Misc: Add margin_t & Store frame extents with it & Misc

- Add margin_t, a structure that represents margins around a rectangle.

 - Store frame extents of a window with margin_t, replacing the 4
   fields ({left,right,top,bottom}_width) in struct _win.

 - Add two helper macros, cmemzero() and cmemzero_one(), that zero out a
   block of memory.

src/common.h

@@ -279,6 +279,17 @@ typedef struct {
   int y;
 } geometry_t;
 
+/// A structure representing margins around a rectangle.
+typedef struct {
+  int top;
+  int left;
+  int bottom;
+  int right;
+} margin_t;
+
+// Or use cmemzero().
+#define MARGIN_INIT { 0, 0, 0, 0 }
+
 /// Enumeration type of window painting mode.
 typedef enum {
   WMODE_TRANS,
@@ -1174,8 +1185,8 @@ typedef struct _win {
   // Frame-opacity-related members
   /// Current window frame opacity. Affected by window opacity.
   double frame_opacity;
-  /// Frame widths. Determined by client window attributes.
+  /// Frame extents. Acquired from _NET_FRAME_EXTENTS.
-  unsigned int left_width, right_width, top_width, bottom_width;
+  margin_t frame_extents;
 
   // Shadow-related members
   /// Whether a window has shadow. Calculated.
@@ -1343,6 +1354,13 @@ allocchk_(const char *func_name, void *ptr) {
 /// @brief Wrapper of ealloc().
 #define crealloc(ptr, nmemb, type) ((type *) allocchk(realloc((ptr), (nmemb) * sizeof(type))))
 
+/// @brief Zero out the given memory block.
+#define cmemzero(ptr, size) memset((ptr), 0, (size))
+
+/// @brief Wrapper of cmemzero() that handles a pointer to a single item, for
+///        convenience.
+#define cmemzero_one(ptr) cmemzero((ptr), sizeof(*(ptr)))
+
 /**
  * Return whether a struct timeval value is empty.
  */

src/compton.c

@@ -903,10 +903,10 @@ static XserverRegion
 win_get_region_noframe(session_t *ps, win *w, bool use_offset) {
   XRectangle r;
 
-  r.x = (use_offset ? w->a.x: 0) + w->a.border_width + w->left_width;
+  r.x = (use_offset ? w->a.x: 0) + w->a.border_width + w->frame_extents.left;
-  r.y = (use_offset ? w->a.y: 0) + w->a.border_width + w->top_width;
+  r.y = (use_offset ? w->a.y: 0) + w->a.border_width + w->frame_extents.top;
-  r.width = max_i(w->a.width - w->left_width - w->right_width, 0);
+  r.width = max_i(w->a.width - w->frame_extents.left - w->frame_extents.right, 0);
-  r.height = max_i(w->a.height - w->top_width - w->bottom_width, 0);
+  r.height = max_i(w->a.height - w->frame_extents.top - w->frame_extents.bottom, 0);
 
   if (r.width > 0 && r.height > 0)
     return XFixesCreateRegion(ps->dpy, &r, 1);
@@ -1033,20 +1033,17 @@ find_client_win(session_t *ps, Window w) {
  */
 static void
 get_frame_extents(session_t *ps, win *w, Window client) {
-  w->left_width = 0;
+  cmemzero_one(&w->frame_extents);
-  w->right_width = 0;
-  w->top_width = 0;
-  w->bottom_width = 0;
 
   winprop_t prop = wid_get_prop(ps, client, ps->atom_frame_extents,
     4L, XA_CARDINAL, 32);
 
   if (4 == prop.nitems) {
     const long * const extents = prop.data.p32;
-    w->left_width = extents[0];
+    w->frame_extents.left = extents[0];
-    w->right_width = extents[1];
+    w->frame_extents.right = extents[1];
-    w->top_width = extents[2];
+    w->frame_extents.top = extents[2];
-    w->bottom_width = extents[3];
+    w->frame_extents.bottom = extents[3];
 
     if (ps->o.frame_opacity)
       update_reg_ignore_expire(ps, w);
@@ -1054,7 +1051,8 @@ get_frame_extents(session_t *ps, win *w, Window client) {
 
 #ifdef DEBUG_FRAME
   printf_dbgf("(%#010lx): %d, %d, %d, %d\n", w->id,
-      w->left_width, w->right_width, w->top_width, w->bottom_width);
+      w->frame_extents.left, w->frame_extents.right,
+      w->frame_extents.top, w->frame_extents.bottom);
 #endif
 
   free_winprop(&prop);
@@ -1634,10 +1632,10 @@ win_paint_win(session_t *ps, win *w, XserverRegion reg_paint,
   }
   else {
     // Painting parameters
-    const int t = w->a.border_width + w->top_width;
+    const int t = w->a.border_width + w->frame_extents.top;
-    const int l = w->a.border_width + w->left_width;
+    const int l = w->a.border_width + w->frame_extents.left;
-    const int b = w->a.border_width + w->bottom_width;
+    const int b = w->a.border_width + w->frame_extents.bottom;
-    const int r = w->a.border_width + w->right_width;
+    const int r = w->a.border_width + w->frame_extents.right;
 
 #define COMP_BDR(cx, cy, cwid, chei) \
     win_render(ps, w, (cx), (cy), (cwid), (chei), w->frame_opacity, \
@@ -2898,10 +2896,7 @@ add_win(session_t *ps, Window id, Window prev) {
     .fade_callback = NULL,
 
     .frame_opacity = 0.0,
-    .left_width = 0,
+    .frame_extents = MARGIN_INIT,
-    .right_width = 0,
-    .top_width = 0,
-    .bottom_width = 0,
 
     .shadow = false,
     .shadow_force = UNSET,

src/compton.h

@@ -503,7 +503,8 @@ update_reg_ignore_expire(session_t *ps, const win *w) {
 static inline bool __attribute__((const))
 win_has_frame(const win *w) {
   return w->a.border_width
-    || w->top_width || w->left_width || w->right_width || w->bottom_width;
+    || w->frame_extents.top || w->frame_extents.left
+    || w->frame_extents.right || w->frame_extents.bottom;
 }
 
 static inline void

src/dbus.c

@@ -723,10 +723,22 @@ cdbus_process_win_get(session_t *ps, DBusMessage *msg) {
   cdbus_m_win_get_do(opacity_set, cdbus_reply_uint32);
 
   cdbus_m_win_get_do(frame_opacity, cdbus_reply_double);
-  cdbus_m_win_get_do(left_width, cdbus_reply_uint32);
+  if (!strcmp("left_width", target)) {
-  cdbus_m_win_get_do(right_width, cdbus_reply_uint32);
+    cdbus_reply_uint32(ps, msg, w->frame_extents.left);
-  cdbus_m_win_get_do(top_width, cdbus_reply_uint32);
+    return true;
-  cdbus_m_win_get_do(bottom_width, cdbus_reply_uint32);
+  }
+  if (!strcmp("right_width", target)) {
+    cdbus_reply_uint32(ps, msg, w->frame_extents.right);
+    return true;
+  }
+  if (!strcmp("top_width", target)) {
+    cdbus_reply_uint32(ps, msg, w->frame_extents.top);
+    return true;
+  }
+  if (!strcmp("bottom_width", target)) {
+    cdbus_reply_uint32(ps, msg, w->frame_extents.bottom);
+    return true;
+  }
 
   cdbus_m_win_get_do(shadow, cdbus_reply_bool);
   cdbus_m_win_get_do(fade, cdbus_reply_bool);