Allow resizing of OS Window framebuffers to a single cell

This is much smaller than before and essentially works around the issue
of the text being scaled when the window is resized to small sizes. Also
has the nice side effect of making the code simpler for the panel
kitten. Fixes #3307

docs/changelog.rst

@@ -62,6 +62,8 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 
 - Fix window icon not working on X11 with 64bits (:iss:`3260`)
 
+- Fix OS window sizes under 100px resulting in scaled display (:iss:`3307`)
+
 
 0.19.3 [2020-12-19]
 -------------------

kittens/panel/main.py

@@ -121,19 +121,17 @@ def setup_x11_window(win_id: int) -> None:
 
 
 def initial_window_size_func(opts: WindowSizeData, cached_values: Dict) -> Callable[[int, int, float, float, float, float], Tuple[int, int]]:
-    from kitty.fast_data_types import glfw_primary_monitor_size, set_smallest_allowed_resize
+    from kitty.fast_data_types import glfw_primary_monitor_size
 
     def initial_window_size(cell_width: int, cell_height: int, dpi_x: float, dpi_y: float, xscale: float, yscale: float) -> Tuple[int, int]:
         global window_width, window_height
         monitor_width, monitor_height = glfw_primary_monitor_size()
         if args.edge in {'top', 'bottom'}:
-            h = window_height = cell_height * args.lines + 1
+            window_height = cell_height * args.lines + 1
             window_width = monitor_width
-            set_smallest_allowed_resize(100, h)
         else:
-            w = window_width = cell_width * args.columns + 1
+            window_width = cell_width * args.columns + 1
             window_height = monitor_height
-            set_smallest_allowed_resize(w, 100)
         return window_width, window_height
 
     return initial_window_size

kitty/fast_data_types.pyi

@@ -521,10 +521,6 @@ def glfw_primary_monitor_size() -> Tuple[int, int]:
     pass
 
 
-def set_smallest_allowed_resize(width: int, height: int) -> None:
-    pass
-
-
 def set_default_window_icon(path: str) -> None:
     pass
 

kitty/glfw.c

@@ -33,7 +33,12 @@ request_tick_callback(void) {
     glfwPostEmptyEvent();
 }
 
-static int min_width = 100, min_height = 100;
+static inline void
+min_size_for_os_window(OSWindow *window, int *min_width, int *min_height) {
+    *min_width = MAX(8u, window->fonts_data->cell_width + 1);
+    *min_height = MAX(8u, window->fonts_data->cell_height + 1);
+}
+
 
 void
 update_os_window_viewport(OSWindow *window, bool notify_boss) {
@@ -46,7 +51,8 @@ update_os_window_viewport(OSWindow *window, bool notify_boss) {
     if (fw == window->viewport_width && fh == window->viewport_height && w == window->window_width && h == window->window_height && xdpi == window->logical_dpi_x && ydpi == window->logical_dpi_y) {
         return; // no change, ignore
     }
-    if (w <= 0 || h <= 0 || fw / w > 5 || fh / h > 5 || fw < min_width || fh < min_height || fw < w || fh < h) {
+    int min_width, min_height; min_size_for_os_window(window, &min_width, &min_height);
+    if (w <= 0 || h <= 0 || fw < min_width || fh < min_height || fw < w || fh < h) {
         log_error("Invalid geometry ignored: framebuffer: %dx%d window: %dx%d\n", fw, fh, w, h);
         if (!window->viewport_updated_at_least_once) {
             window->viewport_width = min_width; window->viewport_height = min_height;
@@ -191,6 +197,7 @@ live_resize_callback(GLFWwindow *w, bool started) {
 static void
 framebuffer_size_callback(GLFWwindow *w, int width, int height) {
     if (!set_callback_window(w)) return;
+    int min_width, min_height; min_size_for_os_window(global_state.callback_os_window, &min_width, &min_height);
     if (width >= min_width && height >= min_height) {
         OSWindow *window = global_state.callback_os_window;
         global_state.has_pending_resizes = true;
@@ -1202,12 +1209,6 @@ set_primary_selection(PyObject UNUSED *self, PyObject *args) {
     Py_RETURN_NONE;
 }
 
-static PyObject*
-set_smallest_allowed_resize(PyObject *self UNUSED, PyObject *args) {
-    if (!PyArg_ParseTuple(args, "ii", &min_width, &min_height)) return NULL;
-    Py_RETURN_NONE;
-}
-
 static PyObject*
 set_custom_cursor(PyObject *self UNUSED, PyObject *args) {
     int shape;
@@ -1345,7 +1346,6 @@ stop_main_loop(void) {
 
 static PyMethodDef module_methods[] = {
     METHODB(set_custom_cursor, METH_VARARGS),
-    METHODB(set_smallest_allowed_resize, METH_VARARGS),
     METHODB(create_os_window, METH_VARARGS),
     METHODB(set_default_window_icon, METH_VARARGS),
     METHODB(get_clipboard_string, METH_NOARGS),