From df8d12fa030f0c1aad3fc27da1fe4f9a1afcaf4f Mon Sep 17 00:00:00 2001
From: Ilia Mirkin <imirkin@alum.mit.edu>
Date: Mon, 25 Jan 2021 18:37:46 -0500
Subject: [PATCH] backend/x11: listen to _NET_WM_STATE changes for determining
 hidden

Some window managers don't unmap windows when they're hidden. Also check
the _NET_WM_STATE property for _NET_WM_STATE_HIDDEN. This way if the
window is hidden or unmapped, then we won't send updates.
---
 backend/x11/backend.c | 44 +++++++++++++++++++++++++++++++++++++++++--
 backend/x11/output.c  |  5 +++--
 include/backend/x11.h |  3 +++
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/backend/x11/backend.c b/backend/x11/backend.c
index 8aebf19b4..b48b3f06f 100644
--- a/backend/x11/backend.c
+++ b/backend/x11/backend.c
@@ -131,9 +131,47 @@ static void handle_x11_event(struct wlr_x11_backend *x11,
 		struct wlr_x11_output *output =
 			get_x11_output_from_window_id(x11, ev->window);
 		if (output != NULL) {
-			wlr_log(WLR_DEBUG, "Window mapped, resuming updates");
+			wlr_log(WLR_DEBUG, "Window mapped%s", !output->hidden ? ", resuming updates" : "");
 			output->mapped = true;
-			wlr_output_send_frame(&output->wlr_output);
+			if (!output->hidden) {
+				wlr_output_send_frame(&output->wlr_output);
+			}
+		}
+		break;
+	}
+	case XCB_PROPERTY_NOTIFY: {
+		xcb_property_notify_event_t *ev = (xcb_property_notify_event_t *)event;
+		struct wlr_x11_output *output =
+			get_x11_output_from_window_id(x11, ev->window);
+		if (output == NULL) {
+			break;
+		}
+		if (ev->atom == x11->atoms.net_wm_state) {
+			xcb_get_property_cookie_t cookie =
+				xcb_get_property(x11->xcb, false, ev->window,
+					ev->atom, XCB_ATOM_ATOM, 0, 32);
+			xcb_get_property_reply_t *reply =
+				xcb_get_property_reply(x11->xcb, cookie, NULL);
+			if (reply->type != XCB_ATOM_ATOM) {
+				free(reply);
+				break;
+			}
+			xcb_atom_t *atoms = xcb_get_property_value(reply);
+			bool was_hidden = output->hidden;
+			output->hidden = false;
+			for (int i = 0; i < xcb_get_property_value_length(reply); i++) {
+				if (atoms[i] == x11->atoms.net_wm_state_hidden) {
+					wlr_log(WLR_DEBUG, "Window hidden, stopping updates");
+					output->hidden = true;
+				}
+			}
+			free(reply);
+			if (was_hidden && !output->hidden) {
+				wlr_log(WLR_DEBUG, "Window no longer hidden%s",  output->mapped ? ", resuming updates" : "");
+				if (output->mapped) {
+					wlr_output_send_frame(&output->wlr_output);
+				}
+			}
 		}
 		break;
 	}
@@ -432,6 +470,8 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	} atom[] = {
 		{ .name = "WM_PROTOCOLS", .atom = &x11->atoms.wm_protocols },
 		{ .name = "WM_DELETE_WINDOW", .atom = &x11->atoms.wm_delete_window },
+		{ .name = "_NET_WM_STATE", .atom = &x11->atoms.net_wm_state },
+		{ .name = "_NET_WM_STATE_HIDDEN", .atom = &x11->atoms.net_wm_state_hidden },
 		{ .name = "_NET_WM_NAME", .atom = &x11->atoms.net_wm_name },
 		{ .name = "UTF8_STRING", .atom = &x11->atoms.utf8_string },
 		{ .name = "_VARIABLE_REFRESH", .atom = &x11->atoms.variable_refresh },
diff --git a/backend/x11/output.c b/backend/x11/output.c
index 68bcc03b0..6a1506896 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -560,7 +560,8 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 		XCB_CW_COLORMAP | XCB_CW_CURSOR;
 	uint32_t values[] = {
 		0,
-		XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY,
+		XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY |
+			XCB_EVENT_MASK_PROPERTY_CHANGE,
 		x11->colormap,
 		x11->transparent_cursor,
 	};
@@ -742,7 +743,7 @@ void handle_x11_present_event(struct wlr_x11_backend *x11,
 		};
 		wlr_output_send_present(&output->wlr_output, &present_event);
 
-		if (output->mapped)
+		if (output->mapped && !output->hidden)
 			wlr_output_send_frame(&output->wlr_output);
 		break;
 	default:
diff --git a/include/backend/x11.h b/include/backend/x11.h
index 6349bece2..8ac262cc4 100644
--- a/include/backend/x11.h
+++ b/include/backend/x11.h
@@ -52,6 +52,7 @@ struct wlr_x11_output {
 
 	uint64_t last_msc;
 	bool mapped;
+	bool hidden;
 
 	struct {
 		struct wlr_swapchain *swapchain;
@@ -99,6 +100,8 @@ struct wlr_x11_backend {
 		xcb_atom_t wm_protocols;
 		xcb_atom_t wm_delete_window;
 		xcb_atom_t net_wm_name;
+		xcb_atom_t net_wm_state;
+		xcb_atom_t net_wm_state_hidden;
 		xcb_atom_t utf8_string;
 		xcb_atom_t variable_refresh;
 	} atoms;