Merge pull request #507 from psychon/closest_screen

Update the definition of "closest screen" to take into account that a
screen is a rectangle and not just the top-left corner.

Closes https://github.com/awesomeWM/awesome/pull/507.

lib/awful/screen.lua

@@ -26,24 +26,42 @@ data.padding = {}
 
 screen.mouse_per_screen = {}
 
+-- @param s Screen number
+-- @param x X coordinate of point
+-- @param y Y coordinate of point
+-- @return The squared distance of the screen to the provided point
+function screen.getdistance_sq(s, x, y)
+    local geom = capi.screen[s].geometry
+    local dist_x, dist_y = 0, 0
+    if x < geom.x then
+        dist_x = geom.x - x
+    elseif x >= geom.x + geom.width then
+        dist_x = x - geom.x - geom.width
+    end
+    if y < geom.y then
+        dist_y = geom.y - y
+    elseif y >= geom.y + geom.height then
+        dist_y = y - geom.y - geom.height
+    end
+    return dist_x * dist_x + dist_y * dist_y
+end
+
 ---
 -- Return Xinerama screen number corresponding to the given (pixel) coordinates.
 -- The number returned can be used as an index into the global
 -- `screen` table/object.
 -- @param x The x coordinate
 -- @param y The y coordinate
--- @param[opt] default The default return value. If unspecified, 1 is returned.
-function screen.getbycoord(x, y, default)
-    for i = 1, capi.screen:count() do
-        local geometry = capi.screen[i].geometry
-        if((x < 0 or (x >= geometry.x and x < geometry.x + geometry.width))
-           and (y < 0 or (y >= geometry.y and y < geometry.y + geometry.height))) then
-            return i
+function screen.getbycoord(x, y)
+    local s = 1
+    local dist = screen.getdistance_sq(s, x, y)
+    for i = 2, capi.screen:count() do
+        local d = screen.getdistance_sq(i, x, y)
+        if d < dist then
+            s, dist = i, d
         end
     end
-    -- No caller expects a nil result here, so just make something up
-    if default == nil then return 1 end
-    return default
+    return s
 end
 
 --- Give the focus to a screen, and move pointer to last known position on this

objects/screen.c

@@ -35,7 +35,6 @@
 #include "objects/client.h"
 #include "objects/drawin.h"
 
-#include <math.h>
 #include <stdio.h>
 
 #include <xcb/xcb.h>
@@ -285,6 +284,38 @@ screen_scan(void)
         screen_scan_x11();
 }
 
+/** Return the squared distance of the given screen to the coordinates.
+ * \param screen The screen
+ * \param x X coordinate
+ * \param y Y coordinate
+ * \return Squared distance of the point to the screen.
+ */
+static unsigned int
+screen_get_distance_squared(screen_t *s, int x, int y)
+{
+    int sx = s->geometry.x, sy = s->geometry.y;
+    int sheight = s->geometry.height, swidth = s->geometry.width;
+    unsigned int dist_x, dist_y;
+
+    /* Calculate distance in X coordinate */
+    if (x < sx)
+        dist_x = sx - x;
+    else if (x < sx + swidth)
+        dist_x = 0;
+    else
+        dist_x = x - sx - swidth;
+
+    /* Calculate distance in Y coordinate */
+    if (y < sy)
+        dist_y = sy - y;
+    else if (y < sy + sheight)
+        dist_y = 0;
+    else
+        dist_y = y - sy - sheight;
+
+    return dist_x * dist_x + dist_y * dist_y;
+}
+
 /** Return the first screen number where the coordinates belong to.
  * \param x X coordinate
  * \param y Y coordinate
@@ -299,14 +330,14 @@ screen_getbycoord(int x, int y)
 
     /* No screen found, find nearest screen. */
     screen_t *nearest_screen = globalconf.screens.tab[0];
-    int nearest_dist = INT_MAX;
+    unsigned int nearest_dist = UINT_MAX;
     foreach(s, globalconf.screens)
     {
-        int dist = sqrt(pow((*s)->geometry.x - x, 2) + pow((*s)->geometry.y - y, 2));
-        if( dist < nearest_dist )
+        unsigned int dist_sq = screen_get_distance_squared(*s, x, y);
+        if(dist_sq < nearest_dist)
         {
-            nearest_dist = dist;
-            nearest_screen = (*s);
+            nearest_dist = dist_sq;
+            nearest_screen = *s;
         }
     }
     return nearest_screen;