Py_BuildValue("d", os_window->font_sz_in_pts);
     END_WITH_OS_WINDOW

kitty/state.h

@@ -42,6 +42,7 @@ typedef struct {
     unsigned long tab_bar_min_tabs;
     DisableLigature disable_ligatures;
     ResizeDrawStrategy resize_draw_strategy;
+    bool resize_in_steps;
     bool sync_to_monitor;
     bool close_on_child_death;
     bool window_alert_on_bell;