set SCALE according to dpi

claculate the scale so that fonts of 14pt will be of physical size 3mm,
this can be changed setting the macro name FONT_14PT_SIZE_MM in main.c

TODO

@@ -16,6 +16,7 @@
 	[ ] that command can be what is selected
 [ ] console: accept input
 [ ] doc: detect file changes with hash
+[ ] add horizontal scroll
 [ ] add a cross to close tab
 [ ] add context menu to various things
 	[ ] document and selection context menu
@@ -53,3 +54,4 @@
 [x] implement visual "ruler" at column 80
 [ ] show hidden files config and binding
 [ ] syntax: highlight FIXME TODO BUG FIX and IMPROVEMENT keywords
+[ ] do not open doc in new tab if current tab has an unchanged document

data/core/docview.lua

@@ -331,7 +331,7 @@ function DocView:draw_line_body(idx, x, y)
     local w = math.ceil(1 * SCALE)
     local lh = self:get_line_height()
     local color = style.guide or style.selection
-    renderer.draw_rect(x + config.line_limit * sw, y, sw, lh, color)
+    renderer.draw_rect(x + config.line_limit * sw, y, w, lh, color)
   end
 
   -- draw line's text

src/main.c

@@ -2,18 +2,26 @@
 
 #include <stdio.h>
 #include <unistd.h>
+#include <math.h>
 #include <SDL2/SDL.h>
 
 #include "api/api.h"
 #include "renderer.h"
 
+#define MAX(a,b) ((a)>(b)?(a):(b))
+
+// TODO: configuration here is required
+#define FONT_14PT_SIZE_MM 3
+
 SDL_Window *window;
 
 static double get_scale(void)
 {
-	float dpi;
+	float dpi, s;
 	SDL_GetDisplayDPI(0, NULL, &dpi, NULL);
-	return 1.0;
+	s = (1.0/dpi)*25.4; // size of a point
+	// as per standard 14 point should be 3mm
+	return floor((FONT_14PT_SIZE_MM/(14*s))*10)/10.0;
 }
 
 static void get_exe_filename(char *buf, int sz)