Split out win related functions to win.c

Also move static function prototypes out of compton.h. Seems like the
previous developers didn't know what header files are for.

Seems to have bugs after the split.

src/common.h

@@ -283,7 +283,7 @@ typedef struct {
 } win_upd_t;
 
 /// Structure representing Window property value.
-typedef struct {
+typedef struct winprop {
   // All pointers have the same length, right?
   // I wanted to use anonymous union but it's a GNU extension...
   union {
@@ -1448,6 +1448,11 @@ timespec_subtract(struct timespec *result,
   return x->tv_sec < y->tv_sec;
 }
 
+static inline double
+get_opacity_percent(win *w) {
+  return ((double) w->opacity) / OPAQUE;
+}
+
 /**
  * Get current time in struct timeval.
  */
@@ -2012,6 +2017,43 @@ rect_is_fullscreen(session_t *ps, int x, int y, unsigned wid, unsigned hei) {
           (y + hei) >= (unsigned int)ps->root_height);
 }
 
+static void
+set_ignore(session_t *ps, unsigned long sequence) {
+  if (ps->o.show_all_xerrors)
+    return;
+
+  ignore_t *i = malloc(sizeof(ignore_t));
+  if (!i) return;
+
+  i->sequence = sequence;
+  i->next = 0;
+  *ps->ignore_tail = i;
+  ps->ignore_tail = &i->next;
+}
+
+/**
+ * Ignore X errors caused by next X request.
+ */
+static inline void
+set_ignore_next(session_t *ps) {
+  set_ignore(ps, NextRequest(ps->dpy));
+}
+
+static inline void
+add_damage(session_t *ps, XserverRegion damage) {
+  // Ignore damage when screen isn't redirected
+  if (!ps->redirected)
+    free_region(ps, &damage);
+
+  if (!damage) return;
+  if (ps->all_damage) {
+    XFixesUnionRegion(ps->dpy, ps->all_damage, ps->all_damage, damage);
+    XFixesDestroyRegion(ps->dpy, damage);
+  } else {
+    ps->all_damage = damage;
+  }
+}
+
 /**
  * Check if a window is a fullscreen window.
  *