Add input and bounding shapes support (#2742)

Basic idea: if the window has a shape, set the parent container shape as
the union of the window shape and the shape of the frame borders.

Co-authored-by: Uli Schlachter <psychon@znc.in>

testcases/t/301-shape.t

@@ -0,0 +1,114 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Test shape support.
+# Ticket: #2742
+use i3test;
+use ExtUtils::PkgConfig;
+
+my %sn_config;
+BEGIN {
+    %sn_config = ExtUtils::PkgConfig->find('xcb-shape');
+}
+
+use Inline C => Config => LIBS => $sn_config{libs}, CCFLAGS => $sn_config{cflags};
+use Inline C => <<'END_OF_C_CODE';
+#include <xcb/shape.h>
+
+static xcb_connection_t *conn;
+
+void init_ctx(void *connptr) {
+    conn = (xcb_connection_t*)connptr;
+}
+
+/*
+ * Set the shape for the window consisting of the following zones:
+ *
+ *   +---+---+
+ *   | A | B |
+ *   +---+---+
+ *   |   C   |
+ *   +-------+
+ *
+ * - Zone A is completly opaque.
+ * - Zone B is clickable through (input shape).
+ * - Zone C is completly transparent (bounding shape).
+ */
+void set_shape(long window_id) {
+    xcb_rectangle_t bounding_rectangle = { 0, 0, 100, 50 };
+    xcb_shape_rectangles(conn, XCB_SHAPE_SO_SET, XCB_SHAPE_SK_BOUNDING,
+                         XCB_CLIP_ORDERING_UNSORTED, window_id,
+                         0, 0, 1, &bounding_rectangle);
+    xcb_rectangle_t input_rectangle = { 0, 0, 50, 50 };
+    xcb_shape_rectangles(conn, XCB_SHAPE_SO_SET, XCB_SHAPE_SK_INPUT,
+                         XCB_CLIP_ORDERING_UNSORTED, window_id,
+                         0, 0, 1, &input_rectangle);
+    xcb_flush(conn);
+}
+END_OF_C_CODE
+
+init_ctx($x->get_xcb_conn());
+
+my ($ws, $win1, $win1_focus, $win2, $win2_focus);
+
+################################################################################
+# Case 1: make floating window, then set shape
+################################################################################
+
+$ws = fresh_workspace;
+
+$win1 = open_floating_window(rect => [0, 0, 100, 100], background_color => '#ff0000');
+$win1_focus = get_focused($ws);
+
+$win2 = open_floating_window(rect => [0, 0, 100, 100], background_color => '#00ff00');
+$win2_focus = get_focused($ws);
+set_shape($win2->id);
+
+$win1->warp_pointer(75, 25);
+sync_with_i3;
+is(get_focused($ws), $win1_focus, 'focus switched to the underlying window');
+
+$win1->warp_pointer(25, 25);
+sync_with_i3;
+is(get_focused($ws), $win2_focus, 'focus switched to the top window');
+
+kill_all_windows;
+
+################################################################################
+# Case 2: set shape first, then make window floating
+################################################################################
+
+$ws = fresh_workspace;
+
+$win1 = open_window(rect => [0, 0, 100, 100], background_color => '#ff0000');
+$win1_focus = get_focused($ws);
+cmd 'floating toggle';
+
+$win2 = open_window(rect => [0, 0, 100, 100], background_color => '#00ff00');
+$win2_focus = get_focused($ws);
+set_shape($win2->id);
+cmd 'floating toggle';
+sync_with_i3;
+
+$win1->warp_pointer(75, 25);
+sync_with_i3;
+is(get_focused($ws), $win1_focus, 'focus switched to the underlying window');
+
+$win1->warp_pointer(25, 25);
+sync_with_i3;
+is(get_focused($ws), $win2_focus, 'focus switched to the top window');
+
+done_testing;